extents.c

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/*
 *  linux/fs/nfs/blocklayout/blocklayout.h
 *
 *  Module for the NFSv4.1 pNFS block layout driver.
 *
 *  Copyright (c) 2006 The Regents of the University of Michigan.
 *  All rights reserved.
 *
 *  Andy Adamson <[email protected]>
 *  Fred Isaman <[email protected]>
 *
 * 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 from the
 * university of michigan as to its fitness for any purpose, and without
 * warranty by the university of michigan of any kind, either express
 * or implied, including without limitation the implied warranties of
 * merchantability and fitness for a particular purpose.  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 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 "blocklayout.h"
#define NFSDBG_FACILITY         NFSDBG_PNFS_LD

/* Bit numbers */
#define EXTENT_INITIALIZED 0
#define EXTENT_WRITTEN     1
#define EXTENT_IN_COMMIT   2
#define INTERNAL_EXISTS    MY_MAX_TAGS
#define INTERNAL_MASK      ((1 << INTERNAL_EXISTS) - 1)

/* Returns largest t<=s s.t. t%base==0 */
static inline sector_t normalize(sector_t s, int base)
{
    sector_t tmp = s; /* Since do_div modifies its argument */
    return s - do_div(tmp, base);
}

static inline sector_t normalize_up(sector_t s, int base)
{
    return normalize(s + base - 1, base);
}

/* Complete stub using list while determine API wanted */

/* Returns tags, or negative */
static int32_t _find_entry(struct my_tree *tree, u64 s)
{
    struct pnfs_inval_tracking *pos;

    dprintk("%s(%llu) enter\n", __func__, s);
    list_for_each_entry_reverse(pos, &tree->mtt_stub, it_link) {
        if (pos->it_sector > s)
            continue;
        else if (pos->it_sector == s)
            return pos->it_tags & INTERNAL_MASK;
        else
            break;
    }
    return -ENOENT;
}

static inline
int _has_tag(struct my_tree *tree, u64 s, int32_t tag)
{
    int32_t tags;

    dprintk("%s(%llu, %i) enter\n", __func__, s, tag);
    s = normalize(s, tree->mtt_step_size);
    tags = _find_entry(tree, s);
    if ((tags < 0) || !(tags & (1 << tag)))
        return 0;
    else
        return 1;
}

/* Creates entry with tag, or if entry already exists, unions tag to it.
 * If storage is not NULL, newly created entry will use it.
 * Returns number of entries added, or negative on error.
 */
static int _add_entry(struct my_tree *tree, u64 s, int32_t tag,
              struct pnfs_inval_tracking *storage)
{
    int found = 0;
    struct pnfs_inval_tracking *pos;

    dprintk("%s(%llu, %i, %p) enter\n", __func__, s, tag, storage);
    list_for_each_entry_reverse(pos, &tree->mtt_stub, it_link) {
        if (pos->it_sector > s)
            continue;
        else if (pos->it_sector == s) {
            found = 1;
            break;
        } else
            break;
    }
    if (found) {
        pos->it_tags |= (1 << tag);
        return 0;
    } else {
        struct pnfs_inval_tracking *new;
        new = storage;
        new->it_sector = s;
        new->it_tags = (1 << tag);
        list_add(&new->it_link, &pos->it_link);
        return 1;
    }
}

/* XXXX Really want option to not create */
/* Over range, unions tag with existing entries, else creates entry with tag */
static int _set_range(struct my_tree *tree, int32_t tag, u64 s, u64 length)
{
    u64 i;

    dprintk("%s(%i, %llu, %llu) enter\n", __func__, tag, s, length);
    for (i = normalize(s, tree->mtt_step_size); i < s + length;
         i += tree->mtt_step_size)
        if (_add_entry(tree, i, tag, NULL))
            return -ENOMEM;
    return 0;
}

/* Ensure that future operations on given range of tree will not malloc */
static int _preload_range(struct pnfs_inval_markings *marks,
        u64 offset, u64 length)
{
    u64 start, end, s;
    int count, i, used = 0, status = -ENOMEM;
    struct pnfs_inval_tracking **storage;
    struct my_tree  *tree = &marks->im_tree;

    dprintk("%s(%llu, %llu) enter\n", __func__, offset, length);
    start = normalize(offset, tree->mtt_step_size);
    end = normalize_up(offset + length, tree->mtt_step_size);
    count = (int)(end - start) / (int)tree->mtt_step_size;

