// SPDX-License-Identifier: GPL-2.0

#include <linux/ceph/ceph_debug.h>

#include <linux/module.h>
#include <linux/err.h>
#include <linux/highmem.h>
#include <linux/mm.h>
#include <linux/pagemap.h>
#include <linux/slab.h>
#include <linux/uaccess.h>
#ifdef CONFIG_BLOCK
#include <linux/bio.h>
#endif

#include <linux/ceph/ceph_features.h>
#include <linux/ceph/libceph.h>
#include <linux/ceph/osd_client.h>
#include <linux/ceph/messenger.h>
#include <linux/ceph/decode.h>
#include <linux/ceph/auth.h>
#include <linux/ceph/pagelist.h>
#include <linux/ceph/striper.h>

#define OSD_OPREPLY_FRONT_LEN   512

static struct kmem_cache        *ceph_osd_request_cache;

static const struct ceph_connection_operations osd_con_ops;

/*
 * Implement client access to distributed object storage cluster.
 *
 * All data objects are stored within a cluster/cloud of OSDs, or
 * "object storage devices."  (Note that Ceph OSDs have _nothing_ to
 * do with the T10 OSD extensions to SCSI.)  Ceph OSDs are simply
 * remote daemons serving up and coordinating consistent and safe
 * access to storage.
 *
 * Cluster membership and the mapping of data objects onto storage devices
 * are described by the osd map.
 *
 * We keep track of pending OSD requests (read, write), resubmit
 * requests to different OSDs when the cluster topology/data layout
 * change, or retry the affected requests when the communications
 * channel with an OSD is reset.
 */

static void link_request(struct ceph_osd *osd, struct ceph_osd_request *req);
static void unlink_request(struct ceph_osd *osd, struct ceph_osd_request *req);
static void link_linger(struct ceph_osd *osd,
                        struct ceph_osd_linger_request *lreq);
static void unlink_linger(struct ceph_osd *osd,
                          struct ceph_osd_linger_request *lreq);
static void clear_backoffs(struct ceph_osd *osd);

#if 1
static inline bool rwsem_is_wrlocked(struct rw_semaphore *sem)
{
        bool wrlocked = true;

        if (unlikely(down_read_trylock(sem))) {
                wrlocked = false;
                up_read(sem);
        }

        return wrlocked;
}
static inline void verify_osdc_locked(struct ceph_osd_client *osdc)
{
        WARN_ON(!rwsem_is_locked(&osdc->lock));
}
static inline void verify_osdc_wrlocked(struct ceph_osd_client *osdc)
{
        WARN_ON(!rwsem_is_wrlocked(&osdc->lock));
}
static inline void verify_osd_locked(struct ceph_osd *osd)
{
        struct ceph_osd_client *osdc = osd->o_osdc;

        WARN_ON(!(mutex_is_locked(&osd->lock) &&
                  rwsem_is_locked(&osdc->lock)) &&
                !rwsem_is_wrlocked(&osdc->lock));
}
static inline void verify_lreq_locked(struct ceph_osd_linger_request *lreq)
{
        WARN_ON(!mutex_is_locked(&lreq->lock));
}
#else
static inline void verify_osdc_locked(struct ceph_osd_client *osdc) { }
static inline void verify_osdc_wrlocked(struct ceph_osd_client *osdc) { }
static inline void verify_osd_locked(struct ceph_osd *osd) { }
static inline void verify_lreq_locked(struct ceph_osd_linger_request *lreq) { }
#endif

/*
 * calculate the mapping of a file extent onto an object, and fill out the
 * request accordingly.  shorten extent as necessary if it crosses an
 * object boundary.
 *
 * fill osd op in request message.
 */
static int calc_layout(struct ceph_file_layout *layout, u64 off, u64 *plen,
                        u64 *objnum, u64 *objoff, u64 *objlen)
{
        u64 orig_len = *plen;
        u32 xlen;

        /* object extent? */
        ceph_calc_file_object_mapping(layout, off, orig_len, objnum,
                                          objoff, &xlen);
        *objlen = xlen;
        if (*objlen < orig_len) {
                *plen = *objlen;
                dout(" skipping last %llu, final file extent %llu~%llu\n",
                     orig_len - *plen, off, *plen);
        }

        dout("calc_layout objnum=%llx %llu~%llu\n", *objnum, *objoff, *objlen);
        return 0;
}

static void ceph_osd_data_init(struct ceph_osd_data *osd_data)
{
        memset(osd_data, 0, sizeof (*osd_data));
        osd_data->type = CEPH_OSD_DATA_TYPE_NONE;
}

/*
 * Consumes @pages if @own_pages is true.
 */
static void ceph_osd_data_pages_init(struct ceph_osd_data *osd_data,
                        struct page **pages, u64 length, u32 alignment,
                        bool pages_from_pool, bool own_pages)
{
        osd_data->type = CEPH_OSD_DATA_TYPE_PAGES;
        osd_data->pages = pages;
        osd_data->length = length;
        osd_data->alignment = alignment;
        osd_data->pages_from_pool = pages_from_pool;
        osd_data->own_pages = own_pages;
}

/*
 * Consumes a ref on @pagelist.
 */
static void ceph_osd_data_pagelist_init(struct ceph_osd_data *osd_data,
                        struct ceph_pagelist *pagelist)
{
        osd_data->type = CEPH_OSD_DATA_TYPE_PAGELIST;
        osd_data->pagelist = pagelist;
}

#ifdef CONFIG_BLOCK
static void ceph_osd_data_bio_init(struct ceph_osd_data *osd_data,
                                   struct ceph_bio_iter *bio_pos,
                                   u32 bio_length)
{
        osd_data->type = CEPH_OSD_DATA_TYPE_BIO;
        osd_data->bio_pos = *bio_pos;
        osd_data->bio_length = bio_length;
}
#endif /* CONFIG_BLOCK */

static void ceph_osd_data_bvecs_init(struct ceph_osd_data *osd_data,
                                     struct ceph_bvec_iter *bvec_pos,
                                     u32 num_bvecs)
{
        osd_data->type = CEPH_OSD_DATA_TYPE_BVECS;
        osd_data->bvec_pos = *bvec_pos;
        osd_data->num_bvecs = num_bvecs;
}

static struct ceph_osd_data *
osd_req_op_raw_data_in(struct ceph_osd_request *osd_req, unsigned int which)
{
        BUG_ON(which >= osd_req->r_num_ops);

        return &osd_req->r_ops[which].raw_data_in;
}

struct ceph_osd_data *
osd_req_op_extent_osd_data(struct ceph_osd_request *osd_req,
                        unsigned int which)
{
        return osd_req_op_data(osd_req, which, extent, osd_data);
}
EXPORT_SYMBOL(osd_req_op_extent_osd_data);

void osd_req_op_raw_data_in_pages(struct ceph_osd_request *osd_req,
                        unsigned int which, struct page **pages,
                        u64 length, u32 alignment,
                        bool pages_from_pool, bool own_pages)
{
        struct ceph_osd_data *osd_data;

        osd_data = osd_req_op_raw_data_in(osd_req, which);
        ceph_osd_data_pages_init(osd_data, pages, length, alignment,
                                pages_from_pool, own_pages);
}
EXPORT_SYMBOL(osd_req_op_raw_data_in_pages);

void osd_req_op_extent_osd_data_pages(struct ceph_osd_request *osd_req,
                        unsigned int which, struct page **pages,
                        u64 length, u32 alignment,
                        bool pages_from_pool, bool own_pages)
{
        struct ceph_osd_data *osd_data;

        osd_data = osd_req_op_data(osd_req, which, extent, osd_data);
        ceph_osd_data_pages_init(osd_data, pages, length, alignment,
                                pages_from_pool, own_pages);
}
EXPORT_SYMBOL(osd_req_op_extent_osd_data_pages);

void osd_req_op_extent_osd_data_pagelist(struct ceph_osd_request *osd_req,
                        unsigned int which, struct ceph_pagelist *pagelist)
{
        struct ceph_osd_data *osd_data;

        osd_data = osd_req_op_data(osd_req, which, extent, osd_data);
        ceph_osd_data_pagelist_init(osd_data, pagelist);
}
EXPORT_SYMBOL(osd_req_op_extent_osd_data_pagelist);

#ifdef CONFIG_BLOCK
void osd_req_op_extent_osd_data_bio(struct ceph_osd_request *osd_req,
                                    unsigned int which,
                                    struct ceph_bio_iter *bio_pos,
                                    u32 bio_length)
{
        struct ceph_osd_data *osd_data;

        osd_data = osd_req_op_data(osd_req, which, extent, osd_data);
        ceph_osd_data_bio_init(osd_data, bio_pos, bio_length);
}
EXPORT_SYMBOL(osd_req_op_extent_osd_data_bio);
#endif /* CONFIG_BLOCK */

void osd_req_op_extent_osd_data_bvecs(struct ceph_osd_request *osd_req,
                                      unsigned int which,
                                      struct bio_vec *bvecs, u32 num_bvecs,
                                      u32 bytes)
{
        struct ceph_osd_data *osd_data;
        struct ceph_bvec_iter it = {
                .bvecs = bvecs,
                .iter = { .bi_size = bytes },
        };

        osd_data = osd_req_op_data(osd_req, which, extent, osd_data);
        ceph_osd_data_bvecs_init(osd_data, &it, num_bvecs);
}
EXPORT_SYMBOL(osd_req_op_extent_osd_data_bvecs);

void osd_req_op_extent_osd_data_bvec_pos(struct ceph_osd_request *osd_req,
                                         unsigned int which,
                                         struct ceph_bvec_iter *bvec_pos)
{
        struct ceph_osd_data *osd_data;

        osd_data = osd_req_op_data(osd_req, which, extent, osd_data);
        ceph_osd_data_bvecs_init(osd_data, bvec_pos, 0);
}
EXPORT_SYMBOL(osd_req_op_extent_osd_data_bvec_pos);

static void osd_req_op_cls_request_info_pagelist(
                        struct ceph_osd_request *osd_req,
                        unsigned int which, struct ceph_pagelist *pagelist)
{
        struct ceph_osd_data *osd_data;

        osd_data = osd_req_op_data(osd_req, which, cls, request_info);
        ceph_osd_data_pagelist_init(osd_data, pagelist);
}

void osd_req_op_cls_request_data_pagelist(
                        struct ceph_osd_request *osd_req,
                        unsigned int which, struct ceph_pagelist *pagelist)
{
        struct ceph_osd_data *osd_data;

        osd_data = osd_req_op_data(osd_req, which, cls, request_data);
        ceph_osd_data_pagelist_init(osd_data, pagelist);
        osd_req->r_ops[which].cls.indata_len += pagelist->length;
        osd_req->r_ops[which].indata_len += pagelist->length;
}
EXPORT_SYMBOL(osd_req_op_cls_request_data_pagelist);

void osd_req_op_cls_request_data_pages(struct ceph_osd_request *osd_req,
                        unsigned int which, struct page **pages, u64 length,
                        u32 alignment, bool pages_from_pool, bool own_pages)
{
        struct ceph_osd_data *osd_data;

        osd_data = osd_req_op_data(osd_req, which, cls, request_data);
        ceph_osd_data_pages_init(osd_data, pages, length, alignment,
                                pages_from_pool, own_pages);
        osd_req->r_ops[which].cls.indata_len += length;
        osd_req->r_ops[which].indata_len += length;
}
EXPORT_SYMBOL(osd_req_op_cls_request_data_pages);

void osd_req_op_cls_request_data_bvecs(struct ceph_osd_request *osd_req,
                                       unsigned int which,
                                       struct bio_vec *bvecs, u32 num_bvecs,
                                       u32 bytes)
{
        struct ceph_osd_data *osd_data;
        struct ceph_bvec_iter it = {
                .bvecs = bvecs,
                .iter = { .bi_size = bytes },
        };

        osd_data = osd_req_op_data(osd_req, which, cls, request_data);
        ceph_osd_data_bvecs_init(osd_data, &it, num_bvecs);
        osd_req->r_ops[which].cls.indata_len += bytes;
        osd_req->r_ops[which].indata_len += bytes;
}
EXPORT_SYMBOL(osd_req_op_cls_request_data_bvecs);

void osd_req_op_cls_response_data_pages(struct ceph_osd_request *osd_req,
                        unsigned int which, struct page **pages, u64 length,
                        u32 alignment, bool pages_from_pool, bool own_pages)
{
        struct ceph_osd_data *osd_data;

        osd_data = osd_req_op_data(osd_req, which, cls, response_data);
        ceph_osd_data_pages_init(osd_data, pages, length, alignment,
                                pages_from_pool, own_pages);
}
EXPORT_SYMBOL(osd_req_op_cls_response_data_pages);

static u64 ceph_osd_data_length(struct ceph_osd_data *osd_data)
{
        switch (osd_data->type) {
        case CEPH_OSD_DATA_TYPE_NONE:
                return 0;
        case CEPH_OSD_DATA_TYPE_PAGES:
                return osd_data->length;
        case CEPH_OSD_DATA_TYPE_PAGELIST:
                return (u64)osd_data->pagelist->length;
#ifdef CONFIG_BLOCK
        case CEPH_OSD_DATA_TYPE_BIO:
                return (u64)osd_data->bio_length;
#endif /* CONFIG_BLOCK */
        case CEPH_OSD_DATA_TYPE_BVECS:
                return osd_data->bvec_pos.iter.bi_size;
        default:
                WARN(true, "unrecognized data type %d\n", (int)osd_data->type);
                return 0;
        }
}

static void ceph_osd_data_release(struct ceph_osd_data *osd_data)
{
        if (osd_data->type == CEPH_OSD_DATA_TYPE_PAGES && osd_data->own_pages) {
                int num_pages;

                num_pages = calc_pages_for((u64)osd_data->alignment,
                                                (u64)osd_data->length);
                ceph_release_page_vector(osd_data->pages, num_pages);
        } else if (osd_data->type == CEPH_OSD_DATA_TYPE_PAGELIST) {
                ceph_pagelist_release(osd_data->pagelist);
        }
        ceph_osd_data_init(osd_data);
}

static void osd_req_op_data_release(struct ceph_osd_request *osd_req,
                        unsigned int which)
{
        struct ceph_osd_req_op *op;

