// SPDX-License-Identifier: GPL-2.0-only
/*
 * Common NFS I/O  operations for the pnfs file based
 * layout drivers.
 *
 * Copyright (c) 2014, Primary Data, Inc. All rights reserved.
 *
 * Tom Haynes <loghyr@primarydata.com>
 */

#include <linux/nfs_fs.h>
#include <linux/nfs_page.h>
#include <linux/sunrpc/addr.h>
#include <linux/module.h>

#include "nfs4session.h"
#include "internal.h"
#include "pnfs.h"

#define NFSDBG_FACILITY         NFSDBG_PNFS

void pnfs_generic_rw_release(void *data)
{
        struct nfs_pgio_header *hdr = data;

        nfs_put_client(hdr->ds_clp);
        hdr->mds_ops->rpc_release(data);
}
EXPORT_SYMBOL_GPL(pnfs_generic_rw_release);

/* Fake up some data that will cause nfs_commit_release to retry the writes. */
void pnfs_generic_prepare_to_resend_writes(struct nfs_commit_data *data)
{
        struct nfs_writeverf *verf = data->res.verf;

        data->task.tk_status = 0;
        memset(&verf->verifier, 0, sizeof(verf->verifier));
        verf->committed = NFS_UNSTABLE;
}
EXPORT_SYMBOL_GPL(pnfs_generic_prepare_to_resend_writes);

void pnfs_generic_write_commit_done(struct rpc_task *task, void *data)
{
        struct nfs_commit_data *wdata = data;

        /* Note this may cause RPC to be resent */
        wdata->mds_ops->rpc_call_done(task, data);
}
EXPORT_SYMBOL_GPL(pnfs_generic_write_commit_done);

void pnfs_generic_commit_release(void *calldata)
{
        struct nfs_commit_data *data = calldata;

        data->completion_ops->completion(data);
        pnfs_put_lseg(data->lseg);
        nfs_put_client(data->ds_clp);
        nfs_commitdata_release(data);
}
EXPORT_SYMBOL_GPL(pnfs_generic_commit_release);

static struct pnfs_layout_segment *
pnfs_free_bucket_lseg(struct pnfs_commit_bucket *bucket)
{
        if (list_empty(&bucket->committing) && list_empty(&bucket->written)) {
                struct pnfs_layout_segment *freeme = bucket->lseg;
                bucket->lseg = NULL;
                return freeme;
        }
        return NULL;
}

/* The generic layer is about to remove the req from the commit list.
 * If this will make the bucket empty, it will need to put the lseg reference.
 * Note this must be called holding nfsi->commit_mutex
 */
void
pnfs_generic_clear_request_commit(struct nfs_page *req,
                                  struct nfs_commit_info *cinfo)
{
        struct pnfs_commit_bucket *bucket = NULL;

        if (!test_and_clear_bit(PG_COMMIT_TO_DS, &req->wb_flags))
                goto out;
        cinfo->ds->nwritten--;
        if (list_is_singular(&req->wb_list))
                bucket = list_first_entry(&req->wb_list,
                                          struct pnfs_commit_bucket, written);
out:
        nfs_request_remove_commit_list(req, cinfo);
        if (bucket)
                pnfs_put_lseg(pnfs_free_bucket_lseg(bucket));
}
EXPORT_SYMBOL_GPL(pnfs_generic_clear_request_commit);

struct pnfs_commit_array *
pnfs_alloc_commit_array(size_t n, gfp_t gfp_flags)
{
        struct pnfs_commit_array *p;
        struct pnfs_commit_bucket *b;

        p = kmalloc(struct_size(p, buckets, n), gfp_flags);
        if (!p)
                return NULL;
        p->nbuckets = n;
        INIT_LIST_HEAD(&p->cinfo_list);
        INIT_LIST_HEAD(&p->lseg_list);
        p->lseg = NULL;
        for (b = &p->buckets[0]; n != 0; b++, n--) {
                INIT_LIST_HEAD(&b->written);
                INIT_LIST_HEAD(&b->committing);
                b->lseg = NULL;
                b->direct_verf.committed = NFS_INVALID_STABLE_HOW;
        }
        return p;
}
EXPORT_SYMBOL_GPL(pnfs_alloc_commit_array);

void
pnfs_free_commit_array(struct pnfs_commit_array *p)
{
        kfree_rcu(p, rcu);
}
EXPORT_SYMBOL_GPL(pnfs_free_commit_array);

static struct pnfs_commit_array *
pnfs_find_commit_array_by_lseg(struct pnfs_ds_commit_info *fl_cinfo,
                struct pnfs_layout_segment *lseg)
{
        struct pnfs_commit_array *array;

        list_for_each_entry_rcu(array, &fl_cinfo->commits, cinfo_list) {
                if (array->lseg == lseg)
                        return array;
        }
        return NULL;
}

struct pnfs_commit_array *
pnfs_add_commit_array(struct pnfs_ds_commit_info *fl_cinfo,
                struct pnfs_commit_array *new,
                struct pnfs_layout_segment *lseg)
{
        struct pnfs_commit_array *array;

