block: add a bdev_max_discard_sectors helper

Add a helper to query the number of sectors support per each discard bio
based on the block device and use this helper to stop various places from
poking into the request_queue to see if discard is supported and if so how
much.  This mirrors what is done e.g. for write zeroes as well.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
Acked-by: Christoph Böhmwalder <christoph.boehmwalder@linbit.com> [drbd]
Acked-by: Coly Li <colyli@suse.de> [bcache]
Acked-by: David Sterba <dsterba@suse.com> [btrfs]
Reviewed-by: Chaitanya Kulkarni <kch@nvidia.com>
Link: https://lore.kernel.org/r/20220415045258.199825-24-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>

drivers/block/drbd/drbd_nl.c

@@ -1439,7 +1439,8 @@ static bool write_ordering_changed(struct disk_conf *a, struct disk_conf *b)
 static void sanitize_disk_conf(struct drbd_device *device, struct disk_conf *disk_conf,
 			       struct drbd_backing_dev *nbc)
 {
-	struct request_queue * const q = nbc->backing_bdev->bd_disk->queue;
+	struct block_device *bdev = nbc->backing_bdev;
+	struct request_queue *q = bdev->bd_disk->queue;
 
 	if (disk_conf->al_extents < DRBD_AL_EXTENTS_MIN)
 		disk_conf->al_extents = DRBD_AL_EXTENTS_MIN;
@@ -1455,6 +1456,7 @@ static void sanitize_disk_conf(struct drbd_device *device, struct disk_conf *dis
 
 	if (disk_conf->rs_discard_granularity) {
 		int orig_value = disk_conf->rs_discard_granularity;
+		sector_t discard_size = bdev_max_discard_sectors(bdev) << 9;
 		int remainder;
 
 		if (q->limits.discard_granularity > disk_conf->rs_discard_granularity)
@@ -1463,8 +1465,8 @@ static void sanitize_disk_conf(struct drbd_device *device, struct disk_conf *dis
 		remainder = disk_conf->rs_discard_granularity % q->limits.discard_granularity;
 		disk_conf->rs_discard_granularity += remainder;
 
-		if (disk_conf->rs_discard_granularity > q->limits.max_discard_sectors << 9)
-			disk_conf->rs_discard_granularity = q->limits.max_discard_sectors << 9;
+		if (disk_conf->rs_discard_granularity > discard_size)
+			disk_conf->rs_discard_granularity = discard_size;
 
 		if (disk_conf->rs_discard_granularity != orig_value)
 			drbd_info(device, "rs_discard_granularity changed to %d\n",

drivers/block/drbd/drbd_receiver.c

@@ -1524,7 +1524,7 @@ int drbd_issue_discard_or_zero_out(struct drbd_device *device, sector_t start, u
 	granularity = max(q->limits.discard_granularity >> 9, 1U);
 	alignment = (bdev_discard_alignment(bdev) >> 9) % granularity;
 
-	max_discard_sectors = min(q->limits.max_discard_sectors, (1U << 22));
+	max_discard_sectors = min(bdev_max_discard_sectors(bdev), (1U << 22));
 	max_discard_sectors -= max_discard_sectors % granularity;
 	if (unlikely(!max_discard_sectors))
 		goto zero_out;

drivers/block/rnbd/rnbd-srv-dev.h

@@ -52,8 +52,7 @@ static inline int rnbd_dev_get_max_discard_sects(const struct rnbd_dev *dev)
 	if (!blk_queue_discard(bdev_get_queue(dev->bdev)))
 		return 0;
 
-	return blk_queue_get_max_sectors(bdev_get_queue(dev->bdev),
-					 REQ_OP_DISCARD);
+	return bdev_max_discard_sectors(dev->bdev);
 }
 
 static inline int rnbd_dev_get_discard_granularity(const struct rnbd_dev *dev)

drivers/md/dm-io.c

@@ -311,7 +311,7 @@ static void do_region(int op, int op_flags, unsigned region,
 	 * Reject unsupported discard and write same requests.
 	 */
 	if (op == REQ_OP_DISCARD)
-		special_cmd_max_sectors = q->limits.max_discard_sectors;
+		special_cmd_max_sectors = bdev_max_discard_sectors(where->bdev);
 	else if (op == REQ_OP_WRITE_ZEROES)
 		special_cmd_max_sectors = q->limits.max_write_zeroes_sectors;
 	if ((op == REQ_OP_DISCARD || op == REQ_OP_WRITE_ZEROES) &&

drivers/target/target_core_device.c

@@ -829,9 +829,8 @@ struct se_device *target_alloc_device(struct se_hba *hba, const char *name)
 }
 
 /*
- * Check if the underlying struct block_device request_queue supports
- * the QUEUE_FLAG_DISCARD bit for UNMAP/WRITE_SAME in SCSI + TRIM
- * in ATA and we need to set TPE=1
+ * Check if the underlying struct block_device supports discard and if yes
+ * configure the UNMAP parameters.
  */
 bool target_configure_unmap_from_queue(struct se_dev_attrib *attrib,
 				       struct block_device *bdev)
@@ -843,7 +842,7 @@ bool target_configure_unmap_from_queue(struct se_dev_attrib *attrib,
 		return false;
 
 	attrib->max_unmap_lba_count =
-		q->limits.max_discard_sectors >> (ilog2(block_size) - 9);
+		bdev_max_discard_sectors(bdev) >> (ilog2(block_size) - 9);
 	/*
 	 * Currently hardcoded to 1 in Linux/SCSI code..
 	 */

fs/f2fs/segment.c

@@ -1196,9 +1196,8 @@ static int __submit_discard_cmd(struct f2fs_sb_info *sbi,
 						unsigned int *issued)
 {
 	struct block_device *bdev = dc->bdev;
-	struct request_queue *q = bdev_get_queue(bdev);
 	unsigned int max_discard_blocks =
-			SECTOR_TO_BLOCK(q->limits.max_discard_sectors);
+			SECTOR_TO_BLOCK(bdev_max_discard_sectors(bdev));
 	struct discard_cmd_control *dcc = SM_I(sbi)->dcc_info;
 	struct list_head *wait_list = (dpolicy->type == DPOLICY_FSTRIM) ?
 					&(dcc->fstrim_list) : &(dcc->wait_list);
@@ -1375,9 +1374,8 @@ static void __update_discard_tree_range(struct f2fs_sb_info *sbi,
 	struct discard_cmd *dc;
 	struct discard_info di = {0};
 	struct rb_node **insert_p = NULL, *insert_parent = NULL;
-	struct request_queue *q = bdev_get_queue(bdev);
 	unsigned int max_discard_blocks =
-			SECTOR_TO_BLOCK(q->limits.max_discard_sectors);
+			SECTOR_TO_BLOCK(bdev_max_discard_sectors(bdev));
 	block_t end = lstart + len;
 
 	dc = (struct discard_cmd *)f2fs_lookup_rb_tree_ret(&dcc->root,

include/linux/blkdev.h

@@ -1254,6 +1254,11 @@ bdev_zone_write_granularity(struct block_device *bdev)
 int bdev_alignment_offset(struct block_device *bdev);
 unsigned int bdev_discard_alignment(struct block_device *bdev);
 
+static inline unsigned int bdev_max_discard_sectors(struct block_device *bdev)
+{
+	return bdev_get_queue(bdev)->limits.max_discard_sectors;
+}
+
 static inline unsigned int bdev_write_zeroes_sectors(struct block_device *bdev)
 {
 	struct request_queue *q = bdev_get_queue(bdev);