Hi Jiufei, On 09/02/2014 05:03 PM, Xue jiufei wrote: > 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 <xuejiufei@xxxxxxxxxx> >> >> 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. You can use PF_MEMALLOC_NOIO to replace PF_FSTRANS, set this flag in ocfs2 and check it in sb shrinker. Thanks, Junxiao. > > Thanks. > XueJiufei > > > -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
