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SubjectRe: [PATCH] xfs: Fix tail rounding in xfs_alloc_file_space()
On Thu, Sep 26, 2019 at 04:22:38PM +0200, Max Reitz wrote:
> To ensure that all blocks touched by the range [offset, offset + count)
> are allocated, we need to calculate the block count from the difference
> of the range end (rounded up) and the range start (rounded down).
>
> Before this patch, we just round up the byte count, which may lead to
> unaligned ranges not being fully allocated:
>
> $ touch test_file
> $ block_size=$(stat -fc '%S' test_file)
> $ fallocate -o $((block_size / 2)) -l $block_size test_file
> $ xfs_bmap test_file
> test_file:
> 0: [0..7]: 1396264..1396271
> 1: [8..15]: hole
>
> There should not be a hole there. Instead, the first two blocks should
> be fully allocated.
>
> With this patch applied, the result is something like this:
>
> $ touch test_file
> $ block_size=$(stat -fc '%S' test_file)
> $ fallocate -o $((block_size / 2)) -l $block_size test_file
> $ xfs_bmap test_file
> test_file:
> 0: [0..15]: 11024..11039

Code looks ok; by any chance do you have an xfstest we could add to the
regresion test suite?

--D

> Signed-off-by: Max Reitz <mreitz@redhat.com>
> ---
> fs/xfs/xfs_bmap_util.c | 4 +++-
> 1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/fs/xfs/xfs_bmap_util.c b/fs/xfs/xfs_bmap_util.c
> index 0910cb75b65d..4f443703065e 100644
> --- a/fs/xfs/xfs_bmap_util.c
> +++ b/fs/xfs/xfs_bmap_util.c
> @@ -864,6 +864,7 @@ xfs_alloc_file_space(
> xfs_filblks_t allocatesize_fsb;
> xfs_extlen_t extsz, temp;
> xfs_fileoff_t startoffset_fsb;
> + xfs_fileoff_t endoffset_fsb;
> int nimaps;
> int quota_flag;
> int rt;
> @@ -891,7 +892,8 @@ xfs_alloc_file_space(
> imapp = &imaps[0];
> nimaps = 1;
> startoffset_fsb = XFS_B_TO_FSBT(mp, offset);
> - allocatesize_fsb = XFS_B_TO_FSB(mp, count);
> + endoffset_fsb = XFS_B_TO_FSB(mp, offset + count);
> + allocatesize_fsb = endoffset_fsb - startoffset_fsb;
>
> /*
> * Allocate file space until done or until there is an error
> --
> 2.23.0
>

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