From: Al Viro <viro@ZenIV.linux.org.uk>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Dave Chinner <david@fromorbit.com>, CAI Qian <caiqian@redhat.com>,
linux-xfs <linux-xfs@vger.kernel.org>,
xfs@oss.sgi.com
Subject: Re: xfs_file_splice_read: possible circular locking dependency detected
Date: Fri, 9 Sep 2016 03:34:52 +0100 [thread overview]
Message-ID: <20160909023452.GO2356@ZenIV.linux.org.uk> (raw)
In-Reply-To: <CA+55aFxrqCng2Qxasc9pyMrKUGFjo==fEaFT1vkH9Lncte3RgQ@mail.gmail.com>
On Thu, Sep 08, 2016 at 07:26:44PM -0700, Linus Torvalds wrote:
> On Thu, Sep 8, 2016 at 7:22 PM, Linus Torvalds
> <torvalds@linux-foundation.org> wrote:
> > On Thu, Sep 8, 2016 at 6:53 PM, Dave Chinner <david@fromorbit.com> wrote:
> >>
> >> So if we race iwth a truncate, the pages in spd.pages[] that are
> >> beyond the new EOF may or may not have been removed from the page
> >> cache.
> >
> > So I'm not sure why we'd need to care?
>
> Side note, just to clarify: I'm not actually convinced that turning
> things into page/offset/len tuples is the right thing to do.
>
> I still suspect that the reference count updates on each page may not
> be a good idea. I suspect we'd easily be better off trying to do
> everything under the pipe lock exactly so that we can *avoid* having
> to do per-page "increment ref-count, then decrement it again". But the
> locking would have to be changed radically for us to be able to do
> that (and the only sane model ios, I think, to make pipe_lock be the
> outermost lock, and outside *every* downcall)
IDGI. Suppose we do splice from file to pipe. Everything had been in
page cache, so we want to end up with pipe_buffers containing references
to those page cache pages. How do you propose to do that without having
grabbed references to them? What's to keep them from being freed by the
time we get to reading from the pipe?
next prev parent reply other threads:[~2016-09-09 2:34 UTC|newest]
Thread overview: 135+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <723420070.1340881.1472835555274.JavaMail.zimbra@redhat.com>
[not found] ` <1832555471.1341372.1472835736236.JavaMail.zimbra@redhat.com>
2016-09-03 0:39 ` xfs_file_splice_read: possible circular locking dependency detected Dave Chinner
2016-09-03 0:57 ` Linus Torvalds
2016-09-03 1:45 ` Al Viro
2016-09-06 23:59 ` Dave Chinner
2016-09-08 20:35 ` Al Viro
2016-09-06 21:53 ` CAI Qian
2016-09-06 23:34 ` Dave Chinner
2016-09-08 15:29 ` CAI Qian
2016-09-08 17:56 ` Al Viro
2016-09-08 18:12 ` Linus Torvalds
2016-09-08 18:18 ` Linus Torvalds
2016-09-08 20:44 ` Al Viro
2016-09-08 20:57 ` Al Viro
2016-09-08 21:23 ` Al Viro
2016-09-08 21:38 ` Dave Chinner
2016-09-08 23:55 ` Al Viro
2016-09-09 1:53 ` Dave Chinner
2016-09-09 2:22 ` Linus Torvalds
2016-09-09 2:26 ` Linus Torvalds
2016-09-09 2:34 ` Al Viro [this message]
2016-09-09 2:50 ` Linus Torvalds
2016-09-09 22:19 ` Al Viro
2016-09-10 2:06 ` Linus Torvalds
2016-09-14 3:16 ` Al Viro
2016-09-14 3:39 ` Nicholas Piggin
2016-09-14 4:01 ` Linus Torvalds
2016-09-18 5:33 ` Al Viro
2016-09-19 3:08 ` Nicholas Piggin
2016-09-19 6:11 ` Al Viro
2016-09-19 7:26 ` Nicholas Piggin
2016-09-14 3:49 ` Linus Torvalds
2016-09-14 4:26 ` Al Viro
2016-09-17 8:20 ` Al Viro
2016-09-17 19:00 ` Al Viro
2016-09-17 20:15 ` Linus Torvalds
2016-09-23 19:00 ` [RFC][CFT] splice_read reworked Al Viro
2016-09-23 19:01 ` [PATCH 01/11] fix memory leaks in tracing_buffers_splice_read() Al Viro
2016-09-23 19:02 ` [PATCH 02/11] splice_to_pipe(): don't open-code wakeup_pipe_readers() Al Viro
2016-09-23 19:02 ` [PATCH 03/11] splice: switch get_iovec_page_array() to iov_iter Al Viro
2016-09-23 19:03 ` [PATCH 04/11] splice: lift pipe_lock out of splice_to_pipe() Al Viro
2016-09-23 19:45 ` Linus Torvalds
2016-09-23 20:10 ` Al Viro
