From: Paul Mackerras <paulus@samba.org>
Date: Thu, 13 Nov 2014 09:15:23 +0000 (+1100)
Subject: Fix thinko in iov_iter_single_seg_count
X-Git-Tag: omap-for-v3.19/fixes-for-merge-window~117^2
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=ad0eab9293485d1c06237e9249f6d4dfa3d93d4d;p=pandora-kernel.git

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>
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