FAILED: patch "[PATCH] cifs: reset iface weights when we cannot find a candidate" failed to apply to 6.1-stable tree

[<gregkh@linuxfoundation.org>]

The patch below does not apply to the 6.1-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@vger.kernel.org>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.1.y
git checkout FETCH_HEAD
git cherry-pick -x 9d5eff7821f6d70f7d1b4d8a60680fba4de868a7
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@vger.kernel.org>' --in-reply-to '2025081845-cork-enable-a1e8@gregkh' --subject-prefix 'PATCH 6.1.y' HEAD^..

Possible dependencies:



thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 9d5eff7821f6d70f7d1b4d8a60680fba4de868a7 Mon Sep 17 00:00:00 2001
From: Shyam Prasad N <sprasad@microsoft.com>
Date: Thu, 17 Jul 2025 17:36:13 +0530
Subject: [PATCH] cifs: reset iface weights when we cannot find a candidate

We now do a weighted selection of server interfaces when allocating
new channels. The weights are decided based on the speed advertised.
The fulfilled weight for an interface is a counter that is used to
track the interface selection. It should be reset back to zero once
all interfaces fulfilling their weight.

In cifs_chan_update_iface, this reset logic was missing. As a result
when the server interface list changes, the client may not be able
to find a new candidate for other channels after all interfaces have
been fulfilled.

Fixes: a6d8fb54a515 ("cifs: distribute channels across interfaces based on speed")
Cc: <stable@vger.kernel.org>
Signed-off-by: Shyam Prasad N <sprasad@microsoft.com>
Signed-off-by: Steve French <stfrench@microsoft.com>

diff --git a/fs/smb/client/sess.c b/fs/smb/client/sess.c
index 330bc3d25bad..0a8c2fcc9ded 100644
--- a/fs/smb/client/sess.c
+++ b/fs/smb/client/sess.c
@@ -332,6 +332,7 @@ cifs_chan_update_iface(struct cifs_ses *ses, struct TCP_Server_Info *server)
 	struct cifs_server_iface *old_iface = NULL;
 	struct cifs_server_iface *last_iface = NULL;
 	struct sockaddr_storage ss;
+	int retry = 0;
 
 	spin_lock(&ses->chan_lock);
 	chan_index = cifs_ses_get_chan_index(ses, server);
@@ -360,6 +361,7 @@ cifs_chan_update_iface(struct cifs_ses *ses, struct TCP_Server_Info *server)
 		return;
 	}
 
+try_again:
 	last_iface = list_last_entry(&ses->iface_list, struct cifs_server_iface,
 				     iface_head);
 	iface_min_speed = last_iface->speed;
@@ -397,6 +399,13 @@ cifs_chan_update_iface(struct cifs_ses *ses, struct TCP_Server_Info *server)
 	}
 
 	if (list_entry_is_head(iface, &ses->iface_list, iface_head)) {
+		list_for_each_entry(iface, &ses->iface_list, iface_head)
+			iface->weight_fulfilled = 0;
+
+		/* see if it can be satisfied in second attempt */
+		if (!retry++)
+			goto try_again;
+
 		iface = NULL;
 		cifs_dbg(FYI, "unable to find a suitable iface\n");
 	}