        array = pnfs_find_commit_array_by_lseg(fl_cinfo, lseg);
        if (array)
                return array;
        new->lseg = lseg;
        refcount_set(&new->refcount, 1);
        list_add_rcu(&new->cinfo_list, &fl_cinfo->commits);
        list_add(&new->lseg_list, &lseg->pls_commits);
        return new;
}
EXPORT_SYMBOL_GPL(pnfs_add_commit_array);

static struct pnfs_commit_array *
pnfs_lookup_commit_array(struct pnfs_ds_commit_info *fl_cinfo,
                struct pnfs_layout_segment *lseg)
{
        struct pnfs_commit_array *array;

        rcu_read_lock();
        array = pnfs_find_commit_array_by_lseg(fl_cinfo, lseg);
        if (!array) {
                rcu_read_unlock();
                fl_cinfo->ops->setup_ds_info(fl_cinfo, lseg);
                rcu_read_lock();
                array = pnfs_find_commit_array_by_lseg(fl_cinfo, lseg);
        }
        rcu_read_unlock();
        return array;
}

static void
pnfs_release_commit_array_locked(struct pnfs_commit_array *array)
{
        list_del_rcu(&array->cinfo_list);
        list_del(&array->lseg_list);
        pnfs_free_commit_array(array);
}

static void
pnfs_put_commit_array_locked(struct pnfs_commit_array *array)
{
        if (refcount_dec_and_test(&array->refcount))
                pnfs_release_commit_array_locked(array);
}

static void
pnfs_put_commit_array(struct pnfs_commit_array *array, struct inode *inode)
{
        if (refcount_dec_and_lock(&array->refcount, &inode->i_lock)) {
                pnfs_release_commit_array_locked(array);
                spin_unlock(&inode->i_lock);
        }
}

static struct pnfs_commit_array *
pnfs_get_commit_array(struct pnfs_commit_array *array)
{
        if (refcount_inc_not_zero(&array->refcount))
                return array;
        return NULL;
}

static void
pnfs_remove_and_free_commit_array(struct pnfs_commit_array *array)
{
        array->lseg = NULL;
        list_del_init(&array->lseg_list);
        pnfs_put_commit_array_locked(array);
}

void
pnfs_generic_ds_cinfo_release_lseg(struct pnfs_ds_commit_info *fl_cinfo,
                struct pnfs_layout_segment *lseg)
{
        struct pnfs_commit_array *array, *tmp;

        list_for_each_entry_safe(array, tmp, &lseg->pls_commits, lseg_list)
                pnfs_remove_and_free_commit_array(array);
}
EXPORT_SYMBOL_GPL(pnfs_generic_ds_cinfo_release_lseg);

void
pnfs_generic_ds_cinfo_destroy(struct pnfs_ds_commit_info *fl_cinfo)
{
        struct pnfs_commit_array *array, *tmp;

        list_for_each_entry_safe(array, tmp, &fl_cinfo->commits, cinfo_list)
                pnfs_remove_and_free_commit_array(array);
}
EXPORT_SYMBOL_GPL(pnfs_generic_ds_cinfo_destroy);

/*
 * Locks the nfs_page requests for commit and moves them to
 * @bucket->committing.
 */
static int
pnfs_bucket_scan_ds_commit_list(struct pnfs_commit_bucket *bucket,
                                struct nfs_commit_info *cinfo,
                                int max)
{
        struct list_head *src = &bucket->written;
        struct list_head *dst = &bucket->committing;
        int ret;

        lockdep_assert_held(&NFS_I(cinfo->inode)->commit_mutex);
        ret = nfs_scan_commit_list(src, dst, cinfo, max);
        if (ret) {
                cinfo->ds->nwritten -= ret;
                cinfo->ds->ncommitting += ret;
        }
        return ret;
}

static int pnfs_bucket_scan_array(struct nfs_commit_info *cinfo,
                                  struct pnfs_commit_bucket *buckets,
                                  unsigned int nbuckets,
                                  int max)
{
        unsigned int i;
        int rv = 0, cnt;

        for (i = 0; i < nbuckets && max != 0; i++) {
                cnt = pnfs_bucket_scan_ds_commit_list(&buckets[i], cinfo, max);
                rv += cnt;
                max -= cnt;
        }
        return rv;
}

/* Move reqs from written to committing lists, returning count
 * of number moved.
 */
int pnfs_generic_scan_commit_lists(struct nfs_commit_info *cinfo, int max)
{
        struct pnfs_ds_commit_info *fl_cinfo = cinfo->ds;
        struct pnfs_commit_array *array;
        int rv = 0, cnt;

        rcu_read_lock();
        list_for_each_entry_rcu(array, &fl_cinfo->commits, cinfo_list) {
                if (!array->lseg || !pnfs_get_commit_array(array))
                        continue;
                rcu_read_unlock();
                cnt = pnfs_bucket_scan_array(cinfo, array->buckets,
                                array->nbuckets, max);
                rcu_read_lock();
                pnfs_put_commit_array(array, cinfo->inode);
                rv += cnt;
                max -= cnt;
                if (!max)
                        break;
        }
        rcu_read_unlock();
        return rv;
}
EXPORT_SYMBOL_GPL(pnfs_generic_scan_commit_lists);

