On Sat, Aug 01 2015 at 2:58am -0400, Ming Lin <mlin@xxxxxxxxxx> wrote: > On Fri, 2015-07-31 at 17:38 -0400, Mike Snitzer wrote: > > > > OK, once setup, to run the 2 tests in question directly you'd do > > something like: > > > > dmtest run --suite thin-provisioning -n discard_a_fragmented_device > > > > dmtest run --suite thin-provisioning -n discard_fully_provisioned_device_benchmark > > > > Again, these tests pass without this patchset. > > It's caused by patch 4. > When discard size >=4G, the bio->bi_iter.bi_size overflows. Thanks for tracking this down! > Below is the new patch. > > Christoph, > Could you also help to review it? > > Now we still do "misaligned" check in blkdev_issue_discard(). > So the same code in blk_bio_discard_split() was removed. But I don't agree with this approach. One of the most meaningful benefits of late bio splitting is the upper layers shouldn't _need_ to depend on the intermediate devices' queue_limits being stacked properly. Your solution to mix discard granularity/alignment checks at the upper layer(s) but then split based on max_discard_sectors at the lower layer defeats that benefit for discards. This will translate to all intermediate layers that might split discards needing to worry about granularity/alignment too (e.g. how dm-thinp will have to care because it must generate discard mappings with associated bios based on how blocks were mapped to thinp). Also, it is unfortunate that IO that doesn't have a payload is being artificially split simply because bio->bi_iter.bi_size is 32bits. Mike -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
