FAILED: patch "[PATCH] fuse: fix missing barrier when checking io-uring readiness" failed to apply to 7.1-stable tree

The patch below does not apply to the 7.1-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 <[email protected]>.

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-7.1.y
git checkout FETCH_HEAD
git cherry-pick -x edb310bc27f0ad83e7fd558a3caf1a94ca511654
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2026083142-mossy-turtle-dc44@gregkh' --subject-prefix 'PATCH 7.1.y' 'HEAD^..'

Possible dependencies:

thanks,

greg k-h

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

From edb310bc27f0ad83e7fd558a3caf1a94ca511654 Mon Sep 17 00:00:00 2001
From: Joanne Koong <[email protected]>
Date: Thu, 16 Jul 2026 11:31:42 -0700
Subject: [PATCH] fuse: fix missing barrier when checking io-uring readiness

fuse_block_alloc() reads fch->initialized and then fch->io_uring. fch->io_uring is set before fch->initialized, ordered by the smp_wmb() in fuse_chan_set_intialized(), but fuse_block_alloc() has no matching read barrier between the two loads.

This may lead a CPU to observe fch->initialized=1 but fch->io_uring=0, and skip the check that blocks request allocation until the io-uring queues are ready. This can reintroduce the lock-order inversion deadlock that commit 3393ff964e0f prevents.

Add an smp_rmb() barrier to pair with the smp_wmb() in fuse_chan_set_initialized() to prevent this.

index 7e81dea4f1c7..a27ea64d763a 100644
@@ -85,7 +85,13 @@ void fuse_chan_set_initialized(struct fuse_chan *fch, struct fuse_chan_param *pa
 
 static bool fuse_block_alloc(struct fuse_chan *fch, bool for_background)
 {
-	return !fch->initialized || (for_background && fch->blocked) ||
+	if (!fch->initialized)
+		return true;
+
+	/* Pairs with smp_wmb() in fuse_chan_set_initialized() */
+	smp_rmb();
+
+	return (for_background && fch->blocked) ||
 	       (fch->io_uring && fch->connected && !fuse_uring_ready(fch));
 }
 

@@ -120,9 +126,6 @@ static struct fuse_req *fuse_get_req(struct fuse_chan *fch, bool for_background)
 			goto out;
 	}
 
-	/* Matches smp_wmb() in fuse_chan_set_initialized() */
-	smp_rmb();
-
 	err = -ENOTCONN;
 	if (!fch->connected)
 		goto out;