    /* Pre-malloc what memory we might need */
    storage = kcalloc(count, sizeof(*storage), GFP_NOFS);
    if (!storage)
        return -ENOMEM;
    for (i = 0; i < count; i++) {
        storage[i] = kmalloc(sizeof(struct pnfs_inval_tracking),
                     GFP_NOFS);
        if (!storage[i])
            goto out_cleanup;
    }

    spin_lock_bh(&marks->im_lock);
    for (s = start; s < end; s += tree->mtt_step_size)
        used += _add_entry(tree, s, INTERNAL_EXISTS, storage[used]);
    spin_unlock_bh(&marks->im_lock);

    status = 0;

 out_cleanup:
    for (i = used; i < count; i++) {
        if (!storage[i])
            break;
        kfree(storage[i]);
    }
    kfree(storage);
    return status;
}

/* We are relying on page lock to serialize this */
int bl_is_sector_init(struct pnfs_inval_markings *marks, sector_t isect)
{
    int rv;

    spin_lock_bh(&marks->im_lock);
    rv = _has_tag(&marks->im_tree, isect, EXTENT_INITIALIZED);
    spin_unlock_bh(&marks->im_lock);
    return rv;
}

/* Assume start, end already sector aligned */
static int
_range_has_tag(struct my_tree *tree, u64 start, u64 end, int32_t tag)
{
    struct pnfs_inval_tracking *pos;
    u64 expect = 0;

    dprintk("%s(%llu, %llu, %i) enter\n", __func__, start, end, tag);
    list_for_each_entry_reverse(pos, &tree->mtt_stub, it_link) {
        if (pos->it_sector >= end)
            continue;
        if (!expect) {
            if ((pos->it_sector == end - tree->mtt_step_size) &&
                (pos->it_tags & (1 << tag))) {
                expect = pos->it_sector - tree->mtt_step_size;
                if (pos->it_sector < tree->mtt_step_size || expect < start)
                    return 1;
                continue;
            } else {
                return 0;
            }
        }
        if (pos->it_sector != expect || !(pos->it_tags & (1 << tag)))
            return 0;
        expect -= tree->mtt_step_size;
        if (expect < start)
            return 1;
    }
    return 0;
}

static int is_range_written(struct pnfs_inval_markings *marks,
                sector_t start, sector_t end)
{
    int rv;

    spin_lock_bh(&marks->im_lock);
    rv = _range_has_tag(&marks->im_tree, start, end, EXTENT_WRITTEN);
    spin_unlock_bh(&marks->im_lock);
    return rv;
}

/* Marks sectors in [offest, offset_length) as having been initialized.
 * All lengths are step-aligned, where step is min(pagesize, blocksize).
 * Currently assumes offset is page-aligned
 */
int bl_mark_sectors_init(struct pnfs_inval_markings *marks,
                 sector_t offset, sector_t length)
{
    sector_t start, end;

    dprintk("%s(offset=%llu,len=%llu) enter\n",
        __func__, (u64)offset, (u64)length);

    start = normalize(offset, marks->im_block_size);
    end = normalize_up(offset + length, marks->im_block_size);
    if (_preload_range(marks, start, end - start))
        goto outerr;

    spin_lock_bh(&marks->im_lock);
    if (_set_range(&marks->im_tree, EXTENT_INITIALIZED, offset, length))
        goto out_unlock;
    spin_unlock_bh(&marks->im_lock);

    return 0;

out_unlock:
    spin_unlock_bh(&marks->im_lock);
outerr:
    return -ENOMEM;
}

/* Marks sectors in [offest, offset+length) as having been written to disk.
 * All lengths should be block aligned.
 */
static int mark_written_sectors(struct pnfs_inval_markings *marks,
                sector_t offset, sector_t length)
{
    int status;

    dprintk("%s(offset=%llu,len=%llu) enter\n", __func__,
        (u64)offset, (u64)length);
    spin_lock_bh(&marks->im_lock);
    status = _set_range(&marks->im_tree, EXTENT_WRITTEN, offset, length);
    spin_unlock_bh(&marks->im_lock);
    return status;
}

static void print_short_extent(struct pnfs_block_short_extent *be)
{
    dprintk("PRINT SHORT EXTENT extent %p\n", be);
    if (be) {
        dprintk("        be_f_offset %llu\n", (u64)be->bse_f_offset);
        dprintk("        be_length   %llu\n", (u64)be->bse_length);
    }
}

static void print_clist(struct list_head *list, unsigned int count)
{
    struct pnfs_block_short_extent *be;
    unsigned int i = 0;

    ifdebug(FACILITY) {
        printk(KERN_DEBUG "****************\n");
        printk(KERN_DEBUG "Extent list looks like:\n");
        list_for_each_entry(be, list, bse_node) {
            i++;
            print_short_extent(be);
        }
        if (i != count)
            printk(KERN_DEBUG "\n\nExpected %u entries\n\n\n", count);
        printk(KERN_DEBUG "****************\n");
    }
}

