pnfs: layoutreturn

[mirror_ubuntu-artful-kernel.git] / fs / nfs / pnfs.c

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

#include <linux/nfs_fs.h>
#include "internal.h"
#include "pnfs.h"
#include "iostat.h"

#define NFSDBG_FACILITY         NFSDBG_PNFS

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

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

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

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

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

        spin_lock(&pnfs_spinlock);
        local = find_pnfs_driver_locked(id);
        spin_unlock(&pnfs_spinlock);
        return local;
}

void
unset_pnfs_layoutdriver(struct nfs_server *nfss)
{
        if (nfss->pnfs_curr_ld)
                module_put(nfss->pnfs_curr_ld->owner);
        nfss->pnfs_curr_ld = NULL;
}

/*
 * Try to set the server's pnfs module to the pnfs layout type specified by id.
 * Currently only one pNFS layout driver per filesystem is supported.
 *
 * @id layout type. Zero (illegal layout type) indicates pNFS not in use.
 */
void
set_pnfs_layoutdriver(struct nfs_server *server, u32 id)
{
        struct pnfs_layoutdriver_type *ld_type = NULL;

        if (id == 0)
                goto out_no_driver;
        if (!(server->nfs_client->cl_exchange_flags &
                 (EXCHGID4_FLAG_USE_NON_PNFS | EXCHGID4_FLAG_USE_PNFS_MDS))) {
                printk(KERN_ERR "%s: id %u cl_exchange_flags 0x%x\n", __func__,
                       id, server->nfs_client->cl_exchange_flags);
                goto out_no_driver;
        }
        ld_type = find_pnfs_driver(id);
        if (!ld_type) {
                request_module("%s-%u", LAYOUT_NFSV4_1_MODULE_PREFIX, id);
                ld_type = find_pnfs_driver(id);
                if (!ld_type) {
                        dprintk("%s: No pNFS module found for %u.\n",
                                __func__, id);
                        goto out_no_driver;
                }
        }
        if (!try_module_get(ld_type->owner)) {
                dprintk("%s: Could not grab reference on module\n", __func__);
                goto out_no_driver;
        }
        server->pnfs_curr_ld = ld_type;

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

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

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

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

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

        return status;
}
EXPORT_SYMBOL_GPL(pnfs_register_layoutdriver);

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

/*
 * pNFS client layout cache
 */

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

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

static void
pnfs_free_layout_hdr(struct pnfs_layout_hdr *lo)
{
        struct pnfs_layoutdriver_type *ld = NFS_SERVER(lo->plh_inode)->pnfs_curr_ld;
        return ld->alloc_layout_hdr ? ld->free_layout_hdr(lo) : kfree(lo);
}

static void
destroy_layout_hdr(struct pnfs_layout_hdr *lo)
{
        dprintk("%s: freeing layout cache %p\n", __func__, lo);
        BUG_ON(!list_empty(&lo->plh_layouts));
        NFS_I(lo->plh_inode)->layout = NULL;
        pnfs_free_layout_hdr(lo);
}

static void
put_layout_hdr_locked(struct pnfs_layout_hdr *lo)
{
        if (atomic_dec_and_test(&lo->plh_refcount))
                destroy_layout_hdr(lo);
}

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

        if (atomic_dec_and_lock(&lo->plh_refcount, &inode->i_lock)) {
                destroy_layout_hdr(lo);
                spin_unlock(&inode->i_lock);
        }
}

static void
init_lseg(struct pnfs_layout_hdr *lo, struct pnfs_layout_segment *lseg)
{
        INIT_LIST_HEAD(&lseg->pls_list);
        atomic_set(&lseg->pls_refcount, 1);
        smp_mb();
        set_bit(NFS_LSEG_VALID, &lseg->pls_flags);
        lseg->pls_layout = lo;
}

static void free_lseg(struct pnfs_layout_segment *lseg)
{
        struct inode *ino = lseg->pls_layout->plh_inode;

        NFS_SERVER(ino)->pnfs_curr_ld->free_lseg(lseg);
        /* Matched by get_layout_hdr in pnfs_insert_layout */
        put_layout_hdr(NFS_I(ino)->layout);
}

static void
put_lseg_common(struct pnfs_layout_segment *lseg)
{
        struct inode *inode = lseg->pls_layout->plh_inode;