2016-09-23 20:36 ` Linus Torvalds
2016-09-24 3:59 ` Al Viro
2016-09-24 17:29 ` Al Viro
2016-09-27 15:38 ` Nicholas Piggin
2016-09-27 15:53 ` Chuck Lever
2016-09-24 3:59 ` [PATCH 04/12] " Al Viro
2016-09-26 13:35 ` Miklos Szeredi
2016-09-27 4:14 ` Al Viro
2016-12-17 19:54 ` Andreas Schwab
2016-12-18 19:28 ` Linus Torvalds
2016-12-18 19:57 ` Andreas Schwab
2016-12-18 20:12 ` Al Viro
2016-12-18 20:30 ` Al Viro
2016-12-18 22:10 ` Linus Torvalds
2016-12-18 22:18 ` Al Viro
2016-12-18 22:22 ` Linus Torvalds
2016-12-18 22:49 ` Andreas Schwab
2016-12-21 18:56 ` Andreas Schwab
2016-12-21 19:12 ` Linus Torvalds
2016-09-24 4:00 ` [PATCH 06/12] new helper: add_to_pipe() Al Viro
2016-09-26 13:49 ` Miklos Szeredi
2016-09-24 4:01 ` [PATCH 10/12] new iov_iter flavour: pipe-backed Al Viro
2016-09-29 20:53 ` Miklos Szeredi
2016-09-29 22:50 ` Al Viro
2016-09-30 7:30 ` Miklos Szeredi
2016-10-03 3:34 ` [RFC] O_DIRECT vs EFAULT (was Re: [PATCH 10/12] new iov_iter flavour: pipe-backed) Al Viro
2016-10-03 17:07 ` Linus Torvalds
2016-10-03 18:54 ` Al Viro
2016-09-24 4:01 ` [PATCH 11/12] switch generic_file_splice_read() to use of ->read_iter() Al Viro
2016-09-24 4:02 ` [PATCH 12/12] switch default_file_splice_read() to use of pipe-backed iov_iter Al Viro
2016-09-23 19:03 ` [PATCH 05/11] skb_splice_bits(): get rid of callback Al Viro
2016-09-23 19:04 ` [PATCH 06/11] new helper: add_to_pipe() Al Viro
2016-09-23 19:04 ` [PATCH 07/11] fuse_dev_splice_read(): switch to add_to_pipe() Al Viro
2016-09-23 19:06 ` [PATCH 08/11] cifs: don't use memcpy() to copy struct iov_iter Al Viro
2016-09-23 19:08 ` [PATCH 09/11] fuse_ioctl_copy_user(): don't open-code copy_page_{to,from}_iter() Al Viro
2016-09-26 9:31 ` Miklos Szeredi
2016-09-23 19:09 ` [PATCH 10/11] new iov_iter flavour: pipe-backed Al Viro
2016-09-23 19:10 ` [PATCH 11/11] switch generic_file_splice_read() to use of ->read_iter() Al Viro
2016-09-30 13:32 ` [RFC][CFT] splice_read reworked CAI Qian
2016-09-30 17:42 ` CAI Qian
2016-09-30 18:33 ` CAI Qian
2016-10-03 1:37 ` Al Viro
2016-10-03 17:49 ` CAI Qian
2016-10-04 17:39 ` local DoS - systemd hang or timeout (WAS: Re: [RFC][CFT] splice_read reworked) CAI Qian
2016-10-04 21:42 ` tj
2016-10-05 14:09 ` CAI Qian
2016-10-05 15:30 ` tj
2016-10-05 15:54 ` CAI Qian
2016-10-05 18:57 ` CAI Qian
2016-10-05 20:05 ` Al Viro
2016-10-06 12:20 ` CAI Qian
2016-10-06 12:25 ` CAI Qian
2016-10-06 16:11 ` CAI Qian
2016-10-06 17:00 ` Linus Torvalds
2016-10-06 18:12 ` CAI Qian
2016-10-07 9:57 ` Dave Chinner
2016-10-07 15:25 ` Linus Torvalds
2016-10-07 7:08 ` Jan Kara
2016-10-07 14:43 ` CAI Qian
2016-10-07 15:27 ` CAI Qian
2016-10-07 18:56 ` CAI Qian
2016-10-09 21:54 ` Dave Chinner
2016-10-10 14:10 ` CAI Qian
2016-10-10 20:14 ` CAI Qian
2016-10-10 21:57 ` Dave Chinner
2016-10-12 19:50 ` [bisected] " CAI Qian
2016-10-12 20:59 ` Dave Chinner
2016-10-13 16:25 ` CAI Qian
2016-10-13 20:49 ` Dave Chinner
2016-10-13 20:56 ` CAI Qian
2016-10-09 21:51 ` Dave Chinner
2016-10-07 9:27 ` Dave Chinner
2016-10-03 1:42 ` [RFC][CFT] splice_read reworked Al Viro
2016-10-03 14:06 ` CAI Qian
2016-10-03 15:20 ` CAI Qian
2016-10-03 21:12 ` Dave Chinner
2016-10-04 13:57 ` CAI Qian
2016-10-03 20:32 ` CAI Qian
2016-10-03 20:35 ` Al Viro
2016-10-04 13:29 ` CAI Qian
2016-10-04 14:28 ` Al Viro
2016-10-04 16:21 ` CAI Qian
2016-10-04 20:12 ` Al Viro
2016-10-05 14:30 ` CAI Qian
2016-10-05 16:07 ` Al Viro
2016-09-09 2:31 ` xfs_file_splice_read: possible circular locking dependency detected Al Viro
2016-09-09 2:39 ` Linus Torvalds
2016-09-09 2:26 ` Al Viro
2016-09-09 2:19 ` Al Viro
2016-09-08 18:01 ` Linus Torvalds
2016-09-08 20:39 ` CAI Qian
2016-09-08 21:19 ` Dave Chinner
2016-09-08 21:30 ` Al Viro
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