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. 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