        WARN_ON(test_bit(NFS_LSEG_VALID, &lseg->pls_flags));
        list_del_init(&lseg->pls_list);
        if (list_empty(&lseg->pls_layout->plh_segs)) {
                set_bit(NFS_LAYOUT_DESTROYED, &lseg->pls_layout->plh_flags);
                /* Matched by initial refcount set in alloc_init_layout_hdr */
                put_layout_hdr_locked(lseg->pls_layout);
        }
        rpc_wake_up(&NFS_SERVER(inode)->roc_rpcwaitq);
}

void
put_lseg(struct pnfs_layout_segment *lseg)
{
        struct inode *inode;

        if (!lseg)
                return;

        dprintk("%s: lseg %p ref %d valid %d\n", __func__, lseg,
                atomic_read(&lseg->pls_refcount),
                test_bit(NFS_LSEG_VALID, &lseg->pls_flags));
        inode = lseg->pls_layout->plh_inode;
        if (atomic_dec_and_lock(&lseg->pls_refcount, &inode->i_lock)) {
                LIST_HEAD(free_me);

                put_lseg_common(lseg);
                list_add(&lseg->pls_list, &free_me);
                spin_unlock(&inode->i_lock);
                pnfs_free_lseg_list(&free_me);
        }
}
EXPORT_SYMBOL_GPL(put_lseg);

static inline u64
end_offset(u64 start, u64 len)
{
        u64 end;

        end = start + len;
        return end >= start ? end : NFS4_MAX_UINT64;
}

/* last octet in a range */
static inline u64
last_byte_offset(u64 start, u64 len)
{
        u64 end;

        BUG_ON(!len);
        end = start + len;
        return end > start ? end - 1 : NFS4_MAX_UINT64;
}

/*
 * is l2 fully contained in l1?
 *   start1                             end1
 *   [----------------------------------)
 *           start2           end2
 *           [----------------)
 */
static inline int
lo_seg_contained(struct pnfs_layout_range *l1,
                 struct pnfs_layout_range *l2)
{
        u64 start1 = l1->offset;
        u64 end1 = end_offset(start1, l1->length);
        u64 start2 = l2->offset;
        u64 end2 = end_offset(start2, l2->length);

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

/*
 * is l1 and l2 intersecting?
 *   start1                             end1
 *   [----------------------------------)
 *                              start2           end2
 *                              [----------------)
 */
static inline int
lo_seg_intersecting(struct pnfs_layout_range *l1,
                    struct pnfs_layout_range *l2)
{
        u64 start1 = l1->offset;
        u64 end1 = end_offset(start1, l1->length);
        u64 start2 = l2->offset;
        u64 end2 = end_offset(start2, l2->length);

        return (end1 == NFS4_MAX_UINT64 || end1 > start2) &&
               (end2 == NFS4_MAX_UINT64 || end2 > start1);
}

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

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

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

/* Returns count of number of matching invalid lsegs remaining in list
 * after call.
 */
int
mark_matching_lsegs_invalid(struct pnfs_layout_hdr *lo,
                            struct list_head *tmp_list,
                            struct pnfs_layout_range *recall_range)
{
        struct pnfs_layout_segment *lseg, *next;
        int invalid = 0, removed = 0;

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

        if (list_empty(&lo->plh_segs)) {
                if (!test_and_set_bit(NFS_LAYOUT_DESTROYED, &lo->plh_flags))
                        put_layout_hdr_locked(lo);
                return 0;
        }
        list_for_each_entry_safe(lseg, next, &lo->plh_segs, pls_list)
                if (!recall_range ||
                    should_free_lseg(&lseg->pls_range, recall_range)) {
                        dprintk("%s: freeing lseg %p iomode %d "
                                "offset %llu length %llu\n", __func__,
                                lseg, lseg->pls_range.iomode, lseg->pls_range.offset,
                                lseg->pls_range.length);
                        invalid++;
                        removed += mark_lseg_invalid(lseg, tmp_list);
                }
        dprintk("%s:Return %i\n", __func__, invalid - removed);
        return invalid - removed;
}

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

        if (list_empty(free_me))
                return;

        lo = list_first_entry(free_me, struct pnfs_layout_segment,
                              pls_list)->pls_layout;

        if (test_bit(NFS_LAYOUT_DESTROYED, &lo->plh_flags)) {
                struct nfs_client *clp;

                clp = NFS_SERVER(lo->plh_inode)->nfs_client;
                spin_lock(&clp->cl_lock);
                list_del_init(&lo->plh_layouts);
                spin_unlock(&clp->cl_lock);
        }
        list_for_each_entry_safe(lseg, tmp, free_me, pls_list) {
                list_del(&lseg->pls_list);
                free_lseg(lseg);
        }
}

void
pnfs_destroy_layout(struct nfs_inode *nfsi)
{
        struct pnfs_layout_hdr *lo;
        LIST_HEAD(tmp_list);

        spin_lock(&nfsi->vfs_inode.i_lock);
        lo = nfsi->layout;
        if (lo) {
                lo->plh_block_lgets++; /* permanently block new LAYOUTGETs */
                mark_matching_lsegs_invalid(lo, &tmp_list, NULL);
        }
        spin_unlock(&nfsi->vfs_inode.i_lock);
        pnfs_free_lseg_list(&tmp_list);
}

