Then it does seem we have everything we need already, and no changes are needed. Because these drives *do* support the logical block size advertised, it's just not optimal. On Thu, Mar 07, 2024 at 04:31:48PM +1100, Dave Chinner wrote: > Sure, doing 512 byte aligned/sized IO to a 4kB sector sizer device > is not optimal. IO will to the file will be completely serialised > because they are sub-fs-block DIO writes, but it does work because > the underlying device allows it. Nobody wanting a performant > application will want to do this, It's a good time to ask though if there may be users who want to opt-in to promote this sort of situation so that the logical block size is lifted to prevent any IOs. For NVMe drives it could be where the atomic >= Indirection Unit (IU). This is applicable even today on a 4k IU drive with 4k atomic support. Who would want this? Since any IO issued to a drive which is smaller than the IU implicates a RMW, it means your if you restrict the drive to only IOs matching the IU could in theory improve endurance. > but there are cases where this case fulfils important functional requirements. Sure. > e.g. fs tools and loop devices that use direct IO to access file > based filesystem images that have 512 byte sector size will just > work on such a fs and storage setup, even though the host filesystem > isn't configured to use 512 byte sector alignment directly > itself.... It would seem like quite a bit of things. This is useful, thanks. Luis
