ocfs2: fix a deadlock while o2net_wq doing direct memory reclaim
Fix a deadlock problem caused by direct memory reclaim in o2net_wq. The
situation is as follows:
1) Receive a connect message from another node, node queues a
work_struct o2net_listen_work.
2) o2net_wq processes this work and call the following functions:
o2net_wq
-> o2net_accept_one
-> sock_create_lite
-> sock_alloc()
-> kmem_cache_alloc with GFP_KERNEL
-> ____cache_alloc_node
->__alloc_pages_nodemask
-> do_try_to_free_pages
-> shrink_slab
-> evict
-> ocfs2_evict_inode
-> ocfs2_drop_lock
-> dlmunlock
-> o2net_send_message_vec
then o2net_wq wait for the unlock reply from master.
3) tcp layer received the reply, call o2net_data_ready() and queue
sc_rx_work, waiting o2net_wq to process this work.
4) 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.
Junxiao Bi's patch "mm: clear __GFP_FS when PF_MEMALLOC_NOIO is set"
(http://ozlabs.org/~akpm/mmots/broken-out/mm-clear-__gfp_fs-when-pf_memalloc_noio-is-set.patch)
clears __GFP_FS in memalloc_noio_flags() besides __GFP_IO. We use
memalloc_noio_save() to set process flag PF_MEMALLOC_NOIO so that all
allocations done by this process are done as if GFP_NOIO was specified.
We are not reentering filesystem while doing memory reclaim.
Signed-off-by: joyce.xue <xuejiufei@huawei.com>
Cc: Junxiao Bi <junxiao.bi@oracle.com>
Cc: Joel Becker <jlbec@evilplan.org>
Cc: Mark Fasheh <mfasheh@suse.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
1 file changed