/*
 *  pNFS functions to call and manage layout drivers.
 *
 *  Copyright (c) 2002 [year of first publication]
 *  The Regents of the University of Michigan
 *  All Rights Reserved
 *
 *  Dean Hildebrand <dhildebz@umich.edu>
 *
 *  Permission is granted to use, copy, create derivative works, and
 *  redistribute this software and such derivative works for any purpose,
 *  so long as the name of the University of Michigan is not used in
 *  any advertising or publicity pertaining to the use or distribution
 *  of this software without specific, written prior authorization. If
 *  the above copyright notice or any other identification of the
 *  University of Michigan is included in any copy of any portion of
 *  this software, then the disclaimer below must also be included.
 *
 *  This software is provided as is, without representation or warranty
 *  of any kind either express or implied, including without limitation
 *  the implied warranties of merchantability, fitness for a particular
 *  purpose, or noninfringement.  The Regents of the University of
 *  Michigan shall not be liable for any damages, including special,
 *  indirect, incidental, or consequential damages, with respect to any
 *  claim arising out of or in connection with the use of the software,
 *  even if it has been or is hereafter advised of the possibility of
 *  such damages.
 */

#include <linux/nfs_fs.h>
#include <linux/nfs_page.h>
#include <linux/module.h>
#include <linux/sort.h>
#include "internal.h"
#include "pnfs.h"
#include "iostat.h"
#include "nfs4trace.h"
#include "delegation.h"
#include "nfs42.h"
#include "nfs4_fs.h"

#define NFSDBG_FACILITY         NFSDBG_PNFS
#define PNFS_LAYOUTGET_RETRY_TIMEOUT (120*HZ)

/* Locking:
 *
 * pnfs_spinlock:
 *      protects pnfs_modules_tbl.
 */
static DEFINE_SPINLOCK(pnfs_spinlock);

/*
 * pnfs_modules_tbl holds all pnfs modules
 */
static LIST_HEAD(pnfs_modules_tbl);

static void pnfs_layoutreturn_before_put_layout_hdr(struct pnfs_layout_hdr *lo);
static void pnfs_free_returned_lsegs(struct pnfs_layout_hdr *lo,
                struct list_head *free_me,
                const struct pnfs_layout_range *range,
                u32 seq);
static bool pnfs_lseg_dec_and_remove_zero(struct pnfs_layout_segment *lseg,
                                struct list_head *tmp_list);

/* Return the registered pnfs layout driver module matching given id */
static struct pnfs_layoutdriver_type *
find_pnfs_driver_locked(u32 id)
{
        struct pnfs_layoutdriver_type *local;

        list_for_each_entry(local, &pnfs_modules_tbl, pnfs_tblid)
                if (local->id == id)
                        goto out;
        local = NULL;
out:
        dprintk("%s: Searching for id %u, found %p\n", __func__, id, local);
        return local;
}

static struct pnfs_layoutdriver_type *
find_pnfs_driver(u32 id)
{
        struct pnfs_layoutdriver_type *local;

        spin_lock(&pnfs_spinlock);
        local = find_pnfs_driver_locked(id);
        if (local != NULL && !try_module_get(local->owner)) {
                dprintk("%s: Could not grab reference on module\n", __func__);
                local = NULL;
        }
        spin_unlock(&pnfs_spinlock);
        return local;
}

void
unset_pnfs_layoutdriver(struct nfs_server *nfss)
{
        if (nfss->pnfs_curr_ld) {
                if (nfss->pnfs_curr_ld->clear_layoutdriver)
                        nfss->pnfs_curr_ld->clear_layoutdriver(nfss);
                /* Decrement the MDS count. Purge the deviceid cache if zero */
                if (atomic_dec_and_test(&nfss->nfs_client->cl_mds_count))
                        nfs4_deviceid_purge_client(nfss->nfs_client);
                module_put(nfss->pnfs_curr_ld->owner);
        }
        nfss->pnfs_curr_ld = NULL;
}

/*
 * When the server sends a list of layout types, we choose one in the order
 * given in the list below.
 *
 * FIXME: should this list be configurable in some fashion? module param?
 *        mount option? something else?
 */
static const u32 ld_prefs[] = {
        LAYOUT_SCSI,
        LAYOUT_BLOCK_VOLUME,
        LAYOUT_OSD2_OBJECTS,
        LAYOUT_FLEX_FILES,
        LAYOUT_NFSV4_1_FILES,
        0
};

static int
ld_cmp(const void *e1, const void *e2)
{
        u32 ld1 = *((u32 *)e1);
        u32 ld2 = *((u32 *)e2);
        int i;

        for (i = 0; ld_prefs[i] != 0; i++) {
                if (ld1 == ld_prefs[i])
                        return -1;

                if (ld2 == ld_prefs[i])
                        return 1;
        }
        return 0;
}

/*
 * Try to set the server's pnfs module to the pnfs layout type specified by id.
 * Currently only one pNFS layout driver per filesystem is supported.
 *
 * @ids array of layout types supported by MDS.
 */
void
set_pnfs_layoutdriver(struct nfs_server *server, const struct nfs_fh *mntfh,
                      struct nfs_fsinfo *fsinfo)
{
        struct pnfs_layoutdriver_type *ld_type = NULL;
        u32 id;
        int i;

        if (fsinfo->nlayouttypes == 0)
                goto out_no_driver;
        if (!(server->nfs_client->cl_exchange_flags &
                 (EXCHGID4_FLAG_USE_NON_PNFS | EXCHGID4_FLAG_USE_PNFS_MDS))) {
                printk(KERN_ERR "NFS: %s: cl_exchange_flags 0x%x\n",
                        __func__, server->nfs_client->cl_exchange_flags);
                goto out_no_driver;
        }

        sort(fsinfo->layouttype, fsinfo->nlayouttypes,
                sizeof(*fsinfo->layouttype), ld_cmp, NULL);

        for (i = 0; i < fsinfo->nlayouttypes; i++) {
                id = fsinfo->layouttype[i];
                ld_type = find_pnfs_driver(id);
                if (!ld_type) {
                        request_module("%s-%u", LAYOUT_NFSV4_1_MODULE_PREFIX,
                                        id);
                        ld_type = find_pnfs_driver(id);
                }
                if (ld_type)
                        break;
        }

        if (!ld_type) {
                dprintk("%s: No pNFS module found!\n", __func__);
                goto out_no_driver;
        }

        server->pnfs_curr_ld = ld_type;
        if (ld_type->set_layoutdriver
            && ld_type->set_layoutdriver(server, mntfh)) {
                printk(KERN_ERR "NFS: %s: Error initializing pNFS layout "
                        "driver %u.\n", __func__, id);
                module_put(ld_type->owner);
                goto out_no_driver;
        }
        /* Bump the MDS count */
        atomic_inc(&server->nfs_client->cl_mds_count);

        dprintk("%s: pNFS module for %u set\n", __func__, id);
        return;

out_no_driver:
        dprintk("%s: Using NFSv4 I/O\n", __func__);
        server->pnfs_curr_ld = NULL;
}

int
pnfs_register_layoutdriver(struct pnfs_layoutdriver_type *ld_type)
{
        int status = -EINVAL;
        struct pnfs_layoutdriver_type *tmp;

        if (ld_type->id == 0) {
                printk(KERN_ERR "NFS: %s id 0 is reserved\n", __func__);
                return status;
        }
        if (!ld_type->alloc_lseg || !ld_type->free_lseg) {
                printk(KERN_ERR "NFS: %s Layout driver must provide "
                       "alloc_lseg and free_lseg.\n", __func__);
                return status;
        }

        spin_lock(&pnfs_spinlock);
        tmp = find_pnfs_driver_locked(ld_type->id);
        if (!tmp) {
                list_add(&ld_type->pnfs_tblid, &pnfs_modules_tbl);
                status = 0;
                dprintk("%s Registering id:%u name:%s\n", __func__, ld_type->id,
                        ld_type->name);
        } else {
                printk(KERN_ERR "NFS: %s Module with id %d already loaded!\n",
                        __func__, ld_type->id);
        }
        spin_unlock(&pnfs_spinlock);

        return status;
}
EXPORT_SYMBOL_GPL(pnfs_register_layoutdriver);

void
pnfs_unregister_layoutdriver(struct pnfs_layoutdriver_type *ld_type)
{
        dprintk("%s Deregistering id:%u\n", __func__, ld_type->id);
        spin_lock(&pnfs_spinlock);
        list_del(&ld_type->pnfs_tblid);
        spin_unlock(&pnfs_spinlock);
}
EXPORT_SYMBOL_GPL(pnfs_unregister_layoutdriver);

/*
 * pNFS client layout cache
 */

/* Need to hold i_lock if caller does not already hold reference */
void
pnfs_get_layout_hdr(struct pnfs_layout_hdr *lo)
{
        refcount_inc(&lo->plh_refcount);
}

static struct pnfs_layout_hdr *
pnfs_alloc_layout_hdr(struct inode *ino, gfp_t gfp_flags)
{
        struct pnfs_layoutdriver_type *ld = NFS_SERVER(ino)->pnfs_curr_ld;
        return ld->alloc_layout_hdr(ino, gfp_flags);
}

static void
pnfs_free_layout_hdr(struct pnfs_layout_hdr *lo)
{
        struct nfs_server *server = NFS_SERVER(lo->plh_inode);
        struct pnfs_layoutdriver_type *ld = server->pnfs_curr_ld;

        if (test_and_clear_bit(NFS_LAYOUT_HASHED, &lo->plh_flags)) {
                struct nfs_client *clp = server->nfs_client;

                spin_lock(&clp->cl_lock);
                list_del_rcu(&lo->plh_layouts);
                spin_unlock(&clp->cl_lock);
        }
        put_cred(lo->plh_lc_cred);
        return ld->free_layout_hdr(lo);
}

static void
pnfs_detach_layout_hdr(struct pnfs_layout_hdr *lo)
{
        struct nfs_inode *nfsi = NFS_I(lo->plh_inode);
        dprintk("%s: freeing layout cache %p\n", __func__, lo);
        nfsi->layout = NULL;
        /* Reset MDS Threshold I/O counters */
        nfsi->write_io = 0;
        nfsi->read_io = 0;
}

void
pnfs_put_layout_hdr(struct pnfs_layout_hdr *lo)
{
        struct inode *inode;
        unsigned long i_state;

        if (!lo)
                return;
        inode = lo->plh_inode;
        pnfs_layoutreturn_before_put_layout_hdr(lo);

        if (refcount_dec_and_lock(&lo->plh_refcount, &inode->i_lock)) {
                if (!list_empty(&lo->plh_segs))
                        WARN_ONCE(1, "NFS: BUG unfreed layout segments.\n");
                pnfs_detach_layout_hdr(lo);
                i_state = inode->i_state;
                spin_unlock(&inode->i_lock);
                pnfs_free_layout_hdr(lo);
                /* Notify pnfs_destroy_layout_final() that we're done */
                if (i_state & (I_FREEING | I_CLEAR))
                        wake_up_var(lo);
        }
}

static struct inode *
pnfs_grab_inode_layout_hdr(struct pnfs_layout_hdr *lo)
{
        struct inode *inode = igrab(lo->plh_inode);
        if (inode)
                return inode;
        set_bit(NFS_LAYOUT_INODE_FREEING, &lo->plh_flags);
        return NULL;
}

/*
 * Compare 2 layout stateid sequence ids, to see which is newer,
 * taking into account wraparound issues.
 */
static bool pnfs_seqid_is_newer(u32 s1, u32 s2)
{
        return (s32)(s1 - s2) > 0;
}

static void pnfs_barrier_update(struct pnfs_layout_hdr *lo, u32 newseq)
{
        if (pnfs_seqid_is_newer(newseq, lo->plh_barrier))
                lo->plh_barrier = newseq;
}

static void
pnfs_set_plh_return_info(struct pnfs_layout_hdr *lo, enum pnfs_iomode iomode,
                         u32 seq)
{
        if (lo->plh_return_iomode != 0 && lo->plh_return_iomode != iomode)
                iomode = IOMODE_ANY;
        lo->plh_return_iomode = iomode;
        set_bit(NFS_LAYOUT_RETURN_REQUESTED, &lo->plh_flags);
        if (seq != 0) {
                WARN_ON_ONCE(lo->plh_return_seq != 0 && lo->plh_return_seq != seq);
                lo->plh_return_seq = seq;
                pnfs_barrier_update(lo, seq);
        }
}

static void
pnfs_clear_layoutreturn_info(struct pnfs_layout_hdr *lo)
{
        struct pnfs_layout_segment *lseg;
        lo->plh_return_iomode = 0;
        lo->plh_return_seq = 0;
        clear_bit(NFS_LAYOUT_RETURN_REQUESTED, &lo->plh_flags);
        list_for_each_entry(lseg, &lo->plh_segs, pls_list) {
                if (!test_bit(NFS_LSEG_LAYOUTRETURN, &lseg->pls_flags))
                        continue;
                pnfs_set_plh_return_info(lo, lseg->pls_range.iomode, 0);
        }
}

static void pnfs_clear_layoutreturn_waitbit(struct pnfs_layout_hdr *lo)
{
        clear_bit_unlock(NFS_LAYOUT_RETURN, &lo->plh_flags);
        clear_bit(NFS_LAYOUT_RETURN_LOCK, &lo->plh_flags);
        smp_mb__after_atomic();
        wake_up_bit(&lo->plh_flags, NFS_LAYOUT_RETURN);
        rpc_wake_up(&NFS_SERVER(lo->plh_inode)->roc_rpcwaitq);
}

static void
pnfs_clear_lseg_state(struct pnfs_layout_segment *lseg,
                struct list_head *free_me)
{
        clear_bit(NFS_LSEG_ROC, &lseg->pls_flags);
        clear_bit(NFS_LSEG_LAYOUTRETURN, &lseg->pls_flags);
        if (test_and_clear_bit(NFS_LSEG_VALID, &lseg->pls_flags))
                pnfs_lseg_dec_and_remove_zero(lseg, free_me);
        if (test_and_clear_bit(NFS_LSEG_LAYOUTCOMMIT, &lseg->pls_flags))
                pnfs_lseg_dec_and_remove_zero(lseg, free_me);
}

