[PATCH 2/2] mmc : implement REQ_OP_WRITE_ZEROES

[Jungseung Lee <js07.lee@samsung.com>]

Some devices return zeroes on read to unmmaped logical blocks.
Use this behavior to implement REQ_OP_WRITES_ZEROES.

Send TRIM operation for the non-partial erase at a convenient time.

Signed-off-by: Jungseung Lee <js07.lee@samsung.com>
---
 drivers/mmc/core/block.c | 8 ++++++--
 drivers/mmc/core/queue.c | 4 ++++
 2 files changed, 10 insertions(+), 2 deletions(-)

diff --git a/drivers/mmc/core/block.c b/drivers/mmc/core/block.c
index ea80ff4..41c4ec1 100644
--- a/drivers/mmc/core/block.c
+++ b/drivers/mmc/core/block.c
@@ -1273,9 +1273,10 @@ static void mmc_blk_issue_discard_rq(struct mmc_queue *mq, struct request *req)
 	struct mmc_card *card = md->queue.card;
 	unsigned int from, nr, arg;
 	int err = 0, type = MMC_BLK_DISCARD;
+	int force_trim = (req_op(req) == REQ_OP_WRITE_ZEROES);
 	blk_status_t status = BLK_STS_OK;
 
-	if (!mmc_can_erase(card)) {
+	if (!mmc_can_erase(card) || (!mmc_can_trim(card) && force_trim)) {
 		status = BLK_STS_NOTSUPP;
 		goto fail;
 	}
@@ -1283,7 +1284,9 @@ static void mmc_blk_issue_discard_rq(struct mmc_queue *mq, struct request *req)
 	from = blk_rq_pos(req);
 	nr = blk_rq_sectors(req);
 
-	if (mmc_can_discard(card))
+	if (force_trim)
+		arg = MMC_TRIM_ARG;
+	else if (mmc_can_discard(card))
 		arg = MMC_DISCARD_ARG;
 	else if (mmc_can_trim(card))
 		arg = MMC_TRIM_ARG;
@@ -2032,6 +2035,7 @@ void mmc_blk_issue_rq(struct mmc_queue *mq, struct request *req)
 				mmc_blk_issue_rw_rq(mq, NULL);
 			mmc_blk_issue_drv_op(mq, req);
 			break;
+		case REQ_OP_WRITE_ZEROES:
 		case REQ_OP_DISCARD:
 			/*
 			 * Complete ongoing async transfer before issuing
diff --git a/drivers/mmc/core/queue.c b/drivers/mmc/core/queue.c
index 4f33d27..dc95b3a 100644
--- a/drivers/mmc/core/queue.c
+++ b/drivers/mmc/core/queue.c
@@ -144,6 +144,10 @@ static void mmc_queue_setup_discard(struct request_queue *q,
 	/* granularity must not be greater than max. discard */
 	if (card->pref_erase > max_discard)
 		q->limits.discard_granularity = 0;
+
+	if (card->quirks & MMC_QUIRK_UNMAPPED_ZEROES)
+		blk_queue_max_write_zeroes_sectors(q, UINT_MAX);
+
 	if (mmc_can_secure_erase_trim(card))
 		queue_flag_set_unlocked(QUEUE_FLAG_SECERASE, q);
 }
-- 
2.10.1