/*
 * Called by the state manger to remove all layouts established under an
 * expired lease.
 */
void
pnfs_destroy_all_layouts(struct nfs_client *clp)
{
        struct pnfs_layout_hdr *lo;
        LIST_HEAD(tmp_list);

        spin_lock(&clp->cl_lock);
        list_splice_init(&clp->cl_layouts, &tmp_list);
        spin_unlock(&clp->cl_lock);

        while (!list_empty(&tmp_list)) {
                lo = list_entry(tmp_list.next, struct pnfs_layout_hdr,
                                plh_layouts);
                dprintk("%s freeing layout for inode %lu\n", __func__,
                        lo->plh_inode->i_ino);
                list_del_init(&lo->plh_layouts);
                pnfs_destroy_layout(NFS_I(lo->plh_inode));
        }
}

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

        oldseq = be32_to_cpu(lo->plh_stateid.stateid.seqid);
        newseq = be32_to_cpu(new->stateid.seqid);
        if ((int)(newseq - oldseq) > 0) {
                memcpy(&lo->plh_stateid, &new->stateid, sizeof(new->stateid));
                if (update_barrier) {
                        u32 new_barrier = be32_to_cpu(new->stateid.seqid);

                        if ((int)(new_barrier - lo->plh_barrier))
                                lo->plh_barrier = new_barrier;
                } else {
                        /* Because of wraparound, we want to keep the barrier
                         * "close" to the current seqids.  It needs to be
                         * within 2**31 to count as "behind", so if it
                         * gets too near that limit, give us a litle leeway
                         * and bring it to within 2**30.
                         * NOTE - and yes, this is all unsigned arithmetic.
                         */
                        if (unlikely((newseq - lo->plh_barrier) > (3 << 29)))
                                lo->plh_barrier = newseq - (1 << 30);
                }
        }
}

/* lget is set to 1 if called from inside send_layoutget call chain */
static bool
pnfs_layoutgets_blocked(struct pnfs_layout_hdr *lo, nfs4_stateid *stateid,
                        int lget)
{
        if ((stateid) &&
            (int)(lo->plh_barrier - be32_to_cpu(stateid->stateid.seqid)) >= 0)
                return true;
        return lo->plh_block_lgets ||
                test_bit(NFS_LAYOUT_DESTROYED, &lo->plh_flags) ||
                test_bit(NFS_LAYOUT_BULK_RECALL, &lo->plh_flags) ||
                (list_empty(&lo->plh_segs) &&
                 (atomic_read(&lo->plh_outstanding) > lget));
}

int
pnfs_choose_layoutget_stateid(nfs4_stateid *dst, struct pnfs_layout_hdr *lo,
                              struct nfs4_state *open_state)
{
        int status = 0;

        dprintk("--> %s\n", __func__);
        spin_lock(&lo->plh_inode->i_lock);
        if (pnfs_layoutgets_blocked(lo, NULL, 1)) {
                status = -EAGAIN;
        } else if (list_empty(&lo->plh_segs)) {
                int seq;

                do {
                        seq = read_seqbegin(&open_state->seqlock);
                        memcpy(dst->data, open_state->stateid.data,
                               sizeof(open_state->stateid.data));
                } while (read_seqretry(&open_state->seqlock, seq));
        } else
                memcpy(dst->data, lo->plh_stateid.data, sizeof(lo->plh_stateid.data));
        spin_unlock(&lo->plh_inode->i_lock);
        dprintk("<-- %s\n", __func__);
        return status;
}

/*
* Get layout from server.
*    for now, assume that whole file layouts are requested.
*    arg->offset: 0
*    arg->length: all ones
*/
static struct pnfs_layout_segment *
send_layoutget(struct pnfs_layout_hdr *lo,
           struct nfs_open_context *ctx,
           struct pnfs_layout_range *range,
           gfp_t gfp_flags)
{
        struct inode *ino = lo->plh_inode;
        struct nfs_server *server = NFS_SERVER(ino);
        struct nfs4_layoutget *lgp;
        struct pnfs_layout_segment *lseg = NULL;
        struct page **pages = NULL;
        int i;
        u32 max_resp_sz, max_pages;

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

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

        /* allocate pages for xdr post processing */
        max_resp_sz = server->nfs_client->cl_session->fc_attrs.max_resp_sz;
        max_pages = max_resp_sz >> PAGE_SHIFT;

        pages = kzalloc(max_pages * sizeof(struct page *), gfp_flags);
        if (!pages)
                goto out_err_free;

        for (i = 0; i < max_pages; i++) {
                pages[i] = alloc_page(gfp_flags);
                if (!pages[i])
                        goto out_err_free;
        }

        lgp->args.minlength = PAGE_CACHE_SIZE;
        if (lgp->args.minlength > range->length)
                lgp->args.minlength = range->length;
        lgp->args.maxcount = PNFS_LAYOUT_MAXSIZE;
        lgp->args.range = *range;
        lgp->args.type = server->pnfs_curr_ld->id;
        lgp->args.inode = ino;
        lgp->args.ctx = get_nfs_open_context(ctx);
        lgp->args.layout.pages = pages;
        lgp->args.layout.pglen = max_pages * PAGE_SIZE;
        lgp->lsegpp = &lseg;
        lgp->gfp_flags = gfp_flags;