/*
 * Update the seqid of a layout stateid after receiving
 * NFS4ERR_OLD_STATEID
 */
bool nfs4_layout_refresh_old_stateid(nfs4_stateid *dst,
                struct pnfs_layout_range *dst_range,
                struct inode *inode)
{
        struct pnfs_layout_hdr *lo;
        struct pnfs_layout_range range = {
                .iomode = IOMODE_ANY,
                .offset = 0,
                .length = NFS4_MAX_UINT64,
        };
        bool ret = false;
        LIST_HEAD(head);
        int err;

        spin_lock(&inode->i_lock);
        lo = NFS_I(inode)->layout;
        if (lo &&  pnfs_layout_is_valid(lo) &&
            nfs4_stateid_match_other(dst, &lo->plh_stateid)) {
                /* Is our call using the most recent seqid? If so, bump it */
                if (!nfs4_stateid_is_newer(&lo->plh_stateid, dst)) {
                        nfs4_stateid_seqid_inc(dst);
                        ret = true;
                        goto out;
                }
                /* Try to update the seqid to the most recent */
                err = pnfs_mark_matching_lsegs_return(lo, &head, &range, 0);
                if (err != -EBUSY) {
                        dst->seqid = lo->plh_stateid.seqid;
                        *dst_range = range;
                        ret = true;
                }
        }
out:
        spin_unlock(&inode->i_lock);
        pnfs_free_lseg_list(&head);
        return ret;
}

/*
 * Mark a pnfs_layout_hdr and all associated layout segments as invalid
 *
 * In order to continue using the pnfs_layout_hdr, a full recovery
 * is required.
 * Note that caller must hold inode->i_lock.
 */
int
pnfs_mark_layout_stateid_invalid(struct pnfs_layout_hdr *lo,
                struct list_head *lseg_list)
{
        struct pnfs_layout_range range = {
                .iomode = IOMODE_ANY,
                .offset = 0,
                .length = NFS4_MAX_UINT64,
        };
        struct pnfs_layout_segment *lseg, *next;

        set_bit(NFS_LAYOUT_INVALID_STID, &lo->plh_flags);
        list_for_each_entry_safe(lseg, next, &lo->plh_segs, pls_list)
                pnfs_clear_lseg_state(lseg, lseg_list);
        pnfs_clear_layoutreturn_info(lo);
        pnfs_free_returned_lsegs(lo, lseg_list, &range, 0);
        if (test_bit(NFS_LAYOUT_RETURN, &lo->plh_flags) &&
            !test_and_set_bit(NFS_LAYOUT_RETURN_LOCK, &lo->plh_flags))
                pnfs_clear_layoutreturn_waitbit(lo);
        return !list_empty(&lo->plh_segs);
}

static int
pnfs_iomode_to_fail_bit(u32 iomode)
{
        return iomode == IOMODE_RW ?
                NFS_LAYOUT_RW_FAILED : NFS_LAYOUT_RO_FAILED;
}

static void
pnfs_layout_set_fail_bit(struct pnfs_layout_hdr *lo, int fail_bit)
{
        lo->plh_retry_timestamp = jiffies;
        if (!test_and_set_bit(fail_bit, &lo->plh_flags))
                refcount_inc(&lo->plh_refcount);
}

static void
pnfs_layout_clear_fail_bit(struct pnfs_layout_hdr *lo, int fail_bit)
{
        if (test_and_clear_bit(fail_bit, &lo->plh_flags))
                refcount_dec(&lo->plh_refcount);
}

static void
pnfs_layout_io_set_failed(struct pnfs_layout_hdr *lo, u32 iomode)
{
        struct inode *inode = lo->plh_inode;
        struct pnfs_layout_range range = {
                .iomode = iomode,
                .offset = 0,
                .length = NFS4_MAX_UINT64,
        };
        LIST_HEAD(head);

        spin_lock(&inode->i_lock);
        pnfs_layout_set_fail_bit(lo, pnfs_iomode_to_fail_bit(iomode));
        pnfs_mark_matching_lsegs_invalid(lo, &head, &range, 0);
        spin_unlock(&inode->i_lock);
        pnfs_free_lseg_list(&head);
        dprintk("%s Setting layout IOMODE_%s fail bit\n", __func__,
                        iomode == IOMODE_RW ?  "RW" : "READ");
}

static bool
pnfs_layout_io_test_failed(struct pnfs_layout_hdr *lo, u32 iomode)
{
        unsigned long start, end;
        int fail_bit = pnfs_iomode_to_fail_bit(iomode);

        if (test_bit(fail_bit, &lo->plh_flags) == 0)
                return false;
        end = jiffies;
        start = end - PNFS_LAYOUTGET_RETRY_TIMEOUT;
        if (!time_in_range(lo->plh_retry_timestamp, start, end)) {
                /* It is time to retry the failed layoutgets */
                pnfs_layout_clear_fail_bit(lo, fail_bit);
                return false;
        }
        return true;
}

static void
pnfs_init_lseg(struct pnfs_layout_hdr *lo, struct pnfs_layout_segment *lseg,
                const struct pnfs_layout_range *range,
                const nfs4_stateid *stateid)
{
        INIT_LIST_HEAD(&lseg->pls_list);
        INIT_LIST_HEAD(&lseg->pls_lc_list);
        INIT_LIST_HEAD(&lseg->pls_commits);
        refcount_set(&lseg->pls_refcount, 1);
        set_bit(NFS_LSEG_VALID, &lseg->pls_flags);
        lseg->pls_layout = lo;
        lseg->pls_range = *range;
        lseg->pls_seq = be32_to_cpu(stateid->seqid);
}

static void pnfs_free_lseg(struct pnfs_layout_segment *lseg)
{
        if (lseg != NULL) {
                struct inode *inode = lseg->pls_layout->plh_inode;
                NFS_SERVER(inode)->pnfs_curr_ld->free_lseg(lseg);
        }
}

static void
pnfs_layout_remove_lseg(struct pnfs_layout_hdr *lo,
                struct pnfs_layout_segment *lseg)
{
        WARN_ON(test_bit(NFS_LSEG_VALID, &lseg->pls_flags));
        list_del_init(&lseg->pls_list);
        /* Matched by pnfs_get_layout_hdr in pnfs_layout_insert_lseg */
        refcount_dec(&lo->plh_refcount);
        if (test_bit(NFS_LSEG_LAYOUTRETURN, &lseg->pls_flags))
                return;
        if (list_empty(&lo->plh_segs) &&
            !test_bit(NFS_LAYOUT_RETURN_REQUESTED, &lo->plh_flags) &&
            !test_bit(NFS_LAYOUT_RETURN, &lo->plh_flags)) {
                if (atomic_read(&lo->plh_outstanding) == 0)
                        set_bit(NFS_LAYOUT_INVALID_STID, &lo->plh_flags);
                clear_bit(NFS_LAYOUT_BULK_RECALL, &lo->plh_flags);
        }
}

static bool
pnfs_cache_lseg_for_layoutreturn(struct pnfs_layout_hdr *lo,
                struct pnfs_layout_segment *lseg)
{
        if (test_and_clear_bit(NFS_LSEG_LAYOUTRETURN, &lseg->pls_flags) &&
            pnfs_layout_is_valid(lo)) {
                pnfs_set_plh_return_info(lo, lseg->pls_range.iomode, 0);
                list_move_tail(&lseg->pls_list, &lo->plh_return_segs);
                return true;
        }
        return false;
}

void
pnfs_put_lseg(struct pnfs_layout_segment *lseg)
{
        struct pnfs_layout_hdr *lo;
        struct inode *inode;

        if (!lseg)
                return;

        dprintk("%s: lseg %p ref %d valid %d\n", __func__, lseg,
                refcount_read(&lseg->pls_refcount),
                test_bit(NFS_LSEG_VALID, &lseg->pls_flags));

        lo = lseg->pls_layout;
        inode = lo->plh_inode;

        if (refcount_dec_and_lock(&lseg->pls_refcount, &inode->i_lock)) {
                if (test_bit(NFS_LSEG_VALID, &lseg->pls_flags)) {
                        spin_unlock(&inode->i_lock);
                        return;
                }
                pnfs_get_layout_hdr(lo);
                pnfs_layout_remove_lseg(lo, lseg);
                if (pnfs_cache_lseg_for_layoutreturn(lo, lseg))
                        lseg = NULL;
                spin_unlock(&inode->i_lock);
                pnfs_free_lseg(lseg);
                pnfs_put_layout_hdr(lo);
        }
}
EXPORT_SYMBOL_GPL(pnfs_put_lseg);

/*
 * is l2 fully contained in l1?
 *   start1                             end1
 *   [----------------------------------)
 *           start2           end2
 *           [----------------)
 */
static bool
pnfs_lseg_range_contained(const struct pnfs_layout_range *l1,
                 const struct pnfs_layout_range *l2)
{
        u64 start1 = l1->offset;
        u64 end1 = pnfs_end_offset(start1, l1->length);
        u64 start2 = l2->offset;
        u64 end2 = pnfs_end_offset(start2, l2->length);

        return (start1 <= start2) && (end1 >= end2);
}

static bool pnfs_lseg_dec_and_remove_zero(struct pnfs_layout_segment *lseg,
                struct list_head *tmp_list)
{
        if (!refcount_dec_and_test(&lseg->pls_refcount))
                return false;
        pnfs_layout_remove_lseg(lseg->pls_layout, lseg);
        list_add(&lseg->pls_list, tmp_list);
        return true;
}

/* Returns 1 if lseg is removed from list, 0 otherwise */
static int mark_lseg_invalid(struct pnfs_layout_segment *lseg,
                             struct list_head *tmp_list)
{
        int rv = 0;

        if (test_and_clear_bit(NFS_LSEG_VALID, &lseg->pls_flags)) {
                /* Remove the reference keeping the lseg in the
                 * list.  It will now be removed when all
                 * outstanding io is finished.
                 */
                dprintk("%s: lseg %p ref %d\n", __func__, lseg,
                        refcount_read(&lseg->pls_refcount));
                if (pnfs_lseg_dec_and_remove_zero(lseg, tmp_list))
                        rv = 1;
        }
        return rv;
}

static bool
pnfs_should_free_range(const struct pnfs_layout_range *lseg_range,
                 const struct pnfs_layout_range *recall_range)
{
        return (recall_range->iomode == IOMODE_ANY ||
                lseg_range->iomode == recall_range->iomode) &&
               pnfs_lseg_range_intersecting(lseg_range, recall_range);
}

static bool
pnfs_match_lseg_recall(const struct pnfs_layout_segment *lseg,
                const struct pnfs_layout_range *recall_range,
                u32 seq)
{
        if (seq != 0 && pnfs_seqid_is_newer(lseg->pls_seq, seq))
                return false;
        if (recall_range == NULL)
                return true;
        return pnfs_should_free_range(&lseg->pls_range, recall_range);
}

/**
 * pnfs_mark_matching_lsegs_invalid - tear down lsegs or mark them for later
 * @lo: layout header containing the lsegs
 * @tmp_list: list head where doomed lsegs should go
 * @recall_range: optional recall range argument to match (may be NULL)
 * @seq: only invalidate lsegs obtained prior to this sequence (may be 0)
 *
 * Walk the list of lsegs in the layout header, and tear down any that should
 * be destroyed. If "recall_range" is specified then the segment must match
 * that range. If "seq" is non-zero, then only match segments that were handed
 * out at or before that sequence.
 *
 * Returns number of matching invalid lsegs remaining in list after scanning
 * it and purging them.
 */
int
pnfs_mark_matching_lsegs_invalid(struct pnfs_layout_hdr *lo,
                            struct list_head *tmp_list,
                            const struct pnfs_layout_range *recall_range,
                            u32 seq)
{
        struct pnfs_layout_segment *lseg, *next;
        int remaining = 0;

        dprintk("%s:Begin lo %p\n", __func__, lo);

        if (list_empty(&lo->plh_segs))
                return 0;
        list_for_each_entry_safe(lseg, next, &lo->plh_segs, pls_list)
                if (pnfs_match_lseg_recall(lseg, recall_range, seq)) {
                        dprintk("%s: freeing lseg %p iomode %d seq %u "
                                "offset %llu length %llu\n", __func__,
                                lseg, lseg->pls_range.iomode, lseg->pls_seq,
                                lseg->pls_range.offset, lseg->pls_range.length);
                        if (!mark_lseg_invalid(lseg, tmp_list))
                                remaining++;
                }
        dprintk("%s:Return %i\n", __func__, remaining);
        return remaining;
}

static void
pnfs_free_returned_lsegs(struct pnfs_layout_hdr *lo,
                struct list_head *free_me,
                const struct pnfs_layout_range *range,
                u32 seq)
{
        struct pnfs_layout_segment *lseg, *next;

        list_for_each_entry_safe(lseg, next, &lo->plh_return_segs, pls_list) {
                if (pnfs_match_lseg_recall(lseg, range, seq))
                        list_move_tail(&lseg->pls_list, free_me);
        }
}

