On 06/11/2025 12:06, Mikulas Patocka wrote:
Neither of them are really used for IO.
atomic_write_unit_max, which is used for IO, will already get a capped
value from atomic_write_hw_unit_max in
blk_atomic_writes_update_limits(). And capping atomic_write_hw_max seems
wrong, since atomic_write_hw_max == UINT_MAX is used
blk_validate_atomic_write_limits() to indicate that atomic writes were
never set up, because no underlying device supported them. I don't think
these caps will actually break things, but in my mind they make some
already confusing limits even more confusing.
Or am I missing some reason why this is needed?
-Ben
How do you think we should modify the limits, to make sure that atomic
write size is capped at BIO_MAX_VECS << PAGE_SHIFT?
The atomic write size is limited elsewhere, specifically
blk_atomic_writes_update_limits() - the limit there is quite similar (to
what is added in this updated patch). So I don't think that we need to
do anything special in dm-crypt, as that block limit is already tighter.
I suppose that this code can be kept with a comment (saying that it is
unnecessary, but safer to keep). Or we can just drop the code and add a
comment (saying that we don't need to limit here, as it is done elsewhere).
Thanks,
John
