On 20/05/24 04:33PM, Damien Le Moal wrote:

On 2024/05/20 12:20, Nitesh Shetty wrote:

quoted

@@ -231,10 +237,11 @@ int blk_set_default_limits(struct queue_limits *lim)
 {
 	/*
 	 * Most defaults are set by capping the bounds in blk_validate_limits,
-	 * but max_user_discard_sectors is special and needs an explicit
-	 * initialization to the max value here.
+	 * but max_user_discard_sectors and max_user_copy_sectors are special
+	 * and needs an explicit initialization to the max value here.

s/needs/need

acked

quoted

 	 */
 	lim->max_user_discard_sectors = UINT_MAX;
+	lim->max_user_copy_sectors = UINT_MAX;
 	return blk_validate_limits(lim);
 }

@@ -316,6 +323,25 @@ void blk_queue_max_discard_sectors(struct request_queue *q,
 }
 EXPORT_SYMBOL(blk_queue_max_discard_sectors);

+/*
+ * blk_queue_max_copy_hw_sectors - set max sectors for a single copy payload
+ * @q:	the request queue for the device
+ * @max_copy_sectors: maximum number of sectors to copy
+ */
+void blk_queue_max_copy_hw_sectors(struct request_queue *q,
+				   unsigned int max_copy_sectors)
+{
+	struct queue_limits *lim = &q->limits;
+
+	if (max_copy_sectors > (BLK_COPY_MAX_BYTES >> SECTOR_SHIFT))
+		max_copy_sectors = BLK_COPY_MAX_BYTES >> SECTOR_SHIFT;
+
+	lim->max_copy_hw_sectors = max_copy_sectors;
+	lim->max_copy_sectors =
+		min(max_copy_sectors, lim->max_user_copy_sectors);
+}
+EXPORT_SYMBOL_GPL(blk_queue_max_copy_hw_sectors);

Hmm... Such helper seems to not fit with Christoph's changes of the limits
initialization as that is not necessarily done using &q->limits but depending on
the driver, a different limit structure. So shouldn't this function be passed a
queue_limits struct pointer instead of the request queue pointer ?

Acked, we made a mistake, we are no longer using this function after moving
to atomic limits change. We will remove this function in next version.

quoted

+
 /**
  * blk_queue_max_secure_erase_sectors - set max sectors for a secure erase
  * @q:  the request queue for the device

@@ -633,6 +659,10 @@ int blk_stack_limits(struct queue_limits *t, struct queue_limits *b,
 	t->max_segment_size = min_not_zero(t->max_segment_size,
 					   b->max_segment_size);

+	t->max_copy_sectors = min(t->max_copy_sectors, b->max_copy_sectors);
+	t->max_copy_hw_sectors = min(t->max_copy_hw_sectors,
+				     b->max_copy_hw_sectors);
+
 	t->misaligned |= b->misaligned;

 	alignment = queue_limit_alignment_offset(b, start);

diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c
index f0f9314ab65c..805c2b6b0393 100644
--- a/block/blk-sysfs.c
+++ b/block/blk-sysfs.c

@@ -205,6 +205,44 @@ static ssize_t queue_discard_zeroes_data_show(struct request_queue *q, char *pag
 	return queue_var_show(0, page);
 }

+static ssize_t queue_copy_hw_max_show(struct request_queue *q, char *page)
+{
+	return sprintf(page, "%llu\n", (unsigned long long)
+		       q->limits.max_copy_hw_sectors << SECTOR_SHIFT);
+}
+
+static ssize_t queue_copy_max_show(struct request_queue *q, char *page)
+{
+	return sprintf(page, "%llu\n", (unsigned long long)
+		       q->limits.max_copy_sectors << SECTOR_SHIFT);
+}

Given that you repeat the same pattern twice, may be add a queue_var64_show()
helper ? (naming can be changed).

