always use REQ_OP_WRITE_ZEROES for zeroing offload

always use REQ_OP_WRITE_ZEROES for zeroing offload

[Christoph Hellwig]

This series makes REQ_OP_WRITE_ZEROES the only zeroing offload
supported by the block layer, and switches existing implementations
of REQ_OP_DISCARD that correctly set discard_zeroes_data to it,
removes incorrect discard_zeroes_data, and also switches WRITE SAME
based zeroing in SCSI to this new method.

The series is against the block for-next tree.

A git tree is also avaiable at:

    git://git.infradead.org/users/hch/block.git discard-rework

Gitweb:

    http://git.infradead.org/users/hch/block.git/shortlog/refs/heads/discard-rework

[PATCH 01/25] ѕd: split sd_setup_discard_cmnd

[Christoph Hellwig]

Split sd_setup_discard_cmnd into one function per provisioning type.  While
this creates some very slight duplication of boilerplate code it keeps the
code modular for additions of new provisioning types, and for reusing the
write same functions for the upcoming scsi implementation of the Write Zeroes
operation.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 drivers/scsi/sd.c | 153 ++++++++++++++++++++++++++++++------------------------
 1 file changed, 84 insertions(+), 69 deletions(-)

diff --git a/drivers/scsi/sd.c b/drivers/scsi/sd.c
index fcfeddc79331..b853f91fb3da 100644
--- a/drivers/scsi/sd.c
+++ b/drivers/scsi/sd.c
@@ -701,93 +701,97 @@ static void sd_config_discard(struct scsi_disk *sdkp, unsigned int mode)
 	queue_flag_set_unlocked(QUEUE_FLAG_DISCARD, q);
 }
 
-/**
- * sd_setup_discard_cmnd - unmap blocks on thinly provisioned device
- * @sdp: scsi device to operate on
- * @rq: Request to prepare
- *
- * Will issue either UNMAP or WRITE SAME(16) depending on preference
- * indicated by target device.
- **/
-static int sd_setup_discard_cmnd(struct scsi_cmnd *cmd)
+static int sd_setup_unmap_cmnd(struct scsi_cmnd *cmd)
 {
-	struct request *rq = cmd->request;
 	struct scsi_device *sdp = cmd->device;
-	struct scsi_disk *sdkp = scsi_disk(rq->rq_disk);
-	sector_t sector = blk_rq_pos(rq);
-	unsigned int nr_sectors = blk_rq_sectors(rq);
-	unsigned int len;
-	int ret;
+	struct request *rq = cmd->request;
+	u64 sector = blk_rq_pos(rq) >> (ilog2(sdp->sector_size) - 9);
+	u32 nr_sectors = blk_rq_sectors(rq) >> (ilog2(sdp->sector_size) - 9);
+	unsigned int data_len = 24;
 	char *buf;
-	struct page *page;
 
-	sector >>= ilog2(sdp->sector_size) - 9;
-	nr_sectors >>= ilog2(sdp->sector_size) - 9;
-
-	page = alloc_page(GFP_ATOMIC | __GFP_ZERO);
-	if (!page)
+	rq->special_vec.bv_page = alloc_page(GFP_ATOMIC | __GFP_ZERO);
+	if (!rq->special_vec.bv_page)
 		return BLKPREP_DEFER;
+	rq->special_vec.bv_offset = 0;
+	rq->special_vec.bv_len = data_len;
+	rq->rq_flags |= RQF_SPECIAL_PAYLOAD;
 
-	switch (sdkp->provisioning_mode) {
-	case SD_LBP_UNMAP:
-		buf = page_address(page);
-
-		cmd->cmd_len = 10;
-		cmd->cmnd[0] = UNMAP;
-		cmd->cmnd[8] = 24;
-
-		put_unaligned_be16(6 + 16, &buf[0]);
-		put_unaligned_be16(16, &buf[2]);
-		put_unaligned_be64(sector, &buf[8]);
-		put_unaligned_be32(nr_sectors, &buf[16]);
+	cmd->cmd_len = 10;
+	cmd->cmnd[0] = UNMAP;
+	cmd->cmnd[8] = 24;
 
-		len = 24;
-		break;
+	buf = page_address(rq->special_vec.bv_page);
+	put_unaligned_be16(6 + 16, &buf[0]);
+	put_unaligned_be16(16, &buf[2]);
+	put_unaligned_be64(sector, &buf[8]);
+	put_unaligned_be32(nr_sectors, &buf[16]);
 
-	case SD_LBP_WS16:
-		cmd->cmd_len = 16;
-		cmd->cmnd[0] = WRITE_SAME_16;
-		cmd->cmnd[1] = 0x8; /* UNMAP */
-		put_unaligned_be64(sector, &cmd->cmnd[2]);
-		put_unaligned_be32(nr_sectors, &cmd->cmnd[10]);
+	cmd->allowed = SD_MAX_RETRIES;
+	cmd->transfersize = data_len;
+	rq->timeout = SD_TIMEOUT;
+	scsi_req(rq)->resid_len = data_len;
 
-		len = sdkp->device->sector_size;
-		break;
+	return scsi_init_io(cmd);
+}
 
-	case SD_LBP_WS10:
-	case SD_LBP_ZERO:
-		cmd->cmd_len = 10;
-		cmd->cmnd[0] = WRITE_SAME;
-		if (sdkp->provisioning_mode == SD_LBP_WS10)
-			cmd->cmnd[1] = 0x8; /* UNMAP */
-		put_unaligned_be32(sector, &cmd->cmnd[2]);
-		put_unaligned_be16(nr_sectors, &cmd->cmnd[7]);
+static int sd_setup_write_same16_cmnd(struct scsi_cmnd *cmd)
+{
+	struct scsi_device *sdp = cmd->device;
+	struct request *rq = cmd->request;
+	u64 sector = blk_rq_pos(rq) >> (ilog2(sdp->sector_size) - 9);
+	u32 nr_sectors = blk_rq_sectors(rq) >> (ilog2(sdp->sector_size) - 9);
+	u32 data_len = sdp->sector_size;
 
-		len = sdkp->device->sector_size;
-		break;
+	rq->special_vec.bv_page = alloc_page(GFP_ATOMIC | __GFP_ZERO);
+	if (!rq->special_vec.bv_page)
+		return BLKPREP_DEFER;
+	rq->special_vec.bv_offset = 0;
+	rq->special_vec.bv_len = data_len;
+	rq->rq_flags |= RQF_SPECIAL_PAYLOAD;
 
-	default:
-		ret = BLKPREP_INVALID;
-		goto out;
-	}
+	cmd->cmd_len = 16;
+	cmd->cmnd[0] = WRITE_SAME_16;
+	cmd->cmnd[1] = 0x8; /* UNMAP */
+	put_unaligned_be64(sector, &cmd->cmnd[2]);
+	put_unaligned_be32(nr_sectors, &cmd->cmnd[10]);
 
+	cmd->allowed = SD_MAX_RETRIES;
+	cmd->transfersize = data_len;
 	rq->timeout = SD_TIMEOUT;
+	scsi_req(rq)->resid_len = data_len;
 
-	cmd->transfersize = len;
-	cmd->allowed = SD_MAX_RETRIES;
+	return scsi_init_io(cmd);
+}
 
-	rq->special_vec.bv_page = page;
-	rq->special_vec.bv_offset = 0;
-	rq->special_vec.bv_len = len;
+static int sd_setup_write_same10_cmnd(struct scsi_cmnd *cmd, bool unmap)
+{
+	struct scsi_device *sdp = cmd->device;
+	struct request *rq = cmd->request;
+	u64 sector = blk_rq_pos(rq) >> (ilog2(sdp->sector_size) - 9);
+	u32 nr_sectors = blk_rq_sectors(rq) >> (ilog2(sdp->sector_size) - 9);
+	u32 data_len = sdp->sector_size;
 
+	rq->special_vec.bv_page = alloc_page(GFP_ATOMIC | __GFP_ZERO);
+	if (!rq->special_vec.bv_page)
+		return BLKPREP_DEFER;
+	rq->special_vec.bv_offset = 0;
+	rq->special_vec.bv_len = data_len;
 	rq->rq_flags |= RQF_SPECIAL_PAYLOAD;
-	scsi_req(rq)->resid_len = len;
 
-	ret = scsi_init_io(cmd);
-out:
-	if (ret != BLKPREP_OK)
-		__free_page(page);
-	return ret;
+	cmd->cmd_len = 10;
+	cmd->cmnd[0] = WRITE_SAME;
+	if (unmap)
+		cmd->cmnd[1] = 0x8; /* UNMAP */
+	put_unaligned_be32(sector, &cmd->cmnd[2]);
+	put_unaligned_be16(nr_sectors, &cmd->cmnd[7]);
+
+	cmd->allowed = SD_MAX_RETRIES;
+	cmd->transfersize = data_len;
+	rq->timeout = SD_TIMEOUT;
+	scsi_req(rq)->resid_len = data_len;
+
+	return scsi_init_io(cmd);
 }
 
 static void sd_config_write_same(struct scsi_disk *sdkp)
@@ -1155,7 +1159,18 @@ static int sd_init_command(struct scsi_cmnd *cmd)
 
 	switch (req_op(rq)) {
 	case REQ_OP_DISCARD:
-		return sd_setup_discard_cmnd(cmd);
+		switch (scsi_disk(rq->rq_disk)->provisioning_mode) {
+		case SD_LBP_UNMAP:
+			return sd_setup_unmap_cmnd(cmd);
+		case SD_LBP_WS16:
+			return sd_setup_write_same16_cmnd(cmd);
+		case SD_LBP_WS10:
+			return sd_setup_write_same10_cmnd(cmd, true);
+		case SD_LBP_ZERO:
+			return sd_setup_write_same10_cmnd(cmd, false);
+		default:
+			return BLKPREP_INVALID;
+		}
 	case REQ_OP_WRITE_SAME:
 		return sd_setup_write_same_cmnd(cmd);
 	case REQ_OP_FLUSH:
-- 
2.11.0

Re: [PATCH 01/25] ѕd: split sd_setup_discard_cmnd

[Martin K. Petersen]

Christoph Hellwig <hch@lst.de> writes:

> Split sd_setup_discard_cmnd into one function per provisioning type.  While
> this creates some very slight duplication of boilerplate code it keeps the
> code modular for additions of new provisioning types, and for reusing the
> write same functions for the upcoming scsi implementation of the Write Zeroes
> operation.

Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>

Minor nit: Patch header should be "sd: ..." instead of " d: ...".

-- 
Martin K. Petersen	Oracle Linux Engineering

[PATCH 02/25] block: renumber REQ_OP_WRITE_ZEROES

[Christoph Hellwig]

Make life easy for implementations that needs to send a data buffer
to the device (e.g. SCSI) by numbering it as a data out command.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 include/linux/blk_types.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/linux/blk_types.h b/include/linux/blk_types.h
index 67bcf8a5326e..4eae30bfbfca 100644
--- a/include/linux/blk_types.h
+++ b/include/linux/blk_types.h
@@ -168,7 +168,7 @@ enum req_opf {
 	/* write the same sector many times */
 	REQ_OP_WRITE_SAME	= 7,
 	/* write the zero filled sector many times */
-	REQ_OP_WRITE_ZEROES	= 8,
+	REQ_OP_WRITE_ZEROES	= 9,
 
 	/* SCSI passthrough using struct scsi_request */
 	REQ_OP_SCSI_IN		= 32,
-- 
2.11.0

Re: [PATCH 02/25] block: renumber REQ_OP_WRITE_ZEROES

[Martin K. Petersen]

Christoph Hellwig <hch@lst.de> writes:

> Make life easy for implementations that needs to send a data buffer
> to the device (e.g. SCSI) by numbering it as a data out command.

Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>

-- 
Martin K. Petersen	Oracle Linux Engineering

[PATCH 03/25] block: implement splitting of REQ_OP_WRITE_ZEROES bios

[Christoph Hellwig]

Copy and past the REQ_OP_WRITE_SAME code to prepare to implementations
that limit the write zeroes size.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 block/blk-merge.c | 17 +++++++++++++++--
 1 file changed, 15 insertions(+), 2 deletions(-)

diff --git a/block/blk-merge.c b/block/blk-merge.c
index 2afa262425d1..3990ae406341 100644
--- a/block/blk-merge.c
+++ b/block/blk-merge.c
@@ -54,6 +54,20 @@ static struct bio *blk_bio_discard_split(struct request_queue *q,
 	return bio_split(bio, split_sectors, GFP_NOIO, bs);
 }
 
+static struct bio *blk_bio_write_zeroes_split(struct request_queue *q,
+		struct bio *bio, struct bio_set *bs, unsigned *nsegs)
+{
+	*nsegs = 1;
+
+	if (!q->limits.max_write_zeroes_sectors)
+		return NULL;
+
+	if (bio_sectors(bio) <= q->limits.max_write_zeroes_sectors)
+		return NULL;
+
+	return bio_split(bio, q->limits.max_write_zeroes_sectors, GFP_NOIO, bs);
+}
+
 static struct bio *blk_bio_write_same_split(struct request_queue *q,
 					    struct bio *bio,
 					    struct bio_set *bs,
@@ -200,8 +214,7 @@ void blk_queue_split(struct request_queue *q, struct bio **bio,
 		split = blk_bio_discard_split(q, *bio, bs, &nsegs);
 		break;
 	case REQ_OP_WRITE_ZEROES:
-		split = NULL;
-		nsegs = (*bio)->bi_phys_segments;
+		split = blk_bio_write_zeroes_split(q, *bio, bs, &nsegs);
 		break;
 	case REQ_OP_WRITE_SAME:
 		split = blk_bio_write_same_split(q, *bio, bs, &nsegs);
-- 
2.11.0

Re: [PATCH 03/25] block: implement splitting of REQ_OP_WRITE_ZEROES bios

[Martin K. Petersen]

Christoph Hellwig <hch@lst.de> writes:

> Copy and past the REQ_OP_WRITE_SAME code to prepare to implementations
> that limit the write zeroes size.

Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>

-- 
Martin K. Petersen	Oracle Linux Engineering

[PATCH 04/25] sd: implement REQ_OP_WRITE_ZEROES

[Christoph Hellwig]

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 drivers/scsi/sd.c     | 31 ++++++++++++++++++++++++++-----
 drivers/scsi/sd_zbc.c |  1 +
 2 files changed, 27 insertions(+), 5 deletions(-)

diff --git a/drivers/scsi/sd.c b/drivers/scsi/sd.c
index b853f91fb3da..d8d9c0bdd93c 100644
--- a/drivers/scsi/sd.c
+++ b/drivers/scsi/sd.c
@@ -735,7 +735,7 @@ static int sd_setup_unmap_cmnd(struct scsi_cmnd *cmd)
 	return scsi_init_io(cmd);
 }
 
-static int sd_setup_write_same16_cmnd(struct scsi_cmnd *cmd)
+static int sd_setup_write_same16_cmnd(struct scsi_cmnd *cmd, bool unmap)
 {
 	struct scsi_device *sdp = cmd->device;
 	struct request *rq = cmd->request;
@@ -752,13 +752,14 @@ static int sd_setup_write_same16_cmnd(struct scsi_cmnd *cmd)
 
 	cmd->cmd_len = 16;
 	cmd->cmnd[0] = WRITE_SAME_16;
-	cmd->cmnd[1] = 0x8; /* UNMAP */
+	if (unmap)
+		cmd->cmnd[1] = 0x8; /* UNMAP */
 	put_unaligned_be64(sector, &cmd->cmnd[2]);
 	put_unaligned_be32(nr_sectors, &cmd->cmnd[10]);
 
 	cmd->allowed = SD_MAX_RETRIES;
 	cmd->transfersize = data_len;
-	rq->timeout = SD_TIMEOUT;
+	rq->timeout = unmap ? SD_TIMEOUT : SD_WRITE_SAME_TIMEOUT;
 	scsi_req(rq)->resid_len = data_len;
 
 	return scsi_init_io(cmd);
@@ -788,12 +789,27 @@ static int sd_setup_write_same10_cmnd(struct scsi_cmnd *cmd, bool unmap)
 
 	cmd->allowed = SD_MAX_RETRIES;
 	cmd->transfersize = data_len;
-	rq->timeout = SD_TIMEOUT;
+	rq->timeout = unmap ? SD_TIMEOUT : SD_WRITE_SAME_TIMEOUT;
 	scsi_req(rq)->resid_len = data_len;
 
 	return scsi_init_io(cmd);
 }
 
+static int sd_setup_write_zeroes_cmnd(struct scsi_cmnd *cmd)
+{
+	struct request *rq = cmd->request;
+	struct scsi_device *sdp = cmd->device;
+	struct scsi_disk *sdkp = scsi_disk(rq->rq_disk);
+	u64 sector = blk_rq_pos(rq) >> (ilog2(sdp->sector_size) - 9);
+	u32 nr_sectors = blk_rq_sectors(rq) >> (ilog2(sdp->sector_size) - 9);
+
+	if (sdp->no_write_same)
+		return BLKPREP_INVALID;
+	if (sdkp->ws16 || sector > 0xffffffff || nr_sectors > 0xffff)
+		return sd_setup_write_same16_cmnd(cmd, false);
+	return sd_setup_write_same10_cmnd(cmd, false);
+}
+
 static void sd_config_write_same(struct scsi_disk *sdkp)
 {
 	struct request_queue *q = sdkp->disk->queue;
@@ -823,6 +839,8 @@ static void sd_config_write_same(struct scsi_disk *sdkp)
 out:
 	blk_queue_max_write_same_sectors(q, sdkp->max_ws_blocks *
 					 (logical_block_size >> 9));
+	blk_queue_max_write_zeroes_sectors(q, sdkp->max_ws_blocks *
+					 (logical_block_size >> 9));
 }
 
 /**
@@ -1163,7 +1181,7 @@ static int sd_init_command(struct scsi_cmnd *cmd)
 		case SD_LBP_UNMAP:
 			return sd_setup_unmap_cmnd(cmd);
 		case SD_LBP_WS16:
-			return sd_setup_write_same16_cmnd(cmd);
+			return sd_setup_write_same16_cmnd(cmd, true);
 		case SD_LBP_WS10:
 			return sd_setup_write_same10_cmnd(cmd, true);
 		case SD_LBP_ZERO:
@@ -1171,6 +1189,8 @@ static int sd_init_command(struct scsi_cmnd *cmd)
 		default:
 			return BLKPREP_INVALID;
 		}
+	case REQ_OP_WRITE_ZEROES:
+		return sd_setup_write_zeroes_cmnd(cmd);
 	case REQ_OP_WRITE_SAME:
 		return sd_setup_write_same_cmnd(cmd);
 	case REQ_OP_FLUSH:
@@ -1810,6 +1830,7 @@ static int sd_done(struct scsi_cmnd *SCpnt)
 
 	switch (req_op(req)) {
 	case REQ_OP_DISCARD:
+	case REQ_OP_WRITE_ZEROES:
 	case REQ_OP_WRITE_SAME:
 	case REQ_OP_ZONE_RESET:
 		if (!result) {
diff --git a/drivers/scsi/sd_zbc.c b/drivers/scsi/sd_zbc.c
index 92620c8ea8ad..1994f7799fce 100644
--- a/drivers/scsi/sd_zbc.c
+++ b/drivers/scsi/sd_zbc.c
@@ -329,6 +329,7 @@ void sd_zbc_complete(struct scsi_cmnd *cmd,
 
 	switch (req_op(rq)) {
 	case REQ_OP_WRITE:
+	case REQ_OP_WRITE_ZEROES:
 	case REQ_OP_WRITE_SAME:
 	case REQ_OP_ZONE_RESET:
 
-- 
2.11.0

Re: [PATCH 04/25] sd: implement REQ_OP_WRITE_ZEROES

[Martin K. Petersen]

Christoph Hellwig <hch@lst.de> writes:

Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>

-- 
Martin K. Petersen	Oracle Linux Engineering

[PATCH 05/25] md: support REQ_OP_WRITE_ZEROES

[Christoph Hellwig]

Copy & paste from the REQ_OP_WRITE_SAME code.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 drivers/md/linear.c    | 1 +
 drivers/md/md.h        | 7 +++++++
 drivers/md/multipath.c | 1 +
 drivers/md/raid0.c     | 2 ++
 drivers/md/raid1.c     | 4 +++-
 drivers/md/raid10.c    | 1 +
 drivers/md/raid5.c     | 1 +
 7 files changed, 16 insertions(+), 1 deletion(-)

diff --git a/drivers/md/linear.c b/drivers/md/linear.c
index 3e38e0207a3e..377a8a3672e3 100644
--- a/drivers/md/linear.c
+++ b/drivers/md/linear.c
@@ -293,6 +293,7 @@ static void linear_make_request(struct mddev *mddev, struct bio *bio)
 						      split, disk_devt(mddev->gendisk),
 						      bio_sector);
 			mddev_check_writesame(mddev, split);
+			mddev_check_write_zeroes(mddev, split);
 			generic_make_request(split);
 		}
 	} while (split != bio);
diff --git a/drivers/md/md.h b/drivers/md/md.h
index dde8ecb760c8..1e76d64ce180 100644
--- a/drivers/md/md.h
+++ b/drivers/md/md.h
@@ -709,4 +709,11 @@ static inline void mddev_check_writesame(struct mddev *mddev, struct bio *bio)
 	    !bdev_get_queue(bio->bi_bdev)->limits.max_write_same_sectors)
 		mddev->queue->limits.max_write_same_sectors = 0;
 }
+
+static inline void mddev_check_write_zeroes(struct mddev *mddev, struct bio *bio)
+{
+	if (bio_op(bio) == REQ_OP_WRITE_ZEROES &&
+	    !bdev_get_queue(bio->bi_bdev)->limits.max_write_zeroes_sectors)
+		mddev->queue->limits.max_write_zeroes_sectors = 0;
+}
 #endif /* _MD_MD_H */
diff --git a/drivers/md/multipath.c b/drivers/md/multipath.c
index 79a12b59250b..e95d521d93e9 100644
--- a/drivers/md/multipath.c
+++ b/drivers/md/multipath.c
@@ -139,6 +139,7 @@ static void multipath_make_request(struct mddev *mddev, struct bio * bio)
 	mp_bh->bio.bi_end_io = multipath_end_request;
 	mp_bh->bio.bi_private = mp_bh;
 	mddev_check_writesame(mddev, &mp_bh->bio);
+	mddev_check_write_zeroes(mddev, &mp_bh->bio);
 	generic_make_request(&mp_bh->bio);
 	return;
 }
diff --git a/drivers/md/raid0.c b/drivers/md/raid0.c
index 93347ca7c7a6..ce7a6a56cf73 100644
--- a/drivers/md/raid0.c
+++ b/drivers/md/raid0.c
@@ -383,6 +383,7 @@ static int raid0_run(struct mddev *mddev)
 
 		blk_queue_max_hw_sectors(mddev->queue, mddev->chunk_sectors);
 		blk_queue_max_write_same_sectors(mddev->queue, mddev->chunk_sectors);
+		blk_queue_max_write_zeroes_sectors(mddev->queue, mddev->chunk_sectors);
 		blk_queue_max_discard_sectors(mddev->queue, mddev->chunk_sectors);
 
 		blk_queue_io_min(mddev->queue, mddev->chunk_sectors << 9);
@@ -504,6 +505,7 @@ static void raid0_make_request(struct mddev *mddev, struct bio *bio)
 						      split, disk_devt(mddev->gendisk),
 						      bio_sector);
 			mddev_check_writesame(mddev, split);
+			mddev_check_write_zeroes(mddev, split);
 			generic_make_request(split);
 		}
 	} while (split != bio);
diff --git a/drivers/md/raid1.c b/drivers/md/raid1.c
index a34f58772022..b59cc100320a 100644
--- a/drivers/md/raid1.c
+++ b/drivers/md/raid1.c
@@ -3177,8 +3177,10 @@ static int raid1_run(struct mddev *mddev)
 	if (IS_ERR(conf))
 		return PTR_ERR(conf);
 
-	if (mddev->queue)
+	if (mddev->queue) {
 		blk_queue_max_write_same_sectors(mddev->queue, 0);
+		blk_queue_max_write_zeroes_sectors(mddev->queue, 0);
+	}
 
 	rdev_for_each(rdev, mddev) {
 		if (!mddev->gendisk)
diff --git a/drivers/md/raid10.c b/drivers/md/raid10.c
index e89a8d78a9ed..28ec3a93acee 100644
--- a/drivers/md/raid10.c
+++ b/drivers/md/raid10.c
@@ -3749,6 +3749,7 @@ static int raid10_run(struct mddev *mddev)
 		blk_queue_max_discard_sectors(mddev->queue,
 					      mddev->chunk_sectors);
 		blk_queue_max_write_same_sectors(mddev->queue, 0);
+		blk_queue_max_write_zeroes_sectors(mddev->queue, 0);
 		blk_queue_io_min(mddev->queue, chunk_size);
 		if (conf->geo.raid_disks % conf->geo.near_copies)
 			blk_queue_io_opt(mddev->queue, chunk_size * conf->geo.raid_disks);
diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index ed5cd705b985..8cf1f86dcd05 100644
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -7272,6 +7272,7 @@ static int raid5_run(struct mddev *mddev)
 		mddev->queue->limits.discard_zeroes_data = 0;
 
 		blk_queue_max_write_same_sectors(mddev->queue, 0);
+		blk_queue_max_write_zeroes_sectors(mddev->queue, 0);
 
 		rdev_for_each(rdev, mddev) {
 			disk_stack_limits(mddev->gendisk, rdev->bdev,
-- 
2.11.0

[PATCH 06/25] dm io: discards don't take a payload

[Christoph Hellwig]

Fix up do_region to not allocate a bio_vec for discards.  We've
got rid of the discard payload allocated by the caller years ago.