        /* Synchronously retrieve layout information from server and
         * store in lseg.
         */
        nfs4_proc_layoutget(lgp);
        if (!lseg) {
                /* remember that LAYOUTGET failed and suspend trying */
                set_bit(lo_fail_bit(range->iomode), &lo->plh_flags);
        }

        /* free xdr pages */
        for (i = 0; i < max_pages; i++)
                __free_page(pages[i]);
        kfree(pages);

        return lseg;

out_err_free:
        /* free any allocated xdr pages, lgp as it's not used */
        if (pages) {
                for (i = 0; i < max_pages; i++) {
                        if (!pages[i])
                                break;
                        __free_page(pages[i]);
                }
                kfree(pages);
        }
        kfree(lgp);
        return NULL;
}

/* Initiates a LAYOUTRETURN(FILE) */
int
_pnfs_return_layout(struct inode *ino)
{
        struct pnfs_layout_hdr *lo = NULL;
        struct nfs_inode *nfsi = NFS_I(ino);
        LIST_HEAD(tmp_list);
        struct nfs4_layoutreturn *lrp;
        nfs4_stateid stateid;
        int status = 0;

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

        spin_lock(&ino->i_lock);
        lo = nfsi->layout;
        if (!lo || !mark_matching_lsegs_invalid(lo, &tmp_list, NULL)) {
                spin_unlock(&ino->i_lock);
                dprintk("%s: no layout segments to return\n", __func__);
                goto out;
        }
        stateid = nfsi->layout->plh_stateid;
        /* Reference matched in nfs4_layoutreturn_release */
        get_layout_hdr(lo);
        spin_unlock(&ino->i_lock);
        pnfs_free_lseg_list(&tmp_list);

        WARN_ON(test_bit(NFS_INO_LAYOUTCOMMIT, &nfsi->flags));

        lrp = kzalloc(sizeof(*lrp), GFP_KERNEL);
        if (unlikely(lrp == NULL)) {
                status = -ENOMEM;
                goto out;
        }

        lrp->args.stateid = stateid;
        lrp->args.layout_type = NFS_SERVER(ino)->pnfs_curr_ld->id;
        lrp->args.inode = ino;
        lrp->clp = NFS_SERVER(ino)->nfs_client;

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

bool pnfs_roc(struct inode *ino)
{
        struct pnfs_layout_hdr *lo;
        struct pnfs_layout_segment *lseg, *tmp;
        LIST_HEAD(tmp_list);
        bool found = false;

        spin_lock(&ino->i_lock);
        lo = NFS_I(ino)->layout;
        if (!lo || !test_and_clear_bit(NFS_LAYOUT_ROC, &lo->plh_flags) ||
            test_bit(NFS_LAYOUT_BULK_RECALL, &lo->plh_flags))
                goto out_nolayout;
        list_for_each_entry_safe(lseg, tmp, &lo->plh_segs, pls_list)
                if (test_bit(NFS_LSEG_ROC, &lseg->pls_flags)) {
                        mark_lseg_invalid(lseg, &tmp_list);
                        found = true;
                }
        if (!found)
                goto out_nolayout;
        lo->plh_block_lgets++;
        get_layout_hdr(lo); /* matched in pnfs_roc_release */
        spin_unlock(&ino->i_lock);
        pnfs_free_lseg_list(&tmp_list);
        return true;

out_nolayout:
        spin_unlock(&ino->i_lock);
        return false;
}

void pnfs_roc_release(struct inode *ino)
{
        struct pnfs_layout_hdr *lo;

        spin_lock(&ino->i_lock);
        lo = NFS_I(ino)->layout;
        lo->plh_block_lgets--;
        put_layout_hdr_locked(lo);
        spin_unlock(&ino->i_lock);
}

void pnfs_roc_set_barrier(struct inode *ino, u32 barrier)
{
        struct pnfs_layout_hdr *lo;

        spin_lock(&ino->i_lock);
        lo = NFS_I(ino)->layout;
        if ((int)(barrier - lo->plh_barrier) > 0)
                lo->plh_barrier = barrier;
        spin_unlock(&ino->i_lock);
}

bool pnfs_roc_drain(struct inode *ino, u32 *barrier)
{
        struct nfs_inode *nfsi = NFS_I(ino);
        struct pnfs_layout_segment *lseg;
        bool found = false;

        spin_lock(&ino->i_lock);
        list_for_each_entry(lseg, &nfsi->layout->plh_segs, pls_list)
                if (test_bit(NFS_LSEG_ROC, &lseg->pls_flags)) {
                        found = true;
                        break;
                }
        if (!found) {
                struct pnfs_layout_hdr *lo = nfsi->layout;
                u32 current_seqid = be32_to_cpu(lo->plh_stateid.stateid.seqid);

