On Wed, Mar 18, 2020 at 01:27:19PM +1100, Dave Chinner wrote: > What is this "atomic block size" going to be, and how is it going to > be advertised to the block layer and filesystems? Enterprise SSDs typically support a few k. That being said without a scatter/gather Write command that isn't very useful except for a few DB log case. That is why the file system implemented atomic semantics that have been my primary interest are a lot more interesting. The NVMe SSDs advertise this size in a really convolulted way, because the limits can be globl, per-namespace and also have nasty offsets. Take a look at Section 6.4 of the NVMe 1.4 spec: https://nvmexpress.org/wp-content/uploads/NVM-Express-1_4-2019.06.10-Ratified.pdf This is how I wired it up for my POC Linux series: http://git.infradead.org/users/hch/xfs.git/commitdiff/66079e128d7fa452f45f8a4ffce1597157098dbe http://git.infradead.org/users/hch/xfs.git/commitdiff/70dc57ff030bf3ce0f37678002ef36b5ab5ed42e http://git.infradead.org/users/hch/xfs.git/commitdiff/b2f1a09c47b4404ef0d18aad576f4b2ca086a3e0