Obviously this wasn't actually harmful given how long it's been
there, but it's still good to avoid the pointless allocation.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 drivers/md/dm-io.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/drivers/md/dm-io.c b/drivers/md/dm-io.c
index 03940bf36f6c..b808cbe22678 100644
--- a/drivers/md/dm-io.c
+++ b/drivers/md/dm-io.c
@@ -328,11 +328,17 @@ static void do_region(int op, int op_flags, unsigned region,
 		/*
 		 * Allocate a suitably sized-bio.
 		 */
-		if ((op == REQ_OP_DISCARD) || (op == REQ_OP_WRITE_SAME))
+		switch (op) {
+		case REQ_OP_DISCARD:
+			num_bvecs = 0;
+			break;
+		case REQ_OP_WRITE_SAME:
 			num_bvecs = 1;
-		else
+			break;
+		default:
 			num_bvecs = min_t(int, BIO_MAX_PAGES,
 					  dm_sector_div_up(remaining, (PAGE_SIZE >> SECTOR_SHIFT)));
+		}
 
 		bio = bio_alloc_bioset(GFP_NOIO, num_bvecs, io->client->bios);
 		bio->bi_iter.bi_sector = where->sector + (where->count - remaining);
-- 
2.11.0

[PATCH 07/25] dm: support REQ_OP_WRITE_ZEROES

[Christoph Hellwig]

Copy & paste from the REQ_OP_WRITE_SAME code.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 drivers/md/dm-core.h          |  1 +
 drivers/md/dm-io.c            |  8 ++++++--
 drivers/md/dm-linear.c        |  1 +
 drivers/md/dm-mpath.c         |  1 +
 drivers/md/dm-rq.c            | 11 ++++++++---
 drivers/md/dm-stripe.c        |  2 ++
 drivers/md/dm-table.c         | 30 ++++++++++++++++++++++++++++++
 drivers/md/dm.c               | 31 ++++++++++++++++++++++++++++---
 include/linux/device-mapper.h |  6 ++++++
 9 files changed, 83 insertions(+), 8 deletions(-)

diff --git a/drivers/md/dm-core.h b/drivers/md/dm-core.h
index 136fda3ff9e5..fea5bd52ada8 100644
--- a/drivers/md/dm-core.h
+++ b/drivers/md/dm-core.h
@@ -132,6 +132,7 @@ void dm_init_md_queue(struct mapped_device *md);
 void dm_init_normal_md_queue(struct mapped_device *md);
 int md_in_flight(struct mapped_device *md);
 void disable_write_same(struct mapped_device *md);
+void disable_write_zeroes(struct mapped_device *md);
 
 static inline struct completion *dm_get_completion_from_kobject(struct kobject *kobj)
 {
diff --git a/drivers/md/dm-io.c b/drivers/md/dm-io.c
index b808cbe22678..3702e502466d 100644
--- a/drivers/md/dm-io.c
+++ b/drivers/md/dm-io.c
@@ -312,9 +312,12 @@ static void do_region(int op, int op_flags, unsigned region,
 	 */
 	if (op == REQ_OP_DISCARD)
 		special_cmd_max_sectors = q->limits.max_discard_sectors;
+	else if (op == REQ_OP_WRITE_ZEROES)
+		special_cmd_max_sectors = q->limits.max_write_zeroes_sectors;
 	else if (op == REQ_OP_WRITE_SAME)
 		special_cmd_max_sectors = q->limits.max_write_same_sectors;
-	if ((op == REQ_OP_DISCARD || op == REQ_OP_WRITE_SAME) &&
+	if ((op == REQ_OP_DISCARD || op == REQ_OP_WRITE_ZEROES ||
+	     op == REQ_OP_WRITE_SAME)  &&
 	    special_cmd_max_sectors == 0) {
 		dec_count(io, region, -EOPNOTSUPP);
 		return;
@@ -330,6 +333,7 @@ static void do_region(int op, int op_flags, unsigned region,
 		 */
 		switch (op) {
 		case REQ_OP_DISCARD:
+		case REQ_OP_WRITE_ZEROES:
 			num_bvecs = 0;
 			break;
 		case REQ_OP_WRITE_SAME:
@@ -347,7 +351,7 @@ static void do_region(int op, int op_flags, unsigned region,
 		bio_set_op_attrs(bio, op, op_flags);
 		store_io_and_region_in_bio(bio, io, region);
 
-		if (op == REQ_OP_DISCARD) {
+		if (op == REQ_OP_DISCARD || op == REQ_OP_WRITE_ZEROES) {
 			num_sectors = min_t(sector_t, special_cmd_max_sectors, remaining);
 			bio->bi_iter.bi_size = num_sectors << SECTOR_SHIFT;
 			remaining -= num_sectors;
diff --git a/drivers/md/dm-linear.c b/drivers/md/dm-linear.c
index 4788b0b989a9..e17fd44ceef5 100644
--- a/drivers/md/dm-linear.c
+++ b/drivers/md/dm-linear.c
@@ -59,6 +59,7 @@ static int linear_ctr(struct dm_target *ti, unsigned int argc, char **argv)
 	ti->num_flush_bios = 1;
 	ti->num_discard_bios = 1;
 	ti->num_write_same_bios = 1;
+	ti->num_write_zeroes_bios = 1;
 	ti->private = lc;
 	return 0;
 
diff --git a/drivers/md/dm-mpath.c b/drivers/md/dm-mpath.c
index 7f223dbed49f..ab55955ed704 100644
--- a/drivers/md/dm-mpath.c
+++ b/drivers/md/dm-mpath.c
@@ -1103,6 +1103,7 @@ static int multipath_ctr(struct dm_target *ti, unsigned argc, char **argv)
 	ti->num_flush_bios = 1;
 	ti->num_discard_bios = 1;
 	ti->num_write_same_bios = 1;
+	ti->num_write_zeroes_bios = 1;
 	if (m->queue_mode == DM_TYPE_BIO_BASED)
 		ti->per_io_data_size = multipath_per_bio_data_size();
 	else
diff --git a/drivers/md/dm-rq.c b/drivers/md/dm-rq.c
index 28955b94d2b2..6006d5d4b06e 100644
--- a/drivers/md/dm-rq.c
+++ b/drivers/md/dm-rq.c
@@ -298,9 +298,14 @@ static void dm_done(struct request *clone, int error, bool mapped)
 			r = rq_end_io(tio->ti, clone, error, &tio->info);
 	}
 
-	if (unlikely(r == -EREMOTEIO && (req_op(clone) == REQ_OP_WRITE_SAME) &&
-		     !clone->q->limits.max_write_same_sectors))
-		disable_write_same(tio->md);
+	if (unlikely(r == -EREMOTEIO)) {
+		if (req_op(clone) == REQ_OP_WRITE_SAME &&
+		    !clone->q->limits.max_write_same_sectors)
+			disable_write_same(tio->md);
+		if (req_op(clone) == REQ_OP_WRITE_ZEROES &&
+		    !clone->q->limits.max_write_zeroes_sectors)
+			disable_write_zeroes(tio->md);
+	}
 
 	if (r <= 0)
 		/* The target wants to complete the I/O */
diff --git a/drivers/md/dm-stripe.c b/drivers/md/dm-stripe.c
index 28193a57bf47..5ef49c121d99 100644
--- a/drivers/md/dm-stripe.c
+++ b/drivers/md/dm-stripe.c
@@ -169,6 +169,7 @@ static int stripe_ctr(struct dm_target *ti, unsigned int argc, char **argv)
 	ti->num_flush_bios = stripes;
 	ti->num_discard_bios = stripes;
 	ti->num_write_same_bios = stripes;
+	ti->num_write_zeroes_bios = stripes;
 
 	sc->chunk_size = chunk_size;
 	if (chunk_size & (chunk_size - 1))
@@ -293,6 +294,7 @@ static int stripe_map(struct dm_target *ti, struct bio *bio)
 		return DM_MAPIO_REMAPPED;
 	}
 	if (unlikely(bio_op(bio) == REQ_OP_DISCARD) ||
+	    unlikely(bio_op(bio) == REQ_OP_WRITE_ZEROES) ||
 	    unlikely(bio_op(bio) == REQ_OP_WRITE_SAME)) {
 		target_bio_nr = dm_bio_get_target_bio_nr(bio);
 		BUG_ON(target_bio_nr >= sc->stripes);
diff --git a/drivers/md/dm-table.c b/drivers/md/dm-table.c
index 3ad16d9c9d5a..5cd665c91ead 100644
--- a/drivers/md/dm-table.c
+++ b/drivers/md/dm-table.c
@@ -1533,6 +1533,34 @@ static bool dm_table_supports_write_same(struct dm_table *t)
 	return true;
 }
 
+static int device_not_write_zeroes_capable(struct dm_target *ti, struct dm_dev *dev,
+					   sector_t start, sector_t len, void *data)
+{
+	struct request_queue *q = bdev_get_queue(dev->bdev);
+
+	return q && !q->limits.max_write_zeroes_sectors;
+}
+
+static bool dm_table_supports_write_zeroes(struct dm_table *t)
+{
+	struct dm_target *ti;
+	unsigned i = 0;
+
+	while (i < dm_table_get_num_targets(t)) {
+		ti = dm_table_get_target(t, i++);
+
+		if (!ti->num_write_zeroes_bios)
+			return false;
+
+		if (!ti->type->iterate_devices ||
+		    ti->type->iterate_devices(ti, device_not_write_zeroes_capable, NULL))
+			return false;
+	}
+
+	return true;
+}
+
+
 static int device_discard_capable(struct dm_target *ti, struct dm_dev *dev,
 				  sector_t start, sector_t len, void *data)
 {
@@ -1603,6 +1631,8 @@ void dm_table_set_restrictions(struct dm_table *t, struct request_queue *q,
 
 	if (!dm_table_supports_write_same(t))
 		q->limits.max_write_same_sectors = 0;
+	if (!dm_table_supports_write_zeroes(t))
+		q->limits.max_write_zeroes_sectors = 0;
 
 	if (dm_table_all_devices_attribute(t, queue_supports_sg_merge))
 		queue_flag_clear_unlocked(QUEUE_FLAG_NO_SG_MERGE, q);
diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index dfb75979e455..e8226359c8f7 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -825,6 +825,14 @@ void disable_write_same(struct mapped_device *md)
 	limits->max_write_same_sectors = 0;
 }
 
+void disable_write_zeroes(struct mapped_device *md)
+{
+	struct queue_limits *limits = dm_get_queue_limits(md);
+
+	/* device doesn't really support WRITE ZEROES, disable it */
+	limits->max_write_zeroes_sectors = 0;
+}
+
 static void clone_endio(struct bio *bio)
 {
 	int error = bio->bi_error;
@@ -851,9 +859,14 @@ static void clone_endio(struct bio *bio)
 		}
 	}
 
-	if (unlikely(r == -EREMOTEIO && (bio_op(bio) == REQ_OP_WRITE_SAME) &&
-		     !bdev_get_queue(bio->bi_bdev)->limits.max_write_same_sectors))
-		disable_write_same(md);
+	if (unlikely(r == -EREMOTEIO)) {
+		if (bio_op(bio) == REQ_OP_WRITE_SAME &&
+		    !bdev_get_queue(bio->bi_bdev)->limits.max_write_same_sectors)
+			disable_write_same(md);
+		if (bio_op(bio) == REQ_OP_WRITE_ZEROES &&
+		    !bdev_get_queue(bio->bi_bdev)->limits.max_write_zeroes_sectors)
+			disable_write_zeroes(md);
+	}
 
 	free_tio(tio);
 	dec_pending(io, error);
@@ -1202,6 +1215,11 @@ static unsigned get_num_write_same_bios(struct dm_target *ti)
 	return ti->num_write_same_bios;
 }
 