/* note free_me must contain lsegs from a single layout_hdr */
void
pnfs_free_lseg_list(struct list_head *free_me)
{
        struct pnfs_layout_segment *lseg, *tmp;

        if (list_empty(free_me))
                return;

        list_for_each_entry_safe(lseg, tmp, free_me, pls_list) {
                list_del(&lseg->pls_list);
                pnfs_free_lseg(lseg);
        }
}

static struct pnfs_layout_hdr *__pnfs_destroy_layout(struct nfs_inode *nfsi)
{
        struct pnfs_layout_hdr *lo;
        LIST_HEAD(tmp_list);

        spin_lock(&nfsi->vfs_inode.i_lock);
        lo = nfsi->layout;
        if (lo) {
                pnfs_get_layout_hdr(lo);
                pnfs_mark_layout_stateid_invalid(lo, &tmp_list);
                pnfs_layout_clear_fail_bit(lo, NFS_LAYOUT_RO_FAILED);
                pnfs_layout_clear_fail_bit(lo, NFS_LAYOUT_RW_FAILED);
                spin_unlock(&nfsi->vfs_inode.i_lock);
                pnfs_free_lseg_list(&tmp_list);
                nfs_commit_inode(&nfsi->vfs_inode, 0);
                pnfs_put_layout_hdr(lo);
        } else
                spin_unlock(&nfsi->vfs_inode.i_lock);
        return lo;
}

void pnfs_destroy_layout(struct nfs_inode *nfsi)
{
        __pnfs_destroy_layout(nfsi);
}
EXPORT_SYMBOL_GPL(pnfs_destroy_layout);

static bool pnfs_layout_removed(struct nfs_inode *nfsi,
                                struct pnfs_layout_hdr *lo)
{
        bool ret;

        spin_lock(&nfsi->vfs_inode.i_lock);
        ret = nfsi->layout != lo;
        spin_unlock(&nfsi->vfs_inode.i_lock);
        return ret;
}

void pnfs_destroy_layout_final(struct nfs_inode *nfsi)
{
        struct pnfs_layout_hdr *lo = __pnfs_destroy_layout(nfsi);

        if (lo)
                wait_var_event(lo, pnfs_layout_removed(nfsi, lo));
}

static bool
pnfs_layout_add_bulk_destroy_list(struct inode *inode,
                struct list_head *layout_list)
{
        struct pnfs_layout_hdr *lo;
        bool ret = false;

        spin_lock(&inode->i_lock);
        lo = NFS_I(inode)->layout;
        if (lo != NULL && list_empty(&lo->plh_bulk_destroy)) {
                pnfs_get_layout_hdr(lo);
                list_add(&lo->plh_bulk_destroy, layout_list);
                ret = true;
        }
        spin_unlock(&inode->i_lock);
        return ret;
}

/* Caller must hold rcu_read_lock and clp->cl_lock */
static int
pnfs_layout_bulk_destroy_byserver_locked(struct nfs_client *clp,
                struct nfs_server *server,
                struct list_head *layout_list)
        __must_hold(&clp->cl_lock)
        __must_hold(RCU)
{
        struct pnfs_layout_hdr *lo, *next;
        struct inode *inode;

        list_for_each_entry_safe(lo, next, &server->layouts, plh_layouts) {
                if (test_bit(NFS_LAYOUT_INVALID_STID, &lo->plh_flags) ||
                    test_bit(NFS_LAYOUT_INODE_FREEING, &lo->plh_flags) ||
                    !list_empty(&lo->plh_bulk_destroy))
                        continue;
                /* If the sb is being destroyed, just bail */
                if (!nfs_sb_active(server->super))
                        break;
                inode = pnfs_grab_inode_layout_hdr(lo);
                if (inode != NULL) {
                        if (test_and_clear_bit(NFS_LAYOUT_HASHED, &lo->plh_flags))
                                list_del_rcu(&lo->plh_layouts);
                        if (pnfs_layout_add_bulk_destroy_list(inode,
                                                layout_list))
                                continue;
                        rcu_read_unlock();
                        spin_unlock(&clp->cl_lock);
                        iput(inode);
                } else {
                        rcu_read_unlock();
                        spin_unlock(&clp->cl_lock);
                }
                nfs_sb_deactive(server->super);
                spin_lock(&clp->cl_lock);
                rcu_read_lock();
                return -EAGAIN;
        }
        return 0;
}

static int
pnfs_layout_free_bulk_destroy_list(struct list_head *layout_list,
                bool is_bulk_recall)
{
        struct pnfs_layout_hdr *lo;
        struct inode *inode;
        LIST_HEAD(lseg_list);
        int ret = 0;

        while (!list_empty(layout_list)) {
                lo = list_entry(layout_list->next, struct pnfs_layout_hdr,
                                plh_bulk_destroy);
                dprintk("%s freeing layout for inode %lu\n", __func__,
                        lo->plh_inode->i_ino);
                inode = lo->plh_inode;

                pnfs_layoutcommit_inode(inode, false);

                spin_lock(&inode->i_lock);
                list_del_init(&lo->plh_bulk_destroy);
                if (pnfs_mark_layout_stateid_invalid(lo, &lseg_list)) {
                        if (is_bulk_recall)
                                set_bit(NFS_LAYOUT_BULK_RECALL, &lo->plh_flags);
                        ret = -EAGAIN;
                }
                spin_unlock(&inode->i_lock);
                pnfs_free_lseg_list(&lseg_list);
                /* Free all lsegs that are attached to commit buckets */
                nfs_commit_inode(inode, 0);
                pnfs_put_layout_hdr(lo);
                nfs_iput_and_deactive(inode);
        }
        return ret;
}

int
pnfs_destroy_layouts_byfsid(struct nfs_client *clp,
                struct nfs_fsid *fsid,
                bool is_recall)
{
        struct nfs_server *server;
        LIST_HEAD(layout_list);

        spin_lock(&clp->cl_lock);
        rcu_read_lock();
restart:
        list_for_each_entry_rcu(server, &clp->cl_superblocks, client_link) {
                if (memcmp(&server->fsid, fsid, sizeof(*fsid)) != 0)
                        continue;
                if (pnfs_layout_bulk_destroy_byserver_locked(clp,
                                server,
                                &layout_list) != 0)
                        goto restart;
        }
        rcu_read_unlock();
        spin_unlock(&clp->cl_lock);

        if (list_empty(&layout_list))
                return 0;
        return pnfs_layout_free_bulk_destroy_list(&layout_list, is_recall);
}

int
pnfs_destroy_layouts_byclid(struct nfs_client *clp,
                bool is_recall)
{
        struct nfs_server *server;
        LIST_HEAD(layout_list);

        spin_lock(&clp->cl_lock);
        rcu_read_lock();
restart:
        list_for_each_entry_rcu(server, &clp->cl_superblocks, client_link) {
                if (pnfs_layout_bulk_destroy_byserver_locked(clp,
                                        server,
                                        &layout_list) != 0)
                        goto restart;
        }
        rcu_read_unlock();
        spin_unlock(&clp->cl_lock);

        if (list_empty(&layout_list))
                return 0;
        return pnfs_layout_free_bulk_destroy_list(&layout_list, is_recall);
}

/*
 * Called by the state manager to remove all layouts established under an
 * expired lease.
 */
void
pnfs_destroy_all_layouts(struct nfs_client *clp)
{
        nfs4_deviceid_mark_client_invalid(clp);
        nfs4_deviceid_purge_client(clp);

        pnfs_destroy_layouts_byclid(clp, false);
}

static void
pnfs_set_layout_cred(struct pnfs_layout_hdr *lo, const struct cred *cred)
{
        const struct cred *old;

        if (cred && cred_fscmp(lo->plh_lc_cred, cred) != 0) {
                old = xchg(&lo->plh_lc_cred, get_cred(cred));
                put_cred(old);
        }
}

/* update lo->plh_stateid with new if is more recent */
void
pnfs_set_layout_stateid(struct pnfs_layout_hdr *lo, const nfs4_stateid *new,
                        const struct cred *cred, bool update_barrier)
{
        u32 oldseq, newseq, new_barrier = 0;

        oldseq = be32_to_cpu(lo->plh_stateid.seqid);
        newseq = be32_to_cpu(new->seqid);

        if (!pnfs_layout_is_valid(lo)) {
                pnfs_set_layout_cred(lo, cred);
                nfs4_stateid_copy(&lo->plh_stateid, new);
                lo->plh_barrier = newseq;
                pnfs_clear_layoutreturn_info(lo);
                clear_bit(NFS_LAYOUT_INVALID_STID, &lo->plh_flags);
                return;
        }
        if (pnfs_seqid_is_newer(newseq, oldseq)) {
                nfs4_stateid_copy(&lo->plh_stateid, new);
                /*
                 * Because of wraparound, we want to keep the barrier
                 * "close" to the current seqids.
                 */
                new_barrier = newseq - atomic_read(&lo->plh_outstanding);
        }
        if (update_barrier)
                new_barrier = be32_to_cpu(new->seqid);
        else if (new_barrier == 0)
                return;
        pnfs_barrier_update(lo, new_barrier);
}

static bool
pnfs_layout_stateid_blocked(const struct pnfs_layout_hdr *lo,
                const nfs4_stateid *stateid)
{

        u32 seqid = be32_to_cpu(stateid->seqid);

        return !pnfs_seqid_is_newer(seqid, lo->plh_barrier) && lo->plh_barrier;
}

/* lget is set to 1 if called from inside send_layoutget call chain */
static bool
pnfs_layoutgets_blocked(const struct pnfs_layout_hdr *lo)
{
        return lo->plh_block_lgets ||
                test_bit(NFS_LAYOUT_BULK_RECALL, &lo->plh_flags);
}

static struct nfs_server *
pnfs_find_server(struct inode *inode, struct nfs_open_context *ctx)
{
        struct nfs_server *server;

        if (inode) {
                server = NFS_SERVER(inode);
        } else {
                struct dentry *parent_dir = dget_parent(ctx->dentry);
                server = NFS_SERVER(parent_dir->d_inode);
                dput(parent_dir);
        }
        return server;
}

static void nfs4_free_pages(struct page **pages, size_t size)
{
        int i;

        if (!pages)
                return;

        for (i = 0; i < size; i++) {
                if (!pages[i])
                        break;
                __free_page(pages[i]);
        }
        kfree(pages);
}

static struct page **nfs4_alloc_pages(size_t size, gfp_t gfp_flags)
{
        struct page **pages;
        int i;

        pages = kmalloc_array(size, sizeof(struct page *), gfp_flags);
        if (!pages) {
                dprintk("%s: can't alloc array of %zu pages\n", __func__, size);
                return NULL;
        }

        for (i = 0; i < size; i++) {
                pages[i] = alloc_page(gfp_flags);
                if (!pages[i]) {
                        dprintk("%s: failed to allocate page\n", __func__);
                        nfs4_free_pages(pages, i);
                        return NULL;
                }
        }

        return pages;
}

static struct nfs4_layoutget *
pnfs_alloc_init_layoutget_args(struct inode *ino,
           struct nfs_open_context *ctx,
           const nfs4_stateid *stateid,
           const struct pnfs_layout_range *range,
           gfp_t gfp_flags)
{
        struct nfs_server *server = pnfs_find_server(ino, ctx);
        size_t max_reply_sz = server->pnfs_curr_ld->max_layoutget_response;
        size_t max_pages = max_response_pages(server);
        struct nfs4_layoutget *lgp;

        dprintk("--> %s\n", __func__);

        lgp = kzalloc(sizeof(*lgp), gfp_flags);
        if (lgp == NULL)
                return NULL;

        if (max_reply_sz) {
                size_t npages = (max_reply_sz + PAGE_SIZE - 1) >> PAGE_SHIFT;
                if (npages < max_pages)
                        max_pages = npages;
        }

        lgp->args.layout.pages = nfs4_alloc_pages(max_pages, gfp_flags);
        if (!lgp->args.layout.pages) {
                kfree(lgp);
                return NULL;
        }
        lgp->args.layout.pglen = max_pages * PAGE_SIZE;
        lgp->res.layoutp = &lgp->args.layout;

        /* Don't confuse uninitialised result and success */
        lgp->res.status = -NFS4ERR_DELAY;

        lgp->args.minlength = PAGE_SIZE;
        if (lgp->args.minlength > range->length)
                lgp->args.minlength = range->length;
        if (ino) {
                loff_t i_size = i_size_read(ino);

                if (range->iomode == IOMODE_READ) {
                        if (range->offset >= i_size)
                                lgp->args.minlength = 0;
                        else if (i_size - range->offset < lgp->args.minlength)
                                lgp->args.minlength = i_size - range->offset;
                }
        }
        lgp->args.maxcount = PNFS_LAYOUT_MAXSIZE;
        pnfs_copy_range(&lgp->args.range, range);
        lgp->args.type = server->pnfs_curr_ld->id;
        lgp->args.inode = ino;
        lgp->args.ctx = get_nfs_open_context(ctx);
        nfs4_stateid_copy(&lgp->args.stateid, stateid);
        lgp->gfp_flags = gfp_flags;
        lgp->cred = ctx->cred;
        return lgp;
}

void pnfs_layoutget_free(struct nfs4_layoutget *lgp)
{
        size_t max_pages = lgp->args.layout.pglen / PAGE_SIZE;

        nfs4_free_pages(lgp->args.layout.pages, max_pages);
        if (lgp->args.inode)
                pnfs_put_layout_hdr(NFS_I(lgp->args.inode)->layout);
        put_nfs_open_context(lgp->args.ctx);
        kfree(lgp);
}

static void pnfs_clear_layoutcommit(struct inode *inode,
                struct list_head *head)
{
        struct nfs_inode *nfsi = NFS_I(inode);
        struct pnfs_layout_segment *lseg, *tmp;

        if (!test_and_clear_bit(NFS_INO_LAYOUTCOMMIT, &nfsi->flags))
                return;
        list_for_each_entry_safe(lseg, tmp, &nfsi->layout->plh_segs, pls_list) {
                if (!test_and_clear_bit(NFS_LSEG_LAYOUTCOMMIT, &lseg->pls_flags))
                        continue;
                pnfs_lseg_dec_and_remove_zero(lseg, head);
        }
}

void pnfs_layoutreturn_free_lsegs(struct pnfs_layout_hdr *lo,
                const nfs4_stateid *arg_stateid,
                const struct pnfs_layout_range *range,
                const nfs4_stateid *stateid)
{
        struct inode *inode = lo->plh_inode;
        LIST_HEAD(freeme);

        spin_lock(&inode->i_lock);
        if (!pnfs_layout_is_valid(lo) ||
            !nfs4_stateid_match_other(&lo->plh_stateid, arg_stateid))
                goto out_unlock;
        if (stateid) {
                u32 seq = be32_to_cpu(arg_stateid->seqid);

                pnfs_mark_matching_lsegs_invalid(lo, &freeme, range, seq);
                pnfs_free_returned_lsegs(lo, &freeme, range, seq);
                pnfs_set_layout_stateid(lo, stateid, NULL, true);
        } else
                pnfs_mark_layout_stateid_invalid(lo, &freeme);
out_unlock:
        pnfs_clear_layoutreturn_waitbit(lo);
        spin_unlock(&inode->i_lock);
        pnfs_free_lseg_list(&freeme);