                /* Since close does not return a layout stateid for use as
                 * a barrier, we choose the worst-case barrier.
                 */
                *barrier = current_seqid + atomic_read(&lo->plh_outstanding);
        }
        spin_unlock(&ino->i_lock);
        return found;
}

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

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

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

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

static void
pnfs_insert_layout(struct pnfs_layout_hdr *lo,
                   struct pnfs_layout_segment *lseg)
{
        struct pnfs_layout_segment *lp;

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

        assert_spin_locked(&lo->plh_inode->i_lock);
        list_for_each_entry(lp, &lo->plh_segs, pls_list) {
                if (cmp_layout(&lseg->pls_range, &lp->pls_range) > 0)
                        continue;
                list_add_tail(&lseg->pls_list, &lp->pls_list);
                dprintk("%s: inserted lseg %p "
                        "iomode %d offset %llu length %llu before "
                        "lp %p iomode %d offset %llu length %llu\n",
                        __func__, lseg, lseg->pls_range.iomode,
                        lseg->pls_range.offset, lseg->pls_range.length,
                        lp, lp->pls_range.iomode, lp->pls_range.offset,
                        lp->pls_range.length);
                goto out;
        }
        list_add_tail(&lseg->pls_list, &lo->plh_segs);
        dprintk("%s: inserted lseg %p "
                "iomode %d offset %llu length %llu at tail\n",
                __func__, lseg, lseg->pls_range.iomode,
                lseg->pls_range.offset, lseg->pls_range.length);
out:
        get_layout_hdr(lo);

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

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

        lo = pnfs_alloc_layout_hdr(ino, gfp_flags);
        if (!lo)
                return NULL;
        atomic_set(&lo->plh_refcount, 1);
        INIT_LIST_HEAD(&lo->plh_layouts);
        INIT_LIST_HEAD(&lo->plh_segs);
        INIT_LIST_HEAD(&lo->plh_bulk_recall);
        lo->plh_inode = ino;
        return lo;
}

static struct pnfs_layout_hdr *
pnfs_find_alloc_layout(struct inode *ino, gfp_t gfp_flags)
{
        struct nfs_inode *nfsi = NFS_I(ino);
        struct pnfs_layout_hdr *new = NULL;

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

        assert_spin_locked(&ino->i_lock);
        if (nfsi->layout) {
                if (test_bit(NFS_LAYOUT_DESTROYED, &nfsi->layout->plh_flags))
                        return NULL;
                else
                        return nfsi->layout;
        }
        spin_unlock(&ino->i_lock);
        new = alloc_init_layout_hdr(ino, gfp_flags);
        spin_lock(&ino->i_lock);

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

/*
 * iomode matching rules:
 * iomode       lseg    match
 * -----        -----   -----
 * ANY          READ    true
 * ANY          RW      true
 * RW           READ    false
 * RW           RW      true
 * READ         READ    true
 * READ         RW      true
 */
static int
is_matching_lseg(struct pnfs_layout_range *ls_range,
                 struct pnfs_layout_range *range)
{
        struct pnfs_layout_range range1;

        if ((range->iomode == IOMODE_RW &&
             ls_range->iomode != IOMODE_RW) ||
            !lo_seg_intersecting(ls_range, range))
                return 0;

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

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

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

        assert_spin_locked(&lo->plh_inode->i_lock);
        list_for_each_entry(lseg, &lo->plh_segs, pls_list) {
                if (test_bit(NFS_LSEG_VALID, &lseg->pls_flags) &&
                    is_matching_lseg(&lseg->pls_range, range)) {
                        ret = get_lseg(lseg);
                        break;
                }
                if (cmp_layout(range, &lseg->pls_range) > 0)
                        break;
        }

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

/*
 * Layout segment is retreived from the server if not cached.
 * The appropriate layout segment is referenced and returned to the caller.
 */
struct pnfs_layout_segment *
pnfs_update_layout(struct inode *ino,
                   struct nfs_open_context *ctx,
                   loff_t pos,
                   u64 count,
                   enum pnfs_iomode iomode,
                   gfp_t gfp_flags)
{
        struct pnfs_layout_range arg = {
                .iomode = iomode,
                .offset = pos,
                .length = count,
        };
        unsigned pg_offset;
        struct nfs_inode *nfsi = NFS_I(ino);
        struct nfs_client *clp = NFS_SERVER(ino)->nfs_client;
        struct pnfs_layout_hdr *lo;
        struct pnfs_layout_segment *lseg = NULL;
        bool first = false;

        if (!pnfs_enabled_sb(NFS_SERVER(ino)))
                return NULL;
        spin_lock(&ino->i_lock);
        lo = pnfs_find_alloc_layout(ino, gfp_flags);
        if (lo == NULL) {
                dprintk("%s ERROR: can't get pnfs_layout_hdr\n", __func__);
                goto out_unlock;
        }

