Re: [RFC PATCH 1/3] block: add copy offload support

On 2/4/22 5:09 AM, Mikulas Patocka wrote:

On Thu, 3 Feb 2022, Bart Van Assche wrote:

quoted

On 2/3/22 10:50, Mikulas Patocka wrote:

quoted

On Tue, 1 Feb 2022, Bart Van Assche wrote:

quoted

On 2/1/22 10:32, Mikulas Patocka wrote:

quoted

   /**
+ * blk_queue_max_copy_sectors - set maximum copy offload sectors for
the
queue
+ * @q:  the request queue for the device
+ * @size:  the maximum copy offload sectors
+ */
+void blk_queue_max_copy_sectors(struct request_queue *q, unsigned int
size)
+{
+	q->limits.max_copy_sectors = size;
+}
+EXPORT_SYMBOL_GPL(blk_queue_max_copy_sectors);

Please either change the unit of 'size' into bytes or change its type into
sector_t.

blk_queue_chunk_sectors, blk_queue_max_discard_sectors,
blk_queue_max_write_same_sectors, blk_queue_max_write_zeroes_sectors,
blk_queue_max_zone_append_sectors also have the unit of sectors and the
argument is "unsigned int". Should blk_queue_max_copy_sectors be
different?

As far as I know using the type sector_t for variables that represent a number
of sectors is a widely followed convention:

$ git grep -w sector_t | wc -l
2575

I would appreciate it if that convention would be used consistently, even if
that means modifying existing code.

Thanks,

Bart.

Changing the sector limit variables in struct queue_limits from
unsigned int to sector_t would increase the size of the structure and
its cache footprint.

And we can't send bios larger than 4GiB anyway because bi_size is
32-bit.

Jens, what do you think about it? Should the sectors limits be
sector_t?

Why make it larger than it needs to?

-- 
Jens Axboe