/* Note: In theory, we should do more checking that devid's match between
 * old and new, but if they don't, the lists are too corrupt to salvage anyway.
 */
/* Note this is very similar to bl_add_merge_extent */
static void add_to_commitlist(struct pnfs_block_layout *bl,
                  struct pnfs_block_short_extent *new)
{
    struct list_head *clist = &bl->bl_commit;
    struct pnfs_block_short_extent *old, *save;
    sector_t end = new->bse_f_offset + new->bse_length;

    dprintk("%s enter\n", __func__);
    print_short_extent(new);
    print_clist(clist, bl->bl_count);
    bl->bl_count++;
    /* Scan for proper place to insert, extending new to the left
     * as much as possible.
     */
    list_for_each_entry_safe(old, save, clist, bse_node) {
        if (new->bse_f_offset < old->bse_f_offset)
            break;
        if (end <= old->bse_f_offset + old->bse_length) {
            /* Range is already in list */
            bl->bl_count--;
            kfree(new);
            return;
        } else if (new->bse_f_offset <=
                old->bse_f_offset + old->bse_length) {
            /* new overlaps or abuts existing be */
            if (new->bse_mdev == old->bse_mdev) {
                /* extend new to fully replace old */
                new->bse_length += new->bse_f_offset -
                        old->bse_f_offset;
                new->bse_f_offset = old->bse_f_offset;
                list_del(&old->bse_node);
                bl->bl_count--;
                kfree(old);
            }
        }
    }
    /* Note that if we never hit the above break, old will not point to a
     * valid extent.  However, in that case &old->bse_node==list.
     */
    list_add_tail(&new->bse_node, &old->bse_node);
    /* Scan forward for overlaps.  If we find any, extend new and
     * remove the overlapped extent.
     */
    old = list_prepare_entry(new, clist, bse_node);
    list_for_each_entry_safe_continue(old, save, clist, bse_node) {
        if (end < old->bse_f_offset)
            break;
        /* new overlaps or abuts old */
        if (new->bse_mdev == old->bse_mdev) {
            if (end < old->bse_f_offset + old->bse_length) {
                /* extend new to fully cover old */
                end = old->bse_f_offset + old->bse_length;
                new->bse_length = end - new->bse_f_offset;
            }
            list_del(&old->bse_node);
            bl->bl_count--;
            kfree(old);
        }
    }
    dprintk("%s: after merging\n", __func__);
    print_clist(clist, bl->bl_count);
}

/* Note the range described by offset, length is guaranteed to be contained
 * within be.
 * new will be freed, either by this function or add_to_commitlist if they
 * decide not to use it, or after LAYOUTCOMMIT uses it in the commitlist.
 */
int bl_mark_for_commit(struct pnfs_block_extent *be,
            sector_t offset, sector_t length,
            struct pnfs_block_short_extent *new)
{
    sector_t new_end, end = offset + length;
    struct pnfs_block_layout *bl = container_of(be->be_inval,
                            struct pnfs_block_layout,
                            bl_inval);

    mark_written_sectors(be->be_inval, offset, length);
    /* We want to add the range to commit list, but it must be
     * block-normalized, and verified that the normalized range has
     * been entirely written to disk.
     */
    new->bse_f_offset = offset;
    offset = normalize(offset, bl->bl_blocksize);
    if (offset < new->bse_f_offset) {
        if (is_range_written(be->be_inval, offset, new->bse_f_offset))
            new->bse_f_offset = offset;
        else
            new->bse_f_offset = offset + bl->bl_blocksize;
    }
    new_end = normalize_up(end, bl->bl_blocksize);
    if (end < new_end) {
        if (is_range_written(be->be_inval, end, new_end))
            end = new_end;
        else
            end = new_end - bl->bl_blocksize;
    }
    if (end <= new->bse_f_offset) {
        kfree(new);
        return 0;
    }
    new->bse_length = end - new->bse_f_offset;
    new->bse_devid = be->be_devid;
    new->bse_mdev = be->be_mdev;