        BUG_ON(which >= osd_req->r_num_ops);
        op = &osd_req->r_ops[which];

        switch (op->op) {
        case CEPH_OSD_OP_READ:
        case CEPH_OSD_OP_WRITE:
        case CEPH_OSD_OP_WRITEFULL:
                ceph_osd_data_release(&op->extent.osd_data);
                break;
        case CEPH_OSD_OP_CALL:
                ceph_osd_data_release(&op->cls.request_info);
                ceph_osd_data_release(&op->cls.request_data);
                ceph_osd_data_release(&op->cls.response_data);
                break;
        case CEPH_OSD_OP_SETXATTR:
        case CEPH_OSD_OP_CMPXATTR:
                ceph_osd_data_release(&op->xattr.osd_data);
                break;
        case CEPH_OSD_OP_STAT:
                ceph_osd_data_release(&op->raw_data_in);
                break;
        case CEPH_OSD_OP_NOTIFY_ACK:
                ceph_osd_data_release(&op->notify_ack.request_data);
                break;
        case CEPH_OSD_OP_NOTIFY:
                ceph_osd_data_release(&op->notify.request_data);
                ceph_osd_data_release(&op->notify.response_data);
                break;
        case CEPH_OSD_OP_LIST_WATCHERS:
                ceph_osd_data_release(&op->list_watchers.response_data);
                break;
        case CEPH_OSD_OP_COPY_FROM2:
                ceph_osd_data_release(&op->copy_from.osd_data);
                break;
        default:
                break;
        }
}

/*
 * Assumes @t is zero-initialized.
 */
static void target_init(struct ceph_osd_request_target *t)
{
        ceph_oid_init(&t->base_oid);
        ceph_oloc_init(&t->base_oloc);
        ceph_oid_init(&t->target_oid);
        ceph_oloc_init(&t->target_oloc);

        ceph_osds_init(&t->acting);
        ceph_osds_init(&t->up);
        t->size = -1;
        t->min_size = -1;

        t->osd = CEPH_HOMELESS_OSD;
}

static void target_copy(struct ceph_osd_request_target *dest,
                        const struct ceph_osd_request_target *src)
{
        ceph_oid_copy(&dest->base_oid, &src->base_oid);
        ceph_oloc_copy(&dest->base_oloc, &src->base_oloc);
        ceph_oid_copy(&dest->target_oid, &src->target_oid);
        ceph_oloc_copy(&dest->target_oloc, &src->target_oloc);

        dest->pgid = src->pgid; /* struct */
        dest->spgid = src->spgid; /* struct */
        dest->pg_num = src->pg_num;
        dest->pg_num_mask = src->pg_num_mask;
        ceph_osds_copy(&dest->acting, &src->acting);
        ceph_osds_copy(&dest->up, &src->up);
        dest->size = src->size;
        dest->min_size = src->min_size;
        dest->sort_bitwise = src->sort_bitwise;
        dest->recovery_deletes = src->recovery_deletes;

        dest->flags = src->flags;
        dest->used_replica = src->used_replica;
        dest->paused = src->paused;

        dest->epoch = src->epoch;
        dest->last_force_resend = src->last_force_resend;

        dest->osd = src->osd;
}

static void target_destroy(struct ceph_osd_request_target *t)
{
        ceph_oid_destroy(&t->base_oid);
        ceph_oloc_destroy(&t->base_oloc);
        ceph_oid_destroy(&t->target_oid);
        ceph_oloc_destroy(&t->target_oloc);
}

/*
 * requests
 */
static void request_release_checks(struct ceph_osd_request *req)
{
        WARN_ON(!RB_EMPTY_NODE(&req->r_node));
        WARN_ON(!RB_EMPTY_NODE(&req->r_mc_node));
        WARN_ON(!list_empty(&req->r_private_item));
        WARN_ON(req->r_osd);
}

static void ceph_osdc_release_request(struct kref *kref)
{
        struct ceph_osd_request *req = container_of(kref,
                                            struct ceph_osd_request, r_kref);
        unsigned int which;

        dout("%s %p (r_request %p r_reply %p)\n", __func__, req,
             req->r_request, req->r_reply);
        request_release_checks(req);

        if (req->r_request)
                ceph_msg_put(req->r_request);
        if (req->r_reply)
                ceph_msg_put(req->r_reply);

        for (which = 0; which < req->r_num_ops; which++)
                osd_req_op_data_release(req, which);

        target_destroy(&req->r_t);
        ceph_put_snap_context(req->r_snapc);

        if (req->r_mempool)
                mempool_free(req, req->r_osdc->req_mempool);
        else if (req->r_num_ops <= CEPH_OSD_SLAB_OPS)
                kmem_cache_free(ceph_osd_request_cache, req);
        else
                kfree(req);
}

void ceph_osdc_get_request(struct ceph_osd_request *req)
{
        dout("%s %p (was %d)\n", __func__, req,
             kref_read(&req->r_kref));
        kref_get(&req->r_kref);
}
EXPORT_SYMBOL(ceph_osdc_get_request);

void ceph_osdc_put_request(struct ceph_osd_request *req)
{
        if (req) {
                dout("%s %p (was %d)\n", __func__, req,
                     kref_read(&req->r_kref));
                kref_put(&req->r_kref, ceph_osdc_release_request);
        }
}
EXPORT_SYMBOL(ceph_osdc_put_request);

static void request_init(struct ceph_osd_request *req)
{
        /* req only, each op is zeroed in osd_req_op_init() */
        memset(req, 0, sizeof(*req));

        kref_init(&req->r_kref);
        init_completion(&req->r_completion);
        RB_CLEAR_NODE(&req->r_node);
        RB_CLEAR_NODE(&req->r_mc_node);
        INIT_LIST_HEAD(&req->r_private_item);

        target_init(&req->r_t);
}

/*
 * This is ugly, but it allows us to reuse linger registration and ping
 * requests, keeping the structure of the code around send_linger{_ping}()
 * reasonable.  Setting up a min_nr=2 mempool for each linger request
 * and dealing with copying ops (this blasts req only, watch op remains
 * intact) isn't any better.
 */
static void request_reinit(struct ceph_osd_request *req)
{
        struct ceph_osd_client *osdc = req->r_osdc;
        bool mempool = req->r_mempool;
        unsigned int num_ops = req->r_num_ops;
        u64 snapid = req->r_snapid;
        struct ceph_snap_context *snapc = req->r_snapc;
        bool linger = req->r_linger;
        struct ceph_msg *request_msg = req->r_request;
        struct ceph_msg *reply_msg = req->r_reply;

        dout("%s req %p\n", __func__, req);
        WARN_ON(kref_read(&req->r_kref) != 1);
        request_release_checks(req);

        WARN_ON(kref_read(&request_msg->kref) != 1);
        WARN_ON(kref_read(&reply_msg->kref) != 1);
        target_destroy(&req->r_t);

        request_init(req);
        req->r_osdc = osdc;
        req->r_mempool = mempool;
        req->r_num_ops = num_ops;
        req->r_snapid = snapid;
        req->r_snapc = snapc;
        req->r_linger = linger;
        req->r_request = request_msg;
        req->r_reply = reply_msg;
}

struct ceph_osd_request *ceph_osdc_alloc_request(struct ceph_osd_client *osdc,
                                               struct ceph_snap_context *snapc,
                                               unsigned int num_ops,
                                               bool use_mempool,
                                               gfp_t gfp_flags)
{
        struct ceph_osd_request *req;

        if (use_mempool) {
                BUG_ON(num_ops > CEPH_OSD_SLAB_OPS);
                req = mempool_alloc(osdc->req_mempool, gfp_flags);
        } else if (num_ops <= CEPH_OSD_SLAB_OPS) {
                req = kmem_cache_alloc(ceph_osd_request_cache, gfp_flags);
        } else {
                BUG_ON(num_ops > CEPH_OSD_MAX_OPS);
                req = kmalloc(struct_size(req, r_ops, num_ops), gfp_flags);
        }
        if (unlikely(!req))
                return NULL;

        request_init(req);
        req->r_osdc = osdc;
        req->r_mempool = use_mempool;
        req->r_num_ops = num_ops;
        req->r_snapid = CEPH_NOSNAP;
        req->r_snapc = ceph_get_snap_context(snapc);

        dout("%s req %p\n", __func__, req);
        return req;
}
EXPORT_SYMBOL(ceph_osdc_alloc_request);

static int ceph_oloc_encoding_size(const struct ceph_object_locator *oloc)
{
        return 8 + 4 + 4 + 4 + (oloc->pool_ns ? oloc->pool_ns->len : 0);
}

static int __ceph_osdc_alloc_messages(struct ceph_osd_request *req, gfp_t gfp,
                                      int num_request_data_items,
                                      int num_reply_data_items)
{
        struct ceph_osd_client *osdc = req->r_osdc;
        struct ceph_msg *msg;
        int msg_size;

        WARN_ON(req->r_request || req->r_reply);
        WARN_ON(ceph_oid_empty(&req->r_base_oid));
        WARN_ON(ceph_oloc_empty(&req->r_base_oloc));

        /* create request message */
        msg_size = CEPH_ENCODING_START_BLK_LEN +
                        CEPH_PGID_ENCODING_LEN + 1; /* spgid */
        msg_size += 4 + 4 + 4; /* hash, osdmap_epoch, flags */
        msg_size += CEPH_ENCODING_START_BLK_LEN +
                        sizeof(struct ceph_osd_reqid); /* reqid */
        msg_size += sizeof(struct ceph_blkin_trace_info); /* trace */
        msg_size += 4 + sizeof(struct ceph_timespec); /* client_inc, mtime */
        msg_size += CEPH_ENCODING_START_BLK_LEN +
                        ceph_oloc_encoding_size(&req->r_base_oloc); /* oloc */
        msg_size += 4 + req->r_base_oid.name_len; /* oid */
        msg_size += 2 + req->r_num_ops * sizeof(struct ceph_osd_op);
        msg_size += 8; /* snapid */
        msg_size += 8; /* snap_seq */
        msg_size += 4 + 8 * (req->r_snapc ? req->r_snapc->num_snaps : 0);
        msg_size += 4 + 8; /* retry_attempt, features */

        if (req->r_mempool)
                msg = ceph_msgpool_get(&osdc->msgpool_op, msg_size,
                                       num_request_data_items);
        else
                msg = ceph_msg_new2(CEPH_MSG_OSD_OP, msg_size,
                                    num_request_data_items, gfp, true);
        if (!msg)
                return -ENOMEM;

        memset(msg->front.iov_base, 0, msg->front.iov_len);
        req->r_request = msg;

        /* create reply message */
        msg_size = OSD_OPREPLY_FRONT_LEN;
        msg_size += req->r_base_oid.name_len;
        msg_size += req->r_num_ops * sizeof(struct ceph_osd_op);

        if (req->r_mempool)
                msg = ceph_msgpool_get(&osdc->msgpool_op_reply, msg_size,
                                       num_reply_data_items);
        else
                msg = ceph_msg_new2(CEPH_MSG_OSD_OPREPLY, msg_size,
                                    num_reply_data_items, gfp, true);
        if (!msg)
                return -ENOMEM;

        req->r_reply = msg;

        return 0;
}

static bool osd_req_opcode_valid(u16 opcode)
{
        switch (opcode) {
#define GENERATE_CASE(op, opcode, str)  case CEPH_OSD_OP_##op: return true;
__CEPH_FORALL_OSD_OPS(GENERATE_CASE)
#undef GENERATE_CASE
        default:
                return false;
        }
}

static void get_num_data_items(struct ceph_osd_request *req,
                               int *num_request_data_items,
                               int *num_reply_data_items)
{
        struct ceph_osd_req_op *op;

        *num_request_data_items = 0;
        *num_reply_data_items = 0;

        for (op = req->r_ops; op != &req->r_ops[req->r_num_ops]; op++) {
                switch (op->op) {
                /* request */
                case CEPH_OSD_OP_WRITE:
                case CEPH_OSD_OP_WRITEFULL:
                case CEPH_OSD_OP_SETXATTR:
                case CEPH_OSD_OP_CMPXATTR:
                case CEPH_OSD_OP_NOTIFY_ACK:
                case CEPH_OSD_OP_COPY_FROM2:
                        *num_request_data_items += 1;
                        break;

                /* reply */
                case CEPH_OSD_OP_STAT:
                case CEPH_OSD_OP_READ:
                case CEPH_OSD_OP_LIST_WATCHERS:
                        *num_reply_data_items += 1;
                        break;

