[PATCH] btrfs: Fix quota reservation leak on preallocated files

[PATCH] btrfs: Fix quota reservation leak on preallocated files

[Justin Maggard]

Commit c6887cd11149 (Btrfs: don't do nocow check unless we have to)
changed the behavior of __btrfs_buffered_write() so that it first tries
to get a data space reservation, and then skips the relatively expensive
nocow check if the reservation succeeded.

If we have quotas enabled, the data space reservation also includes a
quota reservation.  But in the rewrite case, the space has already been
accounted for in qgroups.  So btrfs_check_data_free_space() increases the
quota reservation, but it never gets decreased when the data actually
gets written and overwrites the pre-existing data.  So we're left with
both the qgroup and qgroup reservation accounting for the same space.

This commit adds the missing btrfs_qgroup_free_data() call in the case of
BTRFS_ORDERED_PREALLOC extents.

Signed-off-by: Justin Maggard <jmaggard@netgear.com>
---
 fs/btrfs/inode.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index d94e3f68b9b1..d7881ccf5310 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -3006,6 +3006,8 @@ static int btrfs_finish_ordered_io(struct btrfs_ordered_extent *ordered_extent)
 		compress_type = ordered_extent->compress_type;
 	if (test_bit(BTRFS_ORDERED_PREALLOC, &ordered_extent->flags)) {
 		BUG_ON(compress_type);
+		btrfs_qgroup_free_data(inode, NULL, ordered_extent->file_offset,
+				       ordered_extent->len);
 		ret = btrfs_mark_extent_written(trans, BTRFS_I(inode),
 						ordered_extent->file_offset,
 						ordered_extent->file_offset +
-- 
2.14.2

Re: [PATCH] btrfs: Fix quota reservation leak on preallocated files

[Qu Wenruo]

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On 2017年10月31日 06:29, Justin Maggard wrote:
> Commit c6887cd11149 (Btrfs: don't do nocow check unless we have to)
> changed the behavior of __btrfs_buffered_write() so that it first tries
> to get a data space reservation, and then skips the relatively expensive
> nocow check if the reservation succeeded.
> 
> If we have quotas enabled, the data space reservation also includes a
> quota reservation.  But in the rewrite case, the space has already been
> accounted for in qgroups.  So btrfs_check_data_free_space() increases the
> quota reservation, but it never gets decreased when the data actually
> gets written and overwrites the pre-existing data.  So we're left with
> both the qgroup and qgroup reservation accounting for the same space.
> 
> This commit adds the missing btrfs_qgroup_free_data() call in the case of
> BTRFS_ORDERED_PREALLOC extents.
> 
> Signed-off-by: Justin Maggard <jmaggard@netgear.com>

Reviewed-by: Qu Wenruo <wqu@suse.com>

Thanks,
Qu
> ---
>  fs/btrfs/inode.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
> index d94e3f68b9b1..d7881ccf5310 100644
> --- a/fs/btrfs/inode.c
> +++ b/fs/btrfs/inode.c
> @@ -3006,6 +3006,8 @@ static int btrfs_finish_ordered_io(struct btrfs_ordered_extent *ordered_extent)
>  		compress_type = ordered_extent->compress_type;
>  	if (test_bit(BTRFS_ORDERED_PREALLOC, &ordered_extent->flags)) {
>  		BUG_ON(compress_type);
> +		btrfs_qgroup_free_data(inode, NULL, ordered_extent->file_offset,
> +				       ordered_extent->len);
>  		ret = btrfs_mark_extent_written(trans, BTRFS_I(inode),
>  						ordered_extent->file_offset,
>  						ordered_extent->file_offset +
> 


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