On 21.01.2020 15:24, Mike Snitzer wrote: > On Tue, Jan 21 2020 at 5:42am -0500, > Kirill Tkhai <ktkhai@xxxxxxxxxxxxx> wrote: > >> Since dm inherits limits from underlining block devices, >> this patch directly disables max_allocate_sectors for dm >> till full allocation support is implemented. >> >> This prevents high-level primitives (generic_make_request_checks(), >> __blkdev_issue_write_zeroes(), ...) from sending REQ_ALLOCATE >> requests. >> >> Signed-off-by: Kirill Tkhai <ktkhai@xxxxxxxxxxxxx> >> --- >> drivers/md/dm-table.c | 2 ++ >> drivers/md/md.h | 1 + >> 2 files changed, 3 insertions(+) > > You're mixing DM and MD changes in the same patch. > > But I'm wondering if it might be best to set this default for stacking > devices in blk_set_stacking_limits()? > > And then it is up to each stacking driver to override as needed. Hm. Sound like a good idea. This "lim->max_allocate_sectors = 0" in blk_set_stacking_limits() should work for dm's dm_calculate_queue_limits(), since it calls blk_stack_limits(), which is: t->max_allocate_sectors = min(t->max_allocate_sectors, b->max_allocate_sectors); Could you please tell is this fix is also enough for md? Kirill
