On Mon, 28 Jun 2010 10:18:48 +0200 Jens Axboe <axboe@xxxxxxxxx> wrote: > On 2010-06-28 10:14, FUJITA Tomonori wrote: > > On Mon, 28 Jun 2010 09:57:38 +0200 > > Christoph Hellwig <hch@xxxxxx> wrote: > > > >> On Sun, Jun 27, 2010 at 09:32:07PM +0900, FUJITA Tomonori wrote: > >>> On Sun, 27 Jun 2010 13:07:12 +0200 > >>> Christoph Hellwig <hch@xxxxxx> wrote: > >>> > >>>>> How about this? > >>>> > >>>> As I tried to explain before this utterly confuses the I/O completion > >>>> path. With the patch applied even a simple mkfs.xfs that issues discard > >>>> just hangs. > >>> > >>> Wired. I just tried mkfs.xfs against scsi_debug with my block patches > >>> (I saw one discard command). Seemed that it worked fine. > >> > >> I've tracked it down to the call to scsi_requeue_command in scsi_end_request. > >> When the command is marked BLOCK_PC we'll just get it back as such in > >> ->prep_fn next time, but now it's reverting to the previous state. > > > > If scsi_end_request() calls scsi_requeue_command(), the command has a > > left over (i.e. hasn't finished all the data), right? You hit such > > condition with discard commands? > > > > BLOCK_PC requests don't hit this case since blk_end_request() always > > return false for PC. > > You can get requeues on the ->queuecommand() path as well, for a > variety of reasons, and that would be what Christoph is hitting. Probably, that's would be fine (we need to fix memory leak in that path). I guess that requeue with the partial completion commands might cause problems. -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
