On 17/01/2025 18:29, Darrick J. Wong wrote:
Ok, let's do that then. Just to be clear -- for any RWF_ATOMIC direct
write that's correctly aligned and targets a single mapping in the
correct state, we can build the untorn bio and submit it. For
everything else, prealloc some post EOF blocks, write them there, and
exchange-range them.
I have some doubt about this, but I may be misunderstanding the concept:
So is there any guarantee that what we write into is aligned (after the
exchange-range routine)? If not, surely every subsequent write with
RWF_ATOMIC to that logical range will require this exchange-range routine
until we get something aligned (and correct granularity) - correct?
Correct, you'd still need forcealign to make sure that the new
allocations for exchange-range are aligned to awumin.
Sure, but I think that if we align sb_agblocks to the bdev atomic write
limits at mkfs time and also set extszhint appropriately, then
probability of desired alignment and granularity is appreciably higher.
Thanks,
John
