On Wed, Jan 06 2010 at 3:39am -0500, Martin K. Petersen <martin.petersen@xxxxxxxxxx> wrote: > >>>>> "Mike" == Mike Snitzer <snitzer@xxxxxxxxxx> writes: > > Mike> BTW, the other related concern Alasdair had was that DM shouldn't > Mike> need to know to add the start of the partition to the 'offset' it > Mike> passes to blk_stack_limits() -- sees it as a layering violation. > > Mike> I went over the fact that the 'struct queue_limits' was added to > Mike> abstract out the limit stacking in a way that DM could use too. > Mike> Without passing asymmetric types for the 'top' and 'bottom' device > Mike> to blk_stack_limits(), e.g.: > > I don't particularly care about the symmetry. The current set of > arguments were first and foremost there to meet DM's needs. I don't > think you had access to the bdev at the right time when we originally > came up with this. I think we always had it for the bottom device but not the top.. > However, there are other subsystems that need to stack without an > associated block_device. So instead of changing blk_stack_limits I > propose we use the wrapper below. Yes, looks like osdblk.c's use of blk_queue_stack_limits() > You'll notice that bdev_stack_limits takes a sector offset as argument. > I have a patch that I intend to push at a later date that will convert > the remaining stacking functions to take soft sector offsets instead of > bytes. I deal with the appropriate conversion in the alignment > calculation. That way we avoid the blk_off_t goo entirely and it makes > the difference between absolute offsets and alignment offsets crystal > clear. Looks good. But you're missing the EXPORT_SYMBOL(bdev_stack_limits) > Alasdair, if you are OK with the approach below I propose you give an > Acked-by: and then we can feed the patch through Jens instead of dealing > with a clunky two-stage merge this late in the .33 game. Good point, you can have mine while we're at it. > block: bdev_stack_limits wrapper > > DM does not want to know about partition offsets. Add a partition-aware > wrapper that DM can use when stacking block devices. > > Signed-off-by: Martin K. Petersen <martin.petersen@xxxxxxxxxx> Acked-by: Mike Snitzer <snitzer@xxxxxxxxxx> -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
