On Mon, Jan 13, 2014 at 11:06:33PM -0500, Martin K. Petersen wrote: > >>>>> "Kent" == Kent Overstreet <k...@daterainc.com> writes: > > Kent, > > Kent> I think for discards we can deal with this easily enough - > Kent> __blk_recalc_rq_segments() will have to special case them - but > Kent> there's a similar (but worse) issue with WRITE_SAME, and looking > Kent> at the code it does attempt to merge WRITE_SAME requests too. > > DISCARD bios have no payload going down the stack. They get a payload > attached in the sd driver and will therefore have a single bvec at > completion time. > > WRITE_SAME bios have a single bvec payload throughout their lifetime. > > For both these types of requests we never attempt to merge the actual > payloads. But the block range worked on may shrink or grow as the bio is > split or merged going down the stack. > > IOW, DISCARD, WRITE SAME and the impending COPY requests do not have a > 1:1 mapping between the block range worked on and the size of any bvecs > attached. Your recent changes must have changed the way we handled that > in the past.
Yeah - but with WRITE_SAME bios, wouldn't we at least have to check that they're writing the same data to merge them? -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
