Thu, Feb 17, 2022 at 01:07:00AM -0800, Luis Chamberlain wrote:

The subject says limits for copy-offload...

On Mon, Feb 14, 2022 at 01:29:52PM +0530, Nitesh Shetty wrote:

quoted

Add device limits as sysfs entries,
        - copy_offload (RW)
        - copy_max_bytes (RW)
        - copy_max_hw_bytes (RO)
        - copy_max_range_bytes (RW)
        - copy_max_range_hw_bytes (RO)
        - copy_max_nr_ranges (RW)
        - copy_max_nr_ranges_hw (RO)

Some of these seem like generic... and also I see a few more max_hw ones
not listed above...

queue_limits and sysfs entries are differently named.
All sysfs entries start with copy_* prefix. Also it makes easy to lookup
all copy sysfs.
For queue limits naming, I tried to following existing queue limit
convention (like discard).

quoted

--- a/block/blk-settings.c
+++ b/block/blk-settings.c
+/**
+ * blk_queue_max_copy_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_sectors(struct request_queue *q,
+		unsigned int max_copy_sectors)
+{
+	q->limits.max_hw_copy_sectors = max_copy_sectors;
+	q->limits.max_copy_sectors = max_copy_sectors;
+}
+EXPORT_SYMBOL(blk_queue_max_copy_sectors);

Please use EXPORT_SYMBOL_GPL() for all new things.

acked.

Why is this setting both? The documentation does't seem to say.
What's the point?

This function is used only by driver, while intializing request queue.
I will put this as part of description next time.

quoted

+
+/**
+ * blk_queue_max_copy_range_sectors - set max sectors for a single range, in a copy payload
+ * @q:  the request queue for the device
+ * @max_copy_range_sectors: maximum number of sectors to copy in a single range
+ **/
+void blk_queue_max_copy_range_sectors(struct request_queue *q,
+		unsigned int max_copy_range_sectors)
+{
+	q->limits.max_hw_copy_range_sectors = max_copy_range_sectors;
+	q->limits.max_copy_range_sectors = max_copy_range_sectors;
+}
+EXPORT_SYMBOL(blk_queue_max_copy_range_sectors);

Same here.

quoted

+/**
+ * blk_queue_max_copy_nr_ranges - set max number of ranges, in a copy payload
+ * @q:  the request queue for the device
+ * @max_copy_nr_ranges: maximum number of ranges
+ **/
+void blk_queue_max_copy_nr_ranges(struct request_queue *q,
+		unsigned int max_copy_nr_ranges)
+{
+	q->limits.max_hw_copy_nr_ranges = max_copy_nr_ranges;
+	q->limits.max_copy_nr_ranges = max_copy_nr_ranges;
+}
+EXPORT_SYMBOL(blk_queue_max_copy_nr_ranges);

Same.

quoted

+
 /**
  * blk_queue_max_write_same_sectors - set max sectors for a single write same
  * @q:  the request queue for the device

@@ -541,6 +592,14 @@ 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_hw_copy_sectors = min(t->max_hw_copy_sectors, b->max_hw_copy_sectors);
+	t->max_copy_range_sectors = min(t->max_copy_range_sectors, b->max_copy_range_sectors);
+	t->max_hw_copy_range_sectors = min(t->max_hw_copy_range_sectors,
+						b->max_hw_copy_range_sectors);
+	t->max_copy_nr_ranges = min(t->max_copy_nr_ranges, b->max_copy_nr_ranges);
+	t->max_hw_copy_nr_ranges = min(t->max_hw_copy_nr_ranges, b->max_hw_copy_nr_ranges);
+
 	t->misaligned |= b->misaligned;
 
 	alignment = queue_limit_alignment_offset(b, start);

diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c
index 9f32882ceb2f..9ddd07f142d9 100644
--- a/block/blk-sysfs.c
+++ b/block/blk-sysfs.c

@@ -212,6 +212,129 @@ 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_offload_show(struct request_queue *q, char *page)
+{
+	return queue_var_show(blk_queue_copy(q), page);
+}
+
+static ssize_t queue_copy_offload_store(struct request_queue *q,
+				       const char *page, size_t count)
+{
+	unsigned long copy_offload;
+	ssize_t ret = queue_var_store(&copy_offload, page, count);
+
+	if (ret < 0)
+		return ret;
+
+	if (copy_offload && !q->limits.max_hw_copy_sectors)
+		return -EINVAL;

If the kernel schedules, copy_offload may still be true and
max_hw_copy_sectors may be set to 0. Is that an issue?

This check ensures that, we dont enable offload if device doesnt support
offload. I feel it shouldn't be an issue.

quoted

+
+	if (copy_offload)
+		blk_queue_flag_set(QUEUE_FLAG_COPY, q);
+	else
+		blk_queue_flag_clear(QUEUE_FLAG_COPY, q);

The flag may be set but the queue flag could be set. Is that an issue?

quoted

@@ -597,6 +720,14 @@ 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_RW_ENTRY(queue_copy_offload, "copy_offload");
+QUEUE_RO_ENTRY(queue_copy_max_hw, "copy_max_hw_bytes");
+QUEUE_RW_ENTRY(queue_copy_max, "copy_max_bytes");
+QUEUE_RO_ENTRY(queue_copy_range_max_hw, "copy_max_range_hw_bytes");
+QUEUE_RW_ENTRY(queue_copy_range_max, "copy_max_range_bytes");
+QUEUE_RO_ENTRY(queue_copy_nr_ranges_max_hw, "copy_max_nr_ranges_hw");
+QUEUE_RW_ENTRY(queue_copy_nr_ranges_max, "copy_max_nr_ranges");

Seems like you need to update Documentation/ABI/stable/sysfs-block.

acked. 

quoted

diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index efed3820cbf7..792e6d556589 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h

@@ -254,6 +254,13 @@ struct queue_limits {
 	unsigned int		discard_alignment;
 	unsigned int		zone_write_granularity;
 
+	unsigned long		max_hw_copy_sectors;
+	unsigned long		max_copy_sectors;
+	unsigned int		max_hw_copy_range_sectors;
+	unsigned int		max_copy_range_sectors;
+	unsigned short		max_hw_copy_nr_ranges;
+	unsigned short		max_copy_nr_ranges;

Before limits start growing more.. I wonder if we should just
stuff hw offload stuff to its own struct within queue_limits.

Christoph?

  Luis

Yeah, would like to know community opinion on this.


-- Nitesh