static unsigned int
pnfs_bucket_recover_commit_reqs(struct list_head *dst,
                                struct pnfs_commit_bucket *buckets,
                                unsigned int nbuckets,
                                struct nfs_commit_info *cinfo)
{
        struct pnfs_commit_bucket *b;
        struct pnfs_layout_segment *freeme;
        unsigned int nwritten, ret = 0;
        unsigned int i;

restart:
        for (i = 0, b = buckets; i < nbuckets; i++, b++) {
                nwritten = nfs_scan_commit_list(&b->written, dst, cinfo, 0);
                if (!nwritten)
                        continue;
                ret += nwritten;
                freeme = pnfs_free_bucket_lseg(b);
                if (freeme) {
                        pnfs_put_lseg(freeme);
                        goto restart;
                }
        }
        return ret;
}

/* Pull everything off the committing lists and dump into @dst.  */
void pnfs_generic_recover_commit_reqs(struct list_head *dst,
                                      struct nfs_commit_info *cinfo)
{
        struct pnfs_ds_commit_info *fl_cinfo = cinfo->ds;
        struct pnfs_commit_array *array;
        unsigned int nwritten;

        lockdep_assert_held(&NFS_I(cinfo->inode)->commit_mutex);
        rcu_read_lock();
        list_for_each_entry_rcu(array, &fl_cinfo->commits, cinfo_list) {
                if (!array->lseg || !pnfs_get_commit_array(array))
                        continue;
                rcu_read_unlock();
                nwritten = pnfs_bucket_recover_commit_reqs(dst,
                                                           array->buckets,
                                                           array->nbuckets,
                                                           cinfo);
                rcu_read_lock();
                pnfs_put_commit_array(array, cinfo->inode);
                fl_cinfo->nwritten -= nwritten;
        }
        rcu_read_unlock();
}
EXPORT_SYMBOL_GPL(pnfs_generic_recover_commit_reqs);

static struct nfs_page *
pnfs_bucket_search_commit_reqs(struct pnfs_commit_bucket *buckets,
                unsigned int nbuckets, struct page *page)
{
        struct nfs_page *req;
        struct pnfs_commit_bucket *b;
        unsigned int i;

        /* Linearly search the commit lists for each bucket until a matching
         * request is found */
        for (i = 0, b = buckets; i < nbuckets; i++, b++) {
                list_for_each_entry(req, &b->written, wb_list) {
                        if (req->wb_page == page)
                                return req->wb_head;
                }
                list_for_each_entry(req, &b->committing, wb_list) {
                        if (req->wb_page == page)
                                return req->wb_head;
                }
        }
        return NULL;
}

/* pnfs_generic_search_commit_reqs - Search lists in @cinfo for the head reqest
 *                                 for @page
 * @cinfo - commit info for current inode
 * @page - page to search for matching head request
 *
 * Returns a the head request if one is found, otherwise returns NULL.
 */
struct nfs_page *
pnfs_generic_search_commit_reqs(struct nfs_commit_info *cinfo, struct page *page)
{
        struct pnfs_ds_commit_info *fl_cinfo = cinfo->ds;
        struct pnfs_commit_array *array;
        struct nfs_page *req;

        list_for_each_entry(array, &fl_cinfo->commits, cinfo_list) {
                req = pnfs_bucket_search_commit_reqs(array->buckets,
                                array->nbuckets, page);
                if (req)
                        return req;
        }
        return NULL;
}
EXPORT_SYMBOL_GPL(pnfs_generic_search_commit_reqs);

static struct pnfs_layout_segment *
pnfs_bucket_get_committing(struct list_head *head,
                           struct pnfs_commit_bucket *bucket,
                           struct nfs_commit_info *cinfo)
{
        struct pnfs_layout_segment *lseg;
        struct list_head *pos;

        list_for_each(pos, &bucket->committing)
                cinfo->ds->ncommitting--;
        list_splice_init(&bucket->committing, head);
        lseg = pnfs_free_bucket_lseg(bucket);
        if (!lseg)
                lseg = pnfs_get_lseg(bucket->lseg);
        return lseg;
}

static struct nfs_commit_data *
pnfs_bucket_fetch_commitdata(struct pnfs_commit_bucket *bucket,
                             struct nfs_commit_info *cinfo)
{
        struct nfs_commit_data *data = nfs_commitdata_alloc(false);

        if (!data)
                return NULL;
        data->lseg = pnfs_bucket_get_committing(&data->pages, bucket, cinfo);
        return data;
}

static void pnfs_generic_retry_commit(struct pnfs_commit_bucket *buckets,
                                      unsigned int nbuckets,
                                      struct nfs_commit_info *cinfo,
                                      unsigned int idx)
{
        struct pnfs_commit_bucket *bucket;
        struct pnfs_layout_segment *freeme;
        LIST_HEAD(pages);

        for (bucket = buckets; idx < nbuckets; bucket++, idx++) {
                if (list_empty(&bucket->committing))
                        continue;
                mutex_lock(&NFS_I(cinfo->inode)->commit_mutex);
                freeme = pnfs_bucket_get_committing(&pages, bucket, cinfo);
                mutex_unlock(&NFS_I(cinfo->inode)->commit_mutex);
                nfs_retry_commit(&pages, freeme, cinfo, idx);
                pnfs_put_lseg(freeme);
        }
}

