From: Linus Torvalds <torvalds@linux-foundation.org>
To: "Darrick J. Wong" <darrick.wong@oracle.com>
Cc: Jens Axboe <axboe@kernel.dk>, Eric Biggers <ebiggers3@gmail.com>,
Eryu Guan <guaneryu@gmail.com>,
Fengguang Wu <fengguang.wu@intel.com>,
Lukas Czerner <lczerner@redhat.com>, Jan Kara <jack@suse.cz>,
Jeff Moyer <jmoyer@redhat.com>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
linux-fsdevel <linux-fsdevel@vger.kernel.org>,
xfs <linux-xfs@vger.kernel.org>
Subject: Re: [btrfs] WARNING: CPU: 0 PID: 6379 at fs/direct-io.c:293 dio_complete+0x1d4/0x220
Date: Mon, 13 Nov 2017 14:01:36 -0800 [thread overview]
Message-ID: <CA+55aFzQM747SW959w3CDD=6UypUa7XTqEyHnPaTcFCX+vDLGA@mail.gmail.com> (raw)
In-Reply-To: <20171113215601.GD6246@magnolia>
On Mon, Nov 13, 2017 at 1:56 PM, Darrick J. Wong
<darrick.wong@oracle.com> wrote:
> Wellll... the WARN_ON in question happens when:
>
> a) two programs race to write to the same part of a file, one via the page
> cache and the other via directio
> b) the dio write completes, tries to invalidate the page cache, and fails
> because the corresponding page cannot be invalidated
>
> At this point, the page cache contents don't reflect what's on disk, so
> I don't think we can quietly ignore the situation.
Direct-IO causing cache coherency issues? Really? I'm shocked and
surptised that that could _possibly_ happen.
But why the hell would you want a back-trace for it?
IOW, if you want to warn about it, use "pr_warn_ratelimited()" or
something. What did the backtrace and "looks like a kernel oops"
really help with?
And in the end, maybe even the warning is pointless. You used
direct-IO and cached IO at the same time, and you got coherency
issues. What did you expect? directio is fundamentally broken.
Linus
next prev parent reply other threads:[~2017-11-13 22:01 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <CA+55aFxSJGeN=2X-uX-on1Uq2Nb8+v1aiMDz5H1+tKW_N5Q+6g@mail.gmail.com>
[not found] ` <20171029225155.qcum5i75awrt5tzm@wfg-t540p.sh.intel.com>
2017-10-30 7:20 ` [btrfs] WARNING: CPU: 0 PID: 6379 at fs/direct-io.c:293 dio_complete+0x1d4/0x220 Fengguang Wu
2017-10-30 7:44 ` Eryu Guan
2017-10-31 0:10 ` Fengguang Wu
2017-10-31 6:54 ` Eryu Guan
2017-10-31 7:10 ` Fengguang Wu
2017-11-06 1:13 ` Eric Biggers
2017-11-13 19:13 ` Eric Biggers
2017-11-13 19:16 ` Jens Axboe
2017-11-13 19:21 ` Linus Torvalds
2017-11-13 21:56 ` Darrick J. Wong
2017-11-13 22:01 ` Linus Torvalds [this message]
2017-11-14 17:17 ` Theodore Ts'o
2017-10-31 15:13 ` Filipe Manana
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