On Thu, Feb 09, 2017 at 02:34:53PM -0500, Brian Foster wrote:
> Certain workoads that punch holes into speculative preallocation can
> cause delalloc indirect reservation splits when the delalloc extent is
> split in two. If further splits occur, an already short-handed extent
> can be split into two in a manner that leaves zero indirect blocks for
> one of the two new extents. This occurs because the shortage is large
> enough that the xfs_bmap_split_indlen() algorithm completely drains the
> requested indlen of one of the extents before it honors the existing
> reservation.
>
> This ultimately results in a warning from xfs_bmap_del_extent(). This
> has been observed during file copies of large, sparse files using 'cp
> --sparse=always.'
>
> To avoid this problem, update xfs_bmap_split_indlen() to explicitly
> apply the reservation shortage fairly between both extents. This smooths
> out the overall indlen shortage and defers the situation where we end up
> with a delalloc extent with zero indlen reservation to extreme
> circumstances.
>
> Reported-by: Patrick Dung <mpatdung@xxxxxxxxx>
> Signed-off-by: Brian Foster <bfoster@xxxxxxxxxx>
> ---
> fs/xfs/libxfs/xfs_bmap.c | 61 ++++++++++++++++++++++++++++++++++--------------
> 1 file changed, 43 insertions(+), 18 deletions(-)
>
> diff --git a/fs/xfs/libxfs/xfs_bmap.c b/fs/xfs/libxfs/xfs_bmap.c
> index 49edea4..e27b9ee 100644
> --- a/fs/xfs/libxfs/xfs_bmap.c
> +++ b/fs/xfs/libxfs/xfs_bmap.c
> @@ -4790,6 +4790,7 @@ xfs_bmap_split_indlen(
> xfs_filblks_t len2 = *indlen2;
> xfs_filblks_t nres = len1 + len2; /* new total res. */
> xfs_filblks_t stolen = 0;
> + xfs_filblks_t resfactor;
>
> trace_printk("%d: ores %llu len1 %llu len2 %llu\n", __LINE__, ores, len1, len2);
Is this line a leftover from debug code? Patch doesn't apply with this
line on top of 4.10-rc8 kernel.
Thanks,
Eryu
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