    spin_lock(&bl->bl_ext_lock);
    add_to_commitlist(bl, new);
    spin_unlock(&bl->bl_ext_lock);
    return 0;
}

static void print_bl_extent(struct pnfs_block_extent *be)
{
    dprintk("PRINT EXTENT extent %p\n", be);
    if (be) {
        dprintk("        be_f_offset %llu\n", (u64)be->be_f_offset);
        dprintk("        be_length   %llu\n", (u64)be->be_length);
        dprintk("        be_v_offset %llu\n", (u64)be->be_v_offset);
        dprintk("        be_state    %d\n", be->be_state);
    }
}

static void
destroy_extent(struct kref *kref)
{
    struct pnfs_block_extent *be;

    be = container_of(kref, struct pnfs_block_extent, be_refcnt);
    dprintk("%s be=%p\n", __func__, be);
    kfree(be);
}

void
bl_put_extent(struct pnfs_block_extent *be)
{
    if (be) {
        dprintk("%s enter %p (%i)\n", __func__, be,
            atomic_read(&be->be_refcnt.refcount));
        kref_put(&be->be_refcnt, destroy_extent);
    }
}

struct pnfs_block_extent *bl_alloc_extent(void)
{
    struct pnfs_block_extent *be;

    be = kmalloc(sizeof(struct pnfs_block_extent), GFP_NOFS);
    if (!be)
        return NULL;
    INIT_LIST_HEAD(&be->be_node);
    kref_init(&be->be_refcnt);
    be->be_inval = NULL;
    return be;
}

static void print_elist(struct list_head *list)
{
    struct pnfs_block_extent *be;
    dprintk("****************\n");
    dprintk("Extent list looks like:\n");
    list_for_each_entry(be, list, be_node) {
        print_bl_extent(be);
    }
    dprintk("****************\n");
}

static inline int
extents_consistent(struct pnfs_block_extent *old, struct pnfs_block_extent *new)
{
    /* Note this assumes new->be_f_offset >= old->be_f_offset */
    return (new->be_state == old->be_state) &&
        ((new->be_state == PNFS_BLOCK_NONE_DATA) ||
         ((new->be_v_offset - old->be_v_offset ==
           new->be_f_offset - old->be_f_offset) &&
          new->be_mdev == old->be_mdev));
}

/* Adds new to appropriate list in bl, modifying new and removing existing
 * extents as appropriate to deal with overlaps.
 *
 * See bl_find_get_extent for list constraints.
 *
 * Refcount on new is already set.  If end up not using it, or error out,
 * need to put the reference.
 *
 * bl->bl_ext_lock is held by caller.
 */
int
bl_add_merge_extent(struct pnfs_block_layout *bl,
             struct pnfs_block_extent *new)
{
    struct pnfs_block_extent *be, *tmp;
    sector_t end = new->be_f_offset + new->be_length;
    struct list_head *list;

    dprintk("%s enter with be=%p\n", __func__, new);
    print_bl_extent(new);
    list = &bl->bl_extents[bl_choose_list(new->be_state)];
    print_elist(list);