                /* both */
                case CEPH_OSD_OP_NOTIFY:
                        *num_request_data_items += 1;
                        *num_reply_data_items += 1;
                        break;
                case CEPH_OSD_OP_CALL:
                        *num_request_data_items += 2;
                        *num_reply_data_items += 1;
                        break;

                default:
                        WARN_ON(!osd_req_opcode_valid(op->op));
                        break;
                }
        }
}

/*
 * oid, oloc and OSD op opcode(s) must be filled in before this function
 * is called.
 */
int ceph_osdc_alloc_messages(struct ceph_osd_request *req, gfp_t gfp)
{
        int num_request_data_items, num_reply_data_items;

        get_num_data_items(req, &num_request_data_items, &num_reply_data_items);
        return __ceph_osdc_alloc_messages(req, gfp, num_request_data_items,
                                          num_reply_data_items);
}
EXPORT_SYMBOL(ceph_osdc_alloc_messages);

/*
 * This is an osd op init function for opcodes that have no data or
 * other information associated with them.  It also serves as a
 * common init routine for all the other init functions, below.
 */
struct ceph_osd_req_op *
osd_req_op_init(struct ceph_osd_request *osd_req, unsigned int which,
                 u16 opcode, u32 flags)
{
        struct ceph_osd_req_op *op;

        BUG_ON(which >= osd_req->r_num_ops);
        BUG_ON(!osd_req_opcode_valid(opcode));

        op = &osd_req->r_ops[which];
        memset(op, 0, sizeof (*op));
        op->op = opcode;
        op->flags = flags;

        return op;
}
EXPORT_SYMBOL(osd_req_op_init);

void osd_req_op_extent_init(struct ceph_osd_request *osd_req,
                                unsigned int which, u16 opcode,
                                u64 offset, u64 length,
                                u64 truncate_size, u32 truncate_seq)
{
        struct ceph_osd_req_op *op = osd_req_op_init(osd_req, which,
                                                     opcode, 0);
        size_t payload_len = 0;

        BUG_ON(opcode != CEPH_OSD_OP_READ && opcode != CEPH_OSD_OP_WRITE &&
               opcode != CEPH_OSD_OP_WRITEFULL && opcode != CEPH_OSD_OP_ZERO &&
               opcode != CEPH_OSD_OP_TRUNCATE);

        op->extent.offset = offset;
        op->extent.length = length;
        op->extent.truncate_size = truncate_size;
        op->extent.truncate_seq = truncate_seq;
        if (opcode == CEPH_OSD_OP_WRITE || opcode == CEPH_OSD_OP_WRITEFULL)
                payload_len += length;

        op->indata_len = payload_len;
}
EXPORT_SYMBOL(osd_req_op_extent_init);

void osd_req_op_extent_update(struct ceph_osd_request *osd_req,
                                unsigned int which, u64 length)
{
        struct ceph_osd_req_op *op;
        u64 previous;

        BUG_ON(which >= osd_req->r_num_ops);
        op = &osd_req->r_ops[which];
        previous = op->extent.length;

        if (length == previous)
                return;         /* Nothing to do */
        BUG_ON(length > previous);

        op->extent.length = length;
        if (op->op == CEPH_OSD_OP_WRITE || op->op == CEPH_OSD_OP_WRITEFULL)
                op->indata_len -= previous - length;
}
EXPORT_SYMBOL(osd_req_op_extent_update);

void osd_req_op_extent_dup_last(struct ceph_osd_request *osd_req,
                                unsigned int which, u64 offset_inc)
{
        struct ceph_osd_req_op *op, *prev_op;

        BUG_ON(which + 1 >= osd_req->r_num_ops);

        prev_op = &osd_req->r_ops[which];
        op = osd_req_op_init(osd_req, which + 1, prev_op->op, prev_op->flags);
        /* dup previous one */
        op->indata_len = prev_op->indata_len;
        op->outdata_len = prev_op->outdata_len;
        op->extent = prev_op->extent;
        /* adjust offset */
        op->extent.offset += offset_inc;
        op->extent.length -= offset_inc;

        if (op->op == CEPH_OSD_OP_WRITE || op->op == CEPH_OSD_OP_WRITEFULL)
                op->indata_len -= offset_inc;
}
EXPORT_SYMBOL(osd_req_op_extent_dup_last);

int osd_req_op_cls_init(struct ceph_osd_request *osd_req, unsigned int which,
                        const char *class, const char *method)
{
        struct ceph_osd_req_op *op;
        struct ceph_pagelist *pagelist;
        size_t payload_len = 0;
        size_t size;
        int ret;

        op = osd_req_op_init(osd_req, which, CEPH_OSD_OP_CALL, 0);

        pagelist = ceph_pagelist_alloc(GFP_NOFS);
        if (!pagelist)
                return -ENOMEM;

        op->cls.class_name = class;
        size = strlen(class);
        BUG_ON(size > (size_t) U8_MAX);
        op->cls.class_len = size;
        ret = ceph_pagelist_append(pagelist, class, size);
        if (ret)
                goto err_pagelist_free;
        payload_len += size;

        op->cls.method_name = method;
        size = strlen(method);
        BUG_ON(size > (size_t) U8_MAX);
        op->cls.method_len = size;
        ret = ceph_pagelist_append(pagelist, method, size);
        if (ret)
                goto err_pagelist_free;
        payload_len += size;

        osd_req_op_cls_request_info_pagelist(osd_req, which, pagelist);
        op->indata_len = payload_len;
        return 0;

err_pagelist_free:
        ceph_pagelist_release(pagelist);
        return ret;
}
EXPORT_SYMBOL(osd_req_op_cls_init);

int osd_req_op_xattr_init(struct ceph_osd_request *osd_req, unsigned int which,
                          u16 opcode, const char *name, const void *value,
                          size_t size, u8 cmp_op, u8 cmp_mode)
{
        struct ceph_osd_req_op *op = osd_req_op_init(osd_req, which,
                                                     opcode, 0);
        struct ceph_pagelist *pagelist;
        size_t payload_len;
        int ret;

        BUG_ON(opcode != CEPH_OSD_OP_SETXATTR && opcode != CEPH_OSD_OP_CMPXATTR);

        pagelist = ceph_pagelist_alloc(GFP_NOFS);
        if (!pagelist)
                return -ENOMEM;

        payload_len = strlen(name);
        op->xattr.name_len = payload_len;
        ret = ceph_pagelist_append(pagelist, name, payload_len);
        if (ret)
                goto err_pagelist_free;

        op->xattr.value_len = size;
        ret = ceph_pagelist_append(pagelist, value, size);
        if (ret)
                goto err_pagelist_free;
        payload_len += size;

        op->xattr.cmp_op = cmp_op;
        op->xattr.cmp_mode = cmp_mode;

        ceph_osd_data_pagelist_init(&op->xattr.osd_data, pagelist);
        op->indata_len = payload_len;
        return 0;

err_pagelist_free:
        ceph_pagelist_release(pagelist);
        return ret;
}
EXPORT_SYMBOL(osd_req_op_xattr_init);

/*
 * @watch_opcode: CEPH_OSD_WATCH_OP_*
 */
static void osd_req_op_watch_init(struct ceph_osd_request *req, int which,
                                  u64 cookie, u8 watch_opcode)
{
        struct ceph_osd_req_op *op;

        op = osd_req_op_init(req, which, CEPH_OSD_OP_WATCH, 0);
        op->watch.cookie = cookie;
        op->watch.op = watch_opcode;
        op->watch.gen = 0;
}

/*
 * @flags: CEPH_OSD_OP_ALLOC_HINT_FLAG_*
 */
void osd_req_op_alloc_hint_init(struct ceph_osd_request *osd_req,
                                unsigned int which,
                                u64 expected_object_size,
                                u64 expected_write_size,
                                u32 flags)
{
        struct ceph_osd_req_op *op;

        op = osd_req_op_init(osd_req, which, CEPH_OSD_OP_SETALLOCHINT, 0);
        op->alloc_hint.expected_object_size = expected_object_size;
        op->alloc_hint.expected_write_size = expected_write_size;
        op->alloc_hint.flags = flags;

        /*
         * CEPH_OSD_OP_SETALLOCHINT op is advisory and therefore deemed
         * not worth a feature bit.  Set FAILOK per-op flag to make
         * sure older osds don't trip over an unsupported opcode.
         */
        op->flags |= CEPH_OSD_OP_FLAG_FAILOK;
}
EXPORT_SYMBOL(osd_req_op_alloc_hint_init);

static void ceph_osdc_msg_data_add(struct ceph_msg *msg,
                                struct ceph_osd_data *osd_data)
{
        u64 length = ceph_osd_data_length(osd_data);

        if (osd_data->type == CEPH_OSD_DATA_TYPE_PAGES) {
                BUG_ON(length > (u64) SIZE_MAX);
                if (length)
                        ceph_msg_data_add_pages(msg, osd_data->pages,
                                        length, osd_data->alignment, false);
        } else if (osd_data->type == CEPH_OSD_DATA_TYPE_PAGELIST) {
                BUG_ON(!length);
                ceph_msg_data_add_pagelist(msg, osd_data->pagelist);
#ifdef CONFIG_BLOCK
        } else if (osd_data->type == CEPH_OSD_DATA_TYPE_BIO) {
                ceph_msg_data_add_bio(msg, &osd_data->bio_pos, length);
#endif
        } else if (osd_data->type == CEPH_OSD_DATA_TYPE_BVECS) {
                ceph_msg_data_add_bvecs(msg, &osd_data->bvec_pos);
        } else {
                BUG_ON(osd_data->type != CEPH_OSD_DATA_TYPE_NONE);
        }
}

static u32 osd_req_encode_op(struct ceph_osd_op *dst,
                             const struct ceph_osd_req_op *src)
{
        switch (src->op) {
        case CEPH_OSD_OP_STAT:
                break;
        case CEPH_OSD_OP_READ:
        case CEPH_OSD_OP_WRITE:
        case CEPH_OSD_OP_WRITEFULL:
        case CEPH_OSD_OP_ZERO:
        case CEPH_OSD_OP_TRUNCATE:
                dst->extent.offset = cpu_to_le64(src->extent.offset);
                dst->extent.length = cpu_to_le64(src->extent.length);
                dst->extent.truncate_size =
                        cpu_to_le64(src->extent.truncate_size);
                dst->extent.truncate_seq =
                        cpu_to_le32(src->extent.truncate_seq);
                break;
        case CEPH_OSD_OP_CALL:
                dst->cls.class_len = src->cls.class_len;
                dst->cls.method_len = src->cls.method_len;

                dst->cls.indata_len = cpu_to_le32(src->cls.indata_len);
                break;
        case CEPH_OSD_OP_WATCH:
                dst->watch.cookie = cpu_to_le64(src->watch.cookie);
                dst->watch.ver = cpu_to_le64(0);
                dst->watch.op = src->watch.op;
                dst->watch.gen = cpu_to_le32(src->watch.gen);
                break;
        case CEPH_OSD_OP_NOTIFY_ACK:
                break;
        case CEPH_OSD_OP_NOTIFY:
                dst->notify.cookie = cpu_to_le64(src->notify.cookie);
                break;
        case CEPH_OSD_OP_LIST_WATCHERS:
                break;
        case CEPH_OSD_OP_SETALLOCHINT:
                dst->alloc_hint.expected_object_size =
                    cpu_to_le64(src->alloc_hint.expected_object_size);
                dst->alloc_hint.expected_write_size =
                    cpu_to_le64(src->alloc_hint.expected_write_size);
                dst->alloc_hint.flags = cpu_to_le32(src->alloc_hint.flags);
                break;
        case CEPH_OSD_OP_SETXATTR:
        case CEPH_OSD_OP_CMPXATTR:
                dst->xattr.name_len = cpu_to_le32(src->xattr.name_len);
                dst->xattr.value_len = cpu_to_le32(src->xattr.value_len);
                dst->xattr.cmp_op = src->xattr.cmp_op;
                dst->xattr.cmp_mode = src->xattr.cmp_mode;
                break;
        case CEPH_OSD_OP_CREATE:
        case CEPH_OSD_OP_DELETE:
                break;
        case CEPH_OSD_OP_COPY_FROM2:
                dst->copy_from.snapid = cpu_to_le64(src->copy_from.snapid);
                dst->copy_from.src_version =
                        cpu_to_le64(src->copy_from.src_version);
                dst->copy_from.flags = src->copy_from.flags;
                dst->copy_from.src_fadvise_flags =
                        cpu_to_le32(src->copy_from.src_fadvise_flags);
                break;
        default:
                pr_err("unsupported osd opcode %s\n",
                        ceph_osd_op_name(src->op));
                WARN_ON(1);

                return 0;
        }

        dst->op = cpu_to_le16(src->op);
        dst->flags = cpu_to_le32(src->flags);
        dst->payload_len = cpu_to_le32(src->indata_len);

        return src->indata_len;
}

/*
 * build new request AND message, calculate layout, and adjust file
 * extent as needed.
 *
 * if the file was recently truncated, we include information about its
 * old and new size so that the object can be updated appropriately.  (we
 * avoid synchronously deleting truncated objects because it's slow.)
 */
struct ceph_osd_request *ceph_osdc_new_request(struct ceph_osd_client *osdc,
                                               struct ceph_file_layout *layout,
                                               struct ceph_vino vino,
                                               u64 off, u64 *plen,
                                               unsigned int which, int num_ops,
                                               int opcode, int flags,
                                               struct ceph_snap_context *snapc,
                                               u32 truncate_seq,
                                               u64 truncate_size,
                                               bool use_mempool)
{
        struct ceph_osd_request *req;
        u64 objnum = 0;
        u64 objoff = 0;
        u64 objlen = 0;
        int r;

