From: Jan Kara <jack@suse.cz>
To: Costa Sapuntzakis <costa@purestorage.com>
Cc: Jan Kara <jack@suse.cz>, linux-ext4@vger.kernel.org
Subject: Re: [BUG] invalid superblock checksum possibly due to race
Date: Wed, 1 Jul 2020 18:22:48 +0200 [thread overview]
Message-ID: <20200701162248.GA4355@quack2.suse.cz> (raw)
In-Reply-To: <CAABuPhZrQXQ8-tFu9V3575by5N3RV7jd-OcOjy_pLw_na1OUkw@mail.gmail.com>
Hello!
On Tue 30-06-20 11:34:49, Costa Sapuntzakis wrote:
> > Yes, probably ext4_superblock_csum_set() should use
> >
> > lock_buffer(EXT4_SB(sb)->s_sbh)
> >
> > to synchronize updating of superblock checksum. Will you send a patch?
>
> Yes. I will send a patch.
Thanks!
> I noticed lock_buffer can sleep. That would seem to imply to me that
> lock_buffer can be held across I/Os.
> I worry that this will occasionally significantly slow down this code
> path compared to what it used to be. Are there any things
> about the way ext4 uses buffers that makes this less of a concern?
Yes, buffer lock is a sleeping lock but that's the lock we usually use to
protect consistency of buffer contents. So I prefer to use that lock unless
we have definitive performance data showing we need something more
clever...
Honza
--
Jan Kara <jack@suse.com>
SUSE Labs, CR
prev parent reply other threads:[~2020-07-01 16:22 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-06-24 23:56 [BUG] invalid superblock checksum possibly due to race Costa Sapuntzakis
2020-06-30 11:48 ` Jan Kara
2020-06-30 18:34 ` Costa Sapuntzakis
2020-07-01 16:22 ` Jan Kara [this message]
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