From: Linus Torvalds <torvalds@linux-foundation.org>
To: David Hildenbrand <david@redhat.com>
Cc: Andreas Gruenbacher <agruenba@redhat.com>,
Alexander Viro <viro@zeniv.linux.org.uk>,
linux-s390 <linux-s390@vger.kernel.org>,
Linux-MM <linux-mm@kvack.org>,
linux-fsdevel <linux-fsdevel@vger.kernel.org>,
linux-btrfs <linux-btrfs@vger.kernel.org>
Subject: Re: Buffered I/O broken on s390x with page faults disabled (gfs2)
Date: Tue, 8 Mar 2022 09:40:16 -0800 [thread overview]
Message-ID: <CAHk-=wjHsQywXgNe9D+MQCiMhpyB2Gs5M78CGCpTr9BSeP71bw@mail.gmail.com> (raw)
In-Reply-To: <CAHk-=wh1WJ-s9Gj15yFciq6TOd9OOsE7H=R7rRskdRP6npDktQ@mail.gmail.com>
On Tue, Mar 8, 2022 at 9:26 AM Linus Torvalds
<torvalds@linux-foundation.org> wrote:
>
> Your actual patch looks pretty nasty, though. We avoid marking it
> accessed on purpose (to avoid atomicity issues wrt hw-dirty bits etc),
> but still, that patch makes me go "there has to be a better way".
That better way might be to make q() not use GUP at all.
It doesn't want the page - it just wants to make sure the fault is
handled. For the fault_in_readable() case we already just do the user
access.
The only reason we don't do that for fault_in_safe_writeable() is that
we don't have a good non-destructive user write.
Hmm. The futex code actually uses "fixup_user_fault()" for this case.
Maybe fault_in_safe_writeable() should do that?
Linus
next prev parent reply other threads:[~2022-03-08 17:40 UTC|newest]
Thread overview: 36+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-03-07 22:52 Buffered I/O broken on s390x with page faults disabled (gfs2) Andreas Gruenbacher
2022-03-07 23:18 ` Linus Torvalds
2022-03-08 8:21 ` David Hildenbrand
2022-03-08 8:37 ` David Hildenbrand
2022-03-08 12:11 ` David Hildenbrand
2022-03-08 12:24 ` David Hildenbrand
2022-03-08 13:20 ` Gerald Schaefer
2022-03-08 13:32 ` David Hildenbrand
2022-03-08 14:14 ` Gerald Schaefer
2022-03-08 17:23 ` David Hildenbrand
2022-03-08 17:26 ` Linus Torvalds
2022-03-08 17:40 ` Linus Torvalds [this message]
2022-03-08 19:27 ` Linus Torvalds
2022-03-08 20:03 ` Linus Torvalds
2022-03-08 23:24 ` Andreas Gruenbacher
2022-03-09 0:22 ` Linus Torvalds
2022-03-09 18:42 ` Andreas Gruenbacher
2022-03-09 19:08 ` Linus Torvalds
2022-03-09 20:57 ` Andreas Gruenbacher
2022-03-09 21:08 ` Andreas Gruenbacher
2022-03-10 12:13 ` Filipe Manana
2022-03-09 19:21 ` Linus Torvalds
2022-03-09 19:35 ` Andreas Gruenbacher
2022-03-09 20:18 ` Linus Torvalds
2022-03-09 20:36 ` Andreas Gruenbacher
2022-03-09 20:48 ` Linus Torvalds
2022-03-09 20:54 ` Linus Torvalds
2022-03-10 17:13 ` David Hildenbrand
2022-03-10 18:00 ` Andreas Gruenbacher
2022-03-10 18:35 ` Linus Torvalds
2022-03-10 18:38 ` David Hildenbrand
2022-03-10 18:47 ` Andreas Gruenbacher
2022-03-10 19:22 ` Linus Torvalds
2022-03-10 19:56 ` Linus Torvalds
2022-03-10 20:23 ` Andreas Gruenbacher
2022-03-08 17:47 ` David Hildenbrand
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