        BUG_ON(opcode != CEPH_OSD_OP_READ && opcode != CEPH_OSD_OP_WRITE &&
               opcode != CEPH_OSD_OP_ZERO && opcode != CEPH_OSD_OP_TRUNCATE &&
               opcode != CEPH_OSD_OP_CREATE && opcode != CEPH_OSD_OP_DELETE);

        req = ceph_osdc_alloc_request(osdc, snapc, num_ops, use_mempool,
                                        GFP_NOFS);
        if (!req) {
                r = -ENOMEM;
                goto fail;
        }

        /* calculate max write size */
        r = calc_layout(layout, off, plen, &objnum, &objoff, &objlen);
        if (r)
                goto fail;

        if (opcode == CEPH_OSD_OP_CREATE || opcode == CEPH_OSD_OP_DELETE) {
                osd_req_op_init(req, which, opcode, 0);
        } else {
                u32 object_size = layout->object_size;
                u32 object_base = off - objoff;
                if (!(truncate_seq == 1 && truncate_size == -1ULL)) {
                        if (truncate_size <= object_base) {
                                truncate_size = 0;
                        } else {
                                truncate_size -= object_base;
                                if (truncate_size > object_size)
                                        truncate_size = object_size;
                        }
                }
                osd_req_op_extent_init(req, which, opcode, objoff, objlen,
                                       truncate_size, truncate_seq);
        }

        req->r_base_oloc.pool = layout->pool_id;
        req->r_base_oloc.pool_ns = ceph_try_get_string(layout->pool_ns);
        ceph_oid_printf(&req->r_base_oid, "%llx.%08llx", vino.ino, objnum);
        req->r_flags = flags | osdc->client->options->read_from_replica;

        req->r_snapid = vino.snap;
        if (flags & CEPH_OSD_FLAG_WRITE)
                req->r_data_offset = off;

        if (num_ops > 1)
                /*
                 * This is a special case for ceph_writepages_start(), but it
                 * also covers ceph_uninline_data().  If more multi-op request
                 * use cases emerge, we will need a separate helper.
                 */
                r = __ceph_osdc_alloc_messages(req, GFP_NOFS, num_ops, 0);
        else
                r = ceph_osdc_alloc_messages(req, GFP_NOFS);
        if (r)
                goto fail;

        return req;

fail:
        ceph_osdc_put_request(req);
        return ERR_PTR(r);
}
EXPORT_SYMBOL(ceph_osdc_new_request);

/*
 * We keep osd requests in an rbtree, sorted by ->r_tid.
 */
DEFINE_RB_FUNCS(request, struct ceph_osd_request, r_tid, r_node)
DEFINE_RB_FUNCS(request_mc, struct ceph_osd_request, r_tid, r_mc_node)

/*
 * Call @fn on each OSD request as long as @fn returns 0.
 */
static void for_each_request(struct ceph_osd_client *osdc,
                        int (*fn)(struct ceph_osd_request *req, void *arg),
                        void *arg)
{
        struct rb_node *n, *p;

        for (n = rb_first(&osdc->osds); n; n = rb_next(n)) {
                struct ceph_osd *osd = rb_entry(n, struct ceph_osd, o_node);

                for (p = rb_first(&osd->o_requests); p; ) {
                        struct ceph_osd_request *req =
                            rb_entry(p, struct ceph_osd_request, r_node);

                        p = rb_next(p);
                        if (fn(req, arg))
                                return;
                }
        }

        for (p = rb_first(&osdc->homeless_osd.o_requests); p; ) {
                struct ceph_osd_request *req =
                    rb_entry(p, struct ceph_osd_request, r_node);

                p = rb_next(p);
                if (fn(req, arg))
                        return;
        }
}

static bool osd_homeless(struct ceph_osd *osd)
{
        return osd->o_osd == CEPH_HOMELESS_OSD;
}

static bool osd_registered(struct ceph_osd *osd)
{
        verify_osdc_locked(osd->o_osdc);

        return !RB_EMPTY_NODE(&osd->o_node);
}

/*
 * Assumes @osd is zero-initialized.
 */
static void osd_init(struct ceph_osd *osd)
{
        refcount_set(&osd->o_ref, 1);
        RB_CLEAR_NODE(&osd->o_node);
        osd->o_requests = RB_ROOT;
        osd->o_linger_requests = RB_ROOT;
        osd->o_backoff_mappings = RB_ROOT;
        osd->o_backoffs_by_id = RB_ROOT;
        INIT_LIST_HEAD(&osd->o_osd_lru);
        INIT_LIST_HEAD(&osd->o_keepalive_item);
        osd->o_incarnation = 1;
        mutex_init(&osd->lock);
}

static void osd_cleanup(struct ceph_osd *osd)
{
        WARN_ON(!RB_EMPTY_NODE(&osd->o_node));
        WARN_ON(!RB_EMPTY_ROOT(&osd->o_requests));
        WARN_ON(!RB_EMPTY_ROOT(&osd->o_linger_requests));
        WARN_ON(!RB_EMPTY_ROOT(&osd->o_backoff_mappings));
        WARN_ON(!RB_EMPTY_ROOT(&osd->o_backoffs_by_id));
        WARN_ON(!list_empty(&osd->o_osd_lru));
        WARN_ON(!list_empty(&osd->o_keepalive_item));

        if (osd->o_auth.authorizer) {
                WARN_ON(osd_homeless(osd));
                ceph_auth_destroy_authorizer(osd->o_auth.authorizer);
        }
}

/*
 * Track open sessions with osds.
 */
static struct ceph_osd *create_osd(struct ceph_osd_client *osdc, int onum)
{
        struct ceph_osd *osd;

        WARN_ON(onum == CEPH_HOMELESS_OSD);

        osd = kzalloc(sizeof(*osd), GFP_NOIO | __GFP_NOFAIL);
        osd_init(osd);
        osd->o_osdc = osdc;
        osd->o_osd = onum;

        ceph_con_init(&osd->o_con, osd, &osd_con_ops, &osdc->client->msgr);

        return osd;
}

static struct ceph_osd *get_osd(struct ceph_osd *osd)
{
        if (refcount_inc_not_zero(&osd->o_ref)) {
                dout("get_osd %p %d -> %d\n", osd, refcount_read(&osd->o_ref)-1,
                     refcount_read(&osd->o_ref));
                return osd;
        } else {
                dout("get_osd %p FAIL\n", osd);
                return NULL;
        }
}

static void put_osd(struct ceph_osd *osd)
{
        dout("put_osd %p %d -> %d\n", osd, refcount_read(&osd->o_ref),
             refcount_read(&osd->o_ref) - 1);
        if (refcount_dec_and_test(&osd->o_ref)) {
                osd_cleanup(osd);
                kfree(osd);
        }
}

DEFINE_RB_FUNCS(osd, struct ceph_osd, o_osd, o_node)

static void __move_osd_to_lru(struct ceph_osd *osd)
{
        struct ceph_osd_client *osdc = osd->o_osdc;

        dout("%s osd %p osd%d\n", __func__, osd, osd->o_osd);
        BUG_ON(!list_empty(&osd->o_osd_lru));

        spin_lock(&osdc->osd_lru_lock);
        list_add_tail(&osd->o_osd_lru, &osdc->osd_lru);
        spin_unlock(&osdc->osd_lru_lock);

        osd->lru_ttl = jiffies + osdc->client->options->osd_idle_ttl;
}

static void maybe_move_osd_to_lru(struct ceph_osd *osd)
{
        if (RB_EMPTY_ROOT(&osd->o_requests) &&
            RB_EMPTY_ROOT(&osd->o_linger_requests))
                __move_osd_to_lru(osd);
}

static void __remove_osd_from_lru(struct ceph_osd *osd)
{
        struct ceph_osd_client *osdc = osd->o_osdc;

        dout("%s osd %p osd%d\n", __func__, osd, osd->o_osd);

        spin_lock(&osdc->osd_lru_lock);
        if (!list_empty(&osd->o_osd_lru))
                list_del_init(&osd->o_osd_lru);
        spin_unlock(&osdc->osd_lru_lock);
}

/*
 * Close the connection and assign any leftover requests to the
 * homeless session.
 */
static void close_osd(struct ceph_osd *osd)
{
        struct ceph_osd_client *osdc = osd->o_osdc;
        struct rb_node *n;

        verify_osdc_wrlocked(osdc);
        dout("%s osd %p osd%d\n", __func__, osd, osd->o_osd);

        ceph_con_close(&osd->o_con);

        for (n = rb_first(&osd->o_requests); n; ) {
                struct ceph_osd_request *req =
                    rb_entry(n, struct ceph_osd_request, r_node);

                n = rb_next(n); /* unlink_request() */

                dout(" reassigning req %p tid %llu\n", req, req->r_tid);
                unlink_request(osd, req);
                link_request(&osdc->homeless_osd, req);
        }
        for (n = rb_first(&osd->o_linger_requests); n; ) {
                struct ceph_osd_linger_request *lreq =
                    rb_entry(n, struct ceph_osd_linger_request, node);

                n = rb_next(n); /* unlink_linger() */

                dout(" reassigning lreq %p linger_id %llu\n", lreq,
                     lreq->linger_id);
                unlink_linger(osd, lreq);
                link_linger(&osdc->homeless_osd, lreq);
        }
        clear_backoffs(osd);

        __remove_osd_from_lru(osd);
        erase_osd(&osdc->osds, osd);
        put_osd(osd);
}

/*
 * reset osd connect
 */
static int reopen_osd(struct ceph_osd *osd)
{
        struct ceph_entity_addr *peer_addr;

        dout("%s osd %p osd%d\n", __func__, osd, osd->o_osd);

        if (RB_EMPTY_ROOT(&osd->o_requests) &&
            RB_EMPTY_ROOT(&osd->o_linger_requests)) {
                close_osd(osd);
                return -ENODEV;
        }

        peer_addr = &osd->o_osdc->osdmap->osd_addr[osd->o_osd];
        if (!memcmp(peer_addr, &osd->o_con.peer_addr, sizeof (*peer_addr)) &&
                        !ceph_con_opened(&osd->o_con)) {
                struct rb_node *n;

                dout("osd addr hasn't changed and connection never opened, "
                     "letting msgr retry\n");
                /* touch each r_stamp for handle_timeout()'s benfit */
                for (n = rb_first(&osd->o_requests); n; n = rb_next(n)) {
                        struct ceph_osd_request *req =
                            rb_entry(n, struct ceph_osd_request, r_node);
                        req->r_stamp = jiffies;
                }

                return -EAGAIN;
        }

        ceph_con_close(&osd->o_con);
        ceph_con_open(&osd->o_con, CEPH_ENTITY_TYPE_OSD, osd->o_osd, peer_addr);
        osd->o_incarnation++;

        return 0;
}

static struct ceph_osd *lookup_create_osd(struct ceph_osd_client *osdc, int o,
                                          bool wrlocked)
{
        struct ceph_osd *osd;

        if (wrlocked)
                verify_osdc_wrlocked(osdc);
        else
                verify_osdc_locked(osdc);

        if (o != CEPH_HOMELESS_OSD)
                osd = lookup_osd(&osdc->osds, o);
        else
                osd = &osdc->homeless_osd;
        if (!osd) {
                if (!wrlocked)
                        return ERR_PTR(-EAGAIN);

                osd = create_osd(osdc, o);
                insert_osd(&osdc->osds, osd);
                ceph_con_open(&osd->o_con, CEPH_ENTITY_TYPE_OSD, osd->o_osd,
                              &osdc->osdmap->osd_addr[osd->o_osd]);
        }

        dout("%s osdc %p osd%d -> osd %p\n", __func__, osdc, o, osd);
        return osd;
}

/*
 * Create request <-> OSD session relation.
 *
 * @req has to be assigned a tid, @osd may be homeless.
 */
static void link_request(struct ceph_osd *osd, struct ceph_osd_request *req)
{
        verify_osd_locked(osd);
        WARN_ON(!req->r_tid || req->r_osd);
        dout("%s osd %p osd%d req %p tid %llu\n", __func__, osd, osd->o_osd,
             req, req->r_tid);

        if (!osd_homeless(osd))
                __remove_osd_from_lru(osd);
        else
                atomic_inc(&osd->o_osdc->num_homeless);

        get_osd(osd);
        insert_request(&osd->o_requests, req);
        req->r_osd = osd;
}

static void unlink_request(struct ceph_osd *osd, struct ceph_osd_request *req)
{
        verify_osd_locked(osd);
        WARN_ON(req->r_osd != osd);
        dout("%s osd %p osd%d req %p tid %llu\n", __func__, osd, osd->o_osd,
             req, req->r_tid);

        req->r_osd = NULL;
        erase_request(&osd->o_requests, req);
        put_osd(osd);

        if (!osd_homeless(osd))
                maybe_move_osd_to_lru(osd);
        else
                atomic_dec(&osd->o_osdc->num_homeless);
}

static bool __pool_full(struct ceph_pg_pool_info *pi)
{
        return pi->flags & CEPH_POOL_FLAG_FULL;
}

static bool have_pool_full(struct ceph_osd_client *osdc)
{
        struct rb_node *n;

        for (n = rb_first(&osdc->osdmap->pg_pools); n; n = rb_next(n)) {
                struct ceph_pg_pool_info *pi =
                    rb_entry(n, struct ceph_pg_pool_info, node);

                if (__pool_full(pi))
                        return true;
        }

        return false;
}

static bool pool_full(struct ceph_osd_client *osdc, s64 pool_id)
{
        struct ceph_pg_pool_info *pi;

        pi = ceph_pg_pool_by_id(osdc->osdmap, pool_id);
        if (!pi)
                return false;

        return __pool_full(pi);
}

/*
 * Returns whether a request should be blocked from being sent
 * based on the current osdmap and osd_client settings.
 */
static bool target_should_be_paused(struct ceph_osd_client *osdc,
                                    const struct ceph_osd_request_target *t,
                                    struct ceph_pg_pool_info *pi)
{
        bool pauserd = ceph_osdmap_flag(osdc, CEPH_OSDMAP_PAUSERD);
        bool pausewr = ceph_osdmap_flag(osdc, CEPH_OSDMAP_PAUSEWR) ||
                       ceph_osdmap_flag(osdc, CEPH_OSDMAP_FULL) ||
                       __pool_full(pi);

