On 09/03/2014 11:10 AM, Dave Chinner wrote: > On Wed, Sep 03, 2014 at 09:38:31AM +0800, Junxiao Bi wrote: >> 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. > > No changes to the superblock shrinker, please. The flag should > modify the gfp_mask in the struct shrink_control passed to the > shrinker, just like the noio flag is used in the rest of the mm > code. __GFP_FS seemed imply __GFP_IO, can superblock shrinker check !(sc->gfp_mask & __GFP_IO) and stop? Thanks, Junxiao. > > Cheers, > > Dave. > -- 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
