This is a note to let you know that I've just added the patch titled
cifs: do all necessary checks for credits within or before locking
to the 6.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
cifs-do-all-necessary-checks-for-credits-within-or-b.patch
and it can be found in the queue-6.4 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 57e04461f6fa27afe01e3341a86fbac2830b1983
Author: Shyam Prasad N <sprasad@xxxxxxxxxxxxx>
Date: Thu Jun 22 18:16:04 2023 +0000
cifs: do all necessary checks for credits within or before locking
[ Upstream commit 326a8d04f147e2bf393f6f9cdb74126ee6900607 ]
All the server credits and in-flight info is protected by req_lock.
Once the req_lock is held, and we've determined that we have enough
credits to continue, this lock cannot be dropped till we've made the
changes to credits and in-flight count.
However, we used to drop the lock in order to avoid deadlock with
the recent srv_lock. This could cause the checks already made to be
invalidated.
Fixed it by moving the server status check to before locking req_lock.
Fixes: d7d7a66aacd6 ("cifs: avoid use of global locks for high contention data")
Signed-off-by: Shyam Prasad N <sprasad@xxxxxxxxxxxxx>
Signed-off-by: Steve French <stfrench@xxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/fs/smb/client/smb2ops.c b/fs/smb/client/smb2ops.c
index a8bb9d00d33ad..3bac586e8a8eb 100644
--- a/fs/smb/client/smb2ops.c
+++ b/fs/smb/client/smb2ops.c
@@ -211,6 +211,16 @@ smb2_wait_mtu_credits(struct TCP_Server_Info *server, unsigned int size,
spin_lock(&server->req_lock);
while (1) {
+ spin_unlock(&server->req_lock);
+
+ spin_lock(&server->srv_lock);
+ if (server->tcpStatus == CifsExiting) {
+ spin_unlock(&server->srv_lock);
+ return -ENOENT;
+ }
+ spin_unlock(&server->srv_lock);
+
+ spin_lock(&server->req_lock);
if (server->credits <= 0) {
spin_unlock(&server->req_lock);
cifs_num_waiters_inc(server);
@@ -221,15 +231,6 @@ smb2_wait_mtu_credits(struct TCP_Server_Info *server, unsigned int size,
return rc;
spin_lock(&server->req_lock);
} else {
- spin_unlock(&server->req_lock);
- spin_lock(&server->srv_lock);
- if (server->tcpStatus == CifsExiting) {
- spin_unlock(&server->srv_lock);
- return -ENOENT;
- }
- spin_unlock(&server->srv_lock);
-
- spin_lock(&server->req_lock);
scredits = server->credits;
/* can deadlock with reopen */
if (scredits <= 8) {
diff --git a/fs/smb/client/transport.c b/fs/smb/client/transport.c
index 0474d0bba0a2e..f280502a2aee8 100644
--- a/fs/smb/client/transport.c
+++ b/fs/smb/client/transport.c
@@ -522,6 +522,16 @@ wait_for_free_credits(struct TCP_Server_Info *server, const int num_credits,
}
while (1) {
+ spin_unlock(&server->req_lock);
+
+ spin_lock(&server->srv_lock);
+ if (server->tcpStatus == CifsExiting) {
+ spin_unlock(&server->srv_lock);
+ return -ENOENT;
+ }
+ spin_unlock(&server->srv_lock);
+
+ spin_lock(&server->req_lock);
if (*credits < num_credits) {
scredits = *credits;
spin_unlock(&server->req_lock);
@@ -547,15 +557,6 @@ wait_for_free_credits(struct TCP_Server_Info *server, const int num_credits,
return -ERESTARTSYS;
spin_lock(&server->req_lock);
} else {
- spin_unlock(&server->req_lock);
-
- spin_lock(&server->srv_lock);
- if (server->tcpStatus == CifsExiting) {
- spin_unlock(&server->srv_lock);
- return -ENOENT;
- }
- spin_unlock(&server->srv_lock);
-
/*
* For normal commands, reserve the last MAX_COMPOUND
* credits to compound requests.
@@ -569,7 +570,6 @@ wait_for_free_credits(struct TCP_Server_Info *server, const int num_credits,
* for servers that are slow to hand out credits on
* new sessions.
*/
- spin_lock(&server->req_lock);
if (!optype && num_credits == 1 &&
server->in_flight > 2 * MAX_COMPOUND &&
*credits <= MAX_COMPOUND) {
