On Wed, Oct 27, 2021 at 06:16:19AM -0700, Bart Van Assche wrote: > On 10/26/21 10:27 PM, Christoph Hellwig wrote: > > On Tue, Oct 26, 2021 at 01:10:47PM -0700, Bart Van Assche wrote: > > > If blk_insert_cloned_request() is moved into the device mapper then I > > > think that blk_mq_request_issue_directly() will need to be exported. > > > > Which is even worse. > > > > > How > > > about the (totally untested) patch below for removing the > > > blk_insert_cloned_request() call from the UFS-HPB code? > > > > Which again doesn't fix anything. The problem is that it fans out one > > request into two on the same queue, not the specific interface used. > > That patch fixes the reported issue, namely removing the additional accounting > caused by calling blk_insert_cloned_request(). Please explain why it is > considered wrong to fan out one request into two. That code could be reworked > such that the block layer is not involved as Adrian Hunter explained. However, > before someone spends time on making these changes I think that someone should > provide more information about why it is considered wrong to fan out one request > into two. The original request consumes a tag from that queue's tagset. If the lifetime of that tag depends on that same queue having another free tag, you can deadlock.