}

static bool
pnfs_prepare_layoutreturn(struct pnfs_layout_hdr *lo,
                nfs4_stateid *stateid,
                const struct cred **cred,
                enum pnfs_iomode *iomode)
{
        /* Serialise LAYOUTGET/LAYOUTRETURN */
        if (atomic_read(&lo->plh_outstanding) != 0)
                return false;
        if (test_and_set_bit(NFS_LAYOUT_RETURN_LOCK, &lo->plh_flags))
                return false;
        set_bit(NFS_LAYOUT_RETURN, &lo->plh_flags);
        pnfs_get_layout_hdr(lo);
        nfs4_stateid_copy(stateid, &lo->plh_stateid);
        *cred = get_cred(lo->plh_lc_cred);
        if (test_bit(NFS_LAYOUT_RETURN_REQUESTED, &lo->plh_flags)) {
                if (lo->plh_return_seq != 0)
                        stateid->seqid = cpu_to_be32(lo->plh_return_seq);
                if (iomode != NULL)
                        *iomode = lo->plh_return_iomode;
                pnfs_clear_layoutreturn_info(lo);
        } else if (iomode != NULL)
                *iomode = IOMODE_ANY;
        pnfs_barrier_update(lo, be32_to_cpu(stateid->seqid));
        return true;
}

static void
pnfs_init_layoutreturn_args(struct nfs4_layoutreturn_args *args,
                struct pnfs_layout_hdr *lo,
                const nfs4_stateid *stateid,
                enum pnfs_iomode iomode)
{
        struct inode *inode = lo->plh_inode;

        args->layout_type = NFS_SERVER(inode)->pnfs_curr_ld->id;
        args->inode = inode;
        args->range.iomode = iomode;
        args->range.offset = 0;
        args->range.length = NFS4_MAX_UINT64;
        args->layout = lo;
        nfs4_stateid_copy(&args->stateid, stateid);
}

static int
pnfs_send_layoutreturn(struct pnfs_layout_hdr *lo,
                       const nfs4_stateid *stateid,
                       const struct cred **pcred,
                       enum pnfs_iomode iomode,
                       bool sync)
{
        struct inode *ino = lo->plh_inode;
        struct pnfs_layoutdriver_type *ld = NFS_SERVER(ino)->pnfs_curr_ld;
        struct nfs4_layoutreturn *lrp;
        const struct cred *cred = *pcred;
        int status = 0;

        *pcred = NULL;
        lrp = kzalloc(sizeof(*lrp), GFP_NOFS);
        if (unlikely(lrp == NULL)) {
                status = -ENOMEM;
                spin_lock(&ino->i_lock);
                pnfs_clear_layoutreturn_waitbit(lo);
                spin_unlock(&ino->i_lock);
                put_cred(cred);
                pnfs_put_layout_hdr(lo);
                goto out;
        }

        pnfs_init_layoutreturn_args(&lrp->args, lo, stateid, iomode);
        lrp->args.ld_private = &lrp->ld_private;
        lrp->clp = NFS_SERVER(ino)->nfs_client;
        lrp->cred = cred;
        if (ld->prepare_layoutreturn)
                ld->prepare_layoutreturn(&lrp->args);

        status = nfs4_proc_layoutreturn(lrp, sync);
out:
        dprintk("<-- %s status: %d\n", __func__, status);
        return status;
}

static bool
pnfs_layout_segments_returnable(struct pnfs_layout_hdr *lo,
                                enum pnfs_iomode iomode,
                                u32 seq)
{
        struct pnfs_layout_range recall_range = {
                .length = NFS4_MAX_UINT64,
                .iomode = iomode,
        };
        return pnfs_mark_matching_lsegs_return(lo, &lo->plh_return_segs,
                                               &recall_range, seq) != -EBUSY;
}

/* Return true if layoutreturn is needed */
static bool
pnfs_layout_need_return(struct pnfs_layout_hdr *lo)
{
        if (!test_bit(NFS_LAYOUT_RETURN_REQUESTED, &lo->plh_flags))
                return false;
        return pnfs_layout_segments_returnable(lo, lo->plh_return_iomode,
                                               lo->plh_return_seq);
}

static void pnfs_layoutreturn_before_put_layout_hdr(struct pnfs_layout_hdr *lo)
{
        struct inode *inode= lo->plh_inode;

        if (!test_bit(NFS_LAYOUT_RETURN_REQUESTED, &lo->plh_flags))
                return;
        spin_lock(&inode->i_lock);
        if (pnfs_layout_need_return(lo)) {
                const struct cred *cred;
                nfs4_stateid stateid;
                enum pnfs_iomode iomode;
                bool send;

                send = pnfs_prepare_layoutreturn(lo, &stateid, &cred, &iomode);
                spin_unlock(&inode->i_lock);
                if (send) {
                        /* Send an async layoutreturn so we dont deadlock */
                        pnfs_send_layoutreturn(lo, &stateid, &cred, iomode, false);
                }
        } else
                spin_unlock(&inode->i_lock);
}

/*
 * Initiates a LAYOUTRETURN(FILE), and removes the pnfs_layout_hdr
 * when the layout segment list is empty.
 *
 * Note that a pnfs_layout_hdr can exist with an empty layout segment
 * list when LAYOUTGET has failed, or when LAYOUTGET succeeded, but the
 * deviceid is marked invalid.
 */
int
_pnfs_return_layout(struct inode *ino)
{
        struct pnfs_layout_hdr *lo = NULL;
        struct nfs_inode *nfsi = NFS_I(ino);
        LIST_HEAD(tmp_list);
        const struct cred *cred;
        nfs4_stateid stateid;
        int status = 0;
        bool send, valid_layout;

        dprintk("NFS: %s for inode %lu\n", __func__, ino->i_ino);

        spin_lock(&ino->i_lock);
        lo = nfsi->layout;
        if (!lo) {
                spin_unlock(&ino->i_lock);
                dprintk("NFS: %s no layout to return\n", __func__);
                goto out;
        }
        /* Reference matched in nfs4_layoutreturn_release */
        pnfs_get_layout_hdr(lo);
        /* Is there an outstanding layoutreturn ? */
        if (test_bit(NFS_LAYOUT_RETURN_LOCK, &lo->plh_flags)) {
                spin_unlock(&ino->i_lock);
                if (wait_on_bit(&lo->plh_flags, NFS_LAYOUT_RETURN,
                                        TASK_UNINTERRUPTIBLE))
                        goto out_put_layout_hdr;
                spin_lock(&ino->i_lock);
        }
        valid_layout = pnfs_layout_is_valid(lo);
        pnfs_clear_layoutcommit(ino, &tmp_list);
        pnfs_mark_matching_lsegs_invalid(lo, &tmp_list, NULL, 0);

        if (NFS_SERVER(ino)->pnfs_curr_ld->return_range) {
                struct pnfs_layout_range range = {
                        .iomode         = IOMODE_ANY,
                        .offset         = 0,
                        .length         = NFS4_MAX_UINT64,
                };
                NFS_SERVER(ino)->pnfs_curr_ld->return_range(lo, &range);
        }

        /* Don't send a LAYOUTRETURN if list was initially empty */
        if (!test_bit(NFS_LAYOUT_RETURN_REQUESTED, &lo->plh_flags) ||
                        !valid_layout) {
                spin_unlock(&ino->i_lock);
                dprintk("NFS: %s no layout segments to return\n", __func__);
                goto out_wait_layoutreturn;
        }

        send = pnfs_prepare_layoutreturn(lo, &stateid, &cred, NULL);
        spin_unlock(&ino->i_lock);
        if (send)
                status = pnfs_send_layoutreturn(lo, &stateid, &cred, IOMODE_ANY, true);
out_wait_layoutreturn:
        wait_on_bit(&lo->plh_flags, NFS_LAYOUT_RETURN, TASK_UNINTERRUPTIBLE);
out_put_layout_hdr:
        pnfs_free_lseg_list(&tmp_list);
        pnfs_put_layout_hdr(lo);
out:
        dprintk("<-- %s status: %d\n", __func__, status);
        return status;
}

int
pnfs_commit_and_return_layout(struct inode *inode)
{
        struct pnfs_layout_hdr *lo;
        int ret;

        spin_lock(&inode->i_lock);
        lo = NFS_I(inode)->layout;
        if (lo == NULL) {
                spin_unlock(&inode->i_lock);
                return 0;
        }
        pnfs_get_layout_hdr(lo);
        /* Block new layoutgets and read/write to ds */
        lo->plh_block_lgets++;
        spin_unlock(&inode->i_lock);
        filemap_fdatawait(inode->i_mapping);
        ret = pnfs_layoutcommit_inode(inode, true);
        if (ret == 0)
                ret = _pnfs_return_layout(inode);
        spin_lock(&inode->i_lock);
        lo->plh_block_lgets--;
        spin_unlock(&inode->i_lock);
        pnfs_put_layout_hdr(lo);
        return ret;
}

bool pnfs_roc(struct inode *ino,
                struct nfs4_layoutreturn_args *args,
                struct nfs4_layoutreturn_res *res,
                const struct cred *cred)
{
        struct nfs_inode *nfsi = NFS_I(ino);
        struct nfs_open_context *ctx;
        struct nfs4_state *state;
        struct pnfs_layout_hdr *lo;
        struct pnfs_layout_segment *lseg, *next;
        const struct cred *lc_cred;
        nfs4_stateid stateid;
        enum pnfs_iomode iomode = 0;
        bool layoutreturn = false, roc = false;
        bool skip_read = false;

        if (!nfs_have_layout(ino))
                return false;
retry:
        rcu_read_lock();
        spin_lock(&ino->i_lock);
        lo = nfsi->layout;
        if (!lo || !pnfs_layout_is_valid(lo) ||
            test_bit(NFS_LAYOUT_BULK_RECALL, &lo->plh_flags)) {
                lo = NULL;
                goto out_noroc;
        }
        pnfs_get_layout_hdr(lo);
        if (test_bit(NFS_LAYOUT_RETURN_LOCK, &lo->plh_flags)) {
                spin_unlock(&ino->i_lock);
                rcu_read_unlock();
                wait_on_bit(&lo->plh_flags, NFS_LAYOUT_RETURN,
                                TASK_UNINTERRUPTIBLE);
                pnfs_put_layout_hdr(lo);
                goto retry;
        }

        /* no roc if we hold a delegation */
        if (nfs4_check_delegation(ino, FMODE_READ)) {
                if (nfs4_check_delegation(ino, FMODE_WRITE))
                        goto out_noroc;
                skip_read = true;
        }

        list_for_each_entry_rcu(ctx, &nfsi->open_files, list) {
                state = ctx->state;
                if (state == NULL)
                        continue;
                /* Don't return layout if there is open file state */
                if (state->state & FMODE_WRITE)
                        goto out_noroc;
                if (state->state & FMODE_READ)
                        skip_read = true;
        }


        list_for_each_entry_safe(lseg, next, &lo->plh_segs, pls_list) {
                if (skip_read && lseg->pls_range.iomode == IOMODE_READ)
                        continue;
                /* If we are sending layoutreturn, invalidate all valid lsegs */
                if (!test_and_clear_bit(NFS_LSEG_ROC, &lseg->pls_flags))
                        continue;
                /*
                 * Note: mark lseg for return so pnfs_layout_remove_lseg
                 * doesn't invalidate the layout for us.
                 */
                set_bit(NFS_LSEG_LAYOUTRETURN, &lseg->pls_flags);
                if (!mark_lseg_invalid(lseg, &lo->plh_return_segs))
                        continue;
                pnfs_set_plh_return_info(lo, lseg->pls_range.iomode, 0);
        }

        if (!test_bit(NFS_LAYOUT_RETURN_REQUESTED, &lo->plh_flags))
                goto out_noroc;