static unsigned int
pnfs_bucket_alloc_ds_commits(struct list_head *list,
                             struct pnfs_commit_bucket *buckets,
                             unsigned int nbuckets,
                             struct nfs_commit_info *cinfo)
{
        struct pnfs_commit_bucket *bucket;
        struct nfs_commit_data *data;
        unsigned int i;
        unsigned int nreq = 0;

        for (i = 0, bucket = buckets; i < nbuckets; i++, bucket++) {
                if (list_empty(&bucket->committing))
                        continue;
                mutex_lock(&NFS_I(cinfo->inode)->commit_mutex);
                if (!list_empty(&bucket->committing)) {
                        data = pnfs_bucket_fetch_commitdata(bucket, cinfo);
                        if (!data)
                                goto out_error;
                        data->ds_commit_index = i;
                        list_add_tail(&data->list, list);
                        nreq++;
                }
                mutex_unlock(&NFS_I(cinfo->inode)->commit_mutex);
        }
        return nreq;
out_error:
        mutex_unlock(&NFS_I(cinfo->inode)->commit_mutex);
        /* Clean up on error */
        pnfs_generic_retry_commit(buckets, nbuckets, cinfo, i);
        return nreq;
}

static unsigned int
pnfs_alloc_ds_commits_list(struct list_head *list,
                           struct pnfs_ds_commit_info *fl_cinfo,
                           struct nfs_commit_info *cinfo)
{
        struct pnfs_commit_array *array;
        unsigned int ret = 0;

        rcu_read_lock();
        list_for_each_entry_rcu(array, &fl_cinfo->commits, cinfo_list) {
                if (!array->lseg || !pnfs_get_commit_array(array))
                        continue;
                rcu_read_unlock();
                ret += pnfs_bucket_alloc_ds_commits(list, array->buckets,
                                array->nbuckets, cinfo);
                rcu_read_lock();
                pnfs_put_commit_array(array, cinfo->inode);
        }
        rcu_read_unlock();
        return ret;
}

/* This follows nfs_commit_list pretty closely */
int
pnfs_generic_commit_pagelist(struct inode *inode, struct list_head *mds_pages,
                             int how, struct nfs_commit_info *cinfo,
                             int (*initiate_commit)(struct nfs_commit_data *data,
                                                    int how))
{
        struct pnfs_ds_commit_info *fl_cinfo = cinfo->ds;
        struct nfs_commit_data *data, *tmp;
        LIST_HEAD(list);
        unsigned int nreq = 0;

        if (!list_empty(mds_pages)) {
                data = nfs_commitdata_alloc(true);
                data->ds_commit_index = -1;
                list_splice_init(mds_pages, &data->pages);
                list_add_tail(&data->list, &list);
                nreq++;
        }

        nreq += pnfs_alloc_ds_commits_list(&list, fl_cinfo, cinfo);
        if (nreq == 0)
                goto out;

        list_for_each_entry_safe(data, tmp, &list, list) {
                list_del(&data->list);
                if (data->ds_commit_index < 0) {
                        nfs_init_commit(data, NULL, NULL, cinfo);
                        nfs_initiate_commit(NFS_CLIENT(inode), data,
                                            NFS_PROTO(data->inode),
                                            data->mds_ops, how,
                                            RPC_TASK_CRED_NOREF);
                } else {
                        nfs_init_commit(data, NULL, data->lseg, cinfo);
                        initiate_commit(data, how);
                }
        }
out:
        return PNFS_ATTEMPTED;
}
EXPORT_SYMBOL_GPL(pnfs_generic_commit_pagelist);

/*
 * Data server cache
 *
 * Data servers can be mapped to different device ids.
 * nfs4_pnfs_ds reference counting
 *   - set to 1 on allocation
 *   - incremented when a device id maps a data server already in the cache.
 *   - decremented when deviceid is removed from the cache.
 */
static DEFINE_SPINLOCK(nfs4_ds_cache_lock);
static LIST_HEAD(nfs4_data_server_cache);

/* Debug routines */
static void
print_ds(struct nfs4_pnfs_ds *ds)
{
        if (ds == NULL) {
                printk(KERN_WARNING "%s NULL device\n", __func__);
                return;
        }
        printk(KERN_WARNING "        ds %s\n"
                "        ref count %d\n"
                "        client %p\n"
                "        cl_exchange_flags %x\n",
                ds->ds_remotestr,
                refcount_read(&ds->ds_count), ds->ds_clp,
                ds->ds_clp ? ds->ds_clp->cl_exchange_flags : 0);
}

static bool
same_sockaddr(struct sockaddr *addr1, struct sockaddr *addr2)
{
        struct sockaddr_in *a, *b;
        struct sockaddr_in6 *a6, *b6;

        if (addr1->sa_family != addr2->sa_family)
                return false;

        switch (addr1->sa_family) {
        case AF_INET:
                a = (struct sockaddr_in *)addr1;
                b = (struct sockaddr_in *)addr2;

                if (a->sin_addr.s_addr == b->sin_addr.s_addr &&
                    a->sin_port == b->sin_port)
                        return true;
                break;

        case AF_INET6:
                a6 = (struct sockaddr_in6 *)addr1;
                b6 = (struct sockaddr_in6 *)addr2;

