[PATCH v2 4/5] smb: prevent TIF_NOTIFY_SIGNAL from interrupting

[Christian Brauner <brauner@kernel.org>]

smb blocks every signal during some sends:

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

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

In commit 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.

Acked-by: Paulo Alcantara <pc@manguebit.org>
Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>
---
 fs/smb/client/transport.c | 13 ++++---------
 1 file changed, 4 insertions(+), 9 deletions(-)

diff --git a/fs/smb/client/transport.c b/fs/smb/client/transport.c
index fdf4e50c27ce..35fa699569e9 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"
@@ -172,15 +171,11 @@ 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().
 		 */
-		rc = sock_sendmsg(ssocket, smb_msg);
-		if (rc == -EAGAIN || unlikely(rc == -EINTR && task_work_pending(current))) {
+		scoped_guard(no_notify_signal)
+			rc = sock_sendmsg(ssocket, smb_msg);
+		if (rc == -EAGAIN) {
 			retries++;
 			if (retries >= 14 ||
 			    (!server->noblocksnd && (retries > 2))) {

-- 
2.53.0