        /* ROC in two conditions:
         * 1. there are ROC lsegs
         * 2. we don't send layoutreturn
         */
        /* lo ref dropped in pnfs_roc_release() */
        layoutreturn = pnfs_prepare_layoutreturn(lo, &stateid, &lc_cred, &iomode);
        /* If the creds don't match, we can't compound the layoutreturn */
        if (!layoutreturn || cred_fscmp(cred, lc_cred) != 0)
                goto out_noroc;

        roc = layoutreturn;
        pnfs_init_layoutreturn_args(args, lo, &stateid, iomode);
        res->lrs_present = 0;
        layoutreturn = false;
        put_cred(lc_cred);

out_noroc:
        spin_unlock(&ino->i_lock);
        rcu_read_unlock();
        pnfs_layoutcommit_inode(ino, true);
        if (roc) {
                struct pnfs_layoutdriver_type *ld = NFS_SERVER(ino)->pnfs_curr_ld;
                if (ld->prepare_layoutreturn)
                        ld->prepare_layoutreturn(args);
                pnfs_put_layout_hdr(lo);
                return true;
        }
        if (layoutreturn)
                pnfs_send_layoutreturn(lo, &stateid, &lc_cred, iomode, true);
        pnfs_put_layout_hdr(lo);
        return false;
}

int pnfs_roc_done(struct rpc_task *task, struct nfs4_layoutreturn_args **argpp,
                  struct nfs4_layoutreturn_res **respp, int *ret)
{
        struct nfs4_layoutreturn_args *arg = *argpp;
        int retval = -EAGAIN;

        if (!arg)
                return 0;
        /* Handle Layoutreturn errors */
        switch (*ret) {
        case 0:
                retval = 0;
                break;
        case -NFS4ERR_NOMATCHING_LAYOUT:
                /* Was there an RPC level error? If not, retry */
                if (task->tk_rpc_status == 0)
                        break;
                /* If the call was not sent, let caller handle it */
                if (!RPC_WAS_SENT(task))
                        return 0;
                /*
                 * Otherwise, assume the call succeeded and
                 * that we need to release the layout
                 */
                *ret = 0;
                (*respp)->lrs_present = 0;
                retval = 0;
                break;
        case -NFS4ERR_DELAY:
                /* Let the caller handle the retry */
                *ret = -NFS4ERR_NOMATCHING_LAYOUT;
                return 0;
        case -NFS4ERR_OLD_STATEID:
                if (!nfs4_layout_refresh_old_stateid(&arg->stateid,
                                                     &arg->range, arg->inode))
                        break;
                *ret = -NFS4ERR_NOMATCHING_LAYOUT;
                return -EAGAIN;
        }
        *argpp = NULL;
        *respp = NULL;
        return retval;
}

void pnfs_roc_release(struct nfs4_layoutreturn_args *args,
                struct nfs4_layoutreturn_res *res,
                int ret)
{
        struct pnfs_layout_hdr *lo = args->layout;
        struct inode *inode = args->inode;
        const nfs4_stateid *res_stateid = NULL;
        struct nfs4_xdr_opaque_data *ld_private = args->ld_private;

        switch (ret) {
        case -NFS4ERR_NOMATCHING_LAYOUT:
                spin_lock(&inode->i_lock);
                if (pnfs_layout_is_valid(lo) &&
                    nfs4_stateid_match_other(&args->stateid, &lo->plh_stateid))
                        pnfs_set_plh_return_info(lo, args->range.iomode, 0);
                pnfs_clear_layoutreturn_waitbit(lo);
                spin_unlock(&inode->i_lock);
                break;
        case 0:
                if (res->lrs_present)
                        res_stateid = &res->stateid;
                fallthrough;
        default:
                pnfs_layoutreturn_free_lsegs(lo, &args->stateid, &args->range,
                                             res_stateid);
        }
        trace_nfs4_layoutreturn_on_close(args->inode, &args->stateid, ret);
        if (ld_private && ld_private->ops && ld_private->ops->free)
                ld_private->ops->free(ld_private);
        pnfs_put_layout_hdr(lo);
}

bool pnfs_wait_on_layoutreturn(struct inode *ino, struct rpc_task *task)
{
        struct nfs_inode *nfsi = NFS_I(ino);
        struct pnfs_layout_hdr *lo;
        bool sleep = false;

        /* we might not have grabbed lo reference. so need to check under
         * i_lock */
        spin_lock(&ino->i_lock);
        lo = nfsi->layout;
        if (lo && test_bit(NFS_LAYOUT_RETURN, &lo->plh_flags)) {
                rpc_sleep_on(&NFS_SERVER(ino)->roc_rpcwaitq, task, NULL);
                sleep = true;
        }
        spin_unlock(&ino->i_lock);
        return sleep;
}

/*
 * Compare two layout segments for sorting into layout cache.
 * We want to preferentially return RW over RO layouts, so ensure those
 * are seen first.
 */
static s64
pnfs_lseg_range_cmp(const struct pnfs_layout_range *l1,
           const struct pnfs_layout_range *l2)
{
        s64 d;

        /* high offset > low offset */
        d = l1->offset - l2->offset;
        if (d)
                return d;

        /* short length > long length */
        d = l2->length - l1->length;
        if (d)
                return d;

        /* read > read/write */
        return (int)(l1->iomode == IOMODE_READ) - (int)(l2->iomode == IOMODE_READ);
}

static bool
pnfs_lseg_range_is_after(const struct pnfs_layout_range *l1,
                const struct pnfs_layout_range *l2)
{
        return pnfs_lseg_range_cmp(l1, l2) > 0;
}

static bool
pnfs_lseg_no_merge(struct pnfs_layout_segment *lseg,
                struct pnfs_layout_segment *old)
{
        return false;
}

void
pnfs_generic_layout_insert_lseg(struct pnfs_layout_hdr *lo,
                   struct pnfs_layout_segment *lseg,
                   bool (*is_after)(const struct pnfs_layout_range *,
                           const struct pnfs_layout_range *),
                   bool (*do_merge)(struct pnfs_layout_segment *,
                           struct pnfs_layout_segment *),
                   struct list_head *free_me)
{
        struct pnfs_layout_segment *lp, *tmp;

        dprintk("%s:Begin\n", __func__);

        list_for_each_entry_safe(lp, tmp, &lo->plh_segs, pls_list) {
                if (test_bit(NFS_LSEG_VALID, &lp->pls_flags) == 0)
                        continue;
                if (do_merge(lseg, lp)) {
                        mark_lseg_invalid(lp, free_me);
                        continue;
                }
                if (is_after(&lseg->pls_range, &lp->pls_range))
                        continue;
                list_add_tail(&lseg->pls_list, &lp->pls_list);
                dprintk("%s: inserted lseg %p "
                        "iomode %d offset %llu length %llu before "
                        "lp %p iomode %d offset %llu length %llu\n",
                        __func__, lseg, lseg->pls_range.iomode,
                        lseg->pls_range.offset, lseg->pls_range.length,
                        lp, lp->pls_range.iomode, lp->pls_range.offset,
                        lp->pls_range.length);
                goto out;
        }
        list_add_tail(&lseg->pls_list, &lo->plh_segs);
        dprintk("%s: inserted lseg %p "
                "iomode %d offset %llu length %llu at tail\n",
                __func__, lseg, lseg->pls_range.iomode,
                lseg->pls_range.offset, lseg->pls_range.length);
out:
        pnfs_get_layout_hdr(lo);

        dprintk("%s:Return\n", __func__);
}
EXPORT_SYMBOL_GPL(pnfs_generic_layout_insert_lseg);

static void
pnfs_layout_insert_lseg(struct pnfs_layout_hdr *lo,
                   struct pnfs_layout_segment *lseg,
                   struct list_head *free_me)
{
        struct inode *inode = lo->plh_inode;
        struct pnfs_layoutdriver_type *ld = NFS_SERVER(inode)->pnfs_curr_ld;

        if (ld->add_lseg != NULL)
                ld->add_lseg(lo, lseg, free_me);
        else
                pnfs_generic_layout_insert_lseg(lo, lseg,
                                pnfs_lseg_range_is_after,
                                pnfs_lseg_no_merge,
                                free_me);
}

static struct pnfs_layout_hdr *
alloc_init_layout_hdr(struct inode *ino,
                      struct nfs_open_context *ctx,
                      gfp_t gfp_flags)
{
        struct pnfs_layout_hdr *lo;

        lo = pnfs_alloc_layout_hdr(ino, gfp_flags);
        if (!lo)
                return NULL;
        refcount_set(&lo->plh_refcount, 1);
        INIT_LIST_HEAD(&lo->plh_layouts);
        INIT_LIST_HEAD(&lo->plh_segs);
        INIT_LIST_HEAD(&lo->plh_return_segs);
        INIT_LIST_HEAD(&lo->plh_bulk_destroy);
        lo->plh_inode = ino;
        lo->plh_lc_cred = get_cred(ctx->cred);
        lo->plh_flags |= 1 << NFS_LAYOUT_INVALID_STID;
        return lo;
}

static struct pnfs_layout_hdr *
pnfs_find_alloc_layout(struct inode *ino,
                       struct nfs_open_context *ctx,
                       gfp_t gfp_flags)
        __releases(&ino->i_lock)
        __acquires(&ino->i_lock)
{
        struct nfs_inode *nfsi = NFS_I(ino);
        struct pnfs_layout_hdr *new = NULL;

        dprintk("%s Begin ino=%p layout=%p\n", __func__, ino, nfsi->layout);

        if (nfsi->layout != NULL)
                goto out_existing;
        spin_unlock(&ino->i_lock);
        new = alloc_init_layout_hdr(ino, ctx, gfp_flags);
        spin_lock(&ino->i_lock);

        if (likely(nfsi->layout == NULL)) {     /* Won the race? */
                nfsi->layout = new;
                return new;
        } else if (new != NULL)
                pnfs_free_layout_hdr(new);
out_existing:
        pnfs_get_layout_hdr(nfsi->layout);
        return nfsi->layout;
}

/*
 * iomode matching rules:
 * iomode       lseg    strict match
 *                      iomode
 * -----        -----   ------ -----
 * ANY          READ    N/A    true
 * ANY          RW      N/A    true
 * RW           READ    N/A    false
 * RW           RW      N/A    true
 * READ         READ    N/A    true
 * READ         RW      true   false
 * READ         RW      false  true
 */
static bool
pnfs_lseg_range_match(const struct pnfs_layout_range *ls_range,
                 const struct pnfs_layout_range *range,
                 bool strict_iomode)
{
        struct pnfs_layout_range range1;

        if ((range->iomode == IOMODE_RW &&
             ls_range->iomode != IOMODE_RW) ||
            (range->iomode != ls_range->iomode &&
             strict_iomode) ||
            !pnfs_lseg_range_intersecting(ls_range, range))
                return false;

        /* range1 covers only the first byte in the range */
        range1 = *range;
        range1.length = 1;
        return pnfs_lseg_range_contained(ls_range, &range1);
}

/*
 * lookup range in layout
 */
static struct pnfs_layout_segment *
pnfs_find_lseg(struct pnfs_layout_hdr *lo,
                struct pnfs_layout_range *range,
                bool strict_iomode)
{
        struct pnfs_layout_segment *lseg, *ret = NULL;

        dprintk("%s:Begin\n", __func__);

        list_for_each_entry(lseg, &lo->plh_segs, pls_list) {
                if (test_bit(NFS_LSEG_VALID, &lseg->pls_flags) &&
                    pnfs_lseg_range_match(&lseg->pls_range, range,
                                          strict_iomode)) {
                        ret = pnfs_get_lseg(lseg);
                        break;
                }
        }

        dprintk("%s:Return lseg %p ref %d\n",
                __func__, ret, ret ? refcount_read(&ret->pls_refcount) : 0);
        return ret;
}

/*
 * Use mdsthreshold hints set at each OPEN to determine if I/O should go
 * to the MDS or over pNFS
 *
 * The nfs_inode read_io and write_io fields are cumulative counters reset
 * when there are no layout segments. Note that in pnfs_update_layout iomode
 * is set to IOMODE_READ for a READ request, and set to IOMODE_RW for a
 * WRITE request.
 *
 * A return of true means use MDS I/O.
 *
 * From rfc 5661:
 * If a file's size is smaller than the file size threshold, data accesses
 * SHOULD be sent to the metadata server.  If an I/O request has a length that
 * is below the I/O size threshold, the I/O SHOULD be sent to the metadata
 * server.  If both file size and I/O size are provided, the client SHOULD
 * reach or exceed  both thresholds before sending its read or write
 * requests to the data server.
 */
static bool pnfs_within_mdsthreshold(struct nfs_open_context *ctx,
                                     struct inode *ino, int iomode)
{
        struct nfs4_threshold *t = ctx->mdsthreshold;
        struct nfs_inode *nfsi = NFS_I(ino);
        loff_t fsize = i_size_read(ino);
        bool size = false, size_set = false, io = false, io_set = false, ret = false;

        if (t == NULL)
                return ret;

        dprintk("%s bm=0x%x rd_sz=%llu wr_sz=%llu rd_io=%llu wr_io=%llu\n",
                __func__, t->bm, t->rd_sz, t->wr_sz, t->rd_io_sz, t->wr_io_sz);

        switch (iomode) {
        case IOMODE_READ:
                if (t->bm & THRESHOLD_RD) {
                        dprintk("%s fsize %llu\n", __func__, fsize);
                        size_set = true;
                        if (fsize < t->rd_sz)
                                size = true;
                }
                if (t->bm & THRESHOLD_RD_IO) {
                        dprintk("%s nfsi->read_io %llu\n", __func__,
                                nfsi->read_io);
                        io_set = true;
                        if (nfsi->read_io < t->rd_io_sz)
                                io = true;
                }
                break;
        case IOMODE_RW:
                if (t->bm & THRESHOLD_WR) {
                        dprintk("%s fsize %llu\n", __func__, fsize);
                        size_set = true;
                        if (fsize < t->wr_sz)
                                size = true;
                }
                if (t->bm & THRESHOLD_WR_IO) {
                        dprintk("%s nfsi->write_io %llu\n", __func__,
                                nfsi->write_io);
                        io_set = true;
                        if (nfsi->write_io < t->wr_io_sz)
                                io = true;
                }
                break;
        }
        if (size_set && io_set) {
                if (size && io)
                        ret = true;
        } else if (size || io)
                ret = true;

        dprintk("<-- %s size %d io %d ret %d\n", __func__, size, io, ret);
        return ret;
}

static int pnfs_prepare_to_retry_layoutget(struct pnfs_layout_hdr *lo)
{
        /*
         * send layoutcommit as it can hold up layoutreturn due to lseg
         * reference
         */
        pnfs_layoutcommit_inode(lo->plh_inode, false);
        return wait_on_bit_action(&lo->plh_flags, NFS_LAYOUT_RETURN,
                                   nfs_wait_bit_killable,
                                   TASK_KILLABLE);
}

static void nfs_layoutget_begin(struct pnfs_layout_hdr *lo)
{
        atomic_inc(&lo->plh_outstanding);
}

static void nfs_layoutget_end(struct pnfs_layout_hdr *lo)
{
        if (atomic_dec_and_test(&lo->plh_outstanding))
                wake_up_var(&lo->plh_outstanding);
}

static bool pnfs_is_first_layoutget(struct pnfs_layout_hdr *lo)
{
        return test_bit(NFS_LAYOUT_FIRST_LAYOUTGET, &lo->plh_flags);
}

static void pnfs_clear_first_layoutget(struct pnfs_layout_hdr *lo)
{
        unsigned long *bitlock = &lo->plh_flags;

        clear_bit_unlock(NFS_LAYOUT_FIRST_LAYOUTGET, bitlock);
        smp_mb__after_atomic();
        wake_up_bit(bitlock, NFS_LAYOUT_FIRST_LAYOUTGET);
}

static void _add_to_server_list(struct pnfs_layout_hdr *lo,
                                struct nfs_server *server)
{
        if (!test_and_set_bit(NFS_LAYOUT_HASHED, &lo->plh_flags)) {
                struct nfs_client *clp = server->nfs_client;

