linux-kernel - Re: iov_iter

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Message-ID: <20170830171728.cwe34lhjnkwafe3z@codemonkey.org.uk>
Date:   Wed, 30 Aug 2017 13:17:28 -0400
From:   Dave Jones <davej@...emonkey.org.uk>
To:     "Darrick J. Wong" <darrick.wong@...cle.com>
Cc:     Al Viro <viro@...IV.linux.org.uk>,
        Linux Kernel <linux-kernel@...r.kernel.org>,
        linux-xfs@...r.kernel.org
Subject: Re: iov_iter_pipe warning.

On Wed, Aug 30, 2017 at 10:13:43AM -0700, Darrick J. Wong wrote:


 > > I reverted the debug patches mentioned above, and ran trinity for a while again,
 > > and got this which smells really suspiciously related
 > > 
 > > WARNING: CPU: 1 PID: 10380 at fs/iomap.c:993 iomap_dio_rw+0x825/0x840
 > > RAX: 00000000fffffff0 RBX: ffff88046a64d0e8 RCX: 0000000000000000
 > > 
 > > 
 > > 
 > > That's this..
 > > 
 > >  987         ret = filemap_write_and_wait_range(mapping, start, end);
 > >  988         if (ret)
 > >  989                 goto out_free_dio;
 > >  990 
 > >  991         ret = invalidate_inode_pages2_range(mapping,
 > >  992                         start >> PAGE_SHIFT, end >> PAGE_SHIFT);
 > >  993         WARN_ON_ONCE(ret);
 > > 
 > > 
 > > Plot thickens..
 > 
 > Hm, that's the WARN_ON that comes from a failed pagecache invalidation
 > prior to a dio operation, which implies that something's mixing buffered
 > and dio?

Plausible. Judging by RAX, we got -EBUSY

 > Given that it's syzkaller it wouldn't surprise me to hear that it's
 > doing that... :)

s/syzkaller/trinity/, but yes.

	Dave