                /* LINKLOCAL addresses must have matching scope_id */
                if (ipv6_addr_src_scope(&a6->sin6_addr) ==
                    IPV6_ADDR_SCOPE_LINKLOCAL &&
                    a6->sin6_scope_id != b6->sin6_scope_id)
                        return false;

                if (ipv6_addr_equal(&a6->sin6_addr, &b6->sin6_addr) &&
                    a6->sin6_port == b6->sin6_port)
                        return true;
                break;

        default:
                dprintk("%s: unhandled address family: %u\n",
                        __func__, addr1->sa_family);
                return false;
        }

        return false;
}

/*
 * Checks if 'dsaddrs1' contains a subset of 'dsaddrs2'. If it does,
 * declare a match.
 */
static bool
_same_data_server_addrs_locked(const struct list_head *dsaddrs1,
                               const struct list_head *dsaddrs2)
{
        struct nfs4_pnfs_ds_addr *da1, *da2;
        struct sockaddr *sa1, *sa2;
        bool match = false;

        list_for_each_entry(da1, dsaddrs1, da_node) {
                sa1 = (struct sockaddr *)&da1->da_addr;
                match = false;
                list_for_each_entry(da2, dsaddrs2, da_node) {
                        sa2 = (struct sockaddr *)&da2->da_addr;
                        match = same_sockaddr(sa1, sa2);
                        if (match)
                                break;
                }
                if (!match)
                        break;
        }
        return match;
}

/*
 * Lookup DS by addresses.  nfs4_ds_cache_lock is held
 */
static struct nfs4_pnfs_ds *
_data_server_lookup_locked(const struct list_head *dsaddrs)
{
        struct nfs4_pnfs_ds *ds;

        list_for_each_entry(ds, &nfs4_data_server_cache, ds_node)
                if (_same_data_server_addrs_locked(&ds->ds_addrs, dsaddrs))
                        return ds;
        return NULL;
}

static struct nfs4_pnfs_ds_addr *nfs4_pnfs_ds_addr_alloc(gfp_t gfp_flags)
{
        struct nfs4_pnfs_ds_addr *da = kzalloc(sizeof(*da), gfp_flags);
        if (da)
                INIT_LIST_HEAD(&da->da_node);
        return da;
}

static void nfs4_pnfs_ds_addr_free(struct nfs4_pnfs_ds_addr *da)
{
        kfree(da->da_remotestr);
        kfree(da->da_netid);
        kfree(da);
}

static void destroy_ds(struct nfs4_pnfs_ds *ds)
{
        struct nfs4_pnfs_ds_addr *da;

        dprintk("--> %s\n", __func__);
        ifdebug(FACILITY)
                print_ds(ds);

        nfs_put_client(ds->ds_clp);

        while (!list_empty(&ds->ds_addrs)) {
                da = list_first_entry(&ds->ds_addrs,
                                      struct nfs4_pnfs_ds_addr,
                                      da_node);
                list_del_init(&da->da_node);
                nfs4_pnfs_ds_addr_free(da);
        }

        kfree(ds->ds_remotestr);
        kfree(ds);
}

void nfs4_pnfs_ds_put(struct nfs4_pnfs_ds *ds)
{
        if (refcount_dec_and_lock(&ds->ds_count,
                                &nfs4_ds_cache_lock)) {
                list_del_init(&ds->ds_node);
                spin_unlock(&nfs4_ds_cache_lock);
                destroy_ds(ds);
        }
}
EXPORT_SYMBOL_GPL(nfs4_pnfs_ds_put);

/*
 * Create a string with a human readable address and port to avoid
 * complicated setup around many dprinks.
 */
static char *
nfs4_pnfs_remotestr(struct list_head *dsaddrs, gfp_t gfp_flags)
{
        struct nfs4_pnfs_ds_addr *da;
        char *remotestr;
        size_t len;
        char *p;

        len = 3;        /* '{', '}' and eol */
        list_for_each_entry(da, dsaddrs, da_node) {
                len += strlen(da->da_remotestr) + 1;    /* string plus comma */
        }

        remotestr = kzalloc(len, gfp_flags);
        if (!remotestr)
                return NULL;

        p = remotestr;
        *(p++) = '{';
        len--;
        list_for_each_entry(da, dsaddrs, da_node) {
                size_t ll = strlen(da->da_remotestr);

                if (ll > len)
                        goto out_err;

                memcpy(p, da->da_remotestr, ll);
                p += ll;
                len -= ll;

                if (len < 1)
                        goto out_err;
                (*p++) = ',';
                len--;
        }
        if (len < 2)
                goto out_err;
        *(p++) = '}';
        *p = '\0';
        return remotestr;
out_err:
        kfree(remotestr);
        return NULL;
}