                /* The lo must be on the clp list if there is any
                 * chance of a CB_LAYOUTRECALL(FILE) coming in.
                 */
                spin_lock(&clp->cl_lock);
                list_add_tail_rcu(&lo->plh_layouts, &server->layouts);
                spin_unlock(&clp->cl_lock);
        }
}

/*
 * Layout segment is retreived from the server if not cached.
 * The appropriate layout segment is referenced and returned to the caller.
 */
struct pnfs_layout_segment *
pnfs_update_layout(struct inode *ino,
                   struct nfs_open_context *ctx,
                   loff_t pos,
                   u64 count,
                   enum pnfs_iomode iomode,
                   bool strict_iomode,
                   gfp_t gfp_flags)
{
        struct pnfs_layout_range arg = {
                .iomode = iomode,
                .offset = pos,
                .length = count,
        };
        unsigned pg_offset;
        struct nfs_server *server = NFS_SERVER(ino);
        struct nfs_client *clp = server->nfs_client;
        struct pnfs_layout_hdr *lo = NULL;
        struct pnfs_layout_segment *lseg = NULL;
        struct nfs4_layoutget *lgp;
        nfs4_stateid stateid;
        long timeout = 0;
        unsigned long giveup = jiffies + (clp->cl_lease_time << 1);
        bool first;

        if (!pnfs_enabled_sb(NFS_SERVER(ino))) {
                trace_pnfs_update_layout(ino, pos, count, iomode, lo, lseg,
                                 PNFS_UPDATE_LAYOUT_NO_PNFS);
                goto out;
        }

        if (pnfs_within_mdsthreshold(ctx, ino, iomode)) {
                trace_pnfs_update_layout(ino, pos, count, iomode, lo, lseg,
                                 PNFS_UPDATE_LAYOUT_MDSTHRESH);
                goto out;
        }

lookup_again:
        lseg = ERR_PTR(nfs4_client_recover_expired_lease(clp));
        if (IS_ERR(lseg))
                goto out;
        first = false;
        spin_lock(&ino->i_lock);
        lo = pnfs_find_alloc_layout(ino, ctx, gfp_flags);
        if (lo == NULL) {
                spin_unlock(&ino->i_lock);
                trace_pnfs_update_layout(ino, pos, count, iomode, lo, lseg,
                                 PNFS_UPDATE_LAYOUT_NOMEM);
                goto out;
        }

        /* Do we even need to bother with this? */
        if (test_bit(NFS_LAYOUT_BULK_RECALL, &lo->plh_flags)) {

                trace_pnfs_update_layout(ino, pos, count, iomode, lo, lseg,
                                 PNFS_UPDATE_LAYOUT_BULK_RECALL);
                dprintk("%s matches recall, use MDS\n", __func__);
                goto out_unlock;
        }

        /* if LAYOUTGET already failed once we don't try again */
        if (pnfs_layout_io_test_failed(lo, iomode)) {
                trace_pnfs_update_layout(ino, pos, count, iomode, lo, lseg,
                                 PNFS_UPDATE_LAYOUT_IO_TEST_FAIL);
                goto out_unlock;
        }

        /*
         * If the layout segment list is empty, but there are outstanding
         * layoutget calls, then they might be subject to a layoutrecall.
         */
        if (list_empty(&lo->plh_segs) &&
            atomic_read(&lo->plh_outstanding) != 0) {
                spin_unlock(&ino->i_lock);
                lseg = ERR_PTR(wait_var_event_killable(&lo->plh_outstanding,
                                        !atomic_read(&lo->plh_outstanding)));
                if (IS_ERR(lseg))
                        goto out_put_layout_hdr;
                pnfs_put_layout_hdr(lo);
                goto lookup_again;
        }

        /*
         * Because we free lsegs when sending LAYOUTRETURN, we need to wait
         * for LAYOUTRETURN.
         */
        if (test_bit(NFS_LAYOUT_RETURN, &lo->plh_flags)) {
                spin_unlock(&ino->i_lock);
                dprintk("%s wait for layoutreturn\n", __func__);
                lseg = ERR_PTR(pnfs_prepare_to_retry_layoutget(lo));
                if (!IS_ERR(lseg)) {
                        pnfs_put_layout_hdr(lo);
                        dprintk("%s retrying\n", __func__);
                        trace_pnfs_update_layout(ino, pos, count, iomode, lo,
                                                 lseg,
                                                 PNFS_UPDATE_LAYOUT_RETRY);
                        goto lookup_again;
                }
                trace_pnfs_update_layout(ino, pos, count, iomode, lo, lseg,
                                         PNFS_UPDATE_LAYOUT_RETURN);
                goto out_put_layout_hdr;
        }

        lseg = pnfs_find_lseg(lo, &arg, strict_iomode);
        if (lseg) {
                trace_pnfs_update_layout(ino, pos, count, iomode, lo, lseg,
                                PNFS_UPDATE_LAYOUT_FOUND_CACHED);
                goto out_unlock;
        }

        /*
         * Choose a stateid for the LAYOUTGET. If we don't have a layout
         * stateid, or it has been invalidated, then we must use the open
         * stateid.
         */
        if (test_bit(NFS_LAYOUT_INVALID_STID, &lo->plh_flags)) {
                int status;

                /*
                 * The first layoutget for the file. Need to serialize per
                 * RFC 5661 Errata 3208.
                 */
                if (test_and_set_bit(NFS_LAYOUT_FIRST_LAYOUTGET,
                                     &lo->plh_flags)) {
                        spin_unlock(&ino->i_lock);
                        lseg = ERR_PTR(wait_on_bit(&lo->plh_flags,
                                                NFS_LAYOUT_FIRST_LAYOUTGET,
                                                TASK_KILLABLE));
                        if (IS_ERR(lseg))
                                goto out_put_layout_hdr;
                        pnfs_put_layout_hdr(lo);
                        dprintk("%s retrying\n", __func__);
                        goto lookup_again;
                }

                spin_unlock(&ino->i_lock);
                first = true;
                status = nfs4_select_rw_stateid(ctx->state,
                                        iomode == IOMODE_RW ? FMODE_WRITE : FMODE_READ,
                                        NULL, &stateid, NULL);
                if (status != 0) {
                        lseg = ERR_PTR(status);
                        trace_pnfs_update_layout(ino, pos, count,
                                        iomode, lo, lseg,
                                        PNFS_UPDATE_LAYOUT_INVALID_OPEN);
                        nfs4_schedule_stateid_recovery(server, ctx->state);
                        pnfs_clear_first_layoutget(lo);
                        pnfs_put_layout_hdr(lo);
                        goto lookup_again;
                }
                spin_lock(&ino->i_lock);
        } else {
                nfs4_stateid_copy(&stateid, &lo->plh_stateid);
        }

        if (pnfs_layoutgets_blocked(lo)) {
                trace_pnfs_update_layout(ino, pos, count, iomode, lo, lseg,
                                PNFS_UPDATE_LAYOUT_BLOCKED);
                goto out_unlock;
        }
        nfs_layoutget_begin(lo);
        spin_unlock(&ino->i_lock);

        _add_to_server_list(lo, server);

        pg_offset = arg.offset & ~PAGE_MASK;
        if (pg_offset) {
                arg.offset -= pg_offset;
                arg.length += pg_offset;
        }
        if (arg.length != NFS4_MAX_UINT64)
                arg.length = PAGE_ALIGN(arg.length);

        lgp = pnfs_alloc_init_layoutget_args(ino, ctx, &stateid, &arg, gfp_flags);
        if (!lgp) {
                trace_pnfs_update_layout(ino, pos, count, iomode, lo, NULL,
                                         PNFS_UPDATE_LAYOUT_NOMEM);
                nfs_layoutget_end(lo);
                goto out_put_layout_hdr;
        }

        lseg = nfs4_proc_layoutget(lgp, &timeout);
        trace_pnfs_update_layout(ino, pos, count, iomode, lo, lseg,
                                 PNFS_UPDATE_LAYOUT_SEND_LAYOUTGET);
        nfs_layoutget_end(lo);
        if (IS_ERR(lseg)) {
                switch(PTR_ERR(lseg)) {
                case -EBUSY:
                        if (time_after(jiffies, giveup))
                                lseg = NULL;
                        break;
                case -ERECALLCONFLICT:
                case -EAGAIN:
                        break;
                default:
                        if (!nfs_error_is_fatal(PTR_ERR(lseg))) {
                                pnfs_layout_clear_fail_bit(lo, pnfs_iomode_to_fail_bit(iomode));
                                lseg = NULL;
                        }
                        goto out_put_layout_hdr;
                }
                if (lseg) {
                        if (first)
                                pnfs_clear_first_layoutget(lo);
                        trace_pnfs_update_layout(ino, pos, count,
                                iomode, lo, lseg, PNFS_UPDATE_LAYOUT_RETRY);
                        pnfs_put_layout_hdr(lo);
                        goto lookup_again;
                }
        } else {
                pnfs_layout_clear_fail_bit(lo, pnfs_iomode_to_fail_bit(iomode));
        }

out_put_layout_hdr:
        if (first)
                pnfs_clear_first_layoutget(lo);
        trace_pnfs_update_layout(ino, pos, count, iomode, lo, lseg,
                                 PNFS_UPDATE_LAYOUT_EXIT);
        pnfs_put_layout_hdr(lo);
out:
        dprintk("%s: inode %s/%llu pNFS layout segment %s for "
                        "(%s, offset: %llu, length: %llu)\n",
                        __func__, ino->i_sb->s_id,
                        (unsigned long long)NFS_FILEID(ino),
                        IS_ERR_OR_NULL(lseg) ? "not found" : "found",
                        iomode==IOMODE_RW ?  "read/write" : "read-only",
                        (unsigned long long)pos,
                        (unsigned long long)count);
        return lseg;
out_unlock:
        spin_unlock(&ino->i_lock);
        goto out_put_layout_hdr;
}
EXPORT_SYMBOL_GPL(pnfs_update_layout);

static bool
pnfs_sanity_check_layout_range(struct pnfs_layout_range *range)
{
        switch (range->iomode) {
        case IOMODE_READ:
        case IOMODE_RW:
                break;
        default:
                return false;
        }
        if (range->offset == NFS4_MAX_UINT64)
                return false;
        if (range->length == 0)
                return false;
        if (range->length != NFS4_MAX_UINT64 &&
            range->length > NFS4_MAX_UINT64 - range->offset)
                return false;
        return true;
}

static struct pnfs_layout_hdr *
_pnfs_grab_empty_layout(struct inode *ino, struct nfs_open_context *ctx)
{
        struct pnfs_layout_hdr *lo;

        spin_lock(&ino->i_lock);
        lo = pnfs_find_alloc_layout(ino, ctx, GFP_KERNEL);
        if (!lo)
                goto out_unlock;
        if (!test_bit(NFS_LAYOUT_INVALID_STID, &lo->plh_flags))
                goto out_unlock;
        if (test_bit(NFS_LAYOUT_RETURN, &lo->plh_flags))
                goto out_unlock;
        if (pnfs_layoutgets_blocked(lo))
                goto out_unlock;
        if (test_and_set_bit(NFS_LAYOUT_FIRST_LAYOUTGET, &lo->plh_flags))
                goto out_unlock;
        nfs_layoutget_begin(lo);
        spin_unlock(&ino->i_lock);
        _add_to_server_list(lo, NFS_SERVER(ino));
        return lo;

out_unlock:
        spin_unlock(&ino->i_lock);
        pnfs_put_layout_hdr(lo);
        return NULL;
}

static void _lgopen_prepare_attached(struct nfs4_opendata *data,
                                     struct nfs_open_context *ctx)
{
        struct inode *ino = data->dentry->d_inode;
        struct pnfs_layout_range rng = {
                .iomode = (data->o_arg.fmode & FMODE_WRITE) ?
                          IOMODE_RW: IOMODE_READ,
                .offset = 0,
                .length = NFS4_MAX_UINT64,
        };
        struct nfs4_layoutget *lgp;
        struct pnfs_layout_hdr *lo;