+static unsigned get_num_write_zeroes_bios(struct dm_target *ti)
+{
+	return ti->num_write_zeroes_bios;
+}
+
 typedef bool (*is_split_required_fn)(struct dm_target *ti);
 
 static bool is_split_required_for_discard(struct dm_target *ti)
@@ -1256,6 +1274,11 @@ static int __send_write_same(struct clone_info *ci)
 	return __send_changing_extent_only(ci, get_num_write_same_bios, NULL);
 }
 
+static int __send_write_zeroes(struct clone_info *ci)
+{
+	return __send_changing_extent_only(ci, get_num_write_zeroes_bios, NULL);
+}
+
 /*
  * Select the correct strategy for processing a non-flush bio.
  */
@@ -1270,6 +1293,8 @@ static int __split_and_process_non_flush(struct clone_info *ci)
 		return __send_discard(ci);
 	else if (unlikely(bio_op(bio) == REQ_OP_WRITE_SAME))
 		return __send_write_same(ci);
+	else if (unlikely(bio_op(bio) == REQ_OP_WRITE_ZEROES))
+		return __send_write_zeroes(ci);
 
 	ti = dm_table_find_target(ci->map, ci->sector);
 	if (!dm_target_is_valid(ti))
diff --git a/include/linux/device-mapper.h b/include/linux/device-mapper.h
index a7e6903866fd..3829bee2302a 100644
--- a/include/linux/device-mapper.h
+++ b/include/linux/device-mapper.h
@@ -255,6 +255,12 @@ struct dm_target {
 	unsigned num_write_same_bios;
 
 	/*
+	 * The number of WRITE ZEROES bios that will be submitted to the target.
+	 * The bio number can be accessed with dm_bio_get_target_bio_nr.
+	 */
+	unsigned num_write_zeroes_bios;
+
+	/*
 	 * The minimum number of extra bytes allocated in each io for the
 	 * target to use.
 	 */
-- 
2.11.0

[PATCH 08/25] dm kcopyd: switch to use REQ_OP_WRITE_ZEROES

[Christoph Hellwig]

It seems like the code currently passes whatever it was using for writes
to WRITE SAME.  Just switch it to WRITE ZEROES, although that doesn't
need any payload.

Untested, and confused by the code, maybe someone who understands it
better than me can help..

Not-yet-signed-off-by: Christoph Hellwig <hch@lst.de>
---
 drivers/md/dm-kcopyd.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/md/dm-kcopyd.c b/drivers/md/dm-kcopyd.c
index 9e9d04cb7d51..f85846741d50 100644
--- a/drivers/md/dm-kcopyd.c
+++ b/drivers/md/dm-kcopyd.c
@@ -733,11 +733,11 @@ int dm_kcopyd_copy(struct dm_kcopyd_client *kc, struct dm_io_region *from,
 		job->pages = &zero_page_list;
 
 		/*
-		 * Use WRITE SAME to optimize zeroing if all dests support it.
+		 * Use WRITE ZEROES to optimize zeroing if all dests support it.
 		 */
-		job->rw = REQ_OP_WRITE_SAME;
+		job->rw = REQ_OP_WRITE_ZEROES;
 		for (i = 0; i < job->num_dests; i++)
-			if (!bdev_write_same(job->dests[i].bdev)) {
+			if (!bdev_write_zeroes_sectors(job->dests[i].bdev)) {
 				job->rw = WRITE;
 				break;
 			}
-- 
2.11.0

[PATCH 09/25] block: stop using blkdev_issue_write_same for zeroing

[Christoph Hellwig]

We'll always use the WRITE ZEROES code for zeroing now.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 block/blk-lib.c | 4 ----
 1 file changed, 4 deletions(-)

diff --git a/block/blk-lib.c b/block/blk-lib.c
index e5b853f2b8a2..2a8d638544a7 100644
--- a/block/blk-lib.c
+++ b/block/blk-lib.c
@@ -364,10 +364,6 @@ int blkdev_issue_zeroout(struct block_device *bdev, sector_t sector,
 			return 0;
 	}
 
-	if (!blkdev_issue_write_same(bdev, sector, nr_sects, gfp_mask,
-			ZERO_PAGE(0)))
-		return 0;
-
 	blk_start_plug(&plug);
 	ret = __blkdev_issue_zeroout(bdev, sector, nr_sects, gfp_mask,
 			&bio, discard);
-- 
2.11.0

Re: [PATCH 09/25] block: stop using blkdev_issue_write_same for zeroing

[Martin K. Petersen]

Christoph Hellwig <hch@lst.de> writes:

> We'll always use the WRITE ZEROES code for zeroing now.

Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>

-- 
Martin K. Petersen	Oracle Linux Engineering

[PATCH 10/25] block: add a flags argument to (__)blkdev_issue_zeroout

[Christoph Hellwig]

Turn the existin discard flag into a new BLKDEV_ZERO_UNMAP flag with
similar semantics, but without referring to diѕcard.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 block/blk-lib.c                    | 31 ++++++++++++++-----------------
 block/ioctl.c                      |  2 +-
 drivers/block/drbd/drbd_receiver.c |  9 ++++++---
 drivers/nvme/target/io-cmd.c       |  2 +-
 fs/block_dev.c                     |  2 +-
 fs/dax.c                           |  2 +-
 fs/xfs/xfs_bmap_util.c             |  2 +-
 include/linux/blkdev.h             | 16 ++++++++++------
 8 files changed, 35 insertions(+), 31 deletions(-)

diff --git a/block/blk-lib.c b/block/blk-lib.c
index 2a8d638544a7..f9f24ec69c27 100644
--- a/block/blk-lib.c
+++ b/block/blk-lib.c
@@ -282,14 +282,18 @@ static int __blkdev_issue_write_zeroes(struct block_device *bdev,
  * @nr_sects:	number of sectors to write
  * @gfp_mask:	memory allocation flags (for bio_alloc)
  * @biop:	pointer to anchor bio
- * @discard:	discard flag
+ * @flags:	controls detailed behavior
  *
  * Description:
- *  Generate and issue number of bios with zerofiled pages.
+ *  Zero-fill a block range, either using hardware offload or by explicitly
+ *  writing zeroes to the device.
+ *
+ *  If a device is using logical block provisioning, the underlying space will
+ *  not be released if %flags contains BLKDEV_ZERO_NOUNMAP.
  */
 int __blkdev_issue_zeroout(struct block_device *bdev, sector_t sector,
 		sector_t nr_sects, gfp_t gfp_mask, struct bio **biop,
-		bool discard)
+		unsigned flags)
 {
 	int ret;
 	int bi_size = 0;
@@ -337,28 +341,21 @@ EXPORT_SYMBOL(__blkdev_issue_zeroout);
  * @sector:	start sector
  * @nr_sects:	number of sectors to write
  * @gfp_mask:	memory allocation flags (for bio_alloc)
- * @discard:	whether to discard the block range
+ * @flags:	controls detailed behavior
  *
  * Description:
- *  Zero-fill a block range.  If the discard flag is set and the block
- *  device guarantees that subsequent READ operations to the block range
- *  in question will return zeroes, the blocks will be discarded. Should
- *  the discard request fail, if the discard flag is not set, or if
- *  discard_zeroes_data is not supported, this function will resort to
- *  zeroing the blocks manually, thus provisioning (allocating,
- *  anchoring) them. If the block device supports WRITE ZEROES or WRITE SAME
- *  command(s), blkdev_issue_zeroout() will use it to optimize the process of
- *  clearing the block range. Otherwise the zeroing will be performed
- *  using regular WRITE calls.
+ *  Zero-fill a block range, either using hardware offload or by explicitly
+ *  writing zeroes to the device.  See __blkdev_issue_zeroout() for the
+ *  valid values for %flags.
  */
 int blkdev_issue_zeroout(struct block_device *bdev, sector_t sector,
-			 sector_t nr_sects, gfp_t gfp_mask, bool discard)
+		sector_t nr_sects, gfp_t gfp_mask, unsigned flags)
 {
 	int ret;
 	struct bio *bio = NULL;
 	struct blk_plug plug;
 
-	if (discard) {
+	if (!(flags & BLKDEV_ZERO_NOUNMAP)) {
 		if (!blkdev_issue_discard(bdev, sector, nr_sects, gfp_mask,
 				BLKDEV_DISCARD_ZERO))
 			return 0;
@@ -366,7 +363,7 @@ int blkdev_issue_zeroout(struct block_device *bdev, sector_t sector,
 
 	blk_start_plug(&plug);
 	ret = __blkdev_issue_zeroout(bdev, sector, nr_sects, gfp_mask,
-			&bio, discard);
+			&bio, flags);
 	if (ret == 0 && bio) {
 		ret = submit_bio_wait(bio);
 		bio_put(bio);
diff --git a/block/ioctl.c b/block/ioctl.c
index 7b88820b93d9..8ea00a41be01 100644
--- a/block/ioctl.c
+++ b/block/ioctl.c
@@ -255,7 +255,7 @@ static int blk_ioctl_zeroout(struct block_device *bdev, fmode_t mode,
 	truncate_inode_pages_range(mapping, start, end);
 
 	return blkdev_issue_zeroout(bdev, start >> 9, len >> 9, GFP_KERNEL,
-				    false);
+			BLKDEV_ZERO_NOUNMAP);
 }
 
 static int put_ushort(unsigned long arg, unsigned short val)
diff --git a/drivers/block/drbd/drbd_receiver.c b/drivers/block/drbd/drbd_receiver.c
index aa6bf9692eff..dc9a6dcd431c 100644
--- a/drivers/block/drbd/drbd_receiver.c
+++ b/drivers/block/drbd/drbd_receiver.c
@@ -1499,19 +1499,22 @@ int drbd_issue_discard_or_zero_out(struct drbd_device *device, sector_t start, u
 		tmp = start + granularity - sector_div(tmp, granularity);
 
 		nr = tmp - start;
-		err |= blkdev_issue_zeroout(bdev, start, nr, GFP_NOIO, 0);
+		err |= blkdev_issue_zeroout(bdev, start, nr, GFP_NOIO,
+				BLKDEV_ZERO_NOUNMAP);
 		nr_sectors -= nr;
 		start = tmp;
 	}
 	while (nr_sectors >= granularity) {
 		nr = min_t(sector_t, nr_sectors, max_discard_sectors);
-		err |= blkdev_issue_discard(bdev, start, nr, GFP_NOIO, 0);
+		err |= blkdev_issue_discard(bdev, start, nr, GFP_NOIO,
+				BLKDEV_ZERO_NOUNMAP);
 		nr_sectors -= nr;
 		start += nr;
 	}
  zero_out:
 	if (nr_sectors) {
-		err |= blkdev_issue_zeroout(bdev, start, nr_sectors, GFP_NOIO, 0);
+		err |= blkdev_issue_zeroout(bdev, start, nr_sectors, GFP_NOIO,
+				BLKDEV_ZERO_NOUNMAP);
 	}
 	return err != 0;
 }
diff --git a/drivers/nvme/target/io-cmd.c b/drivers/nvme/target/io-cmd.c
index 4195115c7e54..7206f9cda575 100644
--- a/drivers/nvme/target/io-cmd.c
+++ b/drivers/nvme/target/io-cmd.c
@@ -184,7 +184,7 @@ static void nvmet_execute_write_zeroes(struct nvmet_req *req)
 		(req->ns->blksize_shift - 9)) + 1;
 
 	if (__blkdev_issue_zeroout(req->ns->bdev, sector, nr_sector,
-				GFP_KERNEL, &bio, true))
+				GFP_KERNEL, &bio, 0))
 		status = NVME_SC_INTERNAL | NVME_SC_DNR;
 
 	if (bio) {
diff --git a/fs/block_dev.c b/fs/block_dev.c
index f2d59f143ef4..2f704c3a816f 100644
--- a/fs/block_dev.c
+++ b/fs/block_dev.c
@@ -2105,7 +2105,7 @@ static long blkdev_fallocate(struct file *file, int mode, loff_t start,
 	case FALLOC_FL_ZERO_RANGE:
 	case FALLOC_FL_ZERO_RANGE | FALLOC_FL_KEEP_SIZE:
 		error = blkdev_issue_zeroout(bdev, start >> 9, len >> 9,
-					    GFP_KERNEL, false);
+					    GFP_KERNEL, BLKDEV_ZERO_NOUNMAP);
 		break;
 	case FALLOC_FL_PUNCH_HOLE | FALLOC_FL_KEEP_SIZE:
 		/* Only punch if the device can do zeroing discard. */
diff --git a/fs/dax.c b/fs/dax.c
index de622d4282a6..2bfbcd726047 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -982,7 +982,7 @@ int __dax_zero_page_range(struct block_device *bdev, sector_t sector,
 		sector_t start_sector = dax.sector + (offset >> 9);
 
 		return blkdev_issue_zeroout(bdev, start_sector,
-				length >> 9, GFP_NOFS, true);
+				length >> 9, GFP_NOFS, 0);
 	} else {
 		if (dax_map_atomic(bdev, &dax) < 0)
 			return PTR_ERR(dax.addr);
diff --git a/fs/xfs/xfs_bmap_util.c b/fs/xfs/xfs_bmap_util.c
index 8b75dcea5966..142bbbe06114 100644
--- a/fs/xfs/xfs_bmap_util.c
+++ b/fs/xfs/xfs_bmap_util.c
@@ -81,7 +81,7 @@ xfs_zero_extent(
 	return blkdev_issue_zeroout(xfs_find_bdev_for_inode(VFS_I(ip)),
 		block << (mp->m_super->s_blocksize_bits - 9),
 		count_fsb << (mp->m_super->s_blocksize_bits - 9),
-		GFP_NOFS, true);
+		GFP_NOFS, 0);
 }
 
 int
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index a2dc6b390d48..e7513ce3dbde 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -1337,23 +1337,27 @@ static inline struct request *blk_map_queue_find_tag(struct blk_queue_tag *bqt,
 	return bqt->tag_index[tag];
 }
 
