linux-kernel - Re: [PATCH] afs: Re-enable freezing once a page fault is interrupted

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Date:   Fri, 18 Jun 2021 13:52:42 -0700
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     David Howells <dhowells@...hat.com>
Cc:     "Matthew Wilcox (Oracle)" <willy@...radead.org>,
        linux-afs@...ts.infradead.org,
        Marc Dionne <marc.dionne@...istor.com>,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] afs: Re-enable freezing once a page fault is interrupted

On Wed, Jun 16, 2021 at 2:22 PM David Howells <dhowells@...hat.com> wrote:
>
> If a task is killed during a page fault, it does not currently call
> sb_end_pagefault(), which means that the filesystem cannot be frozen
> at any time thereafter.  This may be reported by lockdep like this:

I've applied this patch.

Everything in my screams "the sb_start/end_pagefault() code is
completely broken", but in the meantime this patch fixes the immediate
bug.

I suspect that the whole sb_start/end_pagefault thing should just go
away entirely, and the freezer should be re-examined. Alternatively,
it should just be done by generic code, not by the filesystem.

But it is what it is.

           Linus