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xfs: handle nimaps=0 from xfs_bmapi_write in xfs_alloc_file_space

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If xfs_bmapi_write finds a delalloc extent at the requested range, it
tries to convert the entire delalloc extent to a real allocation.

But if the allocator cannot find a single free extent large enough to
cover the start block of the requested range, xfs_bmapi_write will
return 0 but leave *nimaps set to 0.

In that case we simply need to keep looping with the same startoffset_fsb
so that one of the following allocations will eventually reach the
requested range.

Note that this could affect any caller of xfs_bmapi_write that covers
an existing delayed allocation.  As far as I can tell we do not have
any other such caller, though - the regular writeback path uses
xfs_bmapi_convert_delalloc to convert delayed allocations to real ones,
and direct I/O invalidates the page cache first.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: "Darrick J. Wong" <djwong@kernel.org>
Signed-off-by: Chandan Babu R <chandanbabu@kernel.org>
This commit is contained in:
Christoph Hellwig 2023-10-11 07:16:26 +02:00 committed by Chandan Babu R
parent 2b99e410b2
commit 35dc55b9e8
1 changed files with 13 additions and 11 deletions
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24
fs/xfs/xfs_bmap_util.c
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@ -774,12 +774,10 @@ xfs_alloc_file_space(
{
xfs_mount_t *mp = ip->i_mount;
xfs_off_t count;
xfs_filblks_t allocated_fsb;
xfs_filblks_t allocatesize_fsb;
xfs_extlen_t extsz, temp;
xfs_fileoff_t startoffset_fsb;
xfs_fileoff_t endoffset_fsb;
int nimaps;
int rt;
xfs_trans_t *tp;
xfs_bmbt_irec_t imaps[1], *imapp;
@ -802,7 +800,6 @@ xfs_alloc_file_space(
count = len;
imapp = &imaps[0];
nimaps = 1;
startoffset_fsb = XFS_B_TO_FSBT(mp, offset);
endoffset_fsb = XFS_B_TO_FSB(mp, offset + count);
allocatesize_fsb = endoffset_fsb - startoffset_fsb;
@ -813,6 +810,7 @@ xfs_alloc_file_space(
while (allocatesize_fsb && !error) {
xfs_fileoff_t s, e;
unsigned int dblocks, rblocks, resblks;
int nimaps = 1;
/*
* Determine space reservations for data/realtime.
@ -878,15 +876,19 @@ xfs_alloc_file_space(
if (error)
break;
allocated_fsb = imapp->br_blockcount;
if (nimaps == 0) {
error = -ENOSPC;
break;
/*
* If the allocator cannot find a single free extent large
* enough to cover the start block of the requested range,
* xfs_bmapi_write will return 0 but leave *nimaps set to 0.
*
* In that case we simply need to keep looping with the same
* startoffset_fsb so that one of the following allocations
* will eventually reach the requested range.
*/
if (nimaps) {
startoffset_fsb += imapp->br_blockcount;
allocatesize_fsb -= imapp->br_blockcount;
}
startoffset_fsb += allocated_fsb;
allocatesize_fsb -= allocated_fsb;
}
return error;