+extern int blkdev_issue_flush(struct block_device *, gfp_t, sector_t *);
+extern int blkdev_issue_write_same(struct block_device *bdev, sector_t sector,
+		sector_t nr_sects, gfp_t gfp_mask, struct page *page);
 
 #define BLKDEV_DISCARD_SECURE	(1 << 0)	/* issue a secure erase */
 #define BLKDEV_DISCARD_ZERO	(1 << 1)	/* must reliably zero data */
 
-extern int blkdev_issue_flush(struct block_device *, gfp_t, sector_t *);
 extern int blkdev_issue_discard(struct block_device *bdev, sector_t sector,
 		sector_t nr_sects, gfp_t gfp_mask, unsigned long flags);
 extern int __blkdev_issue_discard(struct block_device *bdev, sector_t sector,
 		sector_t nr_sects, gfp_t gfp_mask, int flags,
 		struct bio **biop);
-extern int blkdev_issue_write_same(struct block_device *bdev, sector_t sector,
-		sector_t nr_sects, gfp_t gfp_mask, struct page *page);
+
+#define BLKDEV_ZERO_NOUNMAP	(1 << 0)  /* do not free blocks */
+
 extern int __blkdev_issue_zeroout(struct block_device *bdev, sector_t sector,
 		sector_t nr_sects, gfp_t gfp_mask, struct bio **biop,
-		bool discard);
+		unsigned flags);
 extern int blkdev_issue_zeroout(struct block_device *bdev, sector_t sector,
-		sector_t nr_sects, gfp_t gfp_mask, bool discard);
+		sector_t nr_sects, gfp_t gfp_mask, unsigned flags);
+
 static inline int sb_issue_discard(struct super_block *sb, sector_t block,
 		sector_t nr_blocks, gfp_t gfp_mask, unsigned long flags)
 {
@@ -1367,7 +1371,7 @@ static inline int sb_issue_zeroout(struct super_block *sb, sector_t block,
 	return blkdev_issue_zeroout(sb->s_bdev,
 				    block << (sb->s_blocksize_bits - 9),
 				    nr_blocks << (sb->s_blocksize_bits - 9),
-				    gfp_mask, true);
+				    gfp_mask, 0);
 }
 
 extern int blk_verify_command(unsigned char *cmd, fmode_t has_write_perm);
-- 
2.11.0

Re: [PATCH 10/25] block: add a flags argument to (__)blkdev_issue_zeroout

[Martin K. Petersen]

Christoph Hellwig <hch@lst.de> writes:

> Turn the existin discard flag into a new BLKDEV_ZERO_UNMAP flag with
                  g

> similar semantics, but without referring to di=D1=95card.
                                                s

Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>

--=20
Martin K. Petersen	Oracle Linux Engineering

[PATCH 11/25] block: add a REQ_UNMAP flag for REQ_OP_WRITE_ZEROES

[Christoph Hellwig]

If this flag is set logical provisioning capable device should
release space for the zeroed blocks if possible, if it is not set
devices should keep the blocks anchored.

Also remove an out of sync kerneldoc comment for a static function
that would have become even more out of data with this change.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 block/blk-lib.c           | 19 +++++--------------
 include/linux/blk_types.h |  6 ++++++
 2 files changed, 11 insertions(+), 14 deletions(-)

diff --git a/block/blk-lib.c b/block/blk-lib.c
index f9f24ec69c27..2f6d2cb2e1a2 100644
--- a/block/blk-lib.c
+++ b/block/blk-lib.c
@@ -226,20 +226,9 @@ int blkdev_issue_write_same(struct block_device *bdev, sector_t sector,
 }
 EXPORT_SYMBOL(blkdev_issue_write_same);
 
-/**
- * __blkdev_issue_write_zeroes - generate number of bios with WRITE ZEROES
- * @bdev:	blockdev to issue
- * @sector:	start sector
- * @nr_sects:	number of sectors to write
- * @gfp_mask:	memory allocation flags (for bio_alloc)
- * @biop:	pointer to anchor bio
- *
- * Description:
- *  Generate and issue number of bios(REQ_OP_WRITE_ZEROES) with zerofiled pages.
- */
 static int __blkdev_issue_write_zeroes(struct block_device *bdev,
 		sector_t sector, sector_t nr_sects, gfp_t gfp_mask,
-		struct bio **biop)
+		struct bio **biop, unsigned flags)
 {
 	struct bio *bio = *biop;
 	unsigned int max_write_zeroes_sectors;
@@ -258,7 +247,9 @@ static int __blkdev_issue_write_zeroes(struct block_device *bdev,
 		bio = next_bio(bio, 0, gfp_mask);
 		bio->bi_iter.bi_sector = sector;
 		bio->bi_bdev = bdev;
-		bio_set_op_attrs(bio, REQ_OP_WRITE_ZEROES, 0);
+		bio->bi_opf = REQ_OP_WRITE_ZEROES;
+		if (flags & BLKDEV_ZERO_NOUNMAP)
+			bio->bi_opf |= REQ_NOUNMAP;
 
 		if (nr_sects > max_write_zeroes_sectors) {
 			bio->bi_iter.bi_size = max_write_zeroes_sectors << 9;
@@ -306,7 +297,7 @@ int __blkdev_issue_zeroout(struct block_device *bdev, sector_t sector,
 		return -EINVAL;
 
 	ret = __blkdev_issue_write_zeroes(bdev, sector, nr_sects, gfp_mask,
-			biop);
+			biop, flags);
 	if (ret == 0 || (ret && ret != -EOPNOTSUPP))
 		goto out;
 
diff --git a/include/linux/blk_types.h b/include/linux/blk_types.h
index 4eae30bfbfca..8eaa7dca7057 100644
--- a/include/linux/blk_types.h
+++ b/include/linux/blk_types.h
@@ -195,6 +195,10 @@ enum req_flag_bits {
 	__REQ_PREFLUSH,		/* request for cache flush */
 	__REQ_RAHEAD,		/* read ahead, can fail anytime */
 	__REQ_BACKGROUND,	/* background IO */
+
+	/* command specific flags for REQ_OP_WRITE_ZEROES: */
+	__REQ_NOUNMAP,		/* do not free blocks when zeroing */
+
 	__REQ_NR_BITS,		/* stops here */
 };
 
@@ -212,6 +216,8 @@ enum req_flag_bits {
 #define REQ_RAHEAD		(1ULL << __REQ_RAHEAD)
 #define REQ_BACKGROUND		(1ULL << __REQ_BACKGROUND)
 
+#define REQ_NOUNMAP		(1ULL << __REQ_NOUNMAP)
+
 #define REQ_FAILFAST_MASK \
 	(REQ_FAILFAST_DEV | REQ_FAILFAST_TRANSPORT | REQ_FAILFAST_DRIVER)
 
-- 
2.11.0

Re: [PATCH 11/25] block: add a REQ_UNMAP flag for REQ_OP_WRITE_ZEROES

[Martin K. Petersen]

Christoph Hellwig <hch@lst.de> writes:

> If this flag is set logical provisioning capable device should
> release space for the zeroed blocks if possible, if it is not set
> devices should keep the blocks anchored.
>
> Also remove an out of sync kerneldoc comment for a static function
> that would have become even more out of data with this change.

Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>

-- 
Martin K. Petersen	Oracle Linux Engineering

[PATCH 12/25] block: add a new BLKDEV_ZERO_NOFALLBACK flag

[Christoph Hellwig]

This avoids fallbacks to explicit zeroing in (__)blkdev_issue_zeroout if
the caller doesn't want them.

Also clean up the convoluted check for the return condition that this
new flag is added to.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 block/blk-lib.c        | 5 ++++-
 include/linux/blkdev.h | 1 +
 2 files changed, 5 insertions(+), 1 deletion(-)

diff --git a/block/blk-lib.c b/block/blk-lib.c
index 2f6d2cb2e1a2..2f882e22890b 100644
--- a/block/blk-lib.c
+++ b/block/blk-lib.c
@@ -281,6 +281,9 @@ static int __blkdev_issue_write_zeroes(struct block_device *bdev,
  *
  *  If a device is using logical block provisioning, the underlying space will
  *  not be released if %flags contains BLKDEV_ZERO_NOUNMAP.
+ *
+ *  If %flags contains BLKDEV_ZERO_NOFALLBACK, the function will return
+ *  -EOPNOTSUPP if no explicit hardware offload for zeroing is provided.
  */
 int __blkdev_issue_zeroout(struct block_device *bdev, sector_t sector,
 		sector_t nr_sects, gfp_t gfp_mask, struct bio **biop,
@@ -298,7 +301,7 @@ int __blkdev_issue_zeroout(struct block_device *bdev, sector_t sector,
 
 	ret = __blkdev_issue_write_zeroes(bdev, sector, nr_sects, gfp_mask,
 			biop, flags);
-	if (ret == 0 || (ret && ret != -EOPNOTSUPP))
+	if (ret != -EOPNOTSUPP || (flags & BLKDEV_ZERO_NOFALLBACK))
 		goto out;
 
 	ret = 0;
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index e7513ce3dbde..a5055d760661 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -1351,6 +1351,7 @@ extern int __blkdev_issue_discard(struct block_device *bdev, sector_t sector,
 		struct bio **biop);
 
 #define BLKDEV_ZERO_NOUNMAP	(1 << 0)  /* do not free blocks */
+#define BLKDEV_ZERO_NOFALLBACK	(1 << 1)  /* don't write explicit zeroes */
 
 extern int __blkdev_issue_zeroout(struct block_device *bdev, sector_t sector,
 		sector_t nr_sects, gfp_t gfp_mask, struct bio **biop,
-- 
2.11.0

Re: [PATCH 12/25] block: add a new BLKDEV_ZERO_NOFALLBACK flag

[Martin K. Petersen]

Christoph Hellwig <hch@lst.de> writes:

> This avoids fallbacks to explicit zeroing in (__)blkdev_issue_zeroout
> if the caller doesn't want them.
>
> Also clean up the convoluted check for the return condition that this
> new flag is added to.

Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>

-- 
Martin K. Petersen	Oracle Linux Engineering

[PATCH 13/25] block_dev: use blkdev_issue_zerout for hole punches

[Christoph Hellwig]

This gets us support for non-discard efficient write of zeroes (e.g. NVMe)
and prepare for removing the discard_zeroes_data flag.

