On Mon, Apr 30 2012 at 12:10pm -0400, Alasdair G Kergon <agk@xxxxxxxxxx> wrote: > On Sat, Apr 28, 2012 at 12:44:28AM -0400, Mike Snitzer wrote: > > Required to support a target's use of a non power of 2 blocksize. > > For which targets? striped and thin-pool for starters. > (merge_bvec supported?) Yes. > > + boundary = ti->split_io - do_div(tmp, ti->split_io); > > sector_div()? > > What about 32-bit arch + LBD + large split_io (from raid?) > - Is a 32-bit restriction on split_io unreasonable nowadays? > - OR reasonable on 32bit/LBD? > - OR fallback to old code there? I cannot see why we'd need a split_io that is larger than 32 bits -- a 32bit split_io can support up to 2TB (2**32 * 512b sectors). Even on a LBD (raid) the stripe size (split_io) will not be so large. (though yes we would need to establish a check in DM core that split_io is limited to 32-bit -- even though the 'sector_t' is used for split_io; and the comment inside the 'struct dm_target' would need updating). But what I think what you're driving at is: is there a benefit/reason to maintain the old code for some target that won't ever use non power of 2 split_io (e.g. dm-raid at the moment)? I see no point for the duality in the code but I'm open to the idea if you have a specific reason in mind -- are you concerned about perf on more obscure/older hardware? -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
