linux-kernel - Re: dio_get_page() lockdep complaints

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Message-ID: <4734992C.7000408@oracle.com>
Date:	Fri, 09 Nov 2007 09:30:20 -0800
From:	Zach Brown <zach.brown@...cle.com>
To:	Peter Zijlstra <peterz@...radead.org>
CC:	Jens Axboe <jens.axboe@...cle.com>, linux-kernel@...r.kernel.org,
	akpm@...ux-foundation.org, linux-aio@...ck.org,
	Trond Myklebust <trond.myklebust@....uio.no>,
	Chris Mason <chris.mason@...cle.com>
Subject: Re: dio_get_page() lockdep complaints


So, reiserfs and NFS are nesting i_mutex inside the mmap_sem.

>>        [<b038c6e5>] mutex_lock+0x1c/0x1f
>>        [<b01b17e9>] reiserfs_file_release+0x54/0x447
>>        [<b016afe7>] __fput+0x53/0x101
>>        [<b016b0ee>] fput+0x19/0x1c
>>        [<b015bcd5>] remove_vma+0x3b/0x4d
>>        [<b015c659>] do_munmap+0x17f/0x1cf

>        [<ffffffff802686a1>] _mutex_lock+0x28/0x34
>        [<ffffffff883e71d0>] nfs_revalidate_mapping+0x6d/0xac [nfs]
>        [<ffffffff883e4b51>] nfs_file_mmap+0x5c/0x74 [nfs]
>        [<ffffffff8020df7e>] do_mmap_pgoff+0x51a/0x817
>        [<ffffffff80225d19>] sys_mmap+0x90/0x119

I think i_mutex is fundamentally nested outside of the mmap_sem because
of faulting in the buffered write path.  I think these warnings could be
reproduced with a careful test app which tries buffered writes from an
address which will fault.

DIO just tripped it up because it *always* performs get_user_pages() on
the memory.

So reiser and NFS need to be fixed.  No?

(reiser is grabbing i_mutex from any final fput?  brave!)

- z
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