[PATCH 4/4] smb: prevent TIF_NOTIFY_SIGNAL from interrupting

[Christian Brauner <brauner@kernel.org>]

smb_send_kvec() blocks every signal during a send:

	sigfillset(&mask);
	sigprocmask(SIG_BLOCK, &mask, &oldmask);

An incomplete or partial sent would cause the connection to become out
of sync. That in turn would cause the session to be torn down and
reconnected.

In 00be6f26a2a7 ("smb: client: transport: avoid reconnects triggered
by pending task work") smb hand-rolled its own solution. Have it use the
new no_notify_signal_save() critical section instead.

This stops io_uring from cancelling a send in flight but that's just
like it is today and it is bounded by sk_sndtimeo at around 15s.

Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>
---
 fs/smb/client/transport.c | 13 +++++--------
 1 file changed, 5 insertions(+), 8 deletions(-)

diff --git a/fs/smb/client/transport.c b/fs/smb/client/transport.c
index fdf4e50c27ce..05dc20916c27 100644
--- a/fs/smb/client/transport.c
+++ b/fs/smb/client/transport.c
@@ -22,7 +22,6 @@
 #include <linux/mempool.h>
 #include <linux/sched/signal.h>
 #include <linux/task_io_accounting_ops.h>
-#include <linux/task_work.h>
 #include "cifsglob.h"
 #include "cifsproto.h"
 #include "cifs_debug.h"
@@ -142,6 +141,7 @@ int
 smb_send_kvec(struct TCP_Server_Info *server, struct msghdr *smb_msg,
 	      size_t *sent)
 {
+	unsigned int notify_flags;
 	int rc = 0;
 	int retries = 0;
 	struct socket *ssocket = server->ssocket;
@@ -172,15 +172,12 @@ smb_send_kvec(struct TCP_Server_Info *server, struct msghdr *smb_msg,
 		 * after the retries we will kill the socket and
 		 * reconnect which may clear the network problem.
 		 *
-		 * Even if regular signals are masked, EINTR might be
-		 * propagated from sk_stream_wait_memory() to here when
-		 * TIF_NOTIFY_SIGNAL is used for task work. For example,
-		 * certain io_uring completions will use that. Treat
-		 * having EINTR with pending task work the same as EAGAIN
-		 * to avoid unnecessary reconnects.
+		 * Task work must not abort the send, see signal_pending().
 		 */
+		notify_flags = no_notify_signal_save();
 		rc = sock_sendmsg(ssocket, smb_msg);
-		if (rc == -EAGAIN || unlikely(rc == -EINTR && task_work_pending(current))) {
+		no_notify_signal_restore(notify_flags);
+		if (rc == -EAGAIN) {
 			retries++;
 			if (retries >= 14 ||
 			    (!server->noblocksnd && (retries > 2))) {

-- 
2.53.0