On 23/09/2024 03:57, Dave Chinner wrote:
In the meantime, if mkfs auto-enables atomic writes (when the HW supports),
what will it do to reflink feature (in terms of enabling)?
I didn't say we should always "auto-enable atomic writes".
I said if the hardware is atomic write capable, then mkfs should
always*align the filesystem* to atomic write constraints. A kernel
upgrade will eventually allow reflink and atomic writes to co-exist,
but only if the filesystem is correctly aligned to the hardware
constrains for atomic writes. We need to ensure we leave that
upgrade path open....
.... and only once we have full support can we make "mkfs
auto-enable atomic writes".
ok, fine. The current maximum value of atomic write unit max is 512KB
(assuming 4K PAGE_SIZE and 512B sector size), so that should not be too
needlessly inefficient for laying out the AGs. However, for 16KB+
PAGE_SIZE, that value could naturally be larger. However having HW which
supports such large atomics would be very unlikely.
Thanks,
John