Also remove a pointless discard support check, which is done in
blkdev_issue_discard already.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 fs/block_dev.c | 10 ++--------
 1 file changed, 2 insertions(+), 8 deletions(-)

diff --git a/fs/block_dev.c b/fs/block_dev.c
index 2f704c3a816f..e405d8e58e31 100644
--- a/fs/block_dev.c
+++ b/fs/block_dev.c
@@ -2069,7 +2069,6 @@ static long blkdev_fallocate(struct file *file, int mode, loff_t start,
 			     loff_t len)
 {
 	struct block_device *bdev = I_BDEV(bdev_file_inode(file));
-	struct request_queue *q = bdev_get_queue(bdev);
 	struct address_space *mapping;
 	loff_t end = start + len - 1;
 	loff_t isize;
@@ -2108,15 +2107,10 @@ static long blkdev_fallocate(struct file *file, int mode, loff_t start,
 					    GFP_KERNEL, BLKDEV_ZERO_NOUNMAP);
 		break;
 	case FALLOC_FL_PUNCH_HOLE | FALLOC_FL_KEEP_SIZE:
-		/* Only punch if the device can do zeroing discard. */
-		if (!blk_queue_discard(q) || !q->limits.discard_zeroes_data)
-			return -EOPNOTSUPP;
-		error = blkdev_issue_discard(bdev, start >> 9, len >> 9,
-					     GFP_KERNEL, 0);
+		error = blkdev_issue_zeroout(bdev, start >> 9, len >> 9,
+					     GFP_KERNEL, BLKDEV_ZERO_NOFALLBACK);
 		break;
 	case FALLOC_FL_PUNCH_HOLE | FALLOC_FL_KEEP_SIZE | FALLOC_FL_NO_HIDE_STALE:
-		if (!blk_queue_discard(q))
-			return -EOPNOTSUPP;
 		error = blkdev_issue_discard(bdev, start >> 9, len >> 9,
 					     GFP_KERNEL, 0);
 		break;
-- 
2.11.0

Re: [PATCH 13/25] block_dev: use blkdev_issue_zerout for hole punches

[Martin K. Petersen]

Christoph Hellwig <hch@lst.de> writes:

> This gets us support for non-discard efficient write of zeroes
> (e.g. NVMe) and prepare for removing the discard_zeroes_data flag.
                         s

Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>

-- 
Martin K. Petersen	Oracle Linux Engineering

[PATCH 14/25] sd: implement unmapping Write Zeroes

[Christoph Hellwig]

Try to use a write same with unmap bit variant if the device supports it
and the caller allows for it.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 drivers/scsi/sd.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/drivers/scsi/sd.c b/drivers/scsi/sd.c
index d8d9c0bdd93c..001593ed0444 100644
--- a/drivers/scsi/sd.c
+++ b/drivers/scsi/sd.c
@@ -803,6 +803,15 @@ static int sd_setup_write_zeroes_cmnd(struct scsi_cmnd *cmd)
 	u64 sector = blk_rq_pos(rq) >> (ilog2(sdp->sector_size) - 9);
 	u32 nr_sectors = blk_rq_sectors(rq) >> (ilog2(sdp->sector_size) - 9);
 
+	if (!(rq->cmd_flags & REQ_NOUNMAP)) {
+		switch (sdkp->provisioning_mode) {
+		case SD_LBP_WS16:
+			return sd_setup_write_same16_cmnd(cmd, true);
+		case SD_LBP_WS10:
+			return sd_setup_write_same10_cmnd(cmd, true);
+		}
+	}
+
 	if (sdp->no_write_same)
 		return BLKPREP_INVALID;
 	if (sdkp->ws16 || sector > 0xffffffff || nr_sectors > 0xffff)
-- 
2.11.0

Re: [PATCH 14/25] sd: implement unmapping Write Zeroes

[Martin K. Petersen]

Christoph Hellwig <hch@lst.de> writes:

> Try to use a write same with unmap bit variant if the device supports it
> and the caller allows for it.

Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>

-- 
Martin K. Petersen	Oracle Linux Engineering

[PATCH 15/25] nvme: implement REQ_OP_WRITE_ZEROES

[Christoph Hellwig]

But now for the real NVMe Write Zeroes yet, just to get rid of the
discard abuse for zeroing.  Also rename the quirk flag to be a bit
more self-explanatory.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 drivers/nvme/host/core.c | 10 +++++-----
 drivers/nvme/host/nvme.h |  6 +++---
 drivers/nvme/host/pci.c  |  6 +++---
 3 files changed, 11 insertions(+), 11 deletions(-)

diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
index 4a6d7f408769..94b41d847b01 100644
--- a/drivers/nvme/host/core.c
+++ b/drivers/nvme/host/core.c
@@ -335,6 +335,8 @@ int nvme_setup_cmd(struct nvme_ns *ns, struct request *req,
 	case REQ_OP_FLUSH:
 		nvme_setup_flush(ns, cmd);
 		break;
+	case REQ_OP_WRITE_ZEROES:
+		/* currently only aliased to deallocate for a few ctrls: */
 	case REQ_OP_DISCARD:
 		ret = nvme_setup_discard(ns, req, cmd);
 		break;
@@ -900,16 +902,14 @@ static void nvme_config_discard(struct nvme_ns *ns)
 	BUILD_BUG_ON(PAGE_SIZE / sizeof(struct nvme_dsm_range) <
 			NVME_DSM_MAX_RANGES);
 
-	if (ctrl->quirks & NVME_QUIRK_DISCARD_ZEROES)
-		ns->queue->limits.discard_zeroes_data = 1;
-	else
-		ns->queue->limits.discard_zeroes_data = 0;
-
 	ns->queue->limits.discard_alignment = logical_block_size;
 	ns->queue->limits.discard_granularity = logical_block_size;
 	blk_queue_max_discard_sectors(ns->queue, UINT_MAX);
 	blk_queue_max_discard_segments(ns->queue, NVME_DSM_MAX_RANGES);
 	queue_flag_set_unlocked(QUEUE_FLAG_DISCARD, ns->queue);
+
+	if (ctrl->quirks & NVME_QUIRK_DEALLOCATE_ZEROES)
+		blk_queue_max_write_zeroes_sectors(ns->queue, UINT_MAX);
 }
 
 static int nvme_revalidate_ns(struct nvme_ns *ns, struct nvme_id_ns **id)
diff --git a/drivers/nvme/host/nvme.h b/drivers/nvme/host/nvme.h
index 2aa20e3e5675..07ebc4a1c8fc 100644
--- a/drivers/nvme/host/nvme.h
+++ b/drivers/nvme/host/nvme.h
@@ -68,10 +68,10 @@ enum nvme_quirks {
 	NVME_QUIRK_IDENTIFY_CNS			= (1 << 1),
 
 	/*
-	 * The controller deterministically returns O's on reads to discarded
-	 * logical blocks.
+	 * The controller deterministically returns O's on reads to
+	 * logical blocks that deallocate was called on.
 	 */
-	NVME_QUIRK_DISCARD_ZEROES		= (1 << 2),
+	NVME_QUIRK_DEALLOCATE_ZEROES		= (1 << 2),
 
 	/*
 	 * The controller needs a delay before starts checking the device
diff --git a/drivers/nvme/host/pci.c b/drivers/nvme/host/pci.c
index 26a5fd05fe88..0a28787267f0 100644
--- a/drivers/nvme/host/pci.c
+++ b/drivers/nvme/host/pci.c
@@ -2135,13 +2135,13 @@ static const struct pci_error_handlers nvme_err_handler = {
 static const struct pci_device_id nvme_id_table[] = {
 	{ PCI_VDEVICE(INTEL, 0x0953),
 		.driver_data = NVME_QUIRK_STRIPE_SIZE |
-				NVME_QUIRK_DISCARD_ZEROES, },
+				NVME_QUIRK_DEALLOCATE_ZEROES, },
 	{ PCI_VDEVICE(INTEL, 0x0a53),
 		.driver_data = NVME_QUIRK_STRIPE_SIZE |
-				NVME_QUIRK_DISCARD_ZEROES, },
+				NVME_QUIRK_DEALLOCATE_ZEROES, },
 	{ PCI_VDEVICE(INTEL, 0x0a54),
 		.driver_data = NVME_QUIRK_STRIPE_SIZE |
-				NVME_QUIRK_DISCARD_ZEROES, },
+				NVME_QUIRK_DEALLOCATE_ZEROES, },
 	{ PCI_VDEVICE(INTEL, 0x5845),	/* Qemu emulated controller */
 		.driver_data = NVME_QUIRK_IDENTIFY_CNS, },
 	{ PCI_DEVICE(0x1c58, 0x0003),	/* HGST adapter */
-- 
2.11.0

Re: [PATCH 15/25] nvme: implement REQ_OP_WRITE_ZEROES

[Martin K. Petersen]

Christoph Hellwig <hch@lst.de> writes:

> But now for the real NVMe Write Zeroes yet, just to get rid of the
> discard abuse for zeroing.  Also rename the quirk flag to be a bit
> more self-explanatory.

Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>

-- 
Martin K. Petersen	Oracle Linux Engineering

[PATCH 16/25] zram: implement REQ_OP_WRITE_ZEROES

[Christoph Hellwig]

Just the same as discard if the block size equals the system page size.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 drivers/block/zram/zram_drv.c | 13 ++++++++-----
 1 file changed, 8 insertions(+), 5 deletions(-)

diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
index dceb5edd1e54..1710b06f04a7 100644
--- a/drivers/block/zram/zram_drv.c
+++ b/drivers/block/zram/zram_drv.c
@@ -829,10 +829,14 @@ static void __zram_make_request(struct zram *zram, struct bio *bio)
 	offset = (bio->bi_iter.bi_sector &
 		  (SECTORS_PER_PAGE - 1)) << SECTOR_SHIFT;
 
-	if (unlikely(bio_op(bio) == REQ_OP_DISCARD)) {
+	switch (bio_op(bio)) {
+	case REQ_OP_DISCARD:
+	case REQ_OP_WRITE_ZEROES:
 		zram_bio_discard(zram, index, offset, bio);
 		bio_endio(bio);
 		return;
+	default:
+		break;
 	}
 
 	bio_for_each_segment(bvec, bio, iter) {
@@ -1192,6 +1196,8 @@ static int zram_add(void)
 	zram->disk->queue->limits.max_sectors = SECTORS_PER_PAGE;
 	zram->disk->queue->limits.chunk_sectors = 0;
 	blk_queue_max_discard_sectors(zram->disk->queue, UINT_MAX);
+	queue_flag_set_unlocked(QUEUE_FLAG_DISCARD, zram->disk->queue);
+
 	/*
 	 * zram_bio_discard() will clear all logical blocks if logical block
 	 * size is identical with physical block size(PAGE_SIZE). But if it is
@@ -1201,10 +1207,7 @@ static int zram_add(void)
 	 * zeroed.
 	 */
 	if (ZRAM_LOGICAL_BLOCK_SIZE == PAGE_SIZE)
-		zram->disk->queue->limits.discard_zeroes_data = 1;
-	else
-		zram->disk->queue->limits.discard_zeroes_data = 0;
-	queue_flag_set_unlocked(QUEUE_FLAG_DISCARD, zram->disk->queue);
+		blk_queue_max_write_zeroes_sectors(zram->disk->queue, UINT_MAX);
 
 	add_disk(zram->disk);
 
-- 
2.11.0

[PATCH 17/25] loop: implement REQ_OP_WRITE_ZEROES

[Christoph Hellwig]

It's identical to discard as hole punches will always leave us with
zeroes on reads.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 drivers/block/loop.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/block/loop.c b/drivers/block/loop.c
index 0ecb6461ed81..265cd2e33ff0 100644
--- a/drivers/block/loop.c
+++ b/drivers/block/loop.c
@@ -528,6 +528,7 @@ static int do_req_filebacked(struct loop_device *lo, struct request *rq)
 	case REQ_OP_FLUSH:
 		return lo_req_flush(lo, rq);
 	case REQ_OP_DISCARD:
+	case REQ_OP_WRITE_ZEROES:
 		return lo_discard(lo, rq, pos);
 	case REQ_OP_WRITE:
 		if (lo->transfer)
@@ -826,6 +827,7 @@ static void loop_config_discard(struct loop_device *lo)
 		q->limits.discard_granularity = 0;
 		q->limits.discard_alignment = 0;
 		blk_queue_max_discard_sectors(q, 0);
+		blk_queue_max_write_zeroes_sectors(q, 0);
 		q->limits.discard_zeroes_data = 0;
 		queue_flag_clear_unlocked(QUEUE_FLAG_DISCARD, q);
 		return;
@@ -834,6 +836,7 @@ static void loop_config_discard(struct loop_device *lo)
 	q->limits.discard_granularity = inode->i_sb->s_blocksize;
 	q->limits.discard_alignment = 0;
 	blk_queue_max_discard_sectors(q, UINT_MAX >> 9);
+	blk_queue_max_write_zeroes_sectors(q, UINT_MAX >> 9);
 	q->limits.discard_zeroes_data = 1;
 	queue_flag_set_unlocked(QUEUE_FLAG_DISCARD, q);
 }
@@ -1660,6 +1663,7 @@ static int loop_queue_rq(struct blk_mq_hw_ctx *hctx,
 	switch (req_op(cmd->rq)) {
 	case REQ_OP_FLUSH:
 	case REQ_OP_DISCARD:
+	case REQ_OP_WRITE_ZEROES:
 		cmd->use_aio = false;
 		break;
 	default:
-- 
2.11.0