/*
 * Given a list of multipath struct nfs4_pnfs_ds_addr, add it to ds cache if
 * uncached and return cached struct nfs4_pnfs_ds.
 */
struct nfs4_pnfs_ds *
nfs4_pnfs_ds_add(struct list_head *dsaddrs, gfp_t gfp_flags)
{
        struct nfs4_pnfs_ds *tmp_ds, *ds = NULL;
        char *remotestr;

        if (list_empty(dsaddrs)) {
                dprintk("%s: no addresses defined\n", __func__);
                goto out;
        }

        ds = kzalloc(sizeof(*ds), gfp_flags);
        if (!ds)
                goto out;

        /* this is only used for debugging, so it's ok if its NULL */
        remotestr = nfs4_pnfs_remotestr(dsaddrs, gfp_flags);

        spin_lock(&nfs4_ds_cache_lock);
        tmp_ds = _data_server_lookup_locked(dsaddrs);
        if (tmp_ds == NULL) {
                INIT_LIST_HEAD(&ds->ds_addrs);
                list_splice_init(dsaddrs, &ds->ds_addrs);
                ds->ds_remotestr = remotestr;
                refcount_set(&ds->ds_count, 1);
                INIT_LIST_HEAD(&ds->ds_node);
                ds->ds_clp = NULL;
                list_add(&ds->ds_node, &nfs4_data_server_cache);
                dprintk("%s add new data server %s\n", __func__,
                        ds->ds_remotestr);
        } else {
                kfree(remotestr);
                kfree(ds);
                refcount_inc(&tmp_ds->ds_count);
                dprintk("%s data server %s found, inc'ed ds_count to %d\n",
                        __func__, tmp_ds->ds_remotestr,
                        refcount_read(&tmp_ds->ds_count));
                ds = tmp_ds;
        }
        spin_unlock(&nfs4_ds_cache_lock);
out:
        return ds;
}
EXPORT_SYMBOL_GPL(nfs4_pnfs_ds_add);

static int nfs4_wait_ds_connect(struct nfs4_pnfs_ds *ds)
{
        might_sleep();
        return wait_on_bit(&ds->ds_state, NFS4DS_CONNECTING, TASK_KILLABLE);
}

static void nfs4_clear_ds_conn_bit(struct nfs4_pnfs_ds *ds)
{
        smp_mb__before_atomic();
        clear_and_wake_up_bit(NFS4DS_CONNECTING, &ds->ds_state);
}

static struct nfs_client *(*get_v3_ds_connect)(
                        struct nfs_server *mds_srv,
                        const struct sockaddr *ds_addr,
                        int ds_addrlen,
                        int ds_proto,
                        unsigned int ds_timeo,
                        unsigned int ds_retrans);

static bool load_v3_ds_connect(void)
{
        if (!get_v3_ds_connect) {
                get_v3_ds_connect = symbol_request(nfs3_set_ds_client);
                WARN_ON_ONCE(!get_v3_ds_connect);
        }

        return(get_v3_ds_connect != NULL);
}

void nfs4_pnfs_v3_ds_connect_unload(void)
{
        if (get_v3_ds_connect) {
                symbol_put(nfs3_set_ds_client);
                get_v3_ds_connect = NULL;
        }
}

static int _nfs4_pnfs_v3_ds_connect(struct nfs_server *mds_srv,
                                 struct nfs4_pnfs_ds *ds,
                                 unsigned int timeo,
                                 unsigned int retrans)
{
        struct nfs_client *clp = ERR_PTR(-EIO);
        struct nfs4_pnfs_ds_addr *da;
        int status = 0;

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

        if (!load_v3_ds_connect())
                return -EPROTONOSUPPORT;

        list_for_each_entry(da, &ds->ds_addrs, da_node) {
                dprintk("%s: DS %s: trying address %s\n",
                        __func__, ds->ds_remotestr, da->da_remotestr);

                if (!IS_ERR(clp)) {
                        struct xprt_create xprt_args = {
                                .ident = da->da_transport,
                                .net = clp->cl_net,
                                .dstaddr = (struct sockaddr *)&da->da_addr,
                                .addrlen = da->da_addrlen,
                                .servername = clp->cl_hostname,
                        };

                        if (da->da_transport != clp->cl_proto)
                                continue;
                        if (da->da_addr.ss_family != clp->cl_addr.ss_family)
                                continue;
                        /* Add this address as an alias */
                        rpc_clnt_add_xprt(clp->cl_rpcclient, &xprt_args,
                                        rpc_clnt_test_and_add_xprt, NULL);
                        continue;
                }
                clp = get_v3_ds_connect(mds_srv,
                                (struct sockaddr *)&da->da_addr,
                                da->da_addrlen, da->da_transport,
                                timeo, retrans);
                if (IS_ERR(clp))
                        continue;
                clp->cl_rpcclient->cl_softerr = 0;
                clp->cl_rpcclient->cl_softrtry = 0;
        }

        if (IS_ERR(clp)) {
                status = PTR_ERR(clp);
                goto out;
        }

        smp_wmb();
        WRITE_ONCE(ds->ds_clp, clp);
        dprintk("%s [new] addr: %s\n", __func__, ds->ds_remotestr);
out:
        return status;
}

static int _nfs4_pnfs_v4_ds_connect(struct nfs_server *mds_srv,
                                 struct nfs4_pnfs_ds *ds,
                                 unsigned int timeo,
                                 unsigned int retrans,
                                 u32 minor_version)
{
        struct nfs_client *clp = ERR_PTR(-EIO);
        struct nfs4_pnfs_ds_addr *da;
        int status = 0;

