From mboxrd@z Thu Jan 1 00:00:00 1970 From: Xue jiufei Subject: Re: [PATCH] fs/super.c: do not shrink fs slab during direct memory reclaim Date: Tue, 2 Sep 2014 17:03:27 +0800 Message-ID: <540587DF.6040302@huawei.com> References: <54004E82.3060608@huawei.com> <20140901235102.GI26465@dastard> Reply-To: Mime-Version: 1.0 Content-Type: text/plain; charset="ISO-8859-1" Content-Transfer-Encoding: 7bit Cc: Andrew Morton , , , , "ocfs2-devel@oss.oracle.com" , Junxiao Bi To: Dave Chinner Return-path: In-Reply-To: <20140901235102.GI26465@dastard> Sender: owner-linux-mm@kvack.org List-Id: linux-fsdevel.vger.kernel.org Hi, Dave On 2014/9/2 7:51, Dave Chinner wrote: > On Fri, Aug 29, 2014 at 05:57:22PM +0800, Xue jiufei wrote: >> The patch trys to solve one deadlock problem caused by cluster >> fs, like ocfs2. And the problem may happen at least in the below >> situations: >> 1)Receiving a connect message from other nodes, node queues a >> work_struct o2net_listen_work. >> 2)o2net_wq processes this work and calls sock_alloc() to allocate >> memory for a new socket. >> 3)It would do direct memory reclaim when available memory is not >> enough and trigger the inode cleanup. That inode being cleaned up >> is happened to be ocfs2 inode, so call evict()->ocfs2_evict_inode() >> ->ocfs2_drop_lock()->dlmunlock()->o2net_send_message_vec(), >> and wait for the unlock response from master. >> 4)tcp layer received the response, call o2net_data_ready() and >> queue sc_rx_work, waiting o2net_wq to process this work. >> 5)o2net_wq is a single thread workqueue, it process the work one by >> one. Right now it is still doing o2net_listen_work and cannot handle >> sc_rx_work. so we deadlock. >> >> It is impossible to set GFP_NOFS for memory allocation in sock_alloc(). >> So we use PF_FSTRANS to avoid the task reentering filesystem when >> available memory is not enough. >> >> Signed-off-by: joyce.xue > > For the second time: use memalloc_noio_save/memalloc_noio_restore. > And please put a great big comment in the code explaining why you > need to do this special thing with memory reclaim flags. > > Cheers, > > Dave. > Thanks for your reply. But I am afraid that memalloc_noio_save/ memalloc_noio_restore can not solve my problem. __GFP_IO is cleared if PF_MEMALLOC_NOIO is set and can avoid doing IO in direct memory reclaim. However, __GFP_FS is still set that can not avoid pruning dcache and icache in memory allocation, resulting in the deadlock I described. Thanks. XueJiufei -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org