        WARN_ON(pi->id != t->target_oloc.pool);
        return ((t->flags & CEPH_OSD_FLAG_READ) && pauserd) ||
               ((t->flags & CEPH_OSD_FLAG_WRITE) && pausewr) ||
               (osdc->osdmap->epoch < osdc->epoch_barrier);
}

static int pick_random_replica(const struct ceph_osds *acting)
{
        int i = prandom_u32() % acting->size;

        dout("%s picked osd%d, primary osd%d\n", __func__,
             acting->osds[i], acting->primary);
        return i;
}

/*
 * Picks the closest replica based on client's location given by
 * crush_location option.  Prefers the primary if the locality is
 * the same.
 */
static int pick_closest_replica(struct ceph_osd_client *osdc,
                                const struct ceph_osds *acting)
{
        struct ceph_options *opt = osdc->client->options;
        int best_i, best_locality;
        int i = 0, locality;

        do {
                locality = ceph_get_crush_locality(osdc->osdmap,
                                                   acting->osds[i],
                                                   &opt->crush_locs);
                if (i == 0 ||
                    (locality >= 0 && best_locality < 0) ||
                    (locality >= 0 && best_locality >= 0 &&
                     locality < best_locality)) {
                        best_i = i;
                        best_locality = locality;
                }
        } while (++i < acting->size);

        dout("%s picked osd%d with locality %d, primary osd%d\n", __func__,
             acting->osds[best_i], best_locality, acting->primary);
        return best_i;
}

enum calc_target_result {
        CALC_TARGET_NO_ACTION = 0,
        CALC_TARGET_NEED_RESEND,
        CALC_TARGET_POOL_DNE,
};

static enum calc_target_result calc_target(struct ceph_osd_client *osdc,
                                           struct ceph_osd_request_target *t,
                                           bool any_change)
{
        struct ceph_pg_pool_info *pi;
        struct ceph_pg pgid, last_pgid;
        struct ceph_osds up, acting;
        bool is_read = t->flags & CEPH_OSD_FLAG_READ;
        bool is_write = t->flags & CEPH_OSD_FLAG_WRITE;
        bool force_resend = false;
        bool unpaused = false;
        bool legacy_change = false;
        bool split = false;
        bool sort_bitwise = ceph_osdmap_flag(osdc, CEPH_OSDMAP_SORTBITWISE);
        bool recovery_deletes = ceph_osdmap_flag(osdc,
                                                 CEPH_OSDMAP_RECOVERY_DELETES);
        enum calc_target_result ct_res;

        t->epoch = osdc->osdmap->epoch;
        pi = ceph_pg_pool_by_id(osdc->osdmap, t->base_oloc.pool);
        if (!pi) {
                t->osd = CEPH_HOMELESS_OSD;
                ct_res = CALC_TARGET_POOL_DNE;
                goto out;
        }

        if (osdc->osdmap->epoch == pi->last_force_request_resend) {
                if (t->last_force_resend < pi->last_force_request_resend) {
                        t->last_force_resend = pi->last_force_request_resend;
                        force_resend = true;
                } else if (t->last_force_resend == 0) {
                        force_resend = true;
                }
        }

        /* apply tiering */
        ceph_oid_copy(&t->target_oid, &t->base_oid);
        ceph_oloc_copy(&t->target_oloc, &t->base_oloc);
        if ((t->flags & CEPH_OSD_FLAG_IGNORE_OVERLAY) == 0) {
                if (is_read && pi->read_tier >= 0)
                        t->target_oloc.pool = pi->read_tier;
                if (is_write && pi->write_tier >= 0)
                        t->target_oloc.pool = pi->write_tier;

                pi = ceph_pg_pool_by_id(osdc->osdmap, t->target_oloc.pool);
                if (!pi) {
                        t->osd = CEPH_HOMELESS_OSD;
                        ct_res = CALC_TARGET_POOL_DNE;
                        goto out;
                }
        }

        __ceph_object_locator_to_pg(pi, &t->target_oid, &t->target_oloc, &pgid);
        last_pgid.pool = pgid.pool;
        last_pgid.seed = ceph_stable_mod(pgid.seed, t->pg_num, t->pg_num_mask);

        ceph_pg_to_up_acting_osds(osdc->osdmap, pi, &pgid, &up, &acting);
        if (any_change &&
            ceph_is_new_interval(&t->acting,
                                 &acting,
                                 &t->up,
                                 &up,
                                 t->size,
                                 pi->size,
                                 t->min_size,
                                 pi->min_size,
                                 t->pg_num,
                                 pi->pg_num,
                                 t->sort_bitwise,
                                 sort_bitwise,
                                 t->recovery_deletes,
                                 recovery_deletes,
                                 &last_pgid))
                force_resend = true;

        if (t->paused && !target_should_be_paused(osdc, t, pi)) {
                t->paused = false;
                unpaused = true;
        }
        legacy_change = ceph_pg_compare(&t->pgid, &pgid) ||
                        ceph_osds_changed(&t->acting, &acting,
                                          t->used_replica || any_change);
        if (t->pg_num)
                split = ceph_pg_is_split(&last_pgid, t->pg_num, pi->pg_num);

        if (legacy_change || force_resend || split) {
                t->pgid = pgid; /* struct */
                ceph_pg_to_primary_shard(osdc->osdmap, pi, &pgid, &t->spgid);
                ceph_osds_copy(&t->acting, &acting);
                ceph_osds_copy(&t->up, &up);
                t->size = pi->size;
                t->min_size = pi->min_size;
                t->pg_num = pi->pg_num;
                t->pg_num_mask = pi->pg_num_mask;
                t->sort_bitwise = sort_bitwise;
                t->recovery_deletes = recovery_deletes;

                if ((t->flags & (CEPH_OSD_FLAG_BALANCE_READS |
                                 CEPH_OSD_FLAG_LOCALIZE_READS)) &&
                    !is_write && pi->type == CEPH_POOL_TYPE_REP &&
                    acting.size > 1) {
                        int pos;

                        WARN_ON(!is_read || acting.osds[0] != acting.primary);
                        if (t->flags & CEPH_OSD_FLAG_BALANCE_READS) {
                                pos = pick_random_replica(&acting);
                        } else {
                                pos = pick_closest_replica(osdc, &acting);
                        }
                        t->osd = acting.osds[pos];
                        t->used_replica = pos > 0;
                } else {
                        t->osd = acting.primary;
                        t->used_replica = false;
                }
        }

        if (unpaused || legacy_change || force_resend || split)
                ct_res = CALC_TARGET_NEED_RESEND;
        else
                ct_res = CALC_TARGET_NO_ACTION;

out:
        dout("%s t %p -> %d%d%d%d ct_res %d osd%d\n", __func__, t, unpaused,
             legacy_change, force_resend, split, ct_res, t->osd);
        return ct_res;
}

static struct ceph_spg_mapping *alloc_spg_mapping(void)
{
        struct ceph_spg_mapping *spg;

        spg = kmalloc(sizeof(*spg), GFP_NOIO);
        if (!spg)
                return NULL;

        RB_CLEAR_NODE(&spg->node);
        spg->backoffs = RB_ROOT;
        return spg;
}

static void free_spg_mapping(struct ceph_spg_mapping *spg)
{
        WARN_ON(!RB_EMPTY_NODE(&spg->node));
        WARN_ON(!RB_EMPTY_ROOT(&spg->backoffs));

        kfree(spg);
}

/*
 * rbtree of ceph_spg_mapping for handling map<spg_t, ...>, similar to
 * ceph_pg_mapping.  Used to track OSD backoffs -- a backoff [range] is
 * defined only within a specific spgid; it does not pass anything to
 * children on split, or to another primary.
 */
DEFINE_RB_FUNCS2(spg_mapping, struct ceph_spg_mapping, spgid, ceph_spg_compare,
                 RB_BYPTR, const struct ceph_spg *, node)

static u64 hoid_get_bitwise_key(const struct ceph_hobject_id *hoid)
{
        return hoid->is_max ? 0x100000000ull : hoid->hash_reverse_bits;
}

static void hoid_get_effective_key(const struct ceph_hobject_id *hoid,
                                   void **pkey, size_t *pkey_len)
{
        if (hoid->key_len) {
                *pkey = hoid->key;
                *pkey_len = hoid->key_len;
        } else {
                *pkey = hoid->oid;
                *pkey_len = hoid->oid_len;
        }
}

static int compare_names(const void *name1, size_t name1_len,
                         const void *name2, size_t name2_len)
{
        int ret;

        ret = memcmp(name1, name2, min(name1_len, name2_len));
        if (!ret) {
                if (name1_len < name2_len)
                        ret = -1;
                else if (name1_len > name2_len)
                        ret = 1;
        }
        return ret;
}

static int hoid_compare(const struct ceph_hobject_id *lhs,
                        const struct ceph_hobject_id *rhs)
{
        void *effective_key1, *effective_key2;
        size_t effective_key1_len, effective_key2_len;
        int ret;

        if (lhs->is_max < rhs->is_max)
                return -1;
        if (lhs->is_max > rhs->is_max)
                return 1;

        if (lhs->pool < rhs->pool)
                return -1;
        if (lhs->pool > rhs->pool)
                return 1;

        if (hoid_get_bitwise_key(lhs) < hoid_get_bitwise_key(rhs))
                return -1;
        if (hoid_get_bitwise_key(lhs) > hoid_get_bitwise_key(rhs))
                return 1;

        ret = compare_names(lhs->nspace, lhs->nspace_len,
                            rhs->nspace, rhs->nspace_len);
        if (ret)
                return ret;

        hoid_get_effective_key(lhs, &effective_key1, &effective_key1_len);
        hoid_get_effective_key(rhs, &effective_key2, &effective_key2_len);
        ret = compare_names(effective_key1, effective_key1_len,
                            effective_key2, effective_key2_len);
        if (ret)
                return ret;

        ret = compare_names(lhs->oid, lhs->oid_len, rhs->oid, rhs->oid_len);
        if (ret)
                return ret;

        if (lhs->snapid < rhs->snapid)
                return -1;
        if (lhs->snapid > rhs->snapid)
                return 1;

        return 0;
}

/*
 * For decoding ->begin and ->end of MOSDBackoff only -- no MIN/MAX
 * compat stuff here.
 *
 * Assumes @hoid is zero-initialized.
 */
static int decode_hoid(void **p, void *end, struct ceph_hobject_id *hoid)
{
        u8 struct_v;
        u32 struct_len;
        int ret;

        ret = ceph_start_decoding(p, end, 4, "hobject_t", &struct_v,
                                  &struct_len);
        if (ret)
                return ret;

        if (struct_v < 4) {
                pr_err("got struct_v %d < 4 of hobject_t\n", struct_v);
                goto e_inval;
        }

        hoid->key = ceph_extract_encoded_string(p, end, &hoid->key_len,
                                                GFP_NOIO);
        if (IS_ERR(hoid->key)) {
                ret = PTR_ERR(hoid->key);
                hoid->key = NULL;
                return ret;
        }

        hoid->oid = ceph_extract_encoded_string(p, end, &hoid->oid_len,
                                                GFP_NOIO);
        if (IS_ERR(hoid->oid)) {
                ret = PTR_ERR(hoid->oid);
                hoid->oid = NULL;
                return ret;
        }

        ceph_decode_64_safe(p, end, hoid->snapid, e_inval);
        ceph_decode_32_safe(p, end, hoid->hash, e_inval);
        ceph_decode_8_safe(p, end, hoid->is_max, e_inval);

        hoid->nspace = ceph_extract_encoded_string(p, end, &hoid->nspace_len,
                                                   GFP_NOIO);
        if (IS_ERR(hoid->nspace)) {
                ret = PTR_ERR(hoid->nspace);
                hoid->nspace = NULL;
                return ret;
        }

        ceph_decode_64_safe(p, end, hoid->pool, e_inval);

        ceph_hoid_build_hash_cache(hoid);
        return 0;

e_inval:
        return -EINVAL;
}

static int hoid_encoding_size(const struct ceph_hobject_id *hoid)
{
        return 8 + 4 + 1 + 8 + /* snapid, hash, is_max, pool */
               4 + hoid->key_len + 4 + hoid->oid_len + 4 + hoid->nspace_len;
}

static void encode_hoid(void **p, void *end, const struct ceph_hobject_id *hoid)
{
        ceph_start_encoding(p, 4, 3, hoid_encoding_size(hoid));
        ceph_encode_string(p, end, hoid->key, hoid->key_len);
        ceph_encode_string(p, end, hoid->oid, hoid->oid_len);
        ceph_encode_64(p, hoid->snapid);
        ceph_encode_32(p, hoid->hash);
        ceph_encode_8(p, hoid->is_max);
        ceph_encode_string(p, end, hoid->nspace, hoid->nspace_len);
        ceph_encode_64(p, hoid->pool);
}

static void free_hoid(struct ceph_hobject_id *hoid)
{
        if (hoid) {
                kfree(hoid->key);
                kfree(hoid->oid);
                kfree(hoid->nspace);
                kfree(hoid);
        }
}

static struct ceph_osd_backoff *alloc_backoff(void)
{
        struct ceph_osd_backoff *backoff;

        backoff = kzalloc(sizeof(*backoff), GFP_NOIO);
        if (!backoff)
                return NULL;