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

        list_for_each_entry(da, &ds->ds_addrs, da_node) {
                dprintk("%s: DS %s: trying address %s\n",
                        __func__, ds->ds_remotestr, da->da_remotestr);

                if (!IS_ERR(clp) && clp->cl_mvops->session_trunk) {
                        struct xprt_create xprt_args = {
                                .ident = da->da_transport,
                                .net = clp->cl_net,
                                .dstaddr = (struct sockaddr *)&da->da_addr,
                                .addrlen = da->da_addrlen,
                                .servername = clp->cl_hostname,
                        };
                        struct nfs4_add_xprt_data xprtdata = {
                                .clp = clp,
                        };
                        struct rpc_add_xprt_test rpcdata = {
                                .add_xprt_test = clp->cl_mvops->session_trunk,
                                .data = &xprtdata,
                        };

                        if (da->da_transport != clp->cl_proto)
                                continue;
                        if (da->da_addr.ss_family != clp->cl_addr.ss_family)
                                continue;
                        /**
                        * Test this address for session trunking and
                        * add as an alias
                        */
                        xprtdata.cred = nfs4_get_clid_cred(clp),
                        rpc_clnt_add_xprt(clp->cl_rpcclient, &xprt_args,
                                          rpc_clnt_setup_test_and_add_xprt,
                                          &rpcdata);
                        if (xprtdata.cred)
                                put_cred(xprtdata.cred);
                } else {
                        clp = nfs4_set_ds_client(mds_srv,
                                                (struct sockaddr *)&da->da_addr,
                                                da->da_addrlen,
                                                da->da_transport, timeo,
                                                retrans, minor_version);
                        if (IS_ERR(clp))
                                continue;

                        status = nfs4_init_ds_session(clp,
                                        mds_srv->nfs_client->cl_lease_time);
                        if (status) {
                                nfs_put_client(clp);
                                clp = ERR_PTR(-EIO);
                                continue;
                        }

                }
        }

        if (IS_ERR(clp)) {
                status = PTR_ERR(clp);
                goto out;
        }

        smp_wmb();
        WRITE_ONCE(ds->ds_clp, clp);
        dprintk("%s [new] addr: %s\n", __func__, ds->ds_remotestr);
out:
        return status;
}

/*
 * Create an rpc connection to the nfs4_pnfs_ds data server.
 * Currently only supports IPv4 and IPv6 addresses.
 * If connection fails, make devid unavailable and return a -errno.
 */
int nfs4_pnfs_ds_connect(struct nfs_server *mds_srv, struct nfs4_pnfs_ds *ds,
                          struct nfs4_deviceid_node *devid, unsigned int timeo,
                          unsigned int retrans, u32 version, u32 minor_version)
{
        int err;

        do {
                err = nfs4_wait_ds_connect(ds);
                if (err || ds->ds_clp)
                        goto out;
                if (nfs4_test_deviceid_unavailable(devid))
                        return -ENODEV;
        } while (test_and_set_bit(NFS4DS_CONNECTING, &ds->ds_state) != 0);

        if (ds->ds_clp)
                goto connect_done;

        switch (version) {
        case 3:
                err = _nfs4_pnfs_v3_ds_connect(mds_srv, ds, timeo, retrans);
                break;
        case 4:
                err = _nfs4_pnfs_v4_ds_connect(mds_srv, ds, timeo, retrans,
                                               minor_version);
                break;
        default:
                dprintk("%s: unsupported DS version %d\n", __func__, version);
                err = -EPROTONOSUPPORT;
        }

connect_done:
        nfs4_clear_ds_conn_bit(ds);
out:
        /*
         * At this point the ds->ds_clp should be ready, but it might have
         * hit an error.
         */
        if (!err) {
                if (!ds->ds_clp || !nfs_client_init_is_complete(ds->ds_clp)) {
                        WARN_ON_ONCE(ds->ds_clp ||
                                !nfs4_test_deviceid_unavailable(devid));
                        return -EINVAL;
                }
                err = nfs_client_init_status(ds->ds_clp);
        }

        return err;
}
EXPORT_SYMBOL_GPL(nfs4_pnfs_ds_connect);

/*
 * Currently only supports ipv4, ipv6 and one multi-path address.
 */
struct nfs4_pnfs_ds_addr *
nfs4_decode_mp_ds_addr(struct net *net, struct xdr_stream *xdr, gfp_t gfp_flags)
{
        struct nfs4_pnfs_ds_addr *da = NULL;
        char *buf, *portstr;
        __be16 port;
        ssize_t nlen, rlen;
        int tmp[2];
        char *netid;
        size_t len;
        char *startsep = "";
        char *endsep = "";


        /* r_netid */
        nlen = xdr_stream_decode_string_dup(xdr, &netid, XDR_MAX_NETOBJ,
                                            gfp_flags);
        if (unlikely(nlen < 0))
                goto out_err;