    /* Scan for proper place to insert, extending new to the left
     * as much as possible.
     */
    list_for_each_entry_safe_reverse(be, tmp, list, be_node) {
        if (new->be_f_offset >= be->be_f_offset + be->be_length)
            break;
        if (new->be_f_offset >= be->be_f_offset) {
            if (end <= be->be_f_offset + be->be_length) {
                /* new is a subset of existing be*/
                if (extents_consistent(be, new)) {
                    dprintk("%s: new is subset, ignoring\n",
                        __func__);
                    bl_put_extent(new);
                    return 0;
                } else {
                    goto out_err;
                }
            } else {
                /* |<--   be   -->|
                 *          |<--   new   -->| */
                if (extents_consistent(be, new)) {
                    /* extend new to fully replace be */
                    new->be_length += new->be_f_offset -
                        be->be_f_offset;
                    new->be_f_offset = be->be_f_offset;
                    new->be_v_offset = be->be_v_offset;
                    dprintk("%s: removing %p\n", __func__, be);
                    list_del(&be->be_node);
                    bl_put_extent(be);
                } else {
                    goto out_err;
                }
            }
        } else if (end >= be->be_f_offset + be->be_length) {
            /* new extent overlap existing be */
            if (extents_consistent(be, new)) {
                /* extend new to fully replace be */
                dprintk("%s: removing %p\n", __func__, be);
                list_del(&be->be_node);
                bl_put_extent(be);
            } else {
                goto out_err;
            }
        } else if (end > be->be_f_offset) {
            /*           |<--   be   -->|
             *|<--   new   -->| */
            if (extents_consistent(new, be)) {
                /* extend new to fully replace be */
                new->be_length += be->be_f_offset + be->be_length -
                    new->be_f_offset - new->be_length;
                dprintk("%s: removing %p\n", __func__, be);
                list_del(&be->be_node);
                bl_put_extent(be);
            } else {
                goto out_err;
            }
        }
    }
    /* Note that if we never hit the above break, be will not point to a
     * valid extent.  However, in that case &be->be_node==list.
     */
    list_add(&new->be_node, &be->be_node);
    dprintk("%s: inserting new\n", __func__);
    print_elist(list);
    /* FIXME - The per-list consistency checks have all been done,
     * should now check cross-list consistency.
     */
    return 0;

 out_err:
    bl_put_extent(new);
    return -EIO;
}

/* Returns extent, or NULL.  If a second READ extent exists, it is returned
 * in cow_read, if given.
 *
 * The extents are kept in two seperate ordered lists, one for READ and NONE,
 * one for READWRITE and INVALID.  Within each list, we assume:
 * 1. Extents are ordered by file offset.
 * 2. For any given isect, there is at most one extents that matches.
 */
struct pnfs_block_extent *
bl_find_get_extent(struct pnfs_block_layout *bl, sector_t isect,
        struct pnfs_block_extent **cow_read)
{
    struct pnfs_block_extent *be, *cow, *ret;
    int i;

    dprintk("%s enter with isect %llu\n", __func__, (u64)isect);
    cow = ret = NULL;
    spin_lock(&bl->bl_ext_lock);
    for (i = 0; i < EXTENT_LISTS; i++) {
        list_for_each_entry_reverse(be, &bl->bl_extents[i], be_node) {
            if (isect >= be->be_f_offset + be->be_length)
                break;
            if (isect >= be->be_f_offset) {
                /* We have found an extent */
                dprintk("%s Get %p (%i)\n", __func__, be,
                    atomic_read(&be->be_refcnt.refcount));
                kref_get(&be->be_refcnt);
                if (!ret)
                    ret = be;
                else if (be->be_state != PNFS_BLOCK_READ_DATA)
                    bl_put_extent(be);
                else
                    cow = be;
                break;
            }
        }
        if (ret &&
            (!cow_read || ret->be_state != PNFS_BLOCK_INVALID_DATA))
            break;
    }
    spin_unlock(&bl->bl_ext_lock);
    if (cow_read)
        *cow_read = cow;
    print_bl_extent(ret);
    return ret;
}

/* Similar to bl_find_get_extent, but called with lock held, and ignores cow */
static struct pnfs_block_extent *
bl_find_get_extent_locked(struct pnfs_block_layout *bl, sector_t isect)
{
    struct pnfs_block_extent *be, *ret = NULL;
    int i;

    dprintk("%s enter with isect %llu\n", __func__, (u64)isect);
    for (i = 0; i < EXTENT_LISTS; i++) {
        if (ret)
            break;
        list_for_each_entry_reverse(be, &bl->bl_extents[i], be_node) {
            if (isect >= be->be_f_offset + be->be_length)
                break;
            if (isect >= be->be_f_offset) {
                /* We have found an extent */
                dprintk("%s Get %p (%i)\n", __func__, be,
                    atomic_read(&be->be_refcnt.refcount));
                kref_get(&be->be_refcnt);
                ret = be;
                break;
            }
        }
    }
    print_bl_extent(ret);
    return ret;
}

int
encode_pnfs_block_layoutupdate(struct pnfs_block_layout *bl,
                   struct xdr_stream *xdr,
                   const struct nfs4_layoutcommit_args *arg)
{
    struct pnfs_block_short_extent *lce, *save;
    unsigned int count = 0;
    __be32 *p, *xdr_start;

    dprintk("%s enter\n", __func__);
    /* BUG - creation of bl_commit is buggy - need to wait for
     * entire block to be marked WRITTEN before it can be added.
     */
    spin_lock(&bl->bl_ext_lock);
    /* Want to adjust for possible truncate */
    /* We now want to adjust argument range */

