Re: [PATCH] blk-mq: Set request mapping to NULL in blk_mq_put_driver_tag

[Ming Lei <ming.lei@redhat.com>]

On Tue, Dec 04, 2018 at 03:30:11PM +0530, Kashyap Desai wrote:
> Problem statement :
> Whenever try to get outstanding request via scsi_host_find_tag,
> block layer will return stale entries instead of actual outstanding
> request. Kernel panic if stale entry is inaccessible or memory is reused.
> Fix :
> Undo request mapping in blk_mq_put_driver_tag  nce request is return.
> 
> More detail :
> Whenever each SDEV entry is created, block layer allocate separate tags
> and static requestis.Those requests are not valid after SDEV is deleted
> from the system. On the fly, block layer maps static rqs to rqs as below
> from blk_mq_get_driver_tag()
> 
> data.hctx->tags->rqs[rq->tag] = rq;
> 
> Above mapping is active in-used requests and it is the same mapping which
> is referred in function scsi_host_find_tag().
> After running some IOs, “data.hctx->tags->rqs[rq->tag]” will have some
> entries which will never be reset in block layer.

However, if rq & rq->tag is valid, data.hctx->tags->rqs[rq->tag] should
have pointed to one active request instead of the stale one, right?

Thanks,
Ming