diff options
author | Xue jiufei | 2014-10-09 15:28:26 -0700 |
---|---|---|
committer | Linus Torvalds | 2014-10-09 22:25:58 -0400 |
commit | b246d3d11e9c04f76a4fd6aae9c61da82bba0afb (patch) | |
tree | 74f3372f48038954afe5939f03ef096944cf6d05 | |
parent | 934f3072c17cc8886f4c043b47eeeb1b12f8de33 (diff) |
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>
-rw-r--r-- | fs/ocfs2/cluster/tcp.c | 20 |
1 files changed, 20 insertions, 0 deletions
diff --git a/fs/ocfs2/cluster/tcp.c b/fs/ocfs2/cluster/tcp.c index 509e6d5415e2..97de0fbd9f78 100644 --- a/fs/ocfs2/cluster/tcp.c +++ b/fs/ocfs2/cluster/tcp.c @@ -1601,7 +1601,15 @@ static void o2net_start_connect(struct work_struct *work) struct sockaddr_in myaddr = {0, }, remoteaddr = {0, }; int ret = 0, stop; unsigned int timeout; + unsigned int noio_flag; + /* + * sock_create allocates the sock with GFP_KERNEL. We must set + * per-process flag PF_MEMALLOC_NOIO so that all allocations done + * by this process are done as if GFP_NOIO was specified. So we + * are not reentering filesystem while doing memory reclaim. + */ + noio_flag = memalloc_noio_save(); /* if we're greater we initiate tx, otherwise we accept */ if (o2nm_this_node() <= o2net_num_from_nn(nn)) goto out; @@ -1710,6 +1718,7 @@ out: if (mynode) o2nm_node_put(mynode); + memalloc_noio_restore(noio_flag); return; } @@ -1836,6 +1845,15 @@ static int o2net_accept_one(struct socket *sock, int *more) struct o2nm_node *local_node = NULL; struct o2net_sock_container *sc = NULL; struct o2net_node *nn; + unsigned int noio_flag; + + /* + * sock_create_lite allocates the sock with GFP_KERNEL. We must set + * per-process flag PF_MEMALLOC_NOIO so that all allocations done + * by this process are done as if GFP_NOIO was specified. So we + * are not reentering filesystem while doing memory reclaim. + */ + noio_flag = memalloc_noio_save(); BUG_ON(sock == NULL); *more = 0; @@ -1952,6 +1970,8 @@ out: o2nm_node_put(local_node); if (sc) sc_put(sc); + + memalloc_noio_restore(noio_flag); return ret; } |