From: Al Viro <viro@ZenIV.linux.org.uk>
To: Paul Mackerras <paulus@samba.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH] Fix thinko in iov_iter_single_seg_count
Date: Thu, 13 Nov 2014 13:05:09 +0000 [thread overview]
Message-ID: <20141113130509.GI7996@ZenIV.linux.org.uk> (raw)
In-Reply-To: <20141113091523.GC26910@iris.ozlabs.ibm.com>
On Thu, Nov 13, 2014 at 08:15:23PM +1100, Paul Mackerras wrote:
> 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.
ACK. Applied, will push today.
prev parent reply other threads:[~2014-11-13 13:05 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-11-13 9:15 [PATCH] Fix thinko in iov_iter_single_seg_count Paul Mackerras
2014-11-13 13:05 ` Al Viro [this message]
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