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authorPaul Mackerras <paulus@samba.org>2014-11-13 20:15:23 +1100
committerAl Viro <viro@zeniv.linux.org.uk>2014-11-13 13:28:55 -0500
commitad0eab9293485d1c06237e9249f6d4dfa3d93d4d (patch)
treed0153dd69d25cfa259bdadd8b17f79e4d5be7ec5
parent7e8631e8b9d4e9f698c09c7e7309c96249180ff9 (diff)
Fix thinko in iov_iter_single_seg_count
The branches of the if (i->type & ITER_BVEC) statement in iov_iter_single_seg_count() are the wrong way around; if ITER_BVEC is clear then we use i->bvec, when we should be using i->iov. This fixes it. In my case, the symptom that this caused was that a KVM guest doing filesystem operations on a virtual disk would result in one of qemu's threads on the host going into an infinite loop in generic_perform_write(). The loop would hit the copied == 0 case and call iov_iter_single_seg_count() to reduce the number of bytes to try to process, but because of the error, iov_iter_single_seg_count() would just return i->count and the loop made no progress and continued forever. Cc: stable@vger.kernel.org # 3.16+ Signed-off-by: Paul Mackerras <paulus@samba.org> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
-rw-r--r--mm/iov_iter.c4
1 files changed, 2 insertions, 2 deletions
diff --git a/mm/iov_iter.c b/mm/iov_iter.c
index eafcf60f6b83..e34a3cb6aad6 100644
--- a/mm/iov_iter.c
+++ b/mm/iov_iter.c
@@ -911,9 +911,9 @@ size_t iov_iter_single_seg_count(const struct iov_iter *i)
if (i->nr_segs == 1)
return i->count;
else if (i->type & ITER_BVEC)
- return min(i->count, i->iov->iov_len - i->iov_offset);
- else
return min(i->count, i->bvec->bv_len - i->iov_offset);
+ else
+ return min(i->count, i->iov->iov_len - i->iov_offset);
}
EXPORT_SYMBOL(iov_iter_single_seg_count);

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