[Devel] [PATCH RHEL9 COMMIT] fs/fuse kio: do not set RPC affinity from a workequeue worker

[Konstantin Khorenko]

The commit is pushed to "branch-rh9-5.14.0-427.55.1.vz9.82.x-ovz" and will appear at git at bitbucket.org:openvz/vzkernel.git
after rh9-5.14.0-427.55.1.vz9.82.4
------>
commit 656d21e8a029763e22b8e95969524e3e8d8ff773
Author: Liu Kui <kui.liu at virtuozzo.com>
Date:   Tue Jul 8 16:14:16 2025 +0800

    fs/fuse kio: do not set RPC affinity from a workequeue worker
    
    A RPC's affinity shouldn't be set from a workqueue worker in case of
    RPC_AFFINITY_RETENT mode, otherwise the RPC could be stuck to one cpu
    forever. When multiple rpcs are stuck to the same cpu overall performance
    degrades significantly.
    
    Fixes: #VSTOR-109481
    https://virtuozzo.atlassian.net/browse/VSTOR-109481
    
    Signed-off-by: Liu Kui <kui.liu at virtuozzo.com>
    
    Feature: fuse: kRPC - single RPC for kernel and userspace
---
 fs/fuse/kio/pcs/pcs_rpc.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/fs/fuse/kio/pcs/pcs_rpc.c b/fs/fuse/kio/pcs/pcs_rpc.c
index 81da47f761555..7e7cc63257702 100644
--- a/fs/fuse/kio/pcs/pcs_rpc.c
+++ b/fs/fuse/kio/pcs/pcs_rpc.c
@@ -802,6 +802,10 @@ static void pcs_rpc_affinity(struct pcs_rpc *ep, bool was_idle)
 				break;
 			fallthrough;
 		case RPC_AFFINITY_RETENT:
+			/* Do not set rpc affinity from a workequeue worker */
+			if (current->flags & PF_WQ_WORKER)
+				break;
+
 			/* Naive socket-to-cpu binding approach */
 			if (time_is_before_jiffies(ep->cpu_stamp) && was_idle) {
 				ep->cpu_stamp = jiffies + rpc_cpu_time_slice;