On Tue, Mar 11, 2025 at 08:19:29AM +0900, Damien Le Moal wrote: > On 3/11/25 02:43, Benjamin Marzinski wrote: > > On Mon, Mar 10, 2025 at 08:59:26AM +0900, Damien Le Moal wrote: > >> On 3/10/25 07:29, Benjamin Marzinski wrote: > >>> dm_revalidate_zones() only allowed devices that had no zone resources > >>> set up to call blk_revalidate_disk_zones(). If the device already had > >>> zone resources, disk->nr_zones would always equal md->nr_zones so > >>> dm_revalidate_zones() returned without doing any work. Instead, always > >>> call blk_revalidate_disk_zones() if you are loading a new zoned table. > >>> > >>> However, if the device emulates zone append operations and already has > >>> zone append emulation resources, the table size cannot change when > >>> loading a new table. Otherwise, all those resources will be garbage. > >>> > >>> If emulated zone append operations are needed and the zone write pointer > >>> offsets of the new table do not match those of the old table, writes to > >>> the device will still fail. This patch allows users to safely grow and > >>> shrink zone devices. But swapping arbitrary zoned tables will still not > >>> work. > >> > >> I do not think that this patch correctly address the shrinking of dm zoned > >> device: blk_revalidate_disk_zones() will look at a smaller set of zones, which > >> will leave already hashed zone write plugs outside of that new zone range in the > >> disk zwplug hash table. disk_revalidate_zone_resources() does not cleanup and > >> reallocate the hash table if the number of zones shrinks. > > > > This is necessary for DM. There could be plugged bios that are on on > > these no longer in-range zones. They will obviously fail when they get > > reissued, but we need to keep the plugs around so that they *do* get > > reissued. A cleaner alternative would be to add code to immediately > > error out all the plugged bios on shrinks, but I was trying to avoid > > adding a bunch of code to deal with these cases (of course simply > > disallowing them adds even less code). > > I am confused now :) > Under the assumption that we do not allow switching to a new table that changes > the zone configuration (in particualr, there is no grow/shrink of the device), > then I do not think we have to do anything special for DM. If we don't allow switching between zoned tables, then we obviously don't need to make DM call blk_revalidate_disk_zones() on a zoned table switch. I was just saying that I know that this patch would leave out-of-range zone plugs behind on a shrink, but that is necessary to allow shrinking while there could still be outstanding plugged bios attached to those plugs. So, if we wanted to allow shrinking, then I think this patch is correct (although erroring out all the out-of-range bios would be a cleaner solution). But assuming we don't allow shrinking, then you are correct. We don't need to do anything special for DM. -Ben > > > -- > Damien Le Moal > Western Digital Research