        /* Heuristic: don't send layoutget if we have cached data */
        if (rng.iomode == IOMODE_READ &&
           (i_size_read(ino) == 0 || ino->i_mapping->nrpages != 0))
                return;

        lo = _pnfs_grab_empty_layout(ino, ctx);
        if (!lo)
                return;
        lgp = pnfs_alloc_init_layoutget_args(ino, ctx, &current_stateid,
                                             &rng, GFP_KERNEL);
        if (!lgp) {
                pnfs_clear_first_layoutget(lo);
                nfs_layoutget_end(lo);
                pnfs_put_layout_hdr(lo);
                return;
        }
        data->lgp = lgp;
        data->o_arg.lg_args = &lgp->args;
        data->o_res.lg_res = &lgp->res;
}

static void _lgopen_prepare_floating(struct nfs4_opendata *data,
                                     struct nfs_open_context *ctx)
{
        struct pnfs_layout_range rng = {
                .iomode = (data->o_arg.fmode & FMODE_WRITE) ?
                          IOMODE_RW: IOMODE_READ,
                .offset = 0,
                .length = NFS4_MAX_UINT64,
        };
        struct nfs4_layoutget *lgp;

        lgp = pnfs_alloc_init_layoutget_args(NULL, ctx, &current_stateid,
                                             &rng, GFP_KERNEL);
        if (!lgp)
                return;
        data->lgp = lgp;
        data->o_arg.lg_args = &lgp->args;
        data->o_res.lg_res = &lgp->res;
}

void pnfs_lgopen_prepare(struct nfs4_opendata *data,
                         struct nfs_open_context *ctx)
{
        struct nfs_server *server = NFS_SERVER(data->dir->d_inode);

        if (!(pnfs_enabled_sb(server) &&
              server->pnfs_curr_ld->flags & PNFS_LAYOUTGET_ON_OPEN))
                return;
        /* Could check on max_ops, but currently hardcoded high enough */
        if (!nfs_server_capable(data->dir->d_inode, NFS_CAP_LGOPEN))
                return;
        if (data->state)
                _lgopen_prepare_attached(data, ctx);
        else
                _lgopen_prepare_floating(data, ctx);
}

void pnfs_parse_lgopen(struct inode *ino, struct nfs4_layoutget *lgp,
                       struct nfs_open_context *ctx)
{
        struct pnfs_layout_hdr *lo;
        struct pnfs_layout_segment *lseg;
        struct nfs_server *srv = NFS_SERVER(ino);
        u32 iomode;

        if (!lgp)
                return;
        dprintk("%s: entered with status %i\n", __func__, lgp->res.status);
        if (lgp->res.status) {
                switch (lgp->res.status) {
                default:
                        break;
                /*
                 * Halt lgopen attempts if the server doesn't recognise
                 * the "current stateid" value, the layout type, or the
                 * layoutget operation as being valid.
                 * Also if it complains about too many ops in the compound
                 * or of the request/reply being too big.
                 */
                case -NFS4ERR_BAD_STATEID:
                case -NFS4ERR_NOTSUPP:
                case -NFS4ERR_REP_TOO_BIG:
                case -NFS4ERR_REP_TOO_BIG_TO_CACHE:
                case -NFS4ERR_REQ_TOO_BIG:
                case -NFS4ERR_TOO_MANY_OPS:
                case -NFS4ERR_UNKNOWN_LAYOUTTYPE:
                        srv->caps &= ~NFS_CAP_LGOPEN;
                }
                return;
        }
        if (!lgp->args.inode) {
                lo = _pnfs_grab_empty_layout(ino, ctx);
                if (!lo)
                        return;
                lgp->args.inode = ino;
        } else
                lo = NFS_I(lgp->args.inode)->layout;

        lseg = pnfs_layout_process(lgp);
        if (!IS_ERR(lseg)) {
                iomode = lgp->args.range.iomode;
                pnfs_layout_clear_fail_bit(lo, pnfs_iomode_to_fail_bit(iomode));
                pnfs_put_lseg(lseg);
        }
}

void nfs4_lgopen_release(struct nfs4_layoutget *lgp)
{
        if (lgp != NULL) {
                struct inode *inode = lgp->args.inode;
                if (inode) {
                        struct pnfs_layout_hdr *lo = NFS_I(inode)->layout;
                        pnfs_clear_first_layoutget(lo);
                        nfs_layoutget_end(lo);
                }
                pnfs_layoutget_free(lgp);
        }
}

struct pnfs_layout_segment *
pnfs_layout_process(struct nfs4_layoutget *lgp)
{
        struct pnfs_layout_hdr *lo = NFS_I(lgp->args.inode)->layout;
        struct nfs4_layoutget_res *res = &lgp->res;
        struct pnfs_layout_segment *lseg;
        struct inode *ino = lo->plh_inode;
        LIST_HEAD(free_me);

        if (!pnfs_sanity_check_layout_range(&res->range))
                return ERR_PTR(-EINVAL);

        /* Inject layout blob into I/O device driver */
        lseg = NFS_SERVER(ino)->pnfs_curr_ld->alloc_lseg(lo, res, lgp->gfp_flags);
        if (IS_ERR_OR_NULL(lseg)) {
                if (!lseg)
                        lseg = ERR_PTR(-ENOMEM);

                dprintk("%s: Could not allocate layout: error %ld\n",
                       __func__, PTR_ERR(lseg));
                return lseg;
        }

        pnfs_init_lseg(lo, lseg, &res->range, &res->stateid);

        spin_lock(&ino->i_lock);
        if (pnfs_layoutgets_blocked(lo)) {
                dprintk("%s forget reply due to state\n", __func__);
                goto out_forget;
        }

        if (nfs4_stateid_match_other(&lo->plh_stateid, &res->stateid)) {
                /* existing state ID, make sure the sequence number matches. */
                if (pnfs_layout_stateid_blocked(lo, &res->stateid)) {
                        if (!pnfs_layout_is_valid(lo) &&
                            pnfs_is_first_layoutget(lo))
                                lo->plh_barrier = 0;
                        dprintk("%s forget reply due to sequence\n", __func__);
                        goto out_forget;
                }
                pnfs_set_layout_stateid(lo, &res->stateid, lgp->cred, false);
        } else if (pnfs_layout_is_valid(lo)) {
                /*
                 * We got an entirely new state ID.  Mark all segments for the
                 * inode invalid, and retry the layoutget
                 */
                struct pnfs_layout_range range = {
                        .iomode = IOMODE_ANY,
                        .length = NFS4_MAX_UINT64,
                };
                pnfs_set_plh_return_info(lo, IOMODE_ANY, 0);
                pnfs_mark_matching_lsegs_return(lo, &lo->plh_return_segs,
                                                &range, 0);
                goto out_forget;
        } else {
                /* We have a completely new layout */
                if (!pnfs_is_first_layoutget(lo))
                        goto out_forget;
                pnfs_set_layout_stateid(lo, &res->stateid, lgp->cred, true);
        }

        pnfs_get_lseg(lseg);
        pnfs_layout_insert_lseg(lo, lseg, &free_me);


        if (res->return_on_close)
                set_bit(NFS_LSEG_ROC, &lseg->pls_flags);

        spin_unlock(&ino->i_lock);
        pnfs_free_lseg_list(&free_me);
        return lseg;

out_forget:
        spin_unlock(&ino->i_lock);
        lseg->pls_layout = lo;
        NFS_SERVER(ino)->pnfs_curr_ld->free_lseg(lseg);
        return ERR_PTR(-EAGAIN);
}

/**
 * pnfs_mark_matching_lsegs_return - Free or return matching layout segments
 * @lo: pointer to layout header
 * @tmp_list: list header to be used with pnfs_free_lseg_list()
 * @return_range: describe layout segment ranges to be returned
 * @seq: stateid seqid to match
 *
 * This function is mainly intended for use by layoutrecall. It attempts
 * to free the layout segment immediately, or else to mark it for return
 * as soon as its reference count drops to zero.
 *
 * Returns
 * - 0: a layoutreturn needs to be scheduled.
 * - EBUSY: there are layout segment that are still in use.
 * - ENOENT: there are no layout segments that need to be returned.
 */
int
pnfs_mark_matching_lsegs_return(struct pnfs_layout_hdr *lo,
                                struct list_head *tmp_list,
                                const struct pnfs_layout_range *return_range,
                                u32 seq)
{
        struct pnfs_layout_segment *lseg, *next;
        int remaining = 0;

        dprintk("%s:Begin lo %p\n", __func__, lo);

        assert_spin_locked(&lo->plh_inode->i_lock);

        list_for_each_entry_safe(lseg, next, &lo->plh_segs, pls_list)
                if (pnfs_match_lseg_recall(lseg, return_range, seq)) {
                        dprintk("%s: marking lseg %p iomode %d "
                                "offset %llu length %llu\n", __func__,
                                lseg, lseg->pls_range.iomode,
                                lseg->pls_range.offset,
                                lseg->pls_range.length);
                        if (mark_lseg_invalid(lseg, tmp_list))
                                continue;
                        remaining++;
                        set_bit(NFS_LSEG_LAYOUTRETURN, &lseg->pls_flags);
                }

        if (remaining) {
                pnfs_set_plh_return_info(lo, return_range->iomode, seq);
                return -EBUSY;
        }

        if (!list_empty(&lo->plh_return_segs)) {
                pnfs_set_plh_return_info(lo, return_range->iomode, seq);
                return 0;
        }

        return -ENOENT;
}

static void
pnfs_mark_layout_for_return(struct inode *inode,
                            const struct pnfs_layout_range *range)
{
        struct pnfs_layout_hdr *lo;
        bool return_now = false;

        spin_lock(&inode->i_lock);
        lo = NFS_I(inode)->layout;
        if (!pnfs_layout_is_valid(lo)) {
                spin_unlock(&inode->i_lock);
                return;
        }
        pnfs_set_plh_return_info(lo, range->iomode, 0);
        /*
         * mark all matching lsegs so that we are sure to have no live
         * segments at hand when sending layoutreturn. See pnfs_put_lseg()
         * for how it works.
         */
        if (pnfs_mark_matching_lsegs_return(lo, &lo->plh_return_segs, range, 0) != -EBUSY) {
                const struct cred *cred;
                nfs4_stateid stateid;
                enum pnfs_iomode iomode;

                return_now = pnfs_prepare_layoutreturn(lo, &stateid, &cred, &iomode);
                spin_unlock(&inode->i_lock);
                if (return_now)
                        pnfs_send_layoutreturn(lo, &stateid, &cred, iomode, false);
        } else {
                spin_unlock(&inode->i_lock);
                nfs_commit_inode(inode, 0);
        }
}

void pnfs_error_mark_layout_for_return(struct inode *inode,
                                       struct pnfs_layout_segment *lseg)
{
        struct pnfs_layout_range range = {
                .iomode = lseg->pls_range.iomode,
                .offset = 0,
                .length = NFS4_MAX_UINT64,
        };

        pnfs_mark_layout_for_return(inode, &range);
}
EXPORT_SYMBOL_GPL(pnfs_error_mark_layout_for_return);

static bool
pnfs_layout_can_be_returned(struct pnfs_layout_hdr *lo)
{
        return pnfs_layout_is_valid(lo) &&
                !test_bit(NFS_LAYOUT_INODE_FREEING, &lo->plh_flags) &&
                !test_bit(NFS_LAYOUT_RETURN, &lo->plh_flags);
}

static struct pnfs_layout_segment *
pnfs_find_first_lseg(struct pnfs_layout_hdr *lo,
                     const struct pnfs_layout_range *range,
                     enum pnfs_iomode iomode)
{
        struct pnfs_layout_segment *lseg;

        list_for_each_entry(lseg, &lo->plh_segs, pls_list) {
                if (!test_bit(NFS_LSEG_VALID, &lseg->pls_flags))
                        continue;
                if (test_bit(NFS_LSEG_LAYOUTRETURN, &lseg->pls_flags))
                        continue;
                if (lseg->pls_range.iomode != iomode && iomode != IOMODE_ANY)
                        continue;
                if (pnfs_lseg_range_intersecting(&lseg->pls_range, range))
                        return lseg;
        }
        return NULL;
}

/* Find open file states whose mode matches that of the range */
static bool
pnfs_should_return_unused_layout(struct pnfs_layout_hdr *lo,
                                 const struct pnfs_layout_range *range)
{
        struct list_head *head;
        struct nfs_open_context *ctx;
        fmode_t mode = 0;

        if (!pnfs_layout_can_be_returned(lo) ||
            !pnfs_find_first_lseg(lo, range, range->iomode))
                return false;

        head = &NFS_I(lo->plh_inode)->open_files;
        list_for_each_entry_rcu(ctx, head, list) {
                if (ctx->state)
                        mode |= ctx->state->state & (FMODE_READ|FMODE_WRITE);
        }

        switch (range->iomode) {
        default:
                break;
        case IOMODE_READ:
                mode &= ~FMODE_WRITE;
                break;
        case IOMODE_RW:
                if (pnfs_find_first_lseg(lo, range, IOMODE_READ))
                        mode &= ~FMODE_READ;
        }
        return mode == 0;
}

static int
pnfs_layout_return_unused_byserver(struct nfs_server *server, void *data)
{
        const struct pnfs_layout_range *range = data;
        struct pnfs_layout_hdr *lo;
        struct inode *inode;
restart:
        rcu_read_lock();
        list_for_each_entry_rcu(lo, &server->layouts, plh_layouts) {
                if (!pnfs_layout_can_be_returned(lo) ||
                    test_bit(NFS_LAYOUT_RETURN_REQUESTED, &lo->plh_flags))
                        continue;
                inode = lo->plh_inode;
                spin_lock(&inode->i_lock);
                if (!pnfs_should_return_unused_layout(lo, range)) {
                        spin_unlock(&inode->i_lock);
                        continue;
                }
                spin_unlock(&inode->i_lock);
                inode = pnfs_grab_inode_layout_hdr(lo);
                if (!inode)
                        continue;
                rcu_read_unlock();
                pnfs_mark_layout_for_return(inode, range);
                iput(inode);
                cond_resched();
                goto restart;
        }
        rcu_read_unlock();
        return 0;
}

void
pnfs_layout_return_unused_byclid(struct nfs_client *clp,
                                 enum pnfs_iomode iomode)
{
        struct pnfs_layout_range range = {
                .iomode = iomode,
                .offset = 0,
                .length = NFS4_MAX_UINT64,
        };

        nfs_client_for_each_server(clp, pnfs_layout_return_unused_byserver,
                        &range);
}

void
pnfs_generic_pg_check_layout(struct nfs_pageio_descriptor *pgio)
{
        if (pgio->pg_lseg == NULL ||
            test_bit(NFS_LSEG_VALID, &pgio->pg_lseg->pls_flags))
                return;
        pnfs_put_lseg(pgio->pg_lseg);
        pgio->pg_lseg = NULL;
}
EXPORT_SYMBOL_GPL(pnfs_generic_pg_check_layout);