        /* r_addr: ip/ip6addr with port in dec octets - see RFC 5665 */
        /* port is ".ABC.DEF", 8 chars max */
        rlen = xdr_stream_decode_string_dup(xdr, &buf, INET6_ADDRSTRLEN +
                                            IPV6_SCOPE_ID_LEN + 8, gfp_flags);
        if (unlikely(rlen < 0))
                goto out_free_netid;

        /* replace port '.' with '-' */
        portstr = strrchr(buf, '.');
        if (!portstr) {
                dprintk("%s: Failed finding expected dot in port\n",
                        __func__);
                goto out_free_buf;
        }
        *portstr = '-';

        /* find '.' between address and port */
        portstr = strrchr(buf, '.');
        if (!portstr) {
                dprintk("%s: Failed finding expected dot between address and "
                        "port\n", __func__);
                goto out_free_buf;
        }
        *portstr = '\0';

        da = nfs4_pnfs_ds_addr_alloc(gfp_flags);
        if (unlikely(!da))
                goto out_free_buf;

        if (!rpc_pton(net, buf, portstr-buf, (struct sockaddr *)&da->da_addr,
                      sizeof(da->da_addr))) {
                dprintk("%s: error parsing address %s\n", __func__, buf);
                goto out_free_da;
        }

        portstr++;
        sscanf(portstr, "%d-%d", &tmp[0], &tmp[1]);
        port = htons((tmp[0] << 8) | (tmp[1]));

        switch (da->da_addr.ss_family) {
        case AF_INET:
                ((struct sockaddr_in *)&da->da_addr)->sin_port = port;
                da->da_addrlen = sizeof(struct sockaddr_in);
                break;

        case AF_INET6:
                ((struct sockaddr_in6 *)&da->da_addr)->sin6_port = port;
                da->da_addrlen = sizeof(struct sockaddr_in6);
                startsep = "[";
                endsep = "]";
                break;

        default:
                dprintk("%s: unsupported address family: %u\n",
                        __func__, da->da_addr.ss_family);
                goto out_free_da;
        }

        da->da_transport = xprt_find_transport_ident(netid);
        if (da->da_transport < 0) {
                dprintk("%s: ERROR: unknown r_netid \"%s\"\n",
                        __func__, netid);
                goto out_free_da;
        }

        da->da_netid = netid;

        /* save human readable address */
        len = strlen(startsep) + strlen(buf) + strlen(endsep) + 7;
        da->da_remotestr = kzalloc(len, gfp_flags);

        /* NULL is ok, only used for dprintk */
        if (da->da_remotestr)
                snprintf(da->da_remotestr, len, "%s%s%s:%u", startsep,
                         buf, endsep, ntohs(port));

        dprintk("%s: Parsed DS addr %s\n", __func__, da->da_remotestr);
        kfree(buf);
        return da;

out_free_da:
        kfree(da);
out_free_buf:
        dprintk("%s: Error parsing DS addr: %s\n", __func__, buf);
        kfree(buf);
out_free_netid:
        kfree(netid);
out_err:
        return NULL;
}
EXPORT_SYMBOL_GPL(nfs4_decode_mp_ds_addr);

void
pnfs_layout_mark_request_commit(struct nfs_page *req,
                                struct pnfs_layout_segment *lseg,
                                struct nfs_commit_info *cinfo,
                                u32 ds_commit_idx)
{
        struct list_head *list;
        struct pnfs_commit_array *array;
        struct pnfs_commit_bucket *bucket;

        mutex_lock(&NFS_I(cinfo->inode)->commit_mutex);
        array = pnfs_lookup_commit_array(cinfo->ds, lseg);
        if (!array || !pnfs_is_valid_lseg(lseg))
                goto out_resched;
        bucket = &array->buckets[ds_commit_idx];
        list = &bucket->written;
        /* Non-empty buckets hold a reference on the lseg.  That ref
         * is normally transferred to the COMMIT call and released
         * there.  It could also be released if the last req is pulled
         * off due to a rewrite, in which case it will be done in
         * pnfs_common_clear_request_commit
         */
        if (!bucket->lseg)
                bucket->lseg = pnfs_get_lseg(lseg);
        set_bit(PG_COMMIT_TO_DS, &req->wb_flags);
        cinfo->ds->nwritten++;

        nfs_request_add_commit_list_locked(req, list, cinfo);
        mutex_unlock(&NFS_I(cinfo->inode)->commit_mutex);
        nfs_mark_page_unstable(req->wb_page, cinfo);
        return;
out_resched:
        mutex_unlock(&NFS_I(cinfo->inode)->commit_mutex);
        cinfo->completion_ops->resched_write(cinfo, req);
}
EXPORT_SYMBOL_GPL(pnfs_layout_mark_request_commit);

int
pnfs_nfs_generic_sync(struct inode *inode, bool datasync)
{
        int ret;

        if (!pnfs_layoutcommit_outstanding(inode))
                return 0;
        ret = nfs_commit_inode(inode, FLUSH_SYNC);
        if (ret < 0)
                return ret;
        if (datasync)
                return 0;
        return pnfs_layoutcommit_inode(inode, true);
}
EXPORT_SYMBOL_GPL(pnfs_nfs_generic_sync);