On 13/12/2023 12:28, Ming Lei wrote:
For NVMe, we use the logical block size. For physical block size, that can
be greater than the logical block size for npwg set, and I don't think it's
suitable use that as minimum atomic write unit.
I highly suspect it is wrong to use logical block size as minimum
support atomic write unit, given physical block size is supposed to
be the minimum atomic write unit.
I would tend to agree, but I am still a bit curious on how npwg is used
to calculate atomic_bs/phys_bs as it seems to be a recommended
performance-related value. It would hint to me that it is the phys_bs,
but is that same as atomic min granularity?
Anyway, I am not too keen on sanitizing this value in this way.
+
+/*
+ * blk_queue_atomic_write_unit_max_sectors - largest unit that can be written
+ * atomically to the device.
+ * @q: the request queue for the device
+ * @sectors: must be a power-of-two.
+ */
+void blk_queue_atomic_write_unit_max_sectors(struct request_queue *q,
+ unsigned int sectors)
+{
+ struct queue_limits *limits = &q->limits;
+
+ limits->atomic_write_unit_max_sectors = sectors;
+}
+EXPORT_SYMBOL(blk_queue_atomic_write_unit_max_sectors);
atomic_write_unit_max_sectors should be >= atomic_write_unit_min_sectors.
Again, we rely on the driver to provide sound values. However, as mentioned,
we can sanitize.
Relying on driver to provide sound value is absolutely bad design from API
viewpoint.
OK, fine, I'll look to revise the API to make it more robust.
Thanks,
John
