On 3/11/22 16:21, Javier González wrote: > On 08.03.2022 05:42, Damien Le Moal wrote: >> On 3/8/22 00:15, Keith Busch wrote: >>> On Mon, Mar 07, 2022 at 03:35:12PM +0100, Javier González wrote: >>>> As I mentioned in the last reply to to Dave, the main concern for me >>>> at the moment is supporting arbitrary zone sizes in the kernel. If we >>>> can agree on a path towards that, we can definitely commit to focus on >>>> ZoneFS and implement support for it on the different places we >>>> maintain in user-space. >>> >>> FWIW, the block layer doesn't require pow2 chunk_sectors anymore, so it >>> looks like that requirement for zone sizes can be relaxed, too. >> >> As long as: >> 1) Userspace does not break (really not sure about that one...) >> 2) No performance regression: the overhead of using multiplications & >> divisions for sector to zone conversions must be acceptable for ZNS (it >> will not matter for SMR HDDs) > > Good. The emulation patches we sent should cover this. > >> All in kernel users of zoned devices will need some patching (zonefs, >> btrfs, f2fs). Some will not work anymore (e.g. f2fs) and others will >> need different constraints (btrfs needs 64K aligned zones). Not all >> zoned devices will be usable anymore, and I am not sure if this >> degradation in the support provided is acceptable. > > We will do the work for btrfs (already have a prototype) and for zonefs > (we need to look into it). F2FS will use the emulation layer for now; > only !PO2 devices will pay the price. We will add a knob in the block > layer so that F2FS can force enable the emulation. No. The FS has no business changing the device. -- Damien Le Moal Western Digital Research