        /* Do we even need to bother with this? */
        if (test_bit(NFS4CLNT_LAYOUTRECALL, &clp->cl_state) ||
            test_bit(NFS_LAYOUT_BULK_RECALL, &lo->plh_flags)) {
                dprintk("%s matches recall, use MDS\n", __func__);
                goto out_unlock;
        }

        /* if LAYOUTGET already failed once we don't try again */
        if (test_bit(lo_fail_bit(iomode), &nfsi->layout->plh_flags))
                goto out_unlock;

        /* Check to see if the layout for the given range already exists */
        lseg = pnfs_find_lseg(lo, &arg);
        if (lseg)
                goto out_unlock;

        if (pnfs_layoutgets_blocked(lo, NULL, 0))
                goto out_unlock;
        atomic_inc(&lo->plh_outstanding);

        get_layout_hdr(lo);
        if (list_empty(&lo->plh_segs))
                first = true;
        spin_unlock(&ino->i_lock);
        if (first) {
                /* The lo must be on the clp list if there is any
                 * chance of a CB_LAYOUTRECALL(FILE) coming in.
                 */
                spin_lock(&clp->cl_lock);
                BUG_ON(!list_empty(&lo->plh_layouts));
                list_add_tail(&lo->plh_layouts, &clp->cl_layouts);
                spin_unlock(&clp->cl_lock);
        }

        pg_offset = arg.offset & ~PAGE_CACHE_MASK;
        if (pg_offset) {
                arg.offset -= pg_offset;
                arg.length += pg_offset;
        }
        arg.length = PAGE_CACHE_ALIGN(arg.length);

        lseg = send_layoutget(lo, ctx, &arg, gfp_flags);
        if (!lseg && first) {
                spin_lock(&clp->cl_lock);
                list_del_init(&lo->plh_layouts);
                spin_unlock(&clp->cl_lock);
        }
        atomic_dec(&lo->plh_outstanding);
        put_layout_hdr(lo);
out:
        dprintk("%s end, state 0x%lx lseg %p\n", __func__,
                nfsi->layout ? nfsi->layout->plh_flags : -1, lseg);
        return lseg;
out_unlock:
        spin_unlock(&ino->i_lock);
        goto out;
}

int
pnfs_layout_process(struct nfs4_layoutget *lgp)
{
        struct pnfs_layout_hdr *lo = NFS_I(lgp->args.inode)->layout;
        struct nfs4_layoutget_res *res = &lgp->res;
        struct pnfs_layout_segment *lseg;
        struct inode *ino = lo->plh_inode;
        struct nfs_client *clp = NFS_SERVER(ino)->nfs_client;
        int status = 0;

        /* Inject layout blob into I/O device driver */
        lseg = NFS_SERVER(ino)->pnfs_curr_ld->alloc_lseg(lo, res, lgp->gfp_flags);
        if (!lseg || IS_ERR(lseg)) {
                if (!lseg)
                        status = -ENOMEM;
                else
                        status = PTR_ERR(lseg);
                dprintk("%s: Could not allocate layout: error %d\n",
                       __func__, status);
                goto out;
        }

        spin_lock(&ino->i_lock);
        if (test_bit(NFS4CLNT_LAYOUTRECALL, &clp->cl_state) ||
            test_bit(NFS_LAYOUT_BULK_RECALL, &lo->plh_flags)) {
                dprintk("%s forget reply due to recall\n", __func__);
                goto out_forget_reply;
        }

        if (pnfs_layoutgets_blocked(lo, &res->stateid, 1)) {
                dprintk("%s forget reply due to state\n", __func__);
                goto out_forget_reply;
        }
        init_lseg(lo, lseg);
        lseg->pls_range = res->range;
        *lgp->lsegpp = get_lseg(lseg);
        pnfs_insert_layout(lo, lseg);

        if (res->return_on_close) {
                set_bit(NFS_LSEG_ROC, &lseg->pls_flags);
                set_bit(NFS_LAYOUT_ROC, &lo->plh_flags);
        }

