From: Al Viro <viro@ZenIV.linux.org.uk>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: Tyler Hicks <tyhicks@canonical.com>,
"Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>,
linux-mm@kvack.org, davej@redhat.com, jboyer@redhat.com,
linux-kernel@vger.kernel.org,
Peter Zijlstra <a.p.zijlstra@chello.nl>,
Mimi Zohar <zohar@linux.vnet.ibm.com>,
David Gibson <david@gibson.dropbear.id.au>
Subject: Re: [PATCH] hugetlbfs: lockdep annotate root inode properly
Date: Thu, 8 Mar 2012 21:49:52 +0000 [thread overview]
Message-ID: <20120308214951.GB23916@ZenIV.linux.org.uk> (raw)
In-Reply-To: <20120308134050.f53a0b2f.akpm@linux-foundation.org>
On Thu, Mar 08, 2012 at 01:40:50PM -0800, Andrew Morton wrote:
> OK, thanks, yup. Taking i_mutex in file_operations.mmap() is wrong.
... or in .release() (munmap() does fput() under mmap_sem).
> Is hugetlbfs actually deadlockable because of this, or is it the case
> that the i_mutex->mmap_sem ordering happens to never happen for this
> filesystem?
Yes, it is. Look at read(2) on hugetlbfs; it copies userland data
while holding ->i_mutex. So we have
read(2):
mutex_lock(&A)
down_read(&B)
mmap(2):
down_write(&B);
mutex_lock(&A);
which is an obvious deadlock.
> So we need to pull the i_mutex out of hugetlbfs_file_mmap().
IIRC, you have a patch in your tree doing just that...
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WARNING: multiple messages have this Message-ID (diff)
From: Al Viro <viro@ZenIV.linux.org.uk>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: Tyler Hicks <tyhicks@canonical.com>,
"Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>,
linux-mm@kvack.org, davej@redhat.com, jboyer@redhat.com,
linux-kernel@vger.kernel.org,
Peter Zijlstra <a.p.zijlstra@chello.nl>,
Mimi Zohar <zohar@linux.vnet.ibm.com>,
David Gibson <david@gibson.dropbear.id.au>
Subject: Re: [PATCH] hugetlbfs: lockdep annotate root inode properly
Date: Thu, 8 Mar 2012 21:49:52 +0000 [thread overview]
Message-ID: <20120308214951.GB23916@ZenIV.linux.org.uk> (raw)
In-Reply-To: <20120308134050.f53a0b2f.akpm@linux-foundation.org>
On Thu, Mar 08, 2012 at 01:40:50PM -0800, Andrew Morton wrote:
> OK, thanks, yup. Taking i_mutex in file_operations.mmap() is wrong.
... or in .release() (munmap() does fput() under mmap_sem).
> Is hugetlbfs actually deadlockable because of this, or is it the case
> that the i_mutex->mmap_sem ordering happens to never happen for this
> filesystem?
Yes, it is. Look at read(2) on hugetlbfs; it copies userland data
while holding ->i_mutex. So we have
read(2):
mutex_lock(&A)
down_read(&B)
mmap(2):
down_write(&B);
mutex_lock(&A);
which is an obvious deadlock.
> So we need to pull the i_mutex out of hugetlbfs_file_mmap().
IIRC, you have a patch in your tree doing just that...
next prev parent reply other threads:[~2012-03-08 21:50 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-03-08 9:15 [PATCH] hugetlbfs: lockdep annotate root inode properly Aneesh Kumar K.V
2012-03-08 9:15 ` Aneesh Kumar K.V
2012-03-08 21:02 ` Andrew Morton
2012-03-08 21:02 ` Andrew Morton
2012-03-08 21:10 ` Dave Jones
2012-03-08 21:10 ` Dave Jones
2012-03-08 21:19 ` Tyler Hicks
2012-03-08 21:40 ` Andrew Morton
2012-03-08 21:40 ` Andrew Morton
2012-03-08 21:49 ` Al Viro [this message]
2012-03-08 21:49 ` Al Viro
2012-03-08 22:19 ` Andrew Morton
2012-03-08 22:19 ` Andrew Morton
2012-03-08 22:33 ` Dave Jones
2012-03-08 22:33 ` Dave Jones
2012-03-08 22:45 ` Andrew Morton
2012-03-08 22:45 ` Andrew Morton
2012-03-09 5:00 ` Aneesh Kumar K.V
2012-03-09 5:00 ` Aneesh Kumar K.V
2012-03-09 5:03 ` Aneesh Kumar K.V
2012-03-09 5:03 ` Aneesh Kumar K.V
2012-03-08 21:44 ` Al Viro
2012-03-08 21:44 ` Al Viro
2012-03-08 22:44 ` Peter Zijlstra
2012-03-08 22:44 ` Peter Zijlstra
2012-03-08 22:46 ` Peter Zijlstra
2012-03-08 22:46 ` Peter Zijlstra
-- strict thread matches above, loose matches on Subject: below --
2012-04-16 20:28 Aneesh Kumar K.V
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