NFS: Don't allow waiting for exiting tasks

Once a task calls exit_signals() it can no longer be signalled. So do
not allow it to do killable waits.

Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>

Author: Trond Myklebust

fs/nfs/inode.c

@@ -74,6 +74,8 @@ nfs_fattr_to_ino_t(struct nfs_fattr *fattr)
 
 int nfs_wait_bit_killable(struct wait_bit_key *key, int mode)
 {
+	if (unlikely(nfs_current_task_exiting()))
+		return -EINTR;
 	schedule();
 	if (signal_pending_state(mode, current))
 		return -ERESTARTSYS;

fs/nfs/internal.h

@@ -912,6 +912,11 @@ static inline u32 nfs_stateid_hash(nfs4_stateid *stateid)
 }
 #endif
 
+static inline bool nfs_current_task_exiting(void)
+{
+	return (current->flags & PF_EXITING) != 0;
+}
+
 static inline bool nfs_error_is_fatal(int err)
 {
 	switch (err) {

fs/nfs/nfs3proc.c

@@ -39,7 +39,7 @@ nfs3_rpc_wrapper(struct rpc_clnt *clnt, struct rpc_message *msg, int flags)
 		__set_current_state(TASK_KILLABLE|TASK_FREEZABLE_UNSAFE);
 		schedule_timeout(NFS_JUKEBOX_RETRY_TIME);
 		res = -ERESTARTSYS;
-	} while (!fatal_signal_pending(current));
+	} while (!fatal_signal_pending(current) && !nfs_current_task_exiting());
 	return res;
 }
 

fs/nfs/nfs4proc.c

@@ -446,6 +446,8 @@ static int nfs4_delay_killable(long *timeout)
 {
 	might_sleep();
 
+	if (unlikely(nfs_current_task_exiting()))
+		return -EINTR;
 	__set_current_state(TASK_KILLABLE|TASK_FREEZABLE_UNSAFE);
 	schedule_timeout(nfs4_update_delay(timeout));
 	if (!__fatal_signal_pending(current))
@@ -457,6 +459,8 @@ static int nfs4_delay_interruptible(long *timeout)
 {
 	might_sleep();
 
+	if (unlikely(nfs_current_task_exiting()))
+		return -EINTR;
 	__set_current_state(TASK_INTERRUPTIBLE|TASK_FREEZABLE_UNSAFE);
 	schedule_timeout(nfs4_update_delay(timeout));
 	if (!signal_pending(current))
@@ -1777,7 +1781,8 @@ static void nfs_set_open_stateid_locked(struct nfs4_state *state,
 		rcu_read_unlock();
 		trace_nfs4_open_stateid_update_wait(state->inode, stateid, 0);
 
-		if (!fatal_signal_pending(current)) {
+		if (!fatal_signal_pending(current) &&
+		    !nfs_current_task_exiting()) {
 			if (schedule_timeout(5*HZ) == 0)
 				status = -EAGAIN;
 			else
@@ -3581,7 +3586,7 @@ static bool nfs4_refresh_open_old_stateid(nfs4_stateid *dst,
 		write_sequnlock(&state->seqlock);
 		trace_nfs4_close_stateid_update_wait(state->inode, dst, 0);
 
-		if (fatal_signal_pending(current))
+		if (fatal_signal_pending(current) || nfs_current_task_exiting())
 			status = -EINTR;
 		else
 			if (schedule_timeout(5*HZ) != 0)