    /* XDR encode the ranges found */
    xdr_start = xdr_reserve_space(xdr, 8);
    if (!xdr_start)
        goto out;
    list_for_each_entry_safe(lce, save, &bl->bl_commit, bse_node) {
        p = xdr_reserve_space(xdr, 7 * 4 + sizeof(lce->bse_devid.data));
        if (!p)
            break;
        p = xdr_encode_opaque_fixed(p, lce->bse_devid.data, NFS4_DEVICEID4_SIZE);
        p = xdr_encode_hyper(p, lce->bse_f_offset << SECTOR_SHIFT);
        p = xdr_encode_hyper(p, lce->bse_length << SECTOR_SHIFT);
        p = xdr_encode_hyper(p, 0LL);
        *p++ = cpu_to_be32(PNFS_BLOCK_READWRITE_DATA);
        list_move_tail(&lce->bse_node, &bl->bl_committing);
        bl->bl_count--;
        count++;
    }
    xdr_start[0] = cpu_to_be32((xdr->p - xdr_start - 1) * 4);
    xdr_start[1] = cpu_to_be32(count);
out:
    spin_unlock(&bl->bl_ext_lock);
    dprintk("%s found %i ranges\n", __func__, count);
    return 0;
}

/* Helper function to set_to_rw that initialize a new extent */
static void
_prep_new_extent(struct pnfs_block_extent *new,
         struct pnfs_block_extent *orig,
         sector_t offset, sector_t length, int state)
{
    kref_init(&new->be_refcnt);
    /* don't need to INIT_LIST_HEAD(&new->be_node) */
    memcpy(&new->be_devid, &orig->be_devid, sizeof(struct nfs4_deviceid));
    new->be_mdev = orig->be_mdev;
    new->be_f_offset = offset;
    new->be_length = length;
    new->be_v_offset = orig->be_v_offset - orig->be_f_offset + offset;
    new->be_state = state;
    new->be_inval = orig->be_inval;
}

/* Tries to merge be with extent in front of it in list.
 * Frees storage if not used.
 */
static struct pnfs_block_extent *
_front_merge(struct pnfs_block_extent *be, struct list_head *head,
         struct pnfs_block_extent *storage)
{
    struct pnfs_block_extent *prev;

    if (!storage)
        goto no_merge;
    if (&be->be_node == head || be->be_node.prev == head)
        goto no_merge;
    prev = list_entry(be->be_node.prev, struct pnfs_block_extent, be_node);
    if ((prev->be_f_offset + prev->be_length != be->be_f_offset) ||
        !extents_consistent(prev, be))
        goto no_merge;
    _prep_new_extent(storage, prev, prev->be_f_offset,
             prev->be_length + be->be_length, prev->be_state);
    list_replace(&prev->be_node, &storage->be_node);
    bl_put_extent(prev);
    list_del(&be->be_node);
    bl_put_extent(be);
    return storage;

 no_merge:
    kfree(storage);
    return be;
}

static u64
set_to_rw(struct pnfs_block_layout *bl, u64 offset, u64 length)
{
    u64 rv = offset + length;
    struct pnfs_block_extent *be, *e1, *e2, *e3, *new, *old;
    struct pnfs_block_extent *children[3];
    struct pnfs_block_extent *merge1 = NULL, *merge2 = NULL;
    int i = 0, j;

    dprintk("%s(%llu, %llu)\n", __func__, offset, length);
    /* Create storage for up to three new extents e1, e2, e3 */
    e1 = kmalloc(sizeof(*e1), GFP_ATOMIC);
    e2 = kmalloc(sizeof(*e2), GFP_ATOMIC);
    e3 = kmalloc(sizeof(*e3), GFP_ATOMIC);
    /* BUG - we are ignoring any failure */
    if (!e1 || !e2 || !e3)
        goto out_nosplit;

