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. -- Dave Chinner david@xxxxxxxxxxxxx -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>