Hi Viro & Andraw Could you help review this patch? Thanks. xuejiufei On 2014/8/29 17:57, 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> > --- > fs/ocfs2/cluster/tcp.c | 7 +++++++ > fs/super.c | 3 +++ > 2 files changed, 10 insertions(+) > > diff --git a/fs/ocfs2/cluster/tcp.c b/fs/ocfs2/cluster/tcp.c > index 681691b..629b4da 100644 > --- a/fs/ocfs2/cluster/tcp.c > +++ b/fs/ocfs2/cluster/tcp.c > @@ -1581,6 +1581,8 @@ static void o2net_start_connect(struct work_struct *work) > int ret = 0, stop; > unsigned int timeout; > > + current->flags |= PF_FSTRANS; > + > /* if we're greater we initiate tx, otherwise we accept */ > if (o2nm_this_node() <= o2net_num_from_nn(nn)) > goto out; > @@ -1683,6 +1685,7 @@ out: > if (mynode) > o2nm_node_put(mynode); > > + current->flags &= ~PF_FSTRANS; > return; > } > > @@ -1809,6 +1812,8 @@ static int o2net_accept_one(struct socket *sock, int *more) > struct o2net_sock_container *sc = NULL; > struct o2net_node *nn; > > + current->flags |= PF_FSTRANS; > + > BUG_ON(sock == NULL); > *more = 0; > ret = sock_create_lite(sock->sk->sk_family, sock->sk->sk_type, > @@ -1918,6 +1923,8 @@ out: > o2nm_node_put(local_node); > if (sc) > sc_put(sc); > + > + current->flags &= ~PF_FSTRANS; > return ret; > } > > diff --git a/fs/super.c b/fs/super.c > index b9a214d..c4a8dc1 100644 > --- a/fs/super.c > +++ b/fs/super.c > @@ -71,6 +71,9 @@ static unsigned long super_cache_scan(struct shrinker *shrink, > if (!(sc->gfp_mask & __GFP_FS)) > return SHRINK_STOP; > > + if (current->flags & PF_FSTRANS) > + return SHRINK_STOP; > + > if (!grab_super_passive(sb)) > return SHRINK_STOP; > > -- 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>