From mboxrd@z Thu Jan 1 00:00:00 1970 From: Dave Chinner Subject: Re: [PATCH] mm: check memory reclaim bugs caused fs reentrance Date: Wed, 12 Nov 2014 08:52:07 +1100 Message-ID: <20141111215207.GW23575@dastard> References: <1415706590-24159-1-git-send-email-dmonakhov@openvz.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-btrfs@vger.kernel.org To: Dmitry Monakhov Return-path: Content-Disposition: inline In-Reply-To: <1415706590-24159-1-git-send-email-dmonakhov@openvz.org> Sender: linux-kernel-owner@vger.kernel.org List-Id: linux-fsdevel.vger.kernel.org On Tue, Nov 11, 2014 at 03:49:50PM +0400, Dmitry Monakhov wrote: > If filesystem holds transaction open 'current->journal_info' it should not > performs memory allocations with __GFP_FS flag enabled otherwise this result in fs > reentarance which lead to: > 1) reentrance to itself : deadlock or internal assertion failure due to incorrect journal credits > 1) entrance to another fs: assertion faulure or silient corruption due to incorrect journal > > Signed-off-by: Dmitry Monakhov > --- > include/linux/kernel.h | 7 +++++++ > mm/dmapool.c | 1 + > mm/mempool.c | 1 + > mm/page_alloc.c | 1 + > mm/slab.c | 1 + > mm/slub.c | 1 + > 6 files changed, 12 insertions(+), 0 deletions(-) > > diff --git a/include/linux/kernel.h b/include/linux/kernel.h > index 3d770f5..69923d4 100644 > --- a/include/linux/kernel.h > +++ b/include/linux/kernel.h > @@ -232,6 +232,13 @@ void might_fault(void); > static inline void might_fault(void) { } > #endif > > +#ifdef CONFIG_PROVE_LOCKING > +#define might_enter_fs_if(cond) \ > + WARN_ON_ONCE((cond) && current->journal_info) XFS does not use current->journal_info, and so this won't ever trigger on XFS. XFS uses PF_FSTRANS to indicate a transaction is in progress. Besides, isn't this redundant functionality? Lockdep already catches these problems with it's reclaim context tracking and it's tracking is more extensive than this simple check like this. lockdep regularly pointed out allocation/reclaim context problems in XFS until we fixed them.... Cheers, Dave. -- Dave Chinner david@fromorbit.com