linux-kernel - Re: xfs mr_lock vs mmap

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Date:	Fri, 17 Jul 2009 11:09:22 -0400
From:	Christoph Hellwig <hch@...radead.org>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Christoph Hellwig <hch@...radead.org>,
	linux-kernel <linux-kernel@...r.kernel.org>, linux-mm@...ck.org
Subject: Re: xfs mr_lock vs mmap_sem lock inversion?

It's a problem in the VM code, which we already discussed a while
ago.  The problem is that the VMA manipultation code calls fput
under the mmap_sem, while we can take mmap_sem ue to a page fault
from inside generic_file_aio_read/write.  So any filesystem
that nees the same lock held over read/write also in release is
crewed.

Now on the positive side I think we can actually get rid of taking
the iolock in ->release in XFS, but I'm sure other filesystems
might continue hitting similar issues.

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