Re: [PATCH stable 5.10 1/3] block: look up holders by bdev

[Yu Kuai <yukuai1@huaweicloud.com>]

Hi, Christoph

在 2022/08/02 13:11, Greg KH 写道:
> On Mon, Aug 01, 2022 at 08:04:58PM +0200, Christoph Hellwig wrote:
>> On Mon, Aug 01, 2022 at 01:19:09PM +0200, Greg KH wrote:
>>> This is very different from the upstream version, and forces the change
>>> onto everyone, not just those who had CONFIG_BLOCK_HOLDER_DEPRECATED
>>> enabled like was done in the main kernel tree.
>>>
>>> Why force this on all and not just use the same option?
>>
>> I'm really worried about backports that are significantly different
>> from the original commit.  To the point where if they are so different
>> and we don't have a grave security or data integrity bug I'm really not
>> very much in favor of backporting them at all.
>>

I do understand that backporting these patches is not good, thanks for
taking time on this patchset.

I decided to push following patch in our version:

diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index 588e8b43efab..c047d5fcb325 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -2149,12 +2149,16 @@ int dm_setup_md_queue(struct mapped_device *md, 
struct dm_table *t)

         switch (type) {
         case DM_TYPE_REQUEST_BASED:
-               md->disk->fops = &dm_rq_blk_dops;
                 r = dm_mq_init_request_queue(md, t);
                 if (r) {
                         DMERR("Cannot initialize queue for 
request-based dm mapped device");
                         return r;
                 }
+               /*
+                * Change the fops after queue is initialized, so that 
bio won't
+                * issued by rq-based path until that.
+                */
+               md->disk->fops = &dm_rq_blk_dops;
                 break;
         case DM_TYPE_BIO_BASED:
         case DM_TYPE_DAX_BIO_BASED:


This way only modify dm, and the problem can be fixed. If you guys think
this is OK, I can send a patch for LTS. Otherwise, if you guys still
think the null-ptr-def problem is uncommon and doesn't worth to fix,
please ignore this mail.

Thanks,
Kuai
> 
> I agree, I'll drop this from my review queue now, thanks.
> 
> greg k-h
> .
>