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xfs: push rounddown_pow_of_two() to after prealloc throttle 

The round down occurs towards the beginning of the function. Push
it down after throttling has occurred. This is to support adding
further transformations to 'alloc_blocks' that might not preserve
power-of-two alignment (and thus could lead to rounding down
multiple times).

Signed-off-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Ben Myers <bpm@sgi.com>
Reviewed-by: Mark Tinguely <tinguely@sgi.com>
Signed-off-by: Ben Myers <bpm@sgi.com>
This commit is contained in:
Brian Foster 2013-03-18 10:51:44 -04:00 committed by Ben Myers
parent 3c58b5f809
commit c9bdbdc074
1 changed files with 17 additions and 2 deletions
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19
fs/xfs/xfs_iomap.c
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@ -389,8 +389,15 @@ xfs_iomap_prealloc_size(
if (!alloc_blocks)
goto check_writeio;
alloc_blocks = XFS_FILEOFF_MIN(MAXEXTLEN,
rounddown_pow_of_two(alloc_blocks));
/*
* MAXEXTLEN is not a power of two value but we round the prealloc down
* to the nearest power of two value after throttling. To prevent the
* round down from unconditionally reducing the maximum supported prealloc
* size, we round up first, apply appropriate throttling, round down and
* cap the value to MAXEXTLEN.
*/
alloc_blocks = XFS_FILEOFF_MIN(roundup_pow_of_two(MAXEXTLEN),
alloc_blocks);
xfs_icsb_sync_counters(mp, XFS_ICSB_LAZY_COUNT);
freesp = mp->m_sb.sb_fdblocks;
@ -407,6 +414,14 @@ xfs_iomap_prealloc_size(
}
if (shift)
alloc_blocks >>= shift;
/*
* rounddown_pow_of_two() returns an undefined result if we pass in
* alloc_blocks = 0.
*/
if (alloc_blocks)
alloc_blocks = rounddown_pow_of_two(alloc_blocks);
if (alloc_blocks > MAXEXTLEN)
alloc_blocks = MAXEXTLEN;
/*
* If we are still trying to allocate more space than is