Commit 00be6f26 authored by Fiona Ebner's avatar Fiona Ebner Committed by Steve French
Browse files

smb: client: transport: avoid reconnects triggered by pending task work 



When io_uring is used in the same task as CIFS, there might be
unnecessary reconnects, causing issues in user-space applications
like QEMU with a log like:

> CIFS: VFS: \\10.10.100.81 Error -512 sending data on socket to server

Certain io_uring completions might be added to task_work with
notify_method being TWA_SIGNAL and thus TIF_NOTIFY_SIGNAL is set for
the task.

In __smb_send_rqst(), signals are masked before calling
smb_send_kvec(), but the masking does not apply to TIF_NOTIFY_SIGNAL.

If sk_stream_wait_memory() is reached via sock_sendmsg() while
TIF_NOTIFY_SIGNAL is set, signal_pending(current) will evaluate to
true there, and -EINTR will be propagated all the way from
sk_stream_wait_memory() to sock_sendmsg() in smb_send_kvec().
Afterwards, __smb_send_rqst() will see that not everything was written
and reconnect.

Signed-off-by: default avatarFiona Ebner <f.ebner@proxmox.com>
Signed-off-by: default avatarSteve French <stfrench@microsoft.com>
parent 17ef15fa

fs/smb/client/transport.c

+9 −1
Original line number Diff line number Diff line
@@ -22,6 +22,7 @@ 
#include <linux/mempool.h>

#include <linux/sched/signal.h>

#include <linux/task_io_accounting_ops.h>

#include <linux/task_work.h>

#include "cifspdu.h"

#include "cifsglob.h"

#include "cifsproto.h"
@@ -173,9 +174,16 @@ smb_send_kvec(struct TCP_Server_Info *server, struct msghdr *smb_msg, 
		 * send a packet.  In most cases if we fail to send

		 * 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.

		 */

		rc = sock_sendmsg(ssocket, smb_msg);

		if (rc == -EAGAIN) {

		if (rc == -EAGAIN || unlikely(rc == -EINTR && task_work_pending(current))) {

			retries++;

			if (retries >= 14 ||

			    (!server->noblocksnd && (retries > 2))) {