[PATCH 06/15] block: add a max_user_discard_sectors queue limit

[Christoph Hellwig]

Add a new max_user_discard_sectors limit that mirrors max_user_sectors
and stores the value that the user manually set.  This now allows
updates of the max_hw_discard_sectors to not worry about the user
limit.

Signed-off-by: Christoph Hellwig <hch at lst.de>
Reviewed-by: Keith Busch <kbusch at kernel.org>
Reviewed-by: Chaitanya Kulkarni <kch at nvidia.com>
Reviewed-by: Ming Lei <ming.lei at redhat.com>
Reviewed-by: Martin K. Petersen <martin.petersen at oracle.com>
Reviewed-by: Hannes Reinecke <hare at suse.de>
---
 block/blk-settings.c   | 18 +++++++++++++++---
 block/blk-sysfs.c      | 17 ++++++++---------
 include/linux/blkdev.h |  1 +
 3 files changed, 24 insertions(+), 12 deletions(-)

diff --git a/block/blk-settings.c b/block/blk-settings.c
index 27b9b4a2a85395..7139c13fe73484 100644
--- a/block/blk-settings.c
+++ b/block/blk-settings.c
@@ -37,6 +37,7 @@ void blk_set_stacking_limits(struct queue_limits *lim)
 	memset(lim, 0, sizeof(*lim));
 	lim->logical_block_size = lim->physical_block_size = lim->io_min = 512;
 	lim->discard_granularity = 512;
+	lim->max_user_discard_sectors = UINT_MAX;
 	lim->dma_alignment = 511;
 	lim->seg_boundary_mask = BLK_SEG_BOUNDARY_MASK;
 
@@ -160,7 +161,9 @@ static int blk_validate_limits(struct queue_limits *lim)
 	if (!lim->max_segments)
 		lim->max_segments = BLK_MAX_SEGMENTS;
 
-	lim->max_discard_sectors = lim->max_hw_discard_sectors;
+	lim->max_discard_sectors =
+		min(lim->max_hw_discard_sectors, lim->max_user_discard_sectors);
+
 	if (!lim->max_discard_segments)
 		lim->max_discard_segments = 1;
 
@@ -226,6 +229,12 @@ static int blk_validate_limits(struct queue_limits *lim)
  */
 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.
+	 */
+	lim->max_user_discard_sectors = UINT_MAX;
 	return blk_validate_limits(lim);
 }
 
@@ -347,8 +356,11 @@ EXPORT_SYMBOL(blk_queue_chunk_sectors);
 void blk_queue_max_discard_sectors(struct request_queue *q,
 		unsigned int max_discard_sectors)
 {
-	q->limits.max_hw_discard_sectors = max_discard_sectors;
-	q->limits.max_discard_sectors = max_discard_sectors;
+	struct queue_limits *lim = &q->limits;
+
+	lim->max_hw_discard_sectors = max_discard_sectors;
+	lim->max_discard_sectors =
+		min(max_discard_sectors, lim->max_user_discard_sectors);
 }
 EXPORT_SYMBOL(blk_queue_max_discard_sectors);
 
diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c
index 26607f9825cb05..a1ec27f0ba4150 100644
--- a/block/blk-sysfs.c
+++ b/block/blk-sysfs.c
@@ -174,23 +174,22 @@ static ssize_t queue_discard_max_show(struct request_queue *q, char *page)
 static ssize_t queue_discard_max_store(struct request_queue *q,
 				       const char *page, size_t count)
 {
-	unsigned long max_discard;
-	ssize_t ret = queue_var_store(&max_discard, page, count);
+	unsigned long max_discard_bytes;
+	ssize_t ret;
 
+	ret = queue_var_store(&max_discard_bytes, page, count);
 	if (ret < 0)
 		return ret;
 
-	if (max_discard & (q->limits.discard_granularity - 1))
+	if (max_discard_bytes & (q->limits.discard_granularity - 1))
 		return -EINVAL;
 
-	max_discard >>= 9;
-	if (max_discard > UINT_MAX)
+	if ((max_discard_bytes >> SECTOR_SHIFT) > UINT_MAX)
 		return -EINVAL;
 
-	if (max_discard > q->limits.max_hw_discard_sectors)
-		max_discard = q->limits.max_hw_discard_sectors;
-
-	q->limits.max_discard_sectors = max_discard;
+	q->limits.max_user_discard_sectors = max_discard_bytes >> SECTOR_SHIFT;
+	q->limits.max_discard_sectors = min(q->limits.max_hw_discard_sectors,
+					    q->limits.max_user_discard_sectors);
 	return ret;
 }
 
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 97c01efed68253..64cca723619083 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -290,6 +290,7 @@ struct queue_limits {
 	unsigned int		io_opt;
 	unsigned int		max_discard_sectors;
 	unsigned int		max_hw_discard_sectors;
+	unsigned int		max_user_discard_sectors;
 	unsigned int		max_secure_erase_sectors;
 	unsigned int		max_write_zeroes_sectors;
 	unsigned int		max_zone_append_sectors;
-- 
2.39.2