<div dir="ltr">Hi
Konstantin:<div><br><div> Thanks for your reply.</div><div>virtio_blk.c is the front-end driver code of the virtio block, which has the following code:<br> /* We need to know how many segments before we allocate. */<br> err = virtio_cread_feature(vdev, VIRTIO_BLK_F_SEG_MAX,<br> struct virtio_blk_config, seg_max,<br> &sg_elems);<br><br> /* We need at least one SG element, whatever they say. */<br> if (err || !sg_elems)<br> sg_elems = 1;<br><br>Eventually, the max number of segments will be configured through the blk_queue_max_segments interface.<br>When I modify the value of the sg_elems due to performance reasons, such as 128, I will find that the<br>front-end operating system cannot be started normally, which is manifested as the Android file system <br>cannot be mounted normally.<br><br>You can do a simple test to modify the default value of sg_elems virtio_blk.c in your company's<br>virtualization solution, as follows:<br>vzkernel$ git diff drivers/block/virtio_blk.c<br>diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c<br>index fd086179f980..0a216c9cb563 100644<br>--- a/drivers/block/virtio_blk.c<br>+++ b/drivers/block/virtio_blk.c<br>@@ -719,7 +719,7 @@ static int virtblk_probe(struct virtio_device *vdev)<br> <br> /* We need at least one SG element, whatever they say. */<br> if (err || !sg_elems)<br>- sg_elems = 1;<br>+ sg_elems = 2;<br> <br> /* Prevent integer overflows and honor max vq size */<br> sg_elems = min_t(u32, sg_elems, VIRTIO_BLK_MAX_SG_ELEMS - 2);<br><br>At this point, the expected test symptom is that the front-end OS does not boot properly.<br><br>In our virtualization solution, we used your company's blk.c as the back-end driver of Virtio Block,<br>found the above problems, and made problem fixes, and at the same time, the performance of Virtio <br>Block has also been improved, so we want to give back to the open source community.<br></div></div></div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">Konstantin Khorenko <<a href="mailto:khorenko@virtuozzo.com">khorenko@virtuozzo.com</a>> 于2024年6月14日周五 19:23写道：<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">Hi Lynch, Andrey,<br>
<br>
thank you for the patch, but can you please describe the problem it fixes in a bit more details?<br>
i see that the patch preserves original req->sector, but why/how that becomes important in case <br>
VIRTIO_BLK_F_MQ feature is set?<br>
<br>
Thank you.<br>
<br>
--<br>
Best regards,<br>
<br>
Konstantin Khorenko,<br>
Virtuozzo Linux Kernel Team<br>
<br>
On 17.05.2024 11:09, Andrey Zhadchenko wrote:<br>
> Hi<br>
> <br>
> Thank you for the patch.<br>
> vhost-blk didn't spark enough interest to be reviewed and merged into<br>
> the upstream and the code is not present here.<br>
> I have forwarded your patch to relevant openvz kernel mailing list.<br>
> <br>
> On 5/17/24 07:34, Lynch wrote:<br>
>> ---<br>
>> drivers/vhost/blk.c | 6 ++++--<br>
>> 1 file changed, 4 insertions(+), 2 deletions(-)<br>
>><br>
>> diff --git a/drivers/vhost/blk.c b/drivers/vhost/blk.c<br>
>> index 44fbf253e773..0e946d9dfc33 100644<br>
>> --- a/drivers/vhost/blk.c<br>
>> +++ b/drivers/vhost/blk.c<br>
>> @@ -251,6 +251,7 @@ static int vhost_blk_bio_make(struct vhost_blk_req *req,<br>
>> struct page **pages, *page;<br>
>> struct bio *bio = NULL;<br>
>> int bio_nr = 0;<br>
>> + sector_t sector_tmp;<br>
>> <br>
>> if (unlikely(req->bi_opf == REQ_OP_FLUSH))<br>
>> return vhost_blk_bio_make_simple(req, bdev);<br>
>> @@ -270,6 +271,7 @@ static int vhost_blk_bio_make(struct vhost_blk_req *req,<br>
>> req->bio = req->inline_bio;<br>
>> }<br>
>> <br>
>> + sector_tmp = req->sector;<br>
>> req->iov_nr = 0;<br>
>> for (i = 0; i < iov_nr; i++) {<br>
>> int pages_nr = iov_num_pages(&iov[i]);<br>
>> @@ -302,7 +304,7 @@ static int vhost_blk_bio_make(struct vhost_blk_req *req,<br>
>> bio = bio_alloc(GFP_KERNEL, pages_nr_total);<br>
>> if (!bio)<br>
>> goto fail;<br>
>> - bio->bi_iter.bi_sector = req->sector;<br>
>> + bio->bi_iter.bi_sector = sector_tmp;<br>
>> bio_set_dev(bio, bdev);<br>
>> bio->bi_private = req;<br>
>> bio->bi_end_io = vhost_blk_req_done;<br>
>> @@ -314,7 +316,7 @@ static int vhost_blk_bio_make(struct vhost_blk_req *req,<br>
>> iov_len -= len;<br>
>> <br>
>> pos = (iov_base & VHOST_BLK_SECTOR_MASK) + iov_len;<br>
>> - req->sector += pos >> VHOST_BLK_SECTOR_BITS;<br>
>> + sector_tmp += pos >> VHOST_BLK_SECTOR_BITS;<br>
>> }<br>
>> <br>
>> pages += pages_nr;<br>
</blockquote></div>