Re: [PATCH 1/2] kill-the-bkl/reiserfs: acquire the inode mutex safely

From: Trenton D. Adams
Date: Sat May 30 2009 - 00:25:37 EST

On Fri, May 29, 2009 at 9:22 PM, Frederic Weisbecker <fweisbec@xxxxxxxxx> wrote:
> On Fri, May 29, 2009 at 09:05:31PM -0600, Trenton D. Adams wrote:
>> On Sat, May 16, 2009 at 12:02 PM, Frederic Weisbecker
>> <fweisbec@xxxxxxxxx> wrote:
>> > While searching a pathname, an inode mutex can be acquired
>> > in do_lookup() which calls reiserfs_lookup() which in turn
>> > acquires the write lock.
>> >
>> > On the other side reiserfs_fill_super() can acquire the write_lock
>> > and then call reiserfs_lookup_privroot() which can acquire an
>> > inode mutex (the root of the mount point).
>> >
>> > So we theoretically risk an AB - BA lock inversion that could lead
>> > to a deadlock.
>> >
>> > As for other lock dependencies found since the bkl to mutex
>> > conversion, the fix is to use reiserfs_mutex_lock_safe() which
>> > drops the lock dependency to the write lock.
>> >
>> I'm curious, did this get applied, and is it related to the following?
>>  I was having these in 2.6.30-rc3.  I am now on 2.6.30-rc7 as of
>> today.  I haven't seen them today.  But then again, I only seen this
>> happen one time.
> Hi,
> No, may be it will come for 2.6.31 but for now it is not merged so
> it's not related.
> If you see such warning anymore, don't hesitate to tell about
> it!
> Thanks!

I was trying to imply that the patch might fix the problem I saw, not
that it was the cause. I only though that because it mentioned a
potential deadlock, and it seems like that is what the problem I saw
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