From: Linus Torvalds <torvalds@linux-foundation.org>
To: David Howells <dhowells@redhat.com>
Cc: Matthew Wilcox <willy@infradead.org>,
Al Viro <viro@zeniv.linux.org.uk>, "Ted Ts'o" <tytso@mit.edu>,
Dave Hansen <dave.hansen@linux.intel.com>,
Andrew Morton <akpm@linux-foundation.org>,
Linux-MM <linux-mm@kvack.org>,
Ext4 Developers List <linux-ext4@vger.kernel.org>,
linux-fsdevel <linux-fsdevel@vger.kernel.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: Do we need to unrevert "fs: do not prefault sys_write() user buffer pages"?
Date: Tue, 22 Jun 2021 11:32:00 -0700 [thread overview]
Message-ID: <CAHk-=wgA4_TkMqOw9GwW7aNe3jBU_yBKZkNWTicz=BKap_=siw@mail.gmail.com> (raw)
In-Reply-To: <3233312.1624386204@warthog.procyon.org.uk>
On Tue, Jun 22, 2021 at 11:23 AM David Howells <dhowells@redhat.com> wrote:
>
> Probably the most obvious way would be to set a flag in task_struct saying
> what you're doing and have the point that would otherwise wait for the page to
> become unlocked skip to the fault fixup code if the page is locked after
> ->readahead() has been invoked and the flag is set, then use get_user() in
> iov_iter_fault_in_readable().
Yeah, the existing user access exception handling code _almost_
handles it, except for one thing: you'd need to have some way to
distinguish between "prefetch successful" and "fault failed".
And yeah, I guess it could be a flag in task_struct, but at that point
my gag reflex starts acting up.
Linus
next prev parent reply other threads:[~2021-06-22 18:32 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-06-22 15:20 Do we need to unrevert "fs: do not prefault sys_write() user buffer pages"? David Howells
2021-06-22 15:27 ` Al Viro
2021-06-22 15:36 ` Al Viro
2021-06-22 17:25 ` Matthew Wilcox
2021-06-22 17:39 ` Linus Torvalds
2021-06-22 17:55 ` David Howells
2021-06-22 18:04 ` Matthew Wilcox
2021-06-22 18:07 ` Linus Torvalds
2021-06-22 18:16 ` Nadav Amit
2021-06-22 18:23 ` Matthew Wilcox
2021-06-22 18:28 ` Linus Torvalds
2021-06-22 18:36 ` Matthew Wilcox
2021-06-22 18:51 ` Nadav Amit
2021-06-22 18:57 ` Linus Torvalds
2021-06-22 18:23 ` David Howells
2021-06-22 18:32 ` Linus Torvalds [this message]
2021-06-22 18:13 ` David Howells
2021-06-22 15:32 ` Linus Torvalds
2021-06-22 15:53 ` Linus Torvalds
2021-06-22 15:32 ` Matthew Wilcox
2021-06-22 16:27 ` David Howells
2021-06-22 21:55 ` David Laight
2021-06-22 22:04 ` Matthew Wilcox
2021-06-22 22:31 ` David Laight
2021-06-22 22:20 ` Dave Chinner
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