[Devel] [PATCH RHEL10 COMMIT] drivers/vhost/blk: fix flush support

[Konstantin Khorenko <khorenko@virtuozzo.com>]

The commit is pushed to "branch-rh10-6.12.0-211.39.1.16.x.vz10-ovz" and will appear at git at bitbucket.org:openvz/vzkernel.git
after rh10-6.12.0-211.39.1.16.9.vz10
------>
commit bc3b45a6f06df2bcd7ef709f5998b10b2bdd5612
Author: Andrey Zhadchenko <andrey.zhadchenko@virtuozzo.com>
Date:   Tue Aug 25 15:51:50 2026 +0300

    drivers/vhost/blk: fix flush support
    
    REQ_OP_FLUSH is a technical flag for requests. For bios the
    correct combination would be REQ_OP_WRITE | REQ_PREFLUSH.
    See an example in blkdev_issue_flush().
    
    https://virtuozzo.atlassian.net/browse/VSTOR-138640
    Fixes: d8722ff88c5d ("drivers/vhost: vhost-blk accelerator for virtio-blk guests")
    Feature: vhost-blk: in-kernel accelerator for virtio-blk guests
    Signed-off-by: Andrey Zhadchenko <andrey.zhadchenko@virtuozzo.com>
    Reviewed-by: Vasileios Almpanis <vasileios.almpanis@virtuozzo.com>
    Reviewed-by: Konstantin Khorenko <khorenko@virtuozzo.com>
---
 drivers/vhost/blk.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/vhost/blk.c b/drivers/vhost/blk.c
index 2c41a073004bc..5c8d5b210c315 100644
--- a/drivers/vhost/blk.c
+++ b/drivers/vhost/blk.c
@@ -274,7 +274,7 @@ static int vhost_blk_bio_make(struct vhost_blk_req *req,
 	sector_t sector = req->sector;
 	unsigned long pos = 0;
 
-	if (unlikely(req->bi_opf == REQ_OP_FLUSH))
+	if (unlikely(req->bi_opf & REQ_PREFLUSH))
 		return vhost_blk_bio_make_simple(req, bdev);
 
 	if (req->bi_opf == REQ_OP_WRITE && req->len & SECTOR_MASK) {
@@ -488,7 +488,7 @@ static int vhost_blk_req_handle(struct vhost_virtqueue *vq,
 		ret = vhost_blk_req_submit(req);
 		break;
 	case VIRTIO_BLK_T_FLUSH:
-		req->bi_opf = REQ_OP_FLUSH;
+		req->bi_opf = REQ_OP_WRITE | REQ_PREFLUSH;
 		ret = vhost_blk_req_submit(req);
 		break;
 	case VIRTIO_BLK_T_GET_ID: