From: Christoph Hellwig <firstname.lastname@example.org>
To: Tetsuo Handa <email@example.com>
Cc: Christoph Hellwig <firstname.lastname@example.org>,
Alexander Viro <email@example.com>,
Jens Axboe <firstname.lastname@example.org>,
Jan Kara <email@example.com>, Matthew Wilcox <firstname.lastname@example.org>
Subject: Re: [PATCH] block: add filemap_invalidate_lock_killable()
Date: Mon, 14 Feb 2022 00:17:09 -0800 [thread overview]
Message-ID: <YgoQBTzb3b0l1SzP@infradead.org> (raw)
On Sat, Feb 12, 2022 at 05:28:09PM +0900, Tetsuo Handa wrote:
> On 2022/01/04 22:26, Tetsuo Handa wrote:
> > On 2022/01/04 16:14, Christoph Hellwig wrote:
> >> On Mon, Jan 03, 2022 at 07:49:11PM +0900, Tetsuo Handa wrote:
> >>> syzbot is reporting hung task at blkdev_fallocate() , for it can take
> >>> minutes with mapping->invalidate_lock held. Since fallocate() has to accept
> >>> size > MAX_RW_COUNT bytes, we can't predict how long it will take. Thus,
> >>> mitigate this problem by using killable wait where possible.
> >> Well, but that also means we want all other users of the invalidate_lock
> >> to be killable, as fallocate vs fallocate synchronization is probably
> >> not the interesting case.
> > Right. But being responsive to SIGKILL is generally preferable.
> > syzbot (and other syzkaller based fuzzing) is reporting many hung task reports,
> > but many of such reports are simply overstressing.
> > We can't use killable lock wait for release operation because it is a "void"
> > function. But we can use killable lock wait for majority of operations which
> > are not "void" functions. Use of killable lock wait where possible can improve
> > situation.
> If there is no alternative, can we apply this patch?
As mentioned before I do not think this patch makes sense. If running
fallocate on the block device under the invalidate lock creates a problem
with long hold time we must get it out from under the lock, not turn one
random caller into a killable lock acquisition.
prev parent reply other threads:[~2022-02-14 8:17 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-01-03 9:11 [syzbot] INFO: task hung in blkdev_fallocate syzbot
2022-01-03 10:49 ` [PATCH] block: add filemap_invalidate_lock_killable() Tetsuo Handa
2022-01-04 7:14 ` Christoph Hellwig
2022-01-04 13:26 ` Tetsuo Handa
2022-02-12 8:28 ` Tetsuo Handa
2022-02-14 8:17 ` Christoph Hellwig [this message]
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