From: Linus Torvalds <torvalds@linux-foundation.org>
To: Andreas Gruenbacher <agruenba@redhat.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>,
Josef Bacik <josef@toxicpanda.com>,
David Sterba <dsterba@suse.com>,
Al Viro <viro@zeniv.linux.org.uk>,
Andrew Morton <akpm@linux-foundation.org>,
Will Deacon <will@kernel.org>,
Matthew Wilcox <willy@infradead.org>,
linux-fsdevel <linux-fsdevel@vger.kernel.org>,
LKML <linux-kernel@vger.kernel.org>,
Linux ARM <linux-arm-kernel@lists.infradead.org>,
linux-btrfs <linux-btrfs@vger.kernel.org>
Subject: Re: [PATCH v2 0/4] Avoid live-lock in fault-in+uaccess loops with sub-page faults
Date: Fri, 3 Dec 2021 09:57:57 -0800 [thread overview]
Message-ID: <CAHk-=wiQAQTGdMNLCKwgnt4EiAXf7Bm6p7NQx5-31S9-qPD8jg@mail.gmail.com> (raw)
In-Reply-To: <CAHc6FU7gXfZk7=Xj+RjxCqkmsrcAhenfbeoqa4AmHd5+vgja7g@mail.gmail.com>
On Fri, Dec 3, 2021 at 7:29 AM Andreas Gruenbacher <agruenba@redhat.com> wrote:
>
>
> We're trying pretty hard to handle large I/O requests efficiently at
> the filesystem level. A small, static upper limit in the fault-in
> functions has the potential to ruin those efforts. So I'm not a fan of
> that.
I don't think fault-in should happen under any sane normal circumstances.
Except for low-memory situations, and then you don't want to fault in
large areas.
Do you really expect to write big areas that the user has never even
touched? That would be literally insane.
And if the user _has_ touched them, then they'll in in-core. Except
for the "swapped out" case.
End result: this is purely a correctness issue, not a performance issue.
Linus
next prev parent reply other threads:[~2021-12-03 17:58 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-12-01 19:37 [PATCH v2 0/4] Avoid live-lock in fault-in+uaccess loops with sub-page faults Catalin Marinas
2021-12-01 19:37 ` [PATCH v2 1/4] mm: Introduce a 'min_size' argument to fault_in_*() Catalin Marinas
2021-12-01 19:37 ` [PATCH v2 2/4] mm: Probe for sub-page faults in fault_in_*() Catalin Marinas
2021-12-01 19:37 ` [PATCH v2 3/4] arm64: Add support for user sub-page fault probing Catalin Marinas
2021-12-01 20:29 ` Mark Rutland
2021-12-02 16:09 ` Catalin Marinas
2021-12-01 19:37 ` [PATCH v2 4/4] btrfs: Avoid live-lock in search_ioctl() on hardware with sub-page faults Catalin Marinas
2021-12-03 15:29 ` [PATCH v2 0/4] Avoid live-lock in fault-in+uaccess loops " Andreas Gruenbacher
2021-12-03 17:57 ` Linus Torvalds [this message]
2021-12-03 18:11 ` Andreas Gruenbacher
2021-12-03 18:25 ` Linus Torvalds
2021-12-03 19:51 ` Catalin Marinas
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