From: Al Viro <viro@ZenIV.linux.org.uk>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: "Alan J. Wylie" <alan@wylie.me.uk>,
Thorsten Leemhuis <regressions@leemhuis.info>,
linux-kernel <linux-kernel@vger.kernel.org>
Subject: Re: 4.9.0 regression in pipe-backed iov_iter with systemd-nspawn
Date: Fri, 13 Jan 2017 20:11:21 +0000 [thread overview]
Message-ID: <20170113201121.GQ1555@ZenIV.linux.org.uk> (raw)
In-Reply-To: <20170113200826.GP1555@ZenIV.linux.org.uk>
On Fri, Jan 13, 2017 at 08:08:27PM +0000, Al Viro wrote:
> Because it's "truncate to size", not "throw everything up to that point
> out".
>
> We have some amount of data pushed into pipe (in this case - 0) and we
> have some buffers allocated by ..._get_pages() past the end of it.
> Some of that we want to keep (again, in this case - none) and have the next
> copy_to_iter() go after those, the rest we discard.
PS: 'size' argument of iov_iter_advance() is the second "some" in the
above - we tell it how much we want to advance by and everything past
that point is, in case of PIPE_ITER, discarded.
next prev parent reply other threads:[~2017-01-13 20:11 UTC|newest]
Thread overview: 42+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-01-12 20:26 4.9.0 regression in pipe-backed iov_iter with systemd-nspawn Alan J. Wylie
2017-01-12 20:31 ` Al Viro
2017-01-12 20:38 ` Alan J. Wylie
2017-01-12 22:26 ` Linus Torvalds
2017-01-12 22:37 ` Al Viro
2017-01-12 22:46 ` Al Viro
2017-01-12 23:02 ` Linus Torvalds
2017-01-12 23:14 ` Al Viro
2017-01-12 23:14 ` Linus Torvalds
2017-01-12 23:27 ` Al Viro
2017-01-12 22:46 ` Alan J. Wylie
2017-01-12 22:58 ` Al Viro
2017-01-12 23:28 ` Linus Torvalds
2017-01-13 4:00 ` Al Viro
2017-01-13 7:38 ` Alan J. Wylie
2017-01-13 7:23 ` Alan J. Wylie
2017-01-13 9:33 ` Al Viro
2017-01-13 9:54 ` Alan J. Wylie
2017-01-13 10:20 ` Al Viro
2017-01-13 10:32 ` Alan J. Wylie
2017-01-13 11:25 ` Al Viro
2017-01-13 11:18 ` Al Viro
2017-01-13 19:33 ` Linus Torvalds
2017-01-13 20:08 ` Al Viro
2017-01-13 20:11 ` Al Viro [this message]
2017-01-13 20:32 ` Linus Torvalds
2017-01-13 20:47 ` Al Viro
2017-01-13 21:55 ` Al Viro
2017-01-13 21:59 ` Al Viro
2017-01-13 22:13 ` Al Viro
2017-01-13 22:50 ` Al Viro
2017-01-14 0:59 ` Linus Torvalds
2017-01-14 1:24 ` Al Viro
2017-01-14 1:43 ` Al Viro
2017-01-14 1:46 ` Linus Torvalds
2017-01-14 1:57 ` Al Viro
2017-01-15 0:53 ` Al Viro
2017-01-14 13:16 ` Alan J. Wylie
2017-01-14 16:29 ` Alan J. Wylie
2017-01-14 17:57 ` Linus Torvalds
2017-01-13 20:08 ` Linus Torvalds
2017-01-13 20:16 ` Al Viro
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