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Btrfs: wait on async pages when shrinking delalloc

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Mitch reported a problem where you could get an ENOSPC error when untarring
a kernel git tree onto a 16gb file system with compress-force=zlib.  This is
because compression is a huge pain, it will return from ->writepages()
without having actually created any ordered extents.  To get around this we
check to see if the async submit counter is up, and if it is wait until it
drops to 0 before doing our normal ordered wait dance.  With this patch I
can now untar a kernel git tree onto a 16gb file system without getting
ENOSPC errors.  Thanks,

Signed-off-by: Josef Bacik <jbacik@fusionio.com>
This commit is contained in:
Josef Bacik 2012-09-06 16:47:00 -04:00 committed by Chris Mason
parent 9e8a4a8b0b
commit dea31f5233
1 changed files with 7 additions and 0 deletions
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7
fs/btrfs/extent-tree.c
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@ -3697,6 +3697,13 @@ static void shrink_delalloc(struct btrfs_root *root, u64 to_reclaim, u64 orig,
writeback_inodes_sb_nr_if_idle(root->fs_info->sb, nr_pages,
WB_REASON_FS_FREE_SPACE);
/*
* We need to wait for the async pages to actually start before
* we do anything.
*/
wait_event(root->fs_info->async_submit_wait,
!atomic_read(&root->fs_info->async_delalloc_pages));
spin_lock(&space_info->lock);
if (space_info->bytes_used + space_info->bytes_reserved +
space_info->bytes_pinned + space_info->bytes_readonly +