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    Subject[PATCH AUTOSEL for 4.14 042/100] btrfs: fix deadlock when writing out space cache
    Date
    From: Josef Bacik <jbacik@fb.com>

    [ Upstream commit b77000ed558daa3bef0899d29bf171b8c9b5e6a8 ]

    If we fail to prepare our pages for whatever reason (out of memory in
    our case) we need to make sure to drop the block_group->data_rwsem,
    otherwise hilarity ensues.

    Signed-off-by: Josef Bacik <jbacik@fb.com>
    Reviewed-by: Omar Sandoval <osandov@fb.com>
    Reviewed-by: Liu Bo <bo.li.liu@oracle.com>
    Reviewed-by: David Sterba <dsterba@suse.com>
    [ add label and use existing unlocking code ]
    Signed-off-by: David Sterba <dsterba@suse.com>

    Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
    ---
    fs/btrfs/free-space-cache.c | 3 ++-
    1 file changed, 2 insertions(+), 1 deletion(-)

    diff --git a/fs/btrfs/free-space-cache.c b/fs/btrfs/free-space-cache.c
    index cdc9f4015ec3..4426d1c73e50 100644
    --- a/fs/btrfs/free-space-cache.c
    +++ b/fs/btrfs/free-space-cache.c
    @@ -1264,7 +1264,7 @@ static int __btrfs_write_out_cache(struct btrfs_root *root, struct inode *inode,
    /* Lock all pages first so we can lock the extent safely. */
    ret = io_ctl_prepare_pages(io_ctl, inode, 0);
    if (ret)
    - goto out;
    + goto out_unlock;

    lock_extent_bits(&BTRFS_I(inode)->io_tree, 0, i_size_read(inode) - 1,
    &cached_state);
    @@ -1358,6 +1358,7 @@ out_nospc_locked:
    out_nospc:
    cleanup_write_cache_enospc(inode, io_ctl, &cached_state);

    +out_unlock:
    if (block_group && (block_group->flags & BTRFS_BLOCK_GROUP_DATA))
    up_write(&block_group->data_rwsem);

    --
    2.11.0
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