        RB_CLEAR_NODE(&backoff->spg_node);
        RB_CLEAR_NODE(&backoff->id_node);
        return backoff;
}

static void free_backoff(struct ceph_osd_backoff *backoff)
{
        WARN_ON(!RB_EMPTY_NODE(&backoff->spg_node));
        WARN_ON(!RB_EMPTY_NODE(&backoff->id_node));

        free_hoid(backoff->begin);
        free_hoid(backoff->end);
        kfree(backoff);
}

/*
 * Within a specific spgid, backoffs are managed by ->begin hoid.
 */
DEFINE_RB_INSDEL_FUNCS2(backoff, struct ceph_osd_backoff, begin, hoid_compare,
                        RB_BYVAL, spg_node);

static struct ceph_osd_backoff *lookup_containing_backoff(struct rb_root *root,
                                            const struct ceph_hobject_id *hoid)
{
        struct rb_node *n = root->rb_node;

        while (n) {
                struct ceph_osd_backoff *cur =
                    rb_entry(n, struct ceph_osd_backoff, spg_node);
                int cmp;

                cmp = hoid_compare(hoid, cur->begin);
                if (cmp < 0) {
                        n = n->rb_left;
                } else if (cmp > 0) {
                        if (hoid_compare(hoid, cur->end) < 0)
                                return cur;

                        n = n->rb_right;
                } else {
                        return cur;
                }
        }

        return NULL;
}

/*
 * Each backoff has a unique id within its OSD session.
 */
DEFINE_RB_FUNCS(backoff_by_id, struct ceph_osd_backoff, id, id_node)

static void clear_backoffs(struct ceph_osd *osd)
{
        while (!RB_EMPTY_ROOT(&osd->o_backoff_mappings)) {
                struct ceph_spg_mapping *spg =
                    rb_entry(rb_first(&osd->o_backoff_mappings),
                             struct ceph_spg_mapping, node);

                while (!RB_EMPTY_ROOT(&spg->backoffs)) {
                        struct ceph_osd_backoff *backoff =
                            rb_entry(rb_first(&spg->backoffs),
                                     struct ceph_osd_backoff, spg_node);

                        erase_backoff(&spg->backoffs, backoff);
                        erase_backoff_by_id(&osd->o_backoffs_by_id, backoff);
                        free_backoff(backoff);
                }
                erase_spg_mapping(&osd->o_backoff_mappings, spg);
                free_spg_mapping(spg);
        }
}

/*
 * Set up a temporary, non-owning view into @t.
 */
static void hoid_fill_from_target(struct ceph_hobject_id *hoid,
                                  const struct ceph_osd_request_target *t)
{
        hoid->key = NULL;
        hoid->key_len = 0;
        hoid->oid = t->target_oid.name;
        hoid->oid_len = t->target_oid.name_len;
        hoid->snapid = CEPH_NOSNAP;
        hoid->hash = t->pgid.seed;
        hoid->is_max = false;
        if (t->target_oloc.pool_ns) {
                hoid->nspace = t->target_oloc.pool_ns->str;
                hoid->nspace_len = t->target_oloc.pool_ns->len;
        } else {
                hoid->nspace = NULL;
                hoid->nspace_len = 0;
        }
        hoid->pool = t->target_oloc.pool;
        ceph_hoid_build_hash_cache(hoid);
}

static bool should_plug_request(struct ceph_osd_request *req)
{
        struct ceph_osd *osd = req->r_osd;
        struct ceph_spg_mapping *spg;
        struct ceph_osd_backoff *backoff;
        struct ceph_hobject_id hoid;

        spg = lookup_spg_mapping(&osd->o_backoff_mappings, &req->r_t.spgid);
        if (!spg)
                return false;

        hoid_fill_from_target(&hoid, &req->r_t);
        backoff = lookup_containing_backoff(&spg->backoffs, &hoid);
        if (!backoff)
                return false;

        dout("%s req %p tid %llu backoff osd%d spgid %llu.%xs%d id %llu\n",
             __func__, req, req->r_tid, osd->o_osd, backoff->spgid.pgid.pool,
             backoff->spgid.pgid.seed, backoff->spgid.shard, backoff->id);
        return true;
}

/*
 * Keep get_num_data_items() in sync with this function.
 */
static void setup_request_data(struct ceph_osd_request *req)
{

        struct ceph_msg *request_msg = req->r_request;
        struct ceph_msg *reply_msg = req->r_reply;
        struct ceph_osd_req_op *op;

        if (req->r_request->num_data_items || req->r_reply->num_data_items)
                return;

        WARN_ON(request_msg->data_length || reply_msg->data_length);
        for (op = req->r_ops; op != &req->r_ops[req->r_num_ops]; op++) {
                switch (op->op) {
                /* request */
                case CEPH_OSD_OP_WRITE:
                case CEPH_OSD_OP_WRITEFULL:
                        WARN_ON(op->indata_len != op->extent.length);
                        ceph_osdc_msg_data_add(request_msg,
                                               &op->extent.osd_data);
                        break;
                case CEPH_OSD_OP_SETXATTR:
                case CEPH_OSD_OP_CMPXATTR:
                        WARN_ON(op->indata_len != op->xattr.name_len +
                                                  op->xattr.value_len);
                        ceph_osdc_msg_data_add(request_msg,
                                               &op->xattr.osd_data);
                        break;
                case CEPH_OSD_OP_NOTIFY_ACK:
                        ceph_osdc_msg_data_add(request_msg,
                                               &op->notify_ack.request_data);
                        break;
                case CEPH_OSD_OP_COPY_FROM2:
                        ceph_osdc_msg_data_add(request_msg,
                                               &op->copy_from.osd_data);
                        break;

                /* reply */
                case CEPH_OSD_OP_STAT:
                        ceph_osdc_msg_data_add(reply_msg,
                                               &op->raw_data_in);
                        break;
                case CEPH_OSD_OP_READ:
                        ceph_osdc_msg_data_add(reply_msg,
                                               &op->extent.osd_data);
                        break;
                case CEPH_OSD_OP_LIST_WATCHERS:
                        ceph_osdc_msg_data_add(reply_msg,
                                               &op->list_watchers.response_data);
                        break;

                /* both */
                case CEPH_OSD_OP_CALL:
                        WARN_ON(op->indata_len != op->cls.class_len +
                                                  op->cls.method_len +
                                                  op->cls.indata_len);
                        ceph_osdc_msg_data_add(request_msg,
                                               &op->cls.request_info);
                        /* optional, can be NONE */
                        ceph_osdc_msg_data_add(request_msg,
                                               &op->cls.request_data);
                        /* optional, can be NONE */
                        ceph_osdc_msg_data_add(reply_msg,
                                               &op->cls.response_data);
                        break;
                case CEPH_OSD_OP_NOTIFY:
                        ceph_osdc_msg_data_add(request_msg,
                                               &op->notify.request_data);
                        ceph_osdc_msg_data_add(reply_msg,
                                               &op->notify.response_data);
                        break;
                }
        }
}

static void encode_pgid(void **p, const struct ceph_pg *pgid)
{
        ceph_encode_8(p, 1);
        ceph_encode_64(p, pgid->pool);
        ceph_encode_32(p, pgid->seed);
        ceph_encode_32(p, -1); /* preferred */
}

static void encode_spgid(void **p, const struct ceph_spg *spgid)
{
        ceph_start_encoding(p, 1, 1, CEPH_PGID_ENCODING_LEN + 1);
        encode_pgid(p, &spgid->pgid);
        ceph_encode_8(p, spgid->shard);
}

static void encode_oloc(void **p, void *end,
                        const struct ceph_object_locator *oloc)
{
        ceph_start_encoding(p, 5, 4, ceph_oloc_encoding_size(oloc));
        ceph_encode_64(p, oloc->pool);
        ceph_encode_32(p, -1); /* preferred */
        ceph_encode_32(p, 0);  /* key len */
        if (oloc->pool_ns)
                ceph_encode_string(p, end, oloc->pool_ns->str,
                                   oloc->pool_ns->len);
        else
                ceph_encode_32(p, 0);
}

static void encode_request_partial(struct ceph_osd_request *req,
                                   struct ceph_msg *msg)
{
        void *p = msg->front.iov_base;
        void *const end = p + msg->front_alloc_len;
        u32 data_len = 0;
        int i;

        if (req->r_flags & CEPH_OSD_FLAG_WRITE) {
                /* snapshots aren't writeable */
                WARN_ON(req->r_snapid != CEPH_NOSNAP);
        } else {
                WARN_ON(req->r_mtime.tv_sec || req->r_mtime.tv_nsec ||
                        req->r_data_offset || req->r_snapc);
        }

        setup_request_data(req);

        encode_spgid(&p, &req->r_t.spgid); /* actual spg */
        ceph_encode_32(&p, req->r_t.pgid.seed); /* raw hash */
        ceph_encode_32(&p, req->r_osdc->osdmap->epoch);
        ceph_encode_32(&p, req->r_flags);

        /* reqid */
        ceph_start_encoding(&p, 2, 2, sizeof(struct ceph_osd_reqid));
        memset(p, 0, sizeof(struct ceph_osd_reqid));
        p += sizeof(struct ceph_osd_reqid);

        /* trace */
        memset(p, 0, sizeof(struct ceph_blkin_trace_info));
        p += sizeof(struct ceph_blkin_trace_info);

        ceph_encode_32(&p, 0); /* client_inc, always 0 */
        ceph_encode_timespec64(p, &req->r_mtime);
        p += sizeof(struct ceph_timespec);

        encode_oloc(&p, end, &req->r_t.target_oloc);
        ceph_encode_string(&p, end, req->r_t.target_oid.name,
                           req->r_t.target_oid.name_len);

        /* ops, can imply data */
        ceph_encode_16(&p, req->r_num_ops);
        for (i = 0; i < req->r_num_ops; i++) {
                data_len += osd_req_encode_op(p, &req->r_ops[i]);
                p += sizeof(struct ceph_osd_op);
        }

        ceph_encode_64(&p, req->r_snapid); /* snapid */
        if (req->r_snapc) {
                ceph_encode_64(&p, req->r_snapc->seq);
                ceph_encode_32(&p, req->r_snapc->num_snaps);
                for (i = 0; i < req->r_snapc->num_snaps; i++)
                        ceph_encode_64(&p, req->r_snapc->snaps[i]);
        } else {
                ceph_encode_64(&p, 0); /* snap_seq */
                ceph_encode_32(&p, 0); /* snaps len */
        }

        ceph_encode_32(&p, req->r_attempts); /* retry_attempt */
        BUG_ON(p > end - 8); /* space for features */

        msg->hdr.version = cpu_to_le16(8); /* MOSDOp v8 */
        /* front_len is finalized in encode_request_finish() */
        msg->front.iov_len = p - msg->front.iov_base;
        msg->hdr.front_len = cpu_to_le32(msg->front.iov_len);
        msg->hdr.data_len = cpu_to_le32(data_len);
        /*
         * The header "data_off" is a hint to the receiver allowing it
         * to align received data into its buffers such that there's no
         * need to re-copy it before writing it to disk (direct I/O).
         */
        msg->hdr.data_off = cpu_to_le16(req->r_data_offset);

        dout("%s req %p msg %p oid %s oid_len %d\n", __func__, req, msg,
             req->r_t.target_oid.name, req->r_t.target_oid.name_len);
}

static void encode_request_finish(struct ceph_msg *msg)
{
        void *p = msg->front.iov_base;
        void *const partial_end = p + msg->front.iov_len;
        void *const end = p + msg->front_alloc_len;

        if (CEPH_HAVE_FEATURE(msg->con->peer_features, RESEND_ON_SPLIT)) {
                /* luminous OSD -- encode features and be done */
                p = partial_end;
                ceph_encode_64(&p, msg->con->peer_features);
        } else {
                struct {
                        char spgid[CEPH_ENCODING_START_BLK_LEN +
                                   CEPH_PGID_ENCODING_LEN + 1];
                        __le32 hash;
                        __le32 epoch;
                        __le32 flags;
                        char reqid[CEPH_ENCODING_START_BLK_LEN +
                                   sizeof(struct ceph_osd_reqid)];
                        char trace[sizeof(struct ceph_blkin_trace_info)];
                        __le32 client_inc;
                        struct ceph_timespec mtime;
                } __packed head;
                struct ceph_pg pgid;
                void *oloc, *oid, *tail;
                int oloc_len, oid_len, tail_len;
                int len;

