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Date: Wed, 1 Jul 2020 18:22:48 +0200 From: Jan Kara <jack@...e.cz> To: Costa Sapuntzakis <costa@...estorage.com> Cc: Jan Kara <jack@...e.cz>, linux-ext4@...r.kernel.org Subject: Re: [BUG] invalid superblock checksum possibly due to race 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@...e.com> SUSE Labs, CR
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