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[PATCH] xfs: Fix rounding in xfs_alloc_fix_len()

To: xfs@xxxxxxxxxxx
Subject: [PATCH] xfs: Fix rounding in xfs_alloc_fix_len()
From: Jan Kara <jack@xxxxxxx>
Date: Wed, 4 Jun 2014 11:48:13 +0200
Cc: Jan Kara <jack@xxxxxxx>
Delivered-to: xfs@xxxxxxxxxxx
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@xxxxxxx>
---
 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

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