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Message-ID: <20100621074756.GA2201@infradead.org> Date: Mon, 21 Jun 2010 03:47:56 -0400 From: Christoph Hellwig <hch@...radead.org> To: Dave Chinner <david@...morbit.com> Cc: Christoph Hellwig <hch@...radead.org>, linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org, viro@...IV.linux.org.uk, josef@...hat.com, jeffmerkey@...il.com Subject: Re: [PATCH 2/5] fsfreeze: emergency thaw will deadlock on s_umount On Mon, Jun 21, 2010 at 11:57:31AM +1000, Dave Chinner wrote: > This patch doesn't try to deal with the bdev/super mismatches; all > it does is prevent an obvious deadlock. Calling freeze/thaw_super > directly will serialise on the s_umount lock, calling > freeze/thaw_bdev() will serialise on the bdev freeze mutex, and if > we mix the two they'll serialise on the s_umount lock. So I think > with this patch serialisation will still occur correctly but avoid > the current deadlock. > > I'll change the commit message to explain this better. I don;t think the explanation alone is enough. Right now thaw_super itself is only serialized by exclusive shared s_umount. thaw_bdev it also serialized by bd_fsfreeze_mutex, but there are callers of thaw_super that do not go through thaw_bdev, so our locking is not enough here. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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