From: Gurudas Pai <gurudas.pai@oracle.com>
To: Miklos Szeredi <miklos@szeredi.hu>
Cc: Hugh Dickins <hughd@google.com>,
hch@infradead.org, akpm@linux-foundation.org,
lkml20101129@newton.leun.net, linux-kernel@vger.kernel.org,
linux-mm@kvack.org
Subject: Re: [PATCH] mm: prevent concurrent unmap_mapping_range() on the same inode
Date: Tue, 08 Feb 2011 17:22:03 +0530 [thread overview]
Message-ID: <4D512E63.1040202@oracle.com> (raw)
In-Reply-To: <E1Pmkpt-0006Cd-Q6@pomaz-ex.szeredi.hu>
> On Wed, 26 Jan 2011, Hugh Dickins wrote:
>> I had wanted to propose that for now you modify just fuse to use
>> i_alloc_sem for serialization there, and I provide a patch to
>> unmap_mapping_range() to give safety to whatever other cases there are
>> (I'm now sure there are other cases, but also sure that I cannot
>> safely identify them all and fix them correctly at source myself -
>> even if I found time to do the patches, they'd need at least a release
>> cycle to bed in with BUG_ONs).
>
> Since fuse is the only one where the BUG has actually been triggered,
> and since there are problems with all the proposed generic approaches,
> I concur. I didn't want to use i_alloc_sem here as it's more
> confusing than a new mutex.
>
> Gurudas, could you please give this patch a go in your testcase?
I found this BUG with nfs, so trying with current patch may not help.
https://lkml.org/lkml/2010/12/29/9
Let me know if I have to run this
>
> From: Miklos Szeredi <mszeredi@suse.cz>
> Subject: fuse: prevent concurrent unmap on the same inode
>
> Running a fuse filesystem with multiple open()'s in parallel can
> trigger a "kernel BUG at mm/truncate.c:475"
>
> The reason is, unmap_mapping_range() is not prepared for more than
> one concurrent invocation per inode.
>
> Truncate and hole punching already serialize with i_mutex. Other
> callers of unmap_mapping_range() do not, and it's difficult to get
> i_mutex protection for all callers. In particular ->d_revalidate(),
> which calls invalidate_inode_pages2_range() in fuse, may be called
> with or without i_mutex.
>
> This patch adds a new mutex to fuse_inode to prevent running multiple
> concurrent unmap_mapping_range() on the same mapping.
Thanks,
-Guru
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next prev parent reply other threads:[~2011-02-08 11:49 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-01-20 12:30 [PATCH] mm: prevent concurrent unmap_mapping_range() on the same inode Miklos Szeredi
2011-01-20 12:40 ` Christoph Hellwig
2011-01-20 14:13 ` Miklos Szeredi
2011-01-22 4:46 ` Hugh Dickins
2011-01-24 19:47 ` Miklos Szeredi
2011-01-27 4:19 ` Hugh Dickins
2011-02-08 10:30 ` Miklos Szeredi
2011-02-08 11:52 ` Gurudas Pai [this message]
2011-02-08 11:59 ` Miklos Szeredi
-- strict thread matches above, loose matches on Subject: below --
2011-02-23 12:49 Miklos Szeredi
2011-02-23 22:20 ` Hugh Dickins
2011-02-23 22:33 ` Linus Torvalds
2011-02-23 23:12 ` Hugh Dickins
2011-03-02 9:48 ` Peter Zijlstra
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