                /*
                 * Pre-luminous OSD -- reencode v8 into v4 using @head
                 * as a temporary buffer.  Encode the raw PG; the rest
                 * is just a matter of moving oloc, oid and tail blobs
                 * around.
                 */
                memcpy(&head, p, sizeof(head));
                p += sizeof(head);

                oloc = p;
                p += CEPH_ENCODING_START_BLK_LEN;
                pgid.pool = ceph_decode_64(&p);
                p += 4 + 4; /* preferred, key len */
                len = ceph_decode_32(&p);
                p += len;   /* nspace */
                oloc_len = p - oloc;

                oid = p;
                len = ceph_decode_32(&p);
                p += len;
                oid_len = p - oid;

                tail = p;
                tail_len = partial_end - p;

                p = msg->front.iov_base;
                ceph_encode_copy(&p, &head.client_inc, sizeof(head.client_inc));
                ceph_encode_copy(&p, &head.epoch, sizeof(head.epoch));
                ceph_encode_copy(&p, &head.flags, sizeof(head.flags));
                ceph_encode_copy(&p, &head.mtime, sizeof(head.mtime));

                /* reassert_version */
                memset(p, 0, sizeof(struct ceph_eversion));
                p += sizeof(struct ceph_eversion);

                BUG_ON(p >= oloc);
                memmove(p, oloc, oloc_len);
                p += oloc_len;

                pgid.seed = le32_to_cpu(head.hash);
                encode_pgid(&p, &pgid); /* raw pg */

                BUG_ON(p >= oid);
                memmove(p, oid, oid_len);
                p += oid_len;

                /* tail -- ops, snapid, snapc, retry_attempt */
                BUG_ON(p >= tail);
                memmove(p, tail, tail_len);
                p += tail_len;

                msg->hdr.version = cpu_to_le16(4); /* MOSDOp v4 */
        }

        BUG_ON(p > end);
        msg->front.iov_len = p - msg->front.iov_base;
        msg->hdr.front_len = cpu_to_le32(msg->front.iov_len);

        dout("%s msg %p tid %llu %u+%u+%u v%d\n", __func__, msg,
             le64_to_cpu(msg->hdr.tid), le32_to_cpu(msg->hdr.front_len),
             le32_to_cpu(msg->hdr.middle_len), le32_to_cpu(msg->hdr.data_len),
             le16_to_cpu(msg->hdr.version));
}

/*
 * @req has to be assigned a tid and registered.
 */
static void send_request(struct ceph_osd_request *req)
{
        struct ceph_osd *osd = req->r_osd;

        verify_osd_locked(osd);
        WARN_ON(osd->o_osd != req->r_t.osd);

        /* backoff? */
        if (should_plug_request(req))
                return;

        /*
         * We may have a previously queued request message hanging
         * around.  Cancel it to avoid corrupting the msgr.
         */
        if (req->r_sent)
                ceph_msg_revoke(req->r_request);

        req->r_flags |= CEPH_OSD_FLAG_KNOWN_REDIR;
        if (req->r_attempts)
                req->r_flags |= CEPH_OSD_FLAG_RETRY;
        else
                WARN_ON(req->r_flags & CEPH_OSD_FLAG_RETRY);

        encode_request_partial(req, req->r_request);

        dout("%s req %p tid %llu to pgid %llu.%x spgid %llu.%xs%d osd%d e%u flags 0x%x attempt %d\n",
             __func__, req, req->r_tid, req->r_t.pgid.pool, req->r_t.pgid.seed,
             req->r_t.spgid.pgid.pool, req->r_t.spgid.pgid.seed,
             req->r_t.spgid.shard, osd->o_osd, req->r_t.epoch, req->r_flags,
             req->r_attempts);

        req->r_t.paused = false;
        req->r_stamp = jiffies;
        req->r_attempts++;

        req->r_sent = osd->o_incarnation;
        req->r_request->hdr.tid = cpu_to_le64(req->r_tid);
        ceph_con_send(&osd->o_con, ceph_msg_get(req->r_request));
}

static void maybe_request_map(struct ceph_osd_client *osdc)
{
        bool continuous = false;

        verify_osdc_locked(osdc);
        WARN_ON(!osdc->osdmap->epoch);

        if (ceph_osdmap_flag(osdc, CEPH_OSDMAP_FULL) ||
            ceph_osdmap_flag(osdc, CEPH_OSDMAP_PAUSERD) ||
            ceph_osdmap_flag(osdc, CEPH_OSDMAP_PAUSEWR)) {
                dout("%s osdc %p continuous\n", __func__, osdc);
                continuous = true;
        } else {
                dout("%s osdc %p onetime\n", __func__, osdc);
        }

        if (ceph_monc_want_map(&osdc->client->monc, CEPH_SUB_OSDMAP,
                               osdc->osdmap->epoch + 1, continuous))
                ceph_monc_renew_subs(&osdc->client->monc);
}

static void complete_request(struct ceph_osd_request *req, int err);
static void send_map_check(struct ceph_osd_request *req);

static void __submit_request(struct ceph_osd_request *req, bool wrlocked)
{
        struct ceph_osd_client *osdc = req->r_osdc;
        struct ceph_osd *osd;
        enum calc_target_result ct_res;
        int err = 0;
        bool need_send = false;
        bool promoted = false;

        WARN_ON(req->r_tid);
        dout("%s req %p wrlocked %d\n", __func__, req, wrlocked);

again:
        ct_res = calc_target(osdc, &req->r_t, false);
        if (ct_res == CALC_TARGET_POOL_DNE && !wrlocked)
                goto promote;

        osd = lookup_create_osd(osdc, req->r_t.osd, wrlocked);
        if (IS_ERR(osd)) {
                WARN_ON(PTR_ERR(osd) != -EAGAIN || wrlocked);
                goto promote;
        }

        if (osdc->abort_err) {
                dout("req %p abort_err %d\n", req, osdc->abort_err);
                err = osdc->abort_err;
        } else if (osdc->osdmap->epoch < osdc->epoch_barrier) {
                dout("req %p epoch %u barrier %u\n", req, osdc->osdmap->epoch,
                     osdc->epoch_barrier);
                req->r_t.paused = true;
                maybe_request_map(osdc);
        } else if ((req->r_flags & CEPH_OSD_FLAG_WRITE) &&
                   ceph_osdmap_flag(osdc, CEPH_OSDMAP_PAUSEWR)) {
                dout("req %p pausewr\n", req);
                req->r_t.paused = true;
                maybe_request_map(osdc);
        } else if ((req->r_flags & CEPH_OSD_FLAG_READ) &&
                   ceph_osdmap_flag(osdc, CEPH_OSDMAP_PAUSERD)) {
                dout("req %p pauserd\n", req);
                req->r_t.paused = true;
                maybe_request_map(osdc);
        } else if ((req->r_flags & CEPH_OSD_FLAG_WRITE) &&
                   !(req->r_flags & (CEPH_OSD_FLAG_FULL_TRY |
                                     CEPH_OSD_FLAG_FULL_FORCE)) &&
                   (ceph_osdmap_flag(osdc, CEPH_OSDMAP_FULL) ||
                    pool_full(osdc, req->r_t.base_oloc.pool))) {
                dout("req %p full/pool_full\n", req);
                if (ceph_test_opt(osdc->client, ABORT_ON_FULL)) {
                        err = -ENOSPC;
                } else {
                        pr_warn_ratelimited("FULL or reached pool quota\n");
                        req->r_t.paused = true;
                        maybe_request_map(osdc);
                }
        } else if (!osd_homeless(osd)) {
                need_send = true;
        } else {
                maybe_request_map(osdc);
        }

        mutex_lock(&osd->lock);
        /*
         * Assign the tid atomically with send_request() to protect
         * multiple writes to the same object from racing with each
         * other, resulting in out of order ops on the OSDs.
         */
        req->r_tid = atomic64_inc_return(&osdc->last_tid);
        link_request(osd, req);
        if (need_send)
                send_request(req);
        else if (err)
                complete_request(req, err);
        mutex_unlock(&osd->lock);

        if (!err && ct_res == CALC_TARGET_POOL_DNE)
                send_map_check(req);

        if (promoted)
                downgrade_write(&osdc->lock);
        return;

promote:
        up_read(&osdc->lock);
        down_write(&osdc->lock);
        wrlocked = true;
        promoted = true;
        goto again;
}

static void account_request(struct ceph_osd_request *req)
{
        WARN_ON(req->r_flags & (CEPH_OSD_FLAG_ACK | CEPH_OSD_FLAG_ONDISK));
        WARN_ON(!(req->r_flags & (CEPH_OSD_FLAG_READ | CEPH_OSD_FLAG_WRITE)));

        req->r_flags |= CEPH_OSD_FLAG_ONDISK;
        atomic_inc(&req->r_osdc->num_requests);

        req->r_start_stamp = jiffies;
        req->r_start_latency = ktime_get();
}

static void submit_request(struct ceph_osd_request *req, bool wrlocked)
{
        ceph_osdc_get_request(req);
        account_request(req);
        __submit_request(req, wrlocked);
}

static void finish_request(struct ceph_osd_request *req)
{
        struct ceph_osd_client *osdc = req->r_osdc;

        WARN_ON(lookup_request_mc(&osdc->map_checks, req->r_tid));
        dout("%s req %p tid %llu\n", __func__, req, req->r_tid);

        req->r_end_latency = ktime_get();

        if (req->r_osd)
                unlink_request(req->r_osd, req);
        atomic_dec(&osdc->num_requests);

        /*
         * If an OSD has failed or returned and a request has been sent
         * twice, it's possible to get a reply and end up here while the
         * request message is queued for delivery.  We will ignore the
         * reply, so not a big deal, but better to try and catch it.
         */
        ceph_msg_revoke(req->r_request);
        ceph_msg_revoke_incoming(req->r_reply);
}

static void __complete_request(struct ceph_osd_request *req)
{
        dout("%s req %p tid %llu cb %ps result %d\n", __func__, req,
             req->r_tid, req->r_callback, req->r_result);

        if (req->r_callback)
                req->r_callback(req);
        complete_all(&req->r_completion);
        ceph_osdc_put_request(req);
}

static void complete_request_workfn(struct work_struct *work)
{
        struct ceph_osd_request *req =
            container_of(work, struct ceph_osd_request, r_complete_work);

        __complete_request(req);
}

/*
 * This is open-coded in handle_reply().
 */
static void complete_request(struct ceph_osd_request *req, int err)
{
        dout("%s req %p tid %llu err %d\n", __func__, req, req->r_tid, err);

        req->r_result = err;
        finish_request(req);

        INIT_WORK(&req->r_complete_work, complete_request_workfn);
        queue_work(req->r_osdc->completion_wq, &req->r_complete_work);
}

static void cancel_map_check(struct ceph_osd_request *req)
{
        struct ceph_osd_client *osdc = req->r_osdc;
        struct ceph_osd_request *lookup_req;

        verify_osdc_wrlocked(osdc);

        lookup_req = lookup_request_mc(&osdc->map_checks, req->r_tid);
        if (!lookup_req)
                return;

        WARN_ON(lookup_req != req);
        erase_request_mc(&osdc->map_checks, req);
        ceph_osdc_put_request(req);
}

static void cancel_request(struct ceph_osd_request *req)
{
        dout("%s req %p tid %llu\n", __func__, req, req->r_tid);

        cancel_map_check(req);
        finish_request(req);
        complete_all(&req->r_completion);
        ceph_osdc_put_request(req);
}

static void abort_request(struct ceph_osd_request *req, int err)
{
        dout("%s req %p tid %llu err %d\n", __func__, req, req->r_tid, err);

        cancel_map_check(req);
        complete_request(req, err);
}

static int abort_fn(struct ceph_osd_request *req, void *arg)
{
        int err = *(int *)arg;

        abort_request(req, err);
        return 0; /* continue iteration */
}

/*
 * Abort all in-flight requests with @err and arrange for all future
 * requests to be failed immediately.
 */
void ceph_osdc_abort_requests(struct ceph_osd_client *osdc, int err)
{
        dout("%s osdc %p err %d\n", __func__, osdc, err);
        down_write(&osdc->lock);
        for_each_request(osdc, abort_fn, &err);
        osdc->abort_err = err;
        up_write(&osdc->lock);
}
EXPORT_SYMBOL(ceph_osdc_abort_requests);

void ceph_osdc_clear_abort_err(struct ceph_osd_client *osdc)
{
        down_write(&osdc->lock);
        osdc->abort_err = 0;
        up_write(&osdc->lock);
}
EXPORT_SYMBOL(ceph_osdc_clear_abort_err);

static void update_epoch_barrier(struct ceph_osd_client *osdc, u32 eb)
{
        if (likely(eb > osdc->epoch_barrier)) {
                dout("updating epoch_barrier from %u to %u\n",
                                osdc->epoch_barrier, eb);
                osdc->epoch_barrier = eb;
                /* Request map if we're not to the barrier yet */
                if (eb > osdc->osdmap->epoch)
                        maybe_request_map(osdc);
        }
}

void ceph_osdc_update_epoch_barrier(struct ceph_osd_client *osdc, u32 eb)
{
        down_read(&osdc->lock);
        if (unlikely(eb > osdc->epoch_barrier)) {
                up_read(&osdc->lock);
                down_write(&osdc->lock);
                update_epoch_barrier(osdc, eb);
                up_write(&osdc->lock);
        } else {
                up_read(&osdc->lock);
        }
}
EXPORT_SYMBOL(ceph_osdc_update_epoch_barrier);