        /* Done processing layoutget. Set the layout stateid */
        pnfs_set_layout_stateid(lo, &res->stateid, false);
        spin_unlock(&ino->i_lock);
out:
        return status;

out_forget_reply:
        spin_unlock(&ino->i_lock);
        lseg->pls_layout = lo;
        NFS_SERVER(ino)->pnfs_curr_ld->free_lseg(lseg);
        goto out;
}

static int pnfs_read_pg_test(struct nfs_pageio_descriptor *pgio,
                             struct nfs_page *prev,
                             struct nfs_page *req)
{
        if (pgio->pg_count == prev->wb_bytes) {
                /* This is first coelesce call for a series of nfs_pages */
                pgio->pg_lseg = pnfs_update_layout(pgio->pg_inode,
                                                   prev->wb_context,
                                                   req_offset(req),
                                                   pgio->pg_count,
                                                   IOMODE_READ,
                                                   GFP_KERNEL);
        } else if (pgio->pg_lseg &&
                   req_offset(req) > end_offset(pgio->pg_lseg->pls_range.offset,
                                                pgio->pg_lseg->pls_range.length))
                return 0;
        return NFS_SERVER(pgio->pg_inode)->pnfs_curr_ld->pg_test(pgio, prev, req);
}

void
pnfs_pageio_init_read(struct nfs_pageio_descriptor *pgio, struct inode *inode)
{
        struct pnfs_layoutdriver_type *ld;

        ld = NFS_SERVER(inode)->pnfs_curr_ld;
        pgio->pg_test = (ld && ld->pg_test) ? pnfs_read_pg_test : NULL;
}

static int pnfs_write_pg_test(struct nfs_pageio_descriptor *pgio,
                              struct nfs_page *prev,
                              struct nfs_page *req)
{
        if (pgio->pg_count == prev->wb_bytes) {
                /* This is first coelesce call for a series of nfs_pages */
                pgio->pg_lseg = pnfs_update_layout(pgio->pg_inode,
                                                   prev->wb_context,
                                                   req_offset(req),
                                                   pgio->pg_count,
                                                   IOMODE_RW,
                                                   GFP_NOFS);
        } else if (pgio->pg_lseg &&
                   req_offset(req) > end_offset(pgio->pg_lseg->pls_range.offset,
                                                pgio->pg_lseg->pls_range.length))
                return 0;
        return NFS_SERVER(pgio->pg_inode)->pnfs_curr_ld->pg_test(pgio, prev, req);
}

void
pnfs_pageio_init_write(struct nfs_pageio_descriptor *pgio, struct inode *inode)
{
        struct pnfs_layoutdriver_type *ld;

        ld = NFS_SERVER(inode)->pnfs_curr_ld;
        pgio->pg_test = (ld && ld->pg_test) ? pnfs_write_pg_test : NULL;
}

/*
 * Called by non rpc-based layout drivers
 */
int
pnfs_ld_write_done(struct nfs_write_data *data)
{
        int status;

        if (!data->pnfs_error) {
                pnfs_set_layoutcommit(data);
                data->mds_ops->rpc_call_done(&data->task, data);
                data->mds_ops->rpc_release(data);
                return 0;
        }

        dprintk("%s: pnfs_error=%d, retry via MDS\n", __func__,
                data->pnfs_error);
        status = nfs_initiate_write(data, NFS_CLIENT(data->inode),
                                    data->mds_ops, NFS_FILE_SYNC);
        return status ? : -EAGAIN;
}
EXPORT_SYMBOL_GPL(pnfs_ld_write_done);

enum pnfs_try_status
pnfs_try_to_write_data(struct nfs_write_data *wdata,
                        const struct rpc_call_ops *call_ops, int how)
{
        struct inode *inode = wdata->inode;
        enum pnfs_try_status trypnfs;
        struct nfs_server *nfss = NFS_SERVER(inode);

        wdata->mds_ops = call_ops;

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

        trypnfs = nfss->pnfs_curr_ld->write_pagelist(wdata, how);
        if (trypnfs == PNFS_NOT_ATTEMPTED) {
                put_lseg(wdata->lseg);
                wdata->lseg = NULL;
        } else
                nfs_inc_stats(inode, NFSIOS_PNFS_WRITE);

        dprintk("%s End (trypnfs:%d)\n", __func__, trypnfs);
        return trypnfs;
}

/*
 * Called by non rpc-based layout drivers
 */
int
pnfs_ld_read_done(struct nfs_read_data *data)
{
        int status;

        if (!data->pnfs_error) {
                __nfs4_read_done_cb(data);
                data->mds_ops->rpc_call_done(&data->task, data);
                data->mds_ops->rpc_release(data);
                return 0;
        }

        dprintk("%s: pnfs_error=%d, retry via MDS\n", __func__,
                data->pnfs_error);
        status = nfs_initiate_read(data, NFS_CLIENT(data->inode),
                                   data->mds_ops);
        return status ? : -EAGAIN;
}
EXPORT_SYMBOL_GPL(pnfs_ld_read_done);

