From: Al Viro <viro@ZenIV.linux.org.uk>
To: Miles Lane <miles.lane@gmail.com>
Cc: LKML <linux-kernel@vger.kernel.org>,
"Theodore Ts'o" <tytso@mit.edu>,
Andreas Dilger <adilger.kernel@dilger.ca>,
Andrew Morton <akpm@linux-foundation.org>
Subject: Re: Linus GIT (3.3.0-rc6+) -- INFO: possible circular locking dependency detected
Date: Mon, 5 Mar 2012 21:33:44 +0000 [thread overview]
Message-ID: <20120305213343.GN23916@ZenIV.linux.org.uk> (raw)
In-Reply-To: <CAHFgRy-V3ZFK6QrC2++Rvyi4e_f-03Xdr9sj4PUJORVq21GiEw@mail.gmail.com>
On Mon, Mar 05, 2012 at 04:08:55PM -0500, Miles Lane wrote:
> [ 107.839634] -> #1 (&mm->mmap_sem){++++++}:
[readdir() grabs ->mmap_sem under ->i_mutex - true, but irrelevant; more
to the point, write() on just about anything will grab ->mmap_sem under
->i_mutex, and that one happens for non-directories]
> [ 107.839665] -> #0 (&sb->s_type->i_mutex_key#13){+.+.+.}:
[generic_file_aio_write() grabs ->i_mutex after being called from
vfs_write(), called from...]
> [ 107.839691] [<ffffffff810e6333>] vfs_write+0xa7/0xee
> [ 107.839694] [<ffffffffa037f266>]
> ecryptfs_write_lower+0x4e/0x73 [ecryptfs]
> [ 107.839700] [<ffffffffa03803d3>]
> ecryptfs_encrypt_page+0x11c/0x182 [ecryptfs]
> [ 107.839704] [<ffffffffa037e967>]
> ecryptfs_writepage+0x31/0x73 [ecryptfs]
> [ 107.839708] [<ffffffff810b448b>] __writepage+0x12/0x31
> [ 107.839710] [<ffffffff810b4b25>] write_cache_pages+0x1e6/0x310
> [ 107.839713] [<ffffffff810b4c8d>] generic_writepages+0x3e/0x54
> [ 107.839716] [<ffffffff810b5e05>] do_writepages+0x26/0x28
> [ 107.839719] [<ffffffff810ae1e4>] __filemap_fdatawrite_range+0x4e/0x50
> [ 107.839722] [<ffffffff810aed55>] filemap_fdatawrite+0x1a/0x1c
> [ 107.839725] [<ffffffff810aed72>] filemap_write_and_wait+0x1b/0x36
> [ 107.839727] [<ffffffffa037c1bb>]
> ecryptfs_vma_close+0x17/0x19 [ecryptfs]
Bloody wonderful... That would do it, all right. Forget about readdir(),
the deadlock is real and has nothing to do with directories. Ecryptfs bug,
AFAICS.
Thread A:
mmap something on ecryptfs, dirty it.
Thread B: open underlying file for write,
later
Thread A: munmap() | Thread B: write() (from unrelated buffer)
A holds ->mmap_sem, B holds ->i_mutex.
A is blocked essentially on attempt to do what B is doing (write to underlying
file; any mutex whatever_fs_write() might be holding around copy_from_user()
will do for that deadlock).
B is blocked trying to fault some pages in.
Fun...
next prev parent reply other threads:[~2012-03-05 21:33 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-03-05 21:08 Linus GIT (3.3.0-rc6+) -- INFO: possible circular locking dependency detected Miles Lane
2012-03-05 21:23 ` Andrew Morton
2012-03-05 21:35 ` Al Viro
2012-03-05 21:46 ` Tyler Hicks
2012-03-05 21:33 ` Al Viro [this message]
2012-03-05 21:46 ` Ted Ts'o
2012-03-05 22:02 ` Ted Ts'o
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