    spin_lock(&bl->bl_ext_lock);
    be = bl_find_get_extent_locked(bl, offset);
    rv = be->be_f_offset + be->be_length;
    if (be->be_state != PNFS_BLOCK_INVALID_DATA) {
        spin_unlock(&bl->bl_ext_lock);
        goto out_nosplit;
    }
    /* Add e* to children, bumping e*'s krefs */
    if (be->be_f_offset != offset) {
        _prep_new_extent(e1, be, be->be_f_offset,
                 offset - be->be_f_offset,
                 PNFS_BLOCK_INVALID_DATA);
        children[i++] = e1;
        print_bl_extent(e1);
    } else
        merge1 = e1;
    _prep_new_extent(e2, be, offset,
             min(length, be->be_f_offset + be->be_length - offset),
             PNFS_BLOCK_READWRITE_DATA);
    children[i++] = e2;
    print_bl_extent(e2);
    if (offset + length < be->be_f_offset + be->be_length) {
        _prep_new_extent(e3, be, e2->be_f_offset + e2->be_length,
                 be->be_f_offset + be->be_length -
                 offset - length,
                 PNFS_BLOCK_INVALID_DATA);
        children[i++] = e3;
        print_bl_extent(e3);
    } else
        merge2 = e3;

    /* Remove be from list, and insert the e* */
    /* We don't get refs on e*, since this list is the base reference
     * set when init'ed.
     */
    if (i < 3)
        children[i] = NULL;
    new = children[0];
    list_replace(&be->be_node, &new->be_node);
    bl_put_extent(be);
    new = _front_merge(new, &bl->bl_extents[RW_EXTENT], merge1);
    for (j = 1; j < i; j++) {
        old = new;
        new = children[j];
        list_add(&new->be_node, &old->be_node);
    }
    if (merge2) {
        /* This is a HACK, should just create a _back_merge function */
        new = list_entry(new->be_node.next,
                 struct pnfs_block_extent, be_node);
        new = _front_merge(new, &bl->bl_extents[RW_EXTENT], merge2);
    }
    spin_unlock(&bl->bl_ext_lock);

    /* Since we removed the base reference above, be is now scheduled for
     * destruction.
     */
    bl_put_extent(be);
    dprintk("%s returns %llu after split\n", __func__, rv);
    return rv;

 out_nosplit:
    kfree(e1);
    kfree(e2);
    kfree(e3);
    dprintk("%s returns %llu without splitting\n", __func__, rv);
    return rv;
}

void
clean_pnfs_block_layoutupdate(struct pnfs_block_layout *bl,
                  const struct nfs4_layoutcommit_args *arg,
                  int status)
{
    struct pnfs_block_short_extent *lce, *save;

    dprintk("%s status %d\n", __func__, status);
    list_for_each_entry_safe(lce, save, &bl->bl_committing, bse_node) {
        if (likely(!status)) {
            u64 offset = lce->bse_f_offset;
            u64 end = offset + lce->bse_length;

            do {
                offset = set_to_rw(bl, offset, end - offset);
            } while (offset < end);
            list_del(&lce->bse_node);

            kfree(lce);
        } else {
            list_del(&lce->bse_node);
            spin_lock(&bl->bl_ext_lock);
            add_to_commitlist(bl, lce);
            spin_unlock(&bl->bl_ext_lock);
        }
    }
}

int bl_push_one_short_extent(struct pnfs_inval_markings *marks)
{
    struct pnfs_block_short_extent *new;

    new = kmalloc(sizeof(*new), GFP_NOFS);
    if (unlikely(!new))
        return -ENOMEM;

    spin_lock_bh(&marks->im_lock);
    list_add(&new->bse_node, &marks->im_extents);
    spin_unlock_bh(&marks->im_lock);

    return 0;
}

struct pnfs_block_short_extent *
bl_pop_one_short_extent(struct pnfs_inval_markings *marks)
{
    struct pnfs_block_short_extent *rv = NULL;

    spin_lock_bh(&marks->im_lock);
    if (!list_empty(&marks->im_extents)) {
        rv = list_entry((&marks->im_extents)->next,
                struct pnfs_block_short_extent, bse_node);
        list_del_init(&rv->bse_node);
    }
    spin_unlock_bh(&marks->im_lock);

    return rv;
}

void bl_free_short_extents(struct pnfs_inval_markings *marks, int num_to_free)
{
    struct pnfs_block_short_extent *se = NULL, *tmp;

    if (num_to_free <= 0)
        return;

    spin_lock(&marks->im_lock);
    list_for_each_entry_safe(se, tmp, &marks->im_extents, bse_node) {
        list_del(&se->bse_node);
        kfree(se);
        if (--num_to_free == 0)
            break;
    }
    spin_unlock(&marks->im_lock);

    BUG_ON(num_to_free > 0);
}