[PATCH 18/25] brd: remove discard support

[Christoph Hellwig]

It's just a in-driver reimplementation of writing zeroes to the pages,
which fails if the discards aren't page aligned.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 drivers/block/brd.c | 54 -----------------------------------------------------
 1 file changed, 54 deletions(-)

diff --git a/drivers/block/brd.c b/drivers/block/brd.c
index 3adc32a3153b..4ec84d504780 100644
--- a/drivers/block/brd.c
+++ b/drivers/block/brd.c
@@ -134,28 +134,6 @@ static struct page *brd_insert_page(struct brd_device *brd, sector_t sector)
 	return page;
 }
 
-static void brd_free_page(struct brd_device *brd, sector_t sector)
-{
-	struct page *page;
-	pgoff_t idx;
-
-	spin_lock(&brd->brd_lock);
-	idx = sector >> PAGE_SECTORS_SHIFT;
-	page = radix_tree_delete(&brd->brd_pages, idx);
-	spin_unlock(&brd->brd_lock);
-	if (page)
-		__free_page(page);
-}
-
-static void brd_zero_page(struct brd_device *brd, sector_t sector)
-{
-	struct page *page;
-
-	page = brd_lookup_page(brd, sector);
-	if (page)
-		clear_highpage(page);
-}
-
 /*
  * Free all backing store pages and radix tree. This must only be called when
  * there are no other users of the device.
@@ -212,24 +190,6 @@ static int copy_to_brd_setup(struct brd_device *brd, sector_t sector, size_t n)
 	return 0;
 }
 
-static void discard_from_brd(struct brd_device *brd,
-			sector_t sector, size_t n)
-{
-	while (n >= PAGE_SIZE) {
-		/*
-		 * Don't want to actually discard pages here because
-		 * re-allocating the pages can result in writeback
-		 * deadlocks under heavy load.
-		 */
-		if (0)
-			brd_free_page(brd, sector);
-		else
-			brd_zero_page(brd, sector);
-		sector += PAGE_SIZE >> SECTOR_SHIFT;
-		n -= PAGE_SIZE;
-	}
-}
-
 /*
  * Copy n bytes from src to the brd starting at sector. Does not sleep.
  */
@@ -338,14 +298,6 @@ static blk_qc_t brd_make_request(struct request_queue *q, struct bio *bio)
 	if (bio_end_sector(bio) > get_capacity(bdev->bd_disk))
 		goto io_error;
 
-	if (unlikely(bio_op(bio) == REQ_OP_DISCARD)) {
-		if (sector & ((PAGE_SIZE >> SECTOR_SHIFT) - 1) ||
-		    bio->bi_iter.bi_size & ~PAGE_MASK)
-			goto io_error;
-		discard_from_brd(brd, sector, bio->bi_iter.bi_size);
-		goto out;
-	}
-
 	bio_for_each_segment(bvec, bio, iter) {
 		unsigned int len = bvec.bv_len;
 		int err;
@@ -357,7 +309,6 @@ static blk_qc_t brd_make_request(struct request_queue *q, struct bio *bio)
 		sector += len >> SECTOR_SHIFT;
 	}
 
-out:
 	bio_endio(bio);
 	return BLK_QC_T_NONE;
 io_error:
@@ -464,11 +415,6 @@ static struct brd_device *brd_alloc(int i)
 	 *  is harmless)
 	 */
 	blk_queue_physical_block_size(brd->brd_queue, PAGE_SIZE);
-
-	brd->brd_queue->limits.discard_granularity = PAGE_SIZE;
-	blk_queue_max_discard_sectors(brd->brd_queue, UINT_MAX);
-	brd->brd_queue->limits.discard_zeroes_data = 1;
-	queue_flag_set_unlocked(QUEUE_FLAG_DISCARD, brd->brd_queue);
 #ifdef CONFIG_BLK_DEV_RAM_DAX
 	queue_flag_set_unlocked(QUEUE_FLAG_DAX, brd->brd_queue);
 #endif
-- 
2.11.0

[PATCH 19/25] rbd: remove the discard_zeroes_data flag

[Christoph Hellwig]

rbd only supports discarding on large alignments, so the zeroing code
would always fall back to explicit writings of zeroes.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 drivers/block/rbd.c | 1 -
 1 file changed, 1 deletion(-)

diff --git a/drivers/block/rbd.c b/drivers/block/rbd.c
index 517838b65964..0ec3b430e81d 100644
--- a/drivers/block/rbd.c
+++ b/drivers/block/rbd.c
@@ -4380,7 +4380,6 @@ static int rbd_init_disk(struct rbd_device *rbd_dev)
 	q->limits.discard_granularity = segment_size;
 	q->limits.discard_alignment = segment_size;
 	blk_queue_max_discard_sectors(q, segment_size / SECTOR_SIZE);
-	q->limits.discard_zeroes_data = 1;
 
 	if (!ceph_test_opt(rbd_dev->rbd_client->client, NOCRC))
 		q->backing_dev_info->capabilities |= BDI_CAP_STABLE_WRITES;
-- 
2.11.0

[PATCH 20/25] rsxx: remove the discard_zeroes_data flag

[Christoph Hellwig]

rsxx only supports discarding on large alignments, so the zeroing code
would always fall back to explicit writings of zeroes.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 drivers/block/rsxx/dev.c | 1 -
 1 file changed, 1 deletion(-)

diff --git a/drivers/block/rsxx/dev.c b/drivers/block/rsxx/dev.c
index f81d70b39d10..9c566364ac9c 100644
--- a/drivers/block/rsxx/dev.c
+++ b/drivers/block/rsxx/dev.c
@@ -300,7 +300,6 @@ int rsxx_setup_dev(struct rsxx_cardinfo *card)
 						RSXX_HW_BLK_SIZE >> 9);
 		card->queue->limits.discard_granularity = RSXX_HW_BLK_SIZE;
 		card->queue->limits.discard_alignment   = RSXX_HW_BLK_SIZE;
-		card->queue->limits.discard_zeroes_data = 1;
 	}
 
 	card->queue->queuedata = card;
-- 
2.11.0

[PATCH 21/25] mmc: remove the discard_zeroes_data flag

[Christoph Hellwig]

mmc only supports discarding on large alignments, so the zeroing code
would always fall back to explicit writings of zeroes.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 drivers/mmc/core/queue.c | 2 --
 1 file changed, 2 deletions(-)

diff --git a/drivers/mmc/core/queue.c b/drivers/mmc/core/queue.c
index 493eb10ce580..4c54ad34e17a 100644
--- a/drivers/mmc/core/queue.c
+++ b/drivers/mmc/core/queue.c
@@ -167,8 +167,6 @@ static void mmc_queue_setup_discard(struct request_queue *q,
 
 	queue_flag_set_unlocked(QUEUE_FLAG_DISCARD, q);
 	blk_queue_max_discard_sectors(q, max_discard);
-	if (card->erased_byte == 0 && !mmc_can_discard(card))
-		q->limits.discard_zeroes_data = 1;
 	q->limits.discard_granularity = card->pref_erase << 9;
 	/* granularity must not be greater than max. discard */
 	if (card->pref_erase > max_discard)
-- 
2.11.0

[PATCH 22/25] block: stop using discards for zeroing

[Christoph Hellwig]

Now that we have REQ_OP_WRITE_ZEROES implemented for all devices that
support efficient zeroing of devices we can remove the call to
blkdev_issue_discard.  This means we only have two ways of zeroing left
and can simply the code.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 block/blk-lib.c | 11 +++++------
 1 file changed, 5 insertions(+), 6 deletions(-)

diff --git a/block/blk-lib.c b/block/blk-lib.c
index 2f882e22890b..7c27211570fa 100644
--- a/block/blk-lib.c
+++ b/block/blk-lib.c
@@ -279,6 +279,11 @@ static int __blkdev_issue_write_zeroes(struct block_device *bdev,
  *  Zero-fill a block range, either using hardware offload or by explicitly
  *  writing zeroes to the device.
  *
+ *  Note that this function may fail with -EOPNOTSUPP if the driver supports
+ *  efficient zeroing operation, but the device capabilities can only be
+ *  discovered by trial and error.  In this case the caller should call the
+ *  function again, and it will use the fallback path.
+ *
  *  If a device is using logical block provisioning, the underlying space will
  *  not be released if %flags contains BLKDEV_ZERO_NOUNMAP.
  *
@@ -349,12 +354,6 @@ int blkdev_issue_zeroout(struct block_device *bdev, sector_t sector,
 	struct bio *bio = NULL;
 	struct blk_plug plug;
 
-	if (!(flags & BLKDEV_ZERO_NOUNMAP)) {
-		if (!blkdev_issue_discard(bdev, sector, nr_sects, gfp_mask,
-				BLKDEV_DISCARD_ZERO))
-			return 0;
-	}
-
 	blk_start_plug(&plug);
 	ret = __blkdev_issue_zeroout(bdev, sector, nr_sects, gfp_mask,
 			&bio, flags);
-- 
2.11.0

Re: [PATCH 22/25] block: stop using discards for zeroing

[Martin K. Petersen]

Christoph Hellwig <hch@lst.de> writes:

> Now that we have REQ_OP_WRITE_ZEROES implemented for all devices that
> support efficient zeroing of devices we can remove the call to

s/of devices/

> blkdev_issue_discard.  This means we only have two ways of zeroing
> left and can simply the code.

simplify

> + *  Note that this function may fail with -EOPNOTSUPP if the driver supports
> + *  efficient zeroing operation, but the device capabilities can only be
> + *  discovered by trial and error.  In this case the caller should call the
> + *  function again, and it will use the fallback path.

Maybe:

"Note that this function may fail with -EOPNOTSUPP if the driver signals
zeroing offload support but the device fails to process the command (for
some devices there is no non-destructive way to verify whether this
operation is actually supported). If -EOPNOTSUPP is returned, the caller
should retry the blkdev_issue_zeroout() and the fallback path will be
used."

Otherwise OK.

Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>

-- 
Martin K. Petersen	Oracle Linux Engineering

[PATCH 23/25] drbd: make intelligent use of blkdev_issue_zeroout

[Christoph Hellwig]

drbd always wants its discard wire operations to zero the blocks, so
use blkdev_issue_zeroout with the BLKDEV_ZERO_UNMAP flag instead of
reinventing it poorly.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 drivers/block/drbd/drbd_debugfs.c  |   3 --
 drivers/block/drbd/drbd_int.h      |   6 ---
 drivers/block/drbd/drbd_receiver.c | 102 ++-----------------------------------
 drivers/block/drbd/drbd_req.c      |   6 +--
 4 files changed, 7 insertions(+), 110 deletions(-)

diff --git a/drivers/block/drbd/drbd_debugfs.c b/drivers/block/drbd/drbd_debugfs.c
index de5c3ee8a790..494837e59f23 100644
--- a/drivers/block/drbd/drbd_debugfs.c
+++ b/drivers/block/drbd/drbd_debugfs.c
@@ -236,9 +236,6 @@ static void seq_print_peer_request_flags(struct seq_file *m, struct drbd_peer_re
 	seq_print_rq_state_bit(m, f & EE_CALL_AL_COMPLETE_IO, &sep, "in-AL");
 	seq_print_rq_state_bit(m, f & EE_SEND_WRITE_ACK, &sep, "C");
 	seq_print_rq_state_bit(m, f & EE_MAY_SET_IN_SYNC, &sep, "set-in-sync");
-
-	if (f & EE_IS_TRIM)
-		__seq_print_rq_state_bit(m, f & EE_IS_TRIM_USE_ZEROOUT, &sep, "zero-out", "trim");
 	seq_print_rq_state_bit(m, f & EE_WRITE_SAME, &sep, "write-same");
 	seq_putc(m, '\n');
 }
diff --git a/drivers/block/drbd/drbd_int.h b/drivers/block/drbd/drbd_int.h
index 724d1c50fc52..d5da45bb03a6 100644
--- a/drivers/block/drbd/drbd_int.h
+++ b/drivers/block/drbd/drbd_int.h
@@ -437,9 +437,6 @@ enum {
 
 	/* is this a TRIM aka REQ_DISCARD? */
 	__EE_IS_TRIM,
-	/* our lower level cannot handle trim,
-	 * and we want to fall back to zeroout instead */
-	__EE_IS_TRIM_USE_ZEROOUT,
 