Acked

quoted

+
+static ssize_t queue_copy_max_store(struct request_queue *q, const char *page,
+				    size_t count)
+{
+	unsigned long max_copy_bytes;
+	struct queue_limits lim;
+	ssize_t ret;
+	int err;
+
+	ret = queue_var_store(&max_copy_bytes, page, count);
+	if (ret < 0)
+		return ret;
+
+	if (max_copy_bytes & (queue_logical_block_size(q) - 1))
+		return -EINVAL;
+
+	blk_mq_freeze_queue(q);
+	lim = queue_limits_start_update(q);
+	lim.max_user_copy_sectors = max_copy_bytes >> SECTOR_SHIFT;

max_copy_bytes is an unsigned long, so 64 bits on 64-bit arch and
max_user_copy_sectors is an unsigned int, so 32-bits. There are thus no
guarantees that this will not overflow. A check is needed.

Acked

quoted

+	err = queue_limits_commit_update(q, &lim);
+	blk_mq_unfreeze_queue(q);
+
+	if (err)

You can reuse ret here. No need for adding the err variable.

Acked

quoted

+		return err;
+	return count;
+}
+
 static ssize_t queue_write_same_max_show(struct request_queue *q, char *page)
 {
 	return queue_var_show(0, page);

@@ -505,6 +543,9 @@ QUEUE_RO_ENTRY(queue_nr_zones, "nr_zones");
 QUEUE_RO_ENTRY(queue_max_open_zones, "max_open_zones");
 QUEUE_RO_ENTRY(queue_max_active_zones, "max_active_zones");

+QUEUE_RO_ENTRY(queue_copy_hw_max, "copy_max_hw_bytes");
+QUEUE_RW_ENTRY(queue_copy_max, "copy_max_bytes");
+
 QUEUE_RW_ENTRY(queue_nomerges, "nomerges");
 QUEUE_RW_ENTRY(queue_rq_affinity, "rq_affinity");
 QUEUE_RW_ENTRY(queue_poll, "io_poll");

@@ -618,6 +659,8 @@ static struct attribute *queue_attrs[] = {
 	&queue_discard_max_entry.attr,
 	&queue_discard_max_hw_entry.attr,
 	&queue_discard_zeroes_data_entry.attr,
+	&queue_copy_hw_max_entry.attr,
+	&queue_copy_max_entry.attr,
 	&queue_write_same_max_entry.attr,
 	&queue_write_zeroes_max_entry.attr,
 	&queue_zone_append_max_entry.attr,

diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index aefdda9f4ec7..109d9f905c3c 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h

@@ -309,6 +309,10 @@ struct queue_limits {
 	unsigned int		discard_alignment;
 	unsigned int		zone_write_granularity;

+	unsigned int		max_copy_hw_sectors;
+	unsigned int		max_copy_sectors;
+	unsigned int		max_user_copy_sectors;
+
 	unsigned short		max_segments;
 	unsigned short		max_integrity_segments;
 	unsigned short		max_discard_segments;

@@ -933,6 +937,8 @@ void blk_queue_max_secure_erase_sectors(struct request_queue *q,
 		unsigned int max_sectors);
 extern void blk_queue_max_discard_sectors(struct request_queue *q,
 		unsigned int max_discard_sectors);
+extern void blk_queue_max_copy_hw_sectors(struct request_queue *q,
+					  unsigned int max_copy_sectors);
 extern void blk_queue_max_write_zeroes_sectors(struct request_queue *q,
 		unsigned int max_write_same_sectors);
 extern void blk_queue_logical_block_size(struct request_queue *, unsigned int);

@@ -1271,6 +1277,14 @@ static inline unsigned int bdev_discard_granularity(struct block_device *bdev)
 	return bdev_get_queue(bdev)->limits.discard_granularity;
 }

+/* maximum copy offload length, this is set to 128MB based on current testing */

Current testing will not be current in a while... So may be simply say
"arbitrary" or something. Also please capitalize the first letter of the
comment. So something like:

/* Arbitrary absolute limit of 128 MB for copy offload. */

quoted

+#define BLK_COPY_MAX_BYTES		(1 << 27)

Also, it is not clear from the name if this is a soft limit or a cap on the
hardware limit... So at least please adjust the comment to say which one it is.

Acked, it is a soft limit.

Thank You,
Nitesh Shetty