/*
 * Check for any intersection between the request and the pgio->pg_lseg,
 * and if none, put this pgio->pg_lseg away.
 */
void
pnfs_generic_pg_check_range(struct nfs_pageio_descriptor *pgio, struct nfs_page *req)
{
        if (pgio->pg_lseg && !pnfs_lseg_request_intersecting(pgio->pg_lseg, req)) {
                pnfs_put_lseg(pgio->pg_lseg);
                pgio->pg_lseg = NULL;
        }
}
EXPORT_SYMBOL_GPL(pnfs_generic_pg_check_range);

void
pnfs_generic_pg_init_read(struct nfs_pageio_descriptor *pgio, struct nfs_page *req)
{
        u64 rd_size = req->wb_bytes;

        pnfs_generic_pg_check_layout(pgio);
        pnfs_generic_pg_check_range(pgio, req);
        if (pgio->pg_lseg == NULL) {
                if (pgio->pg_dreq == NULL)
                        rd_size = i_size_read(pgio->pg_inode) - req_offset(req);
                else
                        rd_size = nfs_dreq_bytes_left(pgio->pg_dreq);

                pgio->pg_lseg = pnfs_update_layout(pgio->pg_inode,
                                                   nfs_req_openctx(req),
                                                   req_offset(req),
                                                   rd_size,
                                                   IOMODE_READ,
                                                   false,
                                                   GFP_KERNEL);
                if (IS_ERR(pgio->pg_lseg)) {
                        pgio->pg_error = PTR_ERR(pgio->pg_lseg);
                        pgio->pg_lseg = NULL;
                        return;
                }
        }
        /* If no lseg, fall back to read through mds */
        if (pgio->pg_lseg == NULL)
                nfs_pageio_reset_read_mds(pgio);

}
EXPORT_SYMBOL_GPL(pnfs_generic_pg_init_read);

void
pnfs_generic_pg_init_write(struct nfs_pageio_descriptor *pgio,
                           struct nfs_page *req, u64 wb_size)
{
        pnfs_generic_pg_check_layout(pgio);
        pnfs_generic_pg_check_range(pgio, req);
        if (pgio->pg_lseg == NULL) {
                pgio->pg_lseg = pnfs_update_layout(pgio->pg_inode,
                                                   nfs_req_openctx(req),
                                                   req_offset(req),
                                                   wb_size,
                                                   IOMODE_RW,
                                                   false,
                                                   GFP_KERNEL);
                if (IS_ERR(pgio->pg_lseg)) {
                        pgio->pg_error = PTR_ERR(pgio->pg_lseg);
                        pgio->pg_lseg = NULL;
                        return;
                }
        }
        /* If no lseg, fall back to write through mds */
        if (pgio->pg_lseg == NULL)
                nfs_pageio_reset_write_mds(pgio);
}
EXPORT_SYMBOL_GPL(pnfs_generic_pg_init_write);

void
pnfs_generic_pg_cleanup(struct nfs_pageio_descriptor *desc)
{
        if (desc->pg_lseg) {
                pnfs_put_lseg(desc->pg_lseg);
                desc->pg_lseg = NULL;
        }
}
EXPORT_SYMBOL_GPL(pnfs_generic_pg_cleanup);

/*
 * Return 0 if @req cannot be coalesced into @pgio, otherwise return the number
 * of bytes (maximum @req->wb_bytes) that can be coalesced.
 */
size_t
pnfs_generic_pg_test(struct nfs_pageio_descriptor *pgio,
                     struct nfs_page *prev, struct nfs_page *req)
{
        unsigned int size;
        u64 seg_end, req_start, seg_left;

        size = nfs_generic_pg_test(pgio, prev, req);
        if (!size)
                return 0;

        /*
         * 'size' contains the number of bytes left in the current page (up
         * to the original size asked for in @req->wb_bytes).
         *
         * Calculate how many bytes are left in the layout segment
         * and if there are less bytes than 'size', return that instead.
         *
         * Please also note that 'end_offset' is actually the offset of the
         * first byte that lies outside the pnfs_layout_range. FIXME?
         *
         */
        if (pgio->pg_lseg) {
                seg_end = pnfs_end_offset(pgio->pg_lseg->pls_range.offset,
                                     pgio->pg_lseg->pls_range.length);
                req_start = req_offset(req);

                /* start of request is past the last byte of this segment */
                if (req_start >= seg_end)
                        return 0;

                /* adjust 'size' iff there are fewer bytes left in the
                 * segment than what nfs_generic_pg_test returned */
                seg_left = seg_end - req_start;
                if (seg_left < size)
                        size = (unsigned int)seg_left;
        }

        return size;
}
EXPORT_SYMBOL_GPL(pnfs_generic_pg_test);

int pnfs_write_done_resend_to_mds(struct nfs_pgio_header *hdr)
{
        struct nfs_pageio_descriptor pgio;

        /* Resend all requests through the MDS */
        nfs_pageio_init_write(&pgio, hdr->inode, FLUSH_STABLE, true,
                              hdr->completion_ops);
        set_bit(NFS_CONTEXT_RESEND_WRITES, &hdr->args.context->flags);
        return nfs_pageio_resend(&pgio, hdr);
}
EXPORT_SYMBOL_GPL(pnfs_write_done_resend_to_mds);

static void pnfs_ld_handle_write_error(struct nfs_pgio_header *hdr)
{

        dprintk("pnfs write error = %d\n", hdr->pnfs_error);
        if (NFS_SERVER(hdr->inode)->pnfs_curr_ld->flags &
            PNFS_LAYOUTRET_ON_ERROR) {
                pnfs_return_layout(hdr->inode);
        }
        if (!test_and_set_bit(NFS_IOHDR_REDO, &hdr->flags))
                hdr->task.tk_status = pnfs_write_done_resend_to_mds(hdr);
}

/*
 * Called by non rpc-based layout drivers
 */
void pnfs_ld_write_done(struct nfs_pgio_header *hdr)
{
        if (likely(!hdr->pnfs_error)) {
                pnfs_set_layoutcommit(hdr->inode, hdr->lseg,
                                hdr->mds_offset + hdr->res.count);
                hdr->mds_ops->rpc_call_done(&hdr->task, hdr);
        }
        trace_nfs4_pnfs_write(hdr, hdr->pnfs_error);
        if (unlikely(hdr->pnfs_error))
                pnfs_ld_handle_write_error(hdr);
        hdr->mds_ops->rpc_release(hdr);
}
EXPORT_SYMBOL_GPL(pnfs_ld_write_done);

static void
pnfs_write_through_mds(struct nfs_pageio_descriptor *desc,
                struct nfs_pgio_header *hdr)
{
        struct nfs_pgio_mirror *mirror = nfs_pgio_current_mirror(desc);

        if (!test_and_set_bit(NFS_IOHDR_REDO, &hdr->flags)) {
                list_splice_tail_init(&hdr->pages, &mirror->pg_list);
                nfs_pageio_reset_write_mds(desc);
                mirror->pg_recoalesce = 1;
        }
        hdr->completion_ops->completion(hdr);
}

static enum pnfs_try_status
pnfs_try_to_write_data(struct nfs_pgio_header *hdr,
                        const struct rpc_call_ops *call_ops,
                        struct pnfs_layout_segment *lseg,
                        int how)
{
        struct inode *inode = hdr->inode;
        enum pnfs_try_status trypnfs;
        struct nfs_server *nfss = NFS_SERVER(inode);

        hdr->mds_ops = call_ops;

        dprintk("%s: Writing ino:%lu %u@%llu (how %d)\n", __func__,
                inode->i_ino, hdr->args.count, hdr->args.offset, how);
        trypnfs = nfss->pnfs_curr_ld->write_pagelist(hdr, how);
        if (trypnfs != PNFS_NOT_ATTEMPTED)
                nfs_inc_stats(inode, NFSIOS_PNFS_WRITE);
        dprintk("%s End (trypnfs:%d)\n", __func__, trypnfs);
        return trypnfs;
}

static void
pnfs_do_write(struct nfs_pageio_descriptor *desc,
              struct nfs_pgio_header *hdr, int how)
{
        const struct rpc_call_ops *call_ops = desc->pg_rpc_callops;
        struct pnfs_layout_segment *lseg = desc->pg_lseg;
        enum pnfs_try_status trypnfs;

        trypnfs = pnfs_try_to_write_data(hdr, call_ops, lseg, how);
        switch (trypnfs) {
        case PNFS_NOT_ATTEMPTED:
                pnfs_write_through_mds(desc, hdr);
        case PNFS_ATTEMPTED:
                break;
        case PNFS_TRY_AGAIN:
                /* cleanup hdr and prepare to redo pnfs */
                if (!test_and_set_bit(NFS_IOHDR_REDO, &hdr->flags)) {
                        struct nfs_pgio_mirror *mirror = nfs_pgio_current_mirror(desc);
                        list_splice_init(&hdr->pages, &mirror->pg_list);
                        mirror->pg_recoalesce = 1;
                }
                hdr->mds_ops->rpc_release(hdr);
        }
}

static void pnfs_writehdr_free(struct nfs_pgio_header *hdr)
{
        pnfs_put_lseg(hdr->lseg);
        nfs_pgio_header_free(hdr);
}

int
pnfs_generic_pg_writepages(struct nfs_pageio_descriptor *desc)
{
        struct nfs_pgio_header *hdr;
        int ret;

        hdr = nfs_pgio_header_alloc(desc->pg_rw_ops);
        if (!hdr) {
                desc->pg_error = -ENOMEM;
                return desc->pg_error;
        }
        nfs_pgheader_init(desc, hdr, pnfs_writehdr_free);

        hdr->lseg = pnfs_get_lseg(desc->pg_lseg);
        ret = nfs_generic_pgio(desc, hdr);
        if (!ret)
                pnfs_do_write(desc, hdr, desc->pg_ioflags);

        return ret;
}
EXPORT_SYMBOL_GPL(pnfs_generic_pg_writepages);

int pnfs_read_done_resend_to_mds(struct nfs_pgio_header *hdr)
{
        struct nfs_pageio_descriptor pgio;

        /* Resend all requests through the MDS */
        nfs_pageio_init_read(&pgio, hdr->inode, true, hdr->completion_ops);
        return nfs_pageio_resend(&pgio, hdr);
}
EXPORT_SYMBOL_GPL(pnfs_read_done_resend_to_mds);

static void pnfs_ld_handle_read_error(struct nfs_pgio_header *hdr)
{
        dprintk("pnfs read error = %d\n", hdr->pnfs_error);
        if (NFS_SERVER(hdr->inode)->pnfs_curr_ld->flags &
            PNFS_LAYOUTRET_ON_ERROR) {
                pnfs_return_layout(hdr->inode);
        }
        if (!test_and_set_bit(NFS_IOHDR_REDO, &hdr->flags))
                hdr->task.tk_status = pnfs_read_done_resend_to_mds(hdr);
}

/*
 * Called by non rpc-based layout drivers
 */
void pnfs_ld_read_done(struct nfs_pgio_header *hdr)
{
        if (likely(!hdr->pnfs_error))
                hdr->mds_ops->rpc_call_done(&hdr->task, hdr);
        trace_nfs4_pnfs_read(hdr, hdr->pnfs_error);
        if (unlikely(hdr->pnfs_error))
                pnfs_ld_handle_read_error(hdr);
        hdr->mds_ops->rpc_release(hdr);
}
EXPORT_SYMBOL_GPL(pnfs_ld_read_done);

static void
pnfs_read_through_mds(struct nfs_pageio_descriptor *desc,
                struct nfs_pgio_header *hdr)
{
        struct nfs_pgio_mirror *mirror = nfs_pgio_current_mirror(desc);

        if (!test_and_set_bit(NFS_IOHDR_REDO, &hdr->flags)) {
                list_splice_tail_init(&hdr->pages, &mirror->pg_list);
                nfs_pageio_reset_read_mds(desc);
                mirror->pg_recoalesce = 1;
        }
        hdr->completion_ops->completion(hdr);
}

/*
 * Call the appropriate parallel I/O subsystem read function.
 */
static enum pnfs_try_status
pnfs_try_to_read_data(struct nfs_pgio_header *hdr,
                       const struct rpc_call_ops *call_ops,
                       struct pnfs_layout_segment *lseg)
{
        struct inode *inode = hdr->inode;
        struct nfs_server *nfss = NFS_SERVER(inode);
        enum pnfs_try_status trypnfs;

        hdr->mds_ops = call_ops;

        dprintk("%s: Reading ino:%lu %u@%llu\n",
                __func__, inode->i_ino, hdr->args.count, hdr->args.offset);

        trypnfs = nfss->pnfs_curr_ld->read_pagelist(hdr);
        if (trypnfs != PNFS_NOT_ATTEMPTED)
                nfs_inc_stats(inode, NFSIOS_PNFS_READ);
        dprintk("%s End (trypnfs:%d)\n", __func__, trypnfs);
        return trypnfs;
}

/* Resend all requests through pnfs. */
void pnfs_read_resend_pnfs(struct nfs_pgio_header *hdr,
                           unsigned int mirror_idx)
{
        struct nfs_pageio_descriptor pgio;

        if (!test_and_set_bit(NFS_IOHDR_REDO, &hdr->flags)) {
                /* Prevent deadlocks with layoutreturn! */
                pnfs_put_lseg(hdr->lseg);