[PATCH] xfs: Fix rounding in xfs_alloc_fix_len()

Jan Kara
2014-06-04T09:48:33Z

Rounding in xfs_alloc_fix_len() is wrong. As the comment states, the
result should be a number of a form (k*prod+mod) however due to sign
mistake the result is different. As a result allocations on raid arrays
could be misaligned in some cases.

This also seems to fix occasional assertion failure:
XFS_WANT_CORRUPTED_GOTO(rlen <= flen, error0)
in xfs_alloc_ag_vextent_size().

Signed-off-by: Jan Kara <jack@suse.cz>
---
fs/xfs/xfs_alloc.c | 14 ++++++--------
1 file changed, 6 insertions(+), 8 deletions(-)

diff --git a/fs/xfs/xfs_alloc.c b/fs/xfs/xfs_alloc.c
index c1cf6a336a72..6a0281b16451 100644
--- a/fs/xfs/xfs_alloc.c
+++ b/fs/xfs/xfs_alloc.c
@@ -257,14 +257,12 @@ xfs_alloc_fix_len(
k = rlen % args->prod;
if (k == args->mod)
return;
- if (k > args->mod) {
- if ((int)(rlen = rlen - k - args->mod) < (int)args->minlen)
- return;
- } else {
- if ((int)(rlen = rlen - args->prod - (args->mod - k)) <
- (int)args->minlen)
- return;
- }
+ if (k > args->mod)
+ rlen = rlen - (k - args->mod);
+ else
+ rlen = rlen - args->prod + (args->mod - k);
+ if ((int)rlen < (int)args->minlen)
+ return;
ASSERT(rlen >= args->minlen);
ASSERT(rlen <= args->maxlen);
args->len = rlen;
--
1.8.1.4