/*
 * We can end up releasing caps as a result of abort_request().
 * In that case, we probably want to ensure that the cap release message
 * has an updated epoch barrier in it, so set the epoch barrier prior to
 * aborting the first request.
 */
static int abort_on_full_fn(struct ceph_osd_request *req, void *arg)
{
        struct ceph_osd_client *osdc = req->r_osdc;
        bool *victims = arg;

        if ((req->r_flags & CEPH_OSD_FLAG_WRITE) &&
            (ceph_osdmap_flag(osdc, CEPH_OSDMAP_FULL) ||
             pool_full(osdc, req->r_t.base_oloc.pool))) {
                if (!*victims) {
                        update_epoch_barrier(osdc, osdc->osdmap->epoch);
                        *victims = true;
                }
                abort_request(req, -ENOSPC);
        }

        return 0; /* continue iteration */
}

/*
 * Drop all pending requests that are stalled waiting on a full condition to
 * clear, and complete them with ENOSPC as the return code. Set the
 * osdc->epoch_barrier to the latest map epoch that we've seen if any were
 * cancelled.
 */
static void ceph_osdc_abort_on_full(struct ceph_osd_client *osdc)
{
        bool victims = false;

        if (ceph_test_opt(osdc->client, ABORT_ON_FULL) &&
            (ceph_osdmap_flag(osdc, CEPH_OSDMAP_FULL) || have_pool_full(osdc)))
                for_each_request(osdc, abort_on_full_fn, &victims);
}

static void check_pool_dne(struct ceph_osd_request *req)
{
        struct ceph_osd_client *osdc = req->r_osdc;
        struct ceph_osdmap *map = osdc->osdmap;

        verify_osdc_wrlocked(osdc);
        WARN_ON(!map->epoch);

        if (req->r_attempts) {
                /*
                 * We sent a request earlier, which means that
                 * previously the pool existed, and now it does not
                 * (i.e., it was deleted).
                 */
                req->r_map_dne_bound = map->epoch;
                dout("%s req %p tid %llu pool disappeared\n", __func__, req,
                     req->r_tid);
        } else {
                dout("%s req %p tid %llu map_dne_bound %u have %u\n", __func__,
                     req, req->r_tid, req->r_map_dne_bound, map->epoch);
        }

        if (req->r_map_dne_bound) {
                if (map->epoch >= req->r_map_dne_bound) {
                        /* we had a new enough map */
                        pr_info_ratelimited("tid %llu pool does not exist\n",
                                            req->r_tid);
                        complete_request(req, -ENOENT);
                }
        } else {
                send_map_check(req);
        }
}

static void map_check_cb(struct ceph_mon_generic_request *greq)
{
        struct ceph_osd_client *osdc = &greq->monc->client->osdc;
        struct ceph_osd_request *req;
        u64 tid = greq->private_data;

        WARN_ON(greq->result || !greq->u.newest);

        down_write(&osdc->lock);
        req = lookup_request_mc(&osdc->map_checks, tid);
        if (!req) {
                dout("%s tid %llu dne\n", __func__, tid);
                goto out_unlock;
        }

        dout("%s req %p tid %llu map_dne_bound %u newest %llu\n", __func__,
             req, req->r_tid, req->r_map_dne_bound, greq->u.newest);
        if (!req->r_map_dne_bound)
                req->r_map_dne_bound = greq->u.newest;
        erase_request_mc(&osdc->map_checks, req);
        check_pool_dne(req);

        ceph_osdc_put_request(req);
out_unlock:
        up_write(&osdc->lock);
}

static void send_map_check(struct ceph_osd_request *req)
{
        struct ceph_osd_client *osdc = req->r_osdc;
        struct ceph_osd_request *lookup_req;
        int ret;

        verify_osdc_wrlocked(osdc);

        lookup_req = lookup_request_mc(&osdc->map_checks, req->r_tid);
        if (lookup_req) {
                WARN_ON(lookup_req != req);
                return;
        }

        ceph_osdc_get_request(req);
        insert_request_mc(&osdc->map_checks, req);
        ret = ceph_monc_get_version_async(&osdc->client->monc, "osdmap",
                                          map_check_cb, req->r_tid);
        WARN_ON(ret);
}

/*
 * lingering requests, watch/notify v2 infrastructure
 */
static void linger_release(struct kref *kref)
{
        struct ceph_osd_linger_request *lreq =
            container_of(kref, struct ceph_osd_linger_request, kref);

        dout("%s lreq %p reg_req %p ping_req %p\n", __func__, lreq,
             lreq->reg_req, lreq->ping_req);
        WARN_ON(!RB_EMPTY_NODE(&lreq->node));
        WARN_ON(!RB_EMPTY_NODE(&lreq->osdc_node));
        WARN_ON(!RB_EMPTY_NODE(&lreq->mc_node));
        WARN_ON(!list_empty(&lreq->scan_item));
        WARN_ON(!list_empty(&lreq->pending_lworks));
        WARN_ON(lreq->osd);

        if (lreq->reg_req)
                ceph_osdc_put_request(lreq->reg_req);
        if (lreq->ping_req)
                ceph_osdc_put_request(lreq->ping_req);
        target_destroy(&lreq->t);
        kfree(lreq);
}

static void linger_put(struct ceph_osd_linger_request *lreq)
{
        if (lreq)
                kref_put(&lreq->kref, linger_release);
}

static struct ceph_osd_linger_request *
linger_get(struct ceph_osd_linger_request *lreq)
{
        kref_get(&lreq->kref);
        return lreq;
}

static struct ceph_osd_linger_request *
linger_alloc(struct ceph_osd_client *osdc)
{
        struct ceph_osd_linger_request *lreq;

        lreq = kzalloc(sizeof(*lreq), GFP_NOIO);
        if (!lreq)
                return NULL;

        kref_init(&lreq->kref);
        mutex_init(&lreq->lock);
        RB_CLEAR_NODE(&lreq->node);
        RB_CLEAR_NODE(&lreq->osdc_node);
        RB_CLEAR_NODE(&lreq->mc_node);
        INIT_LIST_HEAD(&lreq->scan_item);
        INIT_LIST_HEAD(&lreq->pending_lworks);
        init_completion(&lreq->reg_commit_wait);
        init_completion(&lreq->notify_finish_wait);

        lreq->osdc = osdc;
        target_init(&lreq->t);

        dout("%s lreq %p\n", __func__, lreq);
        return lreq;
}

DEFINE_RB_INSDEL_FUNCS(linger, struct ceph_osd_linger_request, linger_id, node)
DEFINE_RB_FUNCS(linger_osdc, struct ceph_osd_linger_request, linger_id, osdc_node)
DEFINE_RB_FUNCS(linger_mc, struct ceph_osd_linger_request, linger_id, mc_node)

/*
 * Create linger request <-> OSD session relation.
 *
 * @lreq has to be registered, @osd may be homeless.
 */
static void link_linger(struct ceph_osd *osd,
                        struct ceph_osd_linger_request *lreq)
{
        verify_osd_locked(osd);
        WARN_ON(!lreq->linger_id || lreq->osd);
        dout("%s osd %p osd%d lreq %p linger_id %llu\n", __func__, osd,
             osd->o_osd, lreq, lreq->linger_id);

        if (!osd_homeless(osd))
                __remove_osd_from_lru(osd);
        else
                atomic_inc(&osd->o_osdc->num_homeless);

        get_osd(osd);
        insert_linger(&osd->o_linger_requests, lreq);
        lreq->osd = osd;
}

static void unlink_linger(struct ceph_osd *osd,
                          struct ceph_osd_linger_request *lreq)
{
        verify_osd_locked(osd);
        WARN_ON(lreq->osd != osd);
        dout("%s osd %p osd%d lreq %p linger_id %llu\n", __func__, osd,
             osd->o_osd, lreq, lreq->linger_id);

        lreq->osd = NULL;
        erase_linger(&osd->o_linger_requests, lreq);
        put_osd(osd);

        if (!osd_homeless(osd))
                maybe_move_osd_to_lru(osd);
        else
                atomic_dec(&osd->o_osdc->num_homeless);
}

static bool __linger_registered(struct ceph_osd_linger_request *lreq)
{
        verify_osdc_locked(lreq->osdc);

        return !RB_EMPTY_NODE(&lreq->osdc_node);
}

static bool linger_registered(struct ceph_osd_linger_request *lreq)
{
        struct ceph_osd_client *osdc = lreq->osdc;
        bool registered;

        down_read(&osdc->lock);
        registered = __linger_registered(lreq);
        up_read(&osdc->lock);

        return registered;
}

static void linger_register(struct ceph_osd_linger_request *lreq)
{
        struct ceph_osd_client *osdc = lreq->osdc;

        verify_osdc_wrlocked(osdc);
        WARN_ON(lreq->linger_id);

        linger_get(lreq);
        lreq->linger_id = ++osdc->last_linger_id;
        insert_linger_osdc(&osdc->linger_requests, lreq);
}

static void linger_unregister(struct ceph_osd_linger_request *lreq)
{
        struct ceph_osd_client *osdc = lreq->osdc;

        verify_osdc_wrlocked(osdc);

        erase_linger_osdc(&osdc->linger_requests, lreq);
        linger_put(lreq);
}

static void cancel_linger_request(struct ceph_osd_request *req)
{
        struct ceph_osd_linger_request *lreq = req->r_priv;

        WARN_ON(!req->r_linger);
        cancel_request(req);
        linger_put(lreq);
}

struct linger_work {
        struct work_struct work;
        struct ceph_osd_linger_request *lreq;
        struct list_head pending_item;
        unsigned long queued_stamp;

        union {
                struct {
                        u64 notify_id;
                        u64 notifier_id;
                        void *payload; /* points into @msg front */
                        size_t payload_len;

                        struct ceph_msg *msg; /* for ceph_msg_put() */
                } notify;
                struct {
                        int err;
                } error;
        };
};

static struct linger_work *lwork_alloc(struct ceph_osd_linger_request *lreq,
                                       work_func_t workfn)
{
        struct linger_work *lwork;

        lwork = kzalloc(sizeof(*lwork), GFP_NOIO);
        if (!lwork)
                return NULL;

        INIT_WORK(&lwork->work, workfn);
        INIT_LIST_HEAD(&lwork->pending_item);
        lwork->lreq = linger_get(lreq);

        return lwork;
}

static void lwork_free(struct linger_work *lwork)
{
        struct ceph_osd_linger_request *lreq = lwork->lreq;

        mutex_lock(&lreq->lock);
        list_del(&lwork->pending_item);
        mutex_unlock(&lreq->lock);

        linger_put(lreq);
        kfree(lwork);
}

static void lwork_queue(struct linger_work *lwork)
{
        struct ceph_osd_linger_request *lreq = lwork->lreq;
        struct ceph_osd_client *osdc = lreq->osdc;

        verify_lreq_locked(lreq);
        WARN_ON(!list_empty(&lwork->pending_item));

        lwork->queued_stamp = jiffies;
        list_add_tail(&lwork->pending_item, &lreq->pending_lworks);
        queue_work(osdc->notify_wq, &lwork->work);
}

static void do_watch_notify(struct work_struct *w)
{
        struct linger_work *lwork = container_of(w, struct linger_work, work);
        struct ceph_osd_linger_request *lreq = lwork->lreq;

        if (!linger_registered(lreq)) {
                dout("%s lreq %p not registered\n", __func__, lreq);
                goto out;
        }

        WARN_ON(!lreq->is_watch);
        dout("%s lreq %p notify_id %llu notifier_id %llu payload_len %zu\n",
             __func__, lreq, lwork->notify.notify_id, lwork->notify.notifier_id,
             lwork->notify.payload_len);
        lreq->wcb(lreq->data, lwork->notify.notify_id, lreq->linger_id,
                  lwork->notify.notifier_id, lwork->notify.payload,
                  lwork->notify.payload_len);

out:
        ceph_msg_put(lwork->notify.msg);
        lwork_free(lwork);
}

static void do_watch_error(struct work_struct *w)
{
        struct linger_work *lwork = container_of(w, struct linger_work, work);
        struct ceph_osd_linger_request *lreq = lwork->lreq;

        if (!linger_registered(lreq)) {
                dout("%s lreq %p not registered\n", __func__, lreq);
                goto out;
        }

        dout("%s lreq %p err %d\n", __func__, lreq, lwork->error.err);
        lreq->errcb(lreq->data, lreq->linger_id, lwork->error.err);

out:
        lwork_free(lwork);
}

static void queue_watch_error(struct ceph_osd_linger_request *lreq)
{
        struct linger_work *lwork;

        lwork = lwork_alloc(lreq, do_watch_error);
        if (!lwork) {
                pr_err("failed to allocate error-lwork\n");
                return;
        }

        lwork->error.err = lreq->last_error;
        lwork_queue(lwork);
}

static void linger_reg_commit_complete(struct ceph_osd_linger_request *lreq,
                                       int result)
{
        if (!completion_done(&lreq->reg_commit_wait)) {
                lreq->reg_commit_error = (result <= 0 ? result : 0);
                complete_all(&lreq->reg_commit_wait);
        }
}

static void linger_commit_cb(struct ceph_osd_request *req)
{
        struct ceph_osd_linger_request *lreq = req->r_priv;