The patch titled
Subject: ocfs2: fix a deadlock while o2net_wq doing direct memory reclaim
has been added to the -mm tree. Its filename is
ocfs2-fix-a-deadlock-while-o2net_wq-doing-direct-memory-reclaim.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/ocfs2-fix-a-deadlock-while-o2net_wq-doing-direct-memory-reclaim.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/ocfs2-fix-a-deadlock-while-o2net_wq-doing-direct-memory-reclaim.patch
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From: Xue jiufei <xuejiufei@xxxxxxxxxx>
Subject: 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@xxxxxxxxxx>
Cc: Junxiao Bi <junxiao.bi@xxxxxxxxxx>
Cc: Joel Becker <jlbec@xxxxxxxxxxxx>
Cc: Mark Fasheh <mfasheh@xxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
fs/ocfs2/cluster/tcp.c | 20 ++++++++++++++++++++
1 file changed, 20 insertions(+)
diff -puN fs/ocfs2/cluster/tcp.c~ocfs2-fix-a-deadlock-while-o2net_wq-doing-direct-memory-reclaim fs/ocfs2/cluster/tcp.c
--- a/fs/ocfs2/cluster/tcp.c~ocfs2-fix-a-deadlock-while-o2net_wq-doing-direct-memory-reclaim
+++ a/fs/ocfs2/cluster/tcp.c
@@ -1601,7 +1601,15 @@ static void o2net_start_connect(struct w
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;
}
@@ -1835,6 +1844,15 @@ static int o2net_accept_one(struct socke
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;
@@ -1951,6 +1969,8 @@ out:
o2nm_node_put(local_node);
if (sc)
sc_put(sc);
+
+ memalloc_noio_restore(noio_flag);
return ret;
}
_
Patches currently in -mm which might be from xuejiufei@xxxxxxxxxx are
ocfs2-free-vol_lable-in-ocfs2_delete_osb.patch
ocfs2-call-o2quo_exit-if-malloc-failed-in-o2net_init.patch
ocfs2-remove-unused-code-in-dlm_new_lockres.patch
ocfs2-free-inode-when-i_count-becomes-zero.patch
ocfs2-dlm-fix-race-between-dispatched_work-and-dlm_lockres_grab_inflight_worker.patch
mm-clear-__gfp_fs-when-pf_memalloc_noio-is-set.patch
ocfs2-fix-a-deadlock-while-o2net_wq-doing-direct-memory-reclaim.patch
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