[Devel] [PATCH RHEL9 COMMIT] vhost-blk: fix allocation size for bio pointers

[Konstantin Khorenko]

The commit is pushed to "branch-rh9-5.14.0-427.37.1.vz9.78.x-ovz" and will appear at git at bitbucket.org:openvz/vzkernel.git
after rh9-5.14.0-427.37.1.vz9.78.4
------>
commit cba0add0f717ea561a7e251f9aff94c42702173b
Author: Pavel Tikhomirov <ptikhomirov at virtuozzo.com>
Date:   Wed Nov 6 17:20:31 2024 +0800

    vhost-blk: fix allocation size for bio pointers
    
    Even pages with continious virtual addresses may not be merged in one
    bio vector in bio_add_page -> bvec_try_merge_page. So it looks like the
    best estimate on the number of required bios we can make is a total
    number of pages in the request divided by BIO_MAX_VECS (worst case is
    when each of BIO_MAX_VECS bio vectors has exactly one page added to it).
    
    Fixes: 17bfe6e0400da ("drivers/vhost: vhost-blk accelerator for virtio-blk guests")
    https://virtuozzo.atlassian.net/browse/VSTOR-94596
    Signed-off-by: Pavel Tikhomirov <ptikhomirov at virtuozzo.com>
    
    Feature: vhost-blk: in-kernel accelerator for virtio-blk guests
---
 drivers/vhost/blk.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/vhost/blk.c b/drivers/vhost/blk.c
index d77e5fc494de..90d20d0eb722 100644
--- a/drivers/vhost/blk.c
+++ b/drivers/vhost/blk.c
@@ -228,7 +228,7 @@ static struct page **vhost_blk_prepare_req(struct vhost_blk_req *req,
 	req->use_inline = false;
 	pl_len = iov_nr * sizeof(req->pl[0]);
 	page_len = total_pages * sizeof(struct page *);
-	bio_len = (total_pages / (UINT_MAX / PAGE_SIZE) + 1) * sizeof(struct bio *);
+	bio_len = (total_pages + BIO_MAX_VECS - 1) / BIO_MAX_VECS * sizeof(struct bio *);
 
 	buf = kmalloc(pl_len + page_len + bio_len, GFP_KERNEL);
 	if (!buf)