+/**
+ * __blkdev_issue_discard_async - queue a discard with async completion
+ * @bdev: blockdev to issue discard for
+ * @sector: start sector
+ * @nr_sects: number of sectors to discard
+ * @gfp_mask: memory allocation flags (for bio_alloc)
+ * @flags: BLKDEV_IFL_* flags to control behaviour
+ * @parent_bio: parent discard bio that all sub discards get chained to
+ *
+ * Description:
+ * Asynchronously issue a discard request for the sectors in question.
+ */
+static int __blkdev_issue_discard_async(struct block_device *bdev, sector_t sector,
+ sector_t nr_sects, gfp_t gfp_mask, unsigned long flags,
+ struct bio *parent_bio)
+{
+ struct request_queue *q = bdev_get_queue(bdev);
+ int type = REQ_WRITE | REQ_DISCARD;
+ struct bio *bio;
+
+ if (!q || !nr_sects)
+ return -ENXIO;
+
+ if (!blk_queue_discard(q))
+ return -EOPNOTSUPP;
+
+ if (flags & BLKDEV_DISCARD_SECURE) {
+ if (!blk_queue_secdiscard(q))
+ return -EOPNOTSUPP;
+ type |= REQ_SECURE;
+ }
+
+ /*
+ * Required bio_put occurs in bio_endio thanks to bio_chain below
+ */
+ bio = bio_alloc(gfp_mask, 1);
+ if (!bio)
+ return -ENOMEM;
+
+ bio_chain(bio, parent_bio);
+
+ bio->bi_iter.bi_sector = sector;
+ bio->bi_bdev = bdev;
+ bio->bi_iter.bi_size = nr_sects << 9;
+
+ submit_bio(type, bio);
+
+ return 0;
+}
+
+static bool block_size_is_power_of_two(struct pool *pool)
+{
+ return pool->sectors_per_block_shift >= 0;
+}
+
+static sector_t block_to_sectors(struct pool *pool, dm_block_t b)
+{
+ return block_size_is_power_of_two(pool) ?
+ (b << pool->sectors_per_block_shift) :
+ (b * pool->sectors_per_block);
+}
+
+static int issue_discard(struct thin_c *tc, dm_block_t data_b, dm_block_t data_e,
+ struct bio *parent_bio)
+{
+ sector_t s = block_to_sectors(tc->pool, data_b);
+ sector_t len = block_to_sectors(tc->pool, data_e - data_b);
+
+ return __blkdev_issue_discard_async(tc->pool_dev->bdev, s, len,
+ GFP_NOWAIT, 0, parent_bio);
+}
+
+/*----------------------------------------------------------------*/
+