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

        rdata->mds_ops = call_ops;

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

        trypnfs = nfss->pnfs_curr_ld->read_pagelist(rdata);
        if (trypnfs == PNFS_NOT_ATTEMPTED) {
                put_lseg(rdata->lseg);
                rdata->lseg = NULL;
        } else {
                nfs_inc_stats(inode, NFSIOS_PNFS_READ);
        }
        dprintk("%s End (trypnfs:%d)\n", __func__, trypnfs);
        return trypnfs;
}

/*
 * Currently there is only one (whole file) write lseg.
 */
static struct pnfs_layout_segment *pnfs_list_write_lseg(struct inode *inode)
{
        struct pnfs_layout_segment *lseg, *rv = NULL;

        list_for_each_entry(lseg, &NFS_I(inode)->layout->plh_segs, pls_list)
                if (lseg->pls_range.iomode == IOMODE_RW)
                        rv = lseg;
        return rv;
}

void
pnfs_set_layoutcommit(struct nfs_write_data *wdata)
{
        struct nfs_inode *nfsi = NFS_I(wdata->inode);
        loff_t end_pos = wdata->args.offset + wdata->res.count;
        bool mark_as_dirty = false;

        spin_lock(&nfsi->vfs_inode.i_lock);
        if (!test_and_set_bit(NFS_INO_LAYOUTCOMMIT, &nfsi->flags)) {
                /* references matched in nfs4_layoutcommit_release */
                get_lseg(wdata->lseg);
                wdata->lseg->pls_lc_cred =
                        get_rpccred(wdata->args.context->state->owner->so_cred);
                mark_as_dirty = true;
                dprintk("%s: Set layoutcommit for inode %lu ",
                        __func__, wdata->inode->i_ino);
        }
        if (end_pos > wdata->lseg->pls_end_pos)
                wdata->lseg->pls_end_pos = end_pos;
        spin_unlock(&nfsi->vfs_inode.i_lock);

        /* if pnfs_layoutcommit_inode() runs between inode locks, the next one
         * will be a noop because NFS_INO_LAYOUTCOMMIT will not be set */
        if (mark_as_dirty)
                mark_inode_dirty_sync(wdata->inode);
}
EXPORT_SYMBOL_GPL(pnfs_set_layoutcommit);

/*
 * For the LAYOUT4_NFSV4_1_FILES layout type, NFS_DATA_SYNC WRITEs and
 * NFS_UNSTABLE WRITEs with a COMMIT to data servers must store enough
 * data to disk to allow the server to recover the data if it crashes.
 * LAYOUTCOMMIT is only needed when the NFL4_UFLG_COMMIT_THRU_MDS flag
 * is off, and a COMMIT is sent to a data server, or
 * if WRITEs to a data server return NFS_DATA_SYNC.
 */
int
pnfs_layoutcommit_inode(struct inode *inode, bool sync)
{
        struct nfs4_layoutcommit_data *data;
        struct nfs_inode *nfsi = NFS_I(inode);
        struct pnfs_layout_segment *lseg;
        struct rpc_cred *cred;
        loff_t end_pos;
        int status = 0;

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

        if (!test_bit(NFS_INO_LAYOUTCOMMIT, &nfsi->flags))
                return 0;

        /* Note kzalloc ensures data->res.seq_res.sr_slot == NULL */
        data = kzalloc(sizeof(*data), GFP_NOFS);
        if (!data) {
                mark_inode_dirty_sync(inode);
                status = -ENOMEM;
                goto out;
        }

        spin_lock(&inode->i_lock);
        if (!test_and_clear_bit(NFS_INO_LAYOUTCOMMIT, &nfsi->flags)) {
                spin_unlock(&inode->i_lock);
                kfree(data);
                goto out;
        }
        /*
         * Currently only one (whole file) write lseg which is referenced
         * in pnfs_set_layoutcommit and will be found.
         */
        lseg = pnfs_list_write_lseg(inode);

        end_pos = lseg->pls_end_pos;
        cred = lseg->pls_lc_cred;
        lseg->pls_end_pos = 0;
        lseg->pls_lc_cred = NULL;

        memcpy(&data->args.stateid.data, nfsi->layout->plh_stateid.data,
                sizeof(nfsi->layout->plh_stateid.data));
        spin_unlock(&inode->i_lock);

        data->args.inode = inode;
        data->lseg = lseg;
        data->cred = cred;
        nfs_fattr_init(&data->fattr);
        data->args.bitmask = NFS_SERVER(inode)->cache_consistency_bitmask;
        data->res.fattr = &data->fattr;
        data->args.lastbytewritten = end_pos - 1;
        data->res.server = NFS_SERVER(inode);

        status = nfs4_proc_layoutcommit(data, sync);
out:
        dprintk("<-- %s status %d\n", __func__, status);
        return status;
}