FAILED: patch "[PATCH] net: ipa: fix atomic update in ipa_endpoint_replenish()" failed to apply to 5.10-stable tree

The patch below does not apply to the 5.10-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 <[email protected]>.

thanks,

greg k-h

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

From 6c0e3b5ce94947b311348c367db9e11dcb2ccc93 Mon Sep 17 00:00:00 2001
From: Alex Elder <[email protected]>
Date: Wed, 12 Jan 2022 07:30:10 -0600
Subject: [PATCH] net: ipa: fix atomic update in ipa_endpoint_replenish()

In ipa_endpoint_replenish(), if an error occurs when attempting to replenish a receive buffer, we just quit and try again later. In that case we increment the backlog count to reflect that the attempt was unsuccessful. Then, if the add_one flag was true we increment the backlog again.

This second increment is not included in the backlog local variable though, and its value determines whether delayed work should be scheduled. This is a bug.

Fix this by determining whether 1 or 2 should be added to the backlog before adding it in a atomic_add_return() call.

index 49d9a077d037..8b055885cf3c 100644
@@ -1080,6 +1080,7 @@ static void ipa_endpoint_replenish(struct ipa_endpoint *endpoint, bool add_one)
 {
 	struct gsi *gsi;
 	u32 backlog;
+	int delta;
 
 	if (!endpoint->replenish_enabled) {
 		if (add_one)

@@ -1097,10 +1098,8 @@ static void ipa_endpoint_replenish(struct ipa_endpoint *endpoint, bool add_one)
 
 try_again_later:
 	/* The last one didn't succeed, so fix the backlog */
-	backlog = atomic_inc_return(&endpoint->replenish_backlog);
-
-	if (add_one)
-		atomic_inc(&endpoint->replenish_backlog);
+	delta = add_one ? 2 : 1;
+	backlog = atomic_add_return(delta, &endpoint->replenish_backlog);
 
 	/* Whenever a receive buffer transaction completes we'll try to
 	 * replenish again.  It's unlikely, but if we fail to supply even