[Devel] [PATCH RHEL10 COMMIT] drivers/vhost/blk: do not complete requests with failed status write

[Konstantin Khorenko]

The commit is pushed to "branch-rh10-6.12.0-211.16.1.12.x.vz10-ovz" and will appear at git at bitbucket.org:openvz/vzkernel.git
after rh10-6.12.0-211.16.1.12.4.vz10
------>
commit 12226fd33eff6dd957deca7d8c7343d3d8fc9a10
Author: Andrey Zhadchenko <andrey.zhadchenko at virtuozzo.com>
Date:   Fri Jun 19 16:33:11 2026 +0300

    drivers/vhost/blk: do not complete requests with failed status write
    
    Given that we failed to write into status memory, it's content is
    undefined. So completing the request is kind of sketchy.
    Just do like vhost-net and vhost-scsi and do not report this
    request completion.
    Do not forget to properly forget the request though.
    
    https://virtuozzo.atlassian.net/browse/VSTOR-134034
    Signed-off-by: Andrey Zhadchenko <andrey.zhadchenko at virtuozzo.com>
    
    ======
    Patchset description:
    vhost-blk: handling of failing requests
    
    This series mainly addresses the handling of failing requests.
    Previously the driver will always retry all requests failed at
    processing and will always complete the requests if they are
    past bio submission point.
    
    Using vhost-net and vhost-scsi as a model, we adopt the following
    approach:
     - requests failed at processing phase with ENOMEM/EAGAIN are re-tried
     - requests failed at processing phase with other errors are not
    reported completed and are not processed further. It is higly likely
    they are just incorrect
     - requests failed at status write after the completion are not
    reported completed
    
    This may sometime lead to guests stalling, but the alternatives are
    always worse.
    
    Also the patchset improves logging and adds a few sanity checks.
    
    Feature: vhost-blk: in-kernel accelerator for virtio-blk guests
    Reviewed-by: Pavel Tikhomirov <ptikhomirov at virtuozzo.com>
---
 drivers/vhost/blk.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/drivers/vhost/blk.c b/drivers/vhost/blk.c
index ef39ab92eee11..cdc82a8961870 100644
--- a/drivers/vhost/blk.c
+++ b/drivers/vhost/blk.c
@@ -594,11 +594,12 @@ static void vhost_blk_handle_host_kick(struct vhost_work *work)
 		vhost_blk_req_cleanup(req);
 
 		status = req->bio_err == 0 ?  VIRTIO_BLK_S_OK : VIRTIO_BLK_S_IOERR;
-		if (vhost_blk_set_status(req, status))
+		if (vhost_blk_set_status(req, status)) {
 			vhostblk_vq_err(blk, vq, "Failed to write status");
-
-		vhost_add_used(vq, req->head, req->len);
-		added = true;
+		} else {
+			vhost_add_used(vq, req->head, req->len);
+			added = true;
+		}
 
 		forget_request(req);
 	}