On 06/01/2025 17:49, Mike Snitzer wrote:
+++ b/drivers/md/dm-table.c
@@ -1593,6 +1593,7 @@ int dm_calculate_queue_limits(struct dm_table *t,
struct queue_limits ti_limits;
unsigned int zone_sectors = 0;
bool zoned = false;
+ bool atomic_writes = true;
dm_set_stacking_limits(limits);
@@ -1602,8 +1603,12 @@ int dm_calculate_queue_limits(struct dm_table *t,
if (!dm_target_passes_integrity(ti->type))
t->integrity_supported = false;
+ if (!dm_target_supports_atomic_writes(ti->type))
+ atomic_writes = false;
}
+ if (atomic_writes)
+ limits->features |= BLK_FEAT_ATOMIC_WRITES_STACKED;
for (unsigned int i = 0; i < t->num_targets; i++) {
struct dm_target *ti = dm_table_get_target(t, i);
@@ -1616,6 +1621,13 @@ int dm_calculate_queue_limits(struct dm_table *t,
goto combine_limits;
}
+ /*
+ * dm_set_device_limits() -> blk_stack_limits() considers
+ * ti_limits as 'top', so set BLK_FEAT_ATOMIC_WRITES_STACKED
+ * here also.
+ */
+ if (atomic_writes)
+ ti_limits.features |= BLK_FEAT_ATOMIC_WRITES_STACKED;
/*
* Combine queue limits of all the devices this target uses.
*/
You're referring to this code that immediately follows this ^ comment
which stacks up the limits of a target's potential to have N component
data devices:
ti->type->iterate_devices(ti, dm_set_device_limits,
&ti_limits);
Your comment and redundant feature flag setting is feels wrong. I'd
expect code comparable to what is done for zoned, e.g.:
if (!zoned && (ti_limits.features & BLK_FEAT_ZONED)) {
/*
* After stacking all limits, validate all devices
* in table support this zoned model and zone sectors.
*/
zoned = (ti_limits.features & BLK_FEAT_ZONED);
zone_sectors = ti_limits.chunk_sectors;
}
Meaning, for zoned devices, a side-effect of the
ti->type->iterate_devices() call (and N blk_stack_limits calls) is
ti_limits.features having BLK_FEAT_ZONED enabled. Why wouldn't the same
side-effect happen for BLK_FEAT_ATOMIC_WRITES_STACKED (speaks to
blk_stack_limits being different/wrong for atomic writes support)?
ok, do I admit that my code did not feel quite right, so I will check
the zoned code as a reference.
Just feels not quite right... but I could be wrong, please see if
there is any "there" there
Will do.
Cheers,
John