 	/* In case a barrier failed,
 	 * we need to resubmit without the barrier flag. */
@@ -482,7 +479,6 @@ enum {
 #define EE_CALL_AL_COMPLETE_IO (1<<__EE_CALL_AL_COMPLETE_IO)
 #define EE_MAY_SET_IN_SYNC     (1<<__EE_MAY_SET_IN_SYNC)
 #define EE_IS_TRIM             (1<<__EE_IS_TRIM)
-#define EE_IS_TRIM_USE_ZEROOUT (1<<__EE_IS_TRIM_USE_ZEROOUT)
 #define EE_RESUBMITTED         (1<<__EE_RESUBMITTED)
 #define EE_WAS_ERROR           (1<<__EE_WAS_ERROR)
 #define EE_HAS_DIGEST          (1<<__EE_HAS_DIGEST)
@@ -1561,8 +1557,6 @@ extern void start_resync_timer_fn(unsigned long data);
 extern void drbd_endio_write_sec_final(struct drbd_peer_request *peer_req);
 
 /* drbd_receiver.c */
-extern int drbd_issue_discard_or_zero_out(struct drbd_device *device,
-		sector_t start, unsigned int nr_sectors, bool discard);
 extern int drbd_receiver(struct drbd_thread *thi);
 extern int drbd_ack_receiver(struct drbd_thread *thi);
 extern void drbd_send_ping_wf(struct work_struct *ws);
diff --git a/drivers/block/drbd/drbd_receiver.c b/drivers/block/drbd/drbd_receiver.c
index dc9a6dcd431c..bc1d296581f9 100644
--- a/drivers/block/drbd/drbd_receiver.c
+++ b/drivers/block/drbd/drbd_receiver.c
@@ -1448,108 +1448,14 @@ void drbd_bump_write_ordering(struct drbd_resource *resource, struct drbd_backin
 		drbd_info(resource, "Method to ensure write ordering: %s\n", write_ordering_str[resource->write_ordering]);
 }
 
-/*
- * We *may* ignore the discard-zeroes-data setting, if so configured.
- *
- * Assumption is that it "discard_zeroes_data=0" is only because the backend
- * may ignore partial unaligned discards.
- *
- * LVM/DM thin as of at least
- *   LVM version:     2.02.115(2)-RHEL7 (2015-01-28)
- *   Library version: 1.02.93-RHEL7 (2015-01-28)
- *   Driver version:  4.29.0
- * still behaves this way.
- *
- * For unaligned (wrt. alignment and granularity) or too small discards,
- * we zero-out the initial (and/or) trailing unaligned partial chunks,
- * but discard all the aligned full chunks.
- *
- * At least for LVM/DM thin, the result is effectively "discard_zeroes_data=1".
- */
-int drbd_issue_discard_or_zero_out(struct drbd_device *device, sector_t start, unsigned int nr_sectors, bool discard)
-{
-	struct block_device *bdev = device->ldev->backing_bdev;
-	struct request_queue *q = bdev_get_queue(bdev);
-	sector_t tmp, nr;
-	unsigned int max_discard_sectors, granularity;
-	int alignment;
-	int err = 0;
-
-	if (!discard)
-		goto zero_out;
-
-	/* Zero-sector (unknown) and one-sector granularities are the same.  */
-	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 -= max_discard_sectors % granularity;
-	if (unlikely(!max_discard_sectors))
-		goto zero_out;
-
-	if (nr_sectors < granularity)
-		goto zero_out;
-
-	tmp = start;
-	if (sector_div(tmp, granularity) != alignment) {
-		if (nr_sectors < 2*granularity)
-			goto zero_out;
-		/* start + gran - (start + gran - align) % gran */
-		tmp = start + granularity - alignment;
-		tmp = start + granularity - sector_div(tmp, granularity);
-
-		nr = tmp - start;
-		err |= blkdev_issue_zeroout(bdev, start, nr, GFP_NOIO,
-				BLKDEV_ZERO_NOUNMAP);
-		nr_sectors -= nr;
-		start = tmp;
-	}
-	while (nr_sectors >= granularity) {
-		nr = min_t(sector_t, nr_sectors, max_discard_sectors);
-		err |= blkdev_issue_discard(bdev, start, nr, GFP_NOIO,
-				BLKDEV_ZERO_NOUNMAP);
-		nr_sectors -= nr;
-		start += nr;
-	}
- zero_out:
-	if (nr_sectors) {
-		err |= blkdev_issue_zeroout(bdev, start, nr_sectors, GFP_NOIO,
-				BLKDEV_ZERO_NOUNMAP);
-	}
-	return err != 0;
-}
-
-static bool can_do_reliable_discards(struct drbd_device *device)
-{
-	struct request_queue *q = bdev_get_queue(device->ldev->backing_bdev);
-	struct disk_conf *dc;
-	bool can_do;
-
-	if (!blk_queue_discard(q))
-		return false;
-
-	if (q->limits.discard_zeroes_data)
-		return true;
-
-	rcu_read_lock();
-	dc = rcu_dereference(device->ldev->disk_conf);
-	can_do = dc->discard_zeroes_if_aligned;
-	rcu_read_unlock();
-	return can_do;
-}
-
 static void drbd_issue_peer_discard(struct drbd_device *device, struct drbd_peer_request *peer_req)
 {
-	/* If the backend cannot discard, or does not guarantee
-	 * read-back zeroes in discarded ranges, we fall back to
-	 * zero-out.  Unless configuration specifically requested
-	 * otherwise. */
-	if (!can_do_reliable_discards(device))
-		peer_req->flags |= EE_IS_TRIM_USE_ZEROOUT;
+	struct block_device *bdev = device->ldev->backing_bdev;
 
-	if (drbd_issue_discard_or_zero_out(device, peer_req->i.sector,
-	    peer_req->i.size >> 9, !(peer_req->flags & EE_IS_TRIM_USE_ZEROOUT)))
+	if (blkdev_issue_zeroout(bdev, peer_req->i.sector, peer_req->i.size >> 9,
+			GFP_NOIO, 0))
 		peer_req->flags |= EE_WAS_ERROR;
+
 	drbd_endio_write_sec_final(peer_req);
 }
 
diff --git a/drivers/block/drbd/drbd_req.c b/drivers/block/drbd/drbd_req.c
index 652114ae1a8a..6da9ea8c48b6 100644
--- a/drivers/block/drbd/drbd_req.c
+++ b/drivers/block/drbd/drbd_req.c
@@ -1148,10 +1148,10 @@ static int drbd_process_write_request(struct drbd_request *req)
 
 static void drbd_process_discard_req(struct drbd_request *req)
 {
-	int err = drbd_issue_discard_or_zero_out(req->device,
-				req->i.sector, req->i.size >> 9, true);
+	struct block_device *bdev = req->device->ldev->backing_bdev;
 
-	if (err)
+	if (blkdev_issue_zeroout(bdev, req->i.sector, req->i.size >> 9,
+			GFP_NOIO, 0))
 		req->private_bio->bi_error = -EIO;
 	bio_endio(req->private_bio);
 }
-- 
2.11.0

[PATCH 24/25] drbd: implement REQ_OP_WRITE_ZEROES

[Christoph Hellwig]

It seems like DRBD assumes its on the wire TRIM request always zeroes data.
Use that fact to implement REQ_OP_WRITE_ZEROES.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 drivers/block/drbd/drbd_main.c     | 3 ++-
 drivers/block/drbd/drbd_nl.c       | 2 ++
 drivers/block/drbd/drbd_receiver.c | 6 +++---
 drivers/block/drbd/drbd_req.c      | 7 +++++--
 drivers/block/drbd/drbd_worker.c   | 4 +++-
 5 files changed, 15 insertions(+), 7 deletions(-)

diff --git a/drivers/block/drbd/drbd_main.c b/drivers/block/drbd/drbd_main.c
index 92c60cbd04ee..8e62d9f65510 100644
--- a/drivers/block/drbd/drbd_main.c
+++ b/drivers/block/drbd/drbd_main.c
@@ -1668,7 +1668,8 @@ static u32 bio_flags_to_wire(struct drbd_connection *connection,
 			(bio->bi_opf & REQ_FUA ? DP_FUA : 0) |
 			(bio->bi_opf & REQ_PREFLUSH ? DP_FLUSH : 0) |
 			(bio_op(bio) == REQ_OP_WRITE_SAME ? DP_WSAME : 0) |
-			(bio_op(bio) == REQ_OP_DISCARD ? DP_DISCARD : 0);
+			(bio_op(bio) == REQ_OP_DISCARD ? DP_DISCARD : 0) |
+			(bio_op(bio) == REQ_OP_WRITE_ZEROES ? DP_DISCARD : 0);
 	else
 		return bio->bi_opf & REQ_SYNC ? DP_RW_SYNC : 0;
 }
diff --git a/drivers/block/drbd/drbd_nl.c b/drivers/block/drbd/drbd_nl.c
index 908c704e20aa..e4516d3b971d 100644
--- a/drivers/block/drbd/drbd_nl.c
+++ b/drivers/block/drbd/drbd_nl.c
@@ -1217,10 +1217,12 @@ static void decide_on_discard_support(struct drbd_device *device,
 		blk_queue_discard_granularity(q, 512);
 		q->limits.max_discard_sectors = drbd_max_discard_sectors(connection);
 		queue_flag_set_unlocked(QUEUE_FLAG_DISCARD, q);
+		q->limits.max_write_zeroes_sectors = drbd_max_discard_sectors(connection);
 	} else {
 		queue_flag_clear_unlocked(QUEUE_FLAG_DISCARD, q);
 		blk_queue_discard_granularity(q, 0);
 		q->limits.max_discard_sectors = 0;
+		q->limits.max_write_zeroes_sectors = 0;
 	}
 }
 
diff --git a/drivers/block/drbd/drbd_receiver.c b/drivers/block/drbd/drbd_receiver.c
index bc1d296581f9..1b0a2be24f39 100644
--- a/drivers/block/drbd/drbd_receiver.c
+++ b/drivers/block/drbd/drbd_receiver.c
@@ -2285,7 +2285,7 @@ static unsigned long wire_flags_to_bio_flags(u32 dpf)
 static unsigned long wire_flags_to_bio_op(u32 dpf)
 {
 	if (dpf & DP_DISCARD)
-		return REQ_OP_DISCARD;
+		return REQ_OP_WRITE_ZEROES;
 	else
 		return REQ_OP_WRITE;
 }
@@ -2476,7 +2476,7 @@ static int receive_Data(struct drbd_connection *connection, struct packet_info *
 	op_flags = wire_flags_to_bio_flags(dp_flags);
 	if (pi->cmd == P_TRIM) {
 		D_ASSERT(peer_device, peer_req->i.size > 0);
-		D_ASSERT(peer_device, op == REQ_OP_DISCARD);
+		D_ASSERT(peer_device, op == REQ_OP_WRITE_ZEROES);
 		D_ASSERT(peer_device, peer_req->pages == NULL);
 	} else if (peer_req->pages == NULL) {
 		D_ASSERT(device, peer_req->i.size == 0);
@@ -4789,7 +4789,7 @@ static int receive_rs_deallocated(struct drbd_connection *connection, struct pac
 
 	if (get_ldev(device)) {
 		struct drbd_peer_request *peer_req;
-		const int op = REQ_OP_DISCARD;
+		const int op = REQ_OP_WRITE_ZEROES;
 
 		peer_req = drbd_alloc_peer_req(peer_device, ID_SYNCER, sector,
 					       size, 0, GFP_NOIO);
diff --git a/drivers/block/drbd/drbd_req.c b/drivers/block/drbd/drbd_req.c
index 6da9ea8c48b6..b5730e17b455 100644
--- a/drivers/block/drbd/drbd_req.c
+++ b/drivers/block/drbd/drbd_req.c
@@ -59,6 +59,7 @@ static struct drbd_request *drbd_req_new(struct drbd_device *device, struct bio
 	drbd_req_make_private_bio(req, bio_src);
 	req->rq_state = (bio_data_dir(bio_src) == WRITE ? RQ_WRITE : 0)
 		      | (bio_op(bio_src) == REQ_OP_WRITE_SAME ? RQ_WSAME : 0)
+		      | (bio_op(bio_src) == REQ_OP_WRITE_ZEROES ? RQ_UNMAP : 0)
 		      | (bio_op(bio_src) == REQ_OP_DISCARD ? RQ_UNMAP : 0);
 	req->device = device;
 	req->master_bio = bio_src;
@@ -1180,7 +1181,8 @@ drbd_submit_req_private_bio(struct drbd_request *req)
 	if (get_ldev(device)) {
 		if (drbd_insert_fault(device, type))
 			bio_io_error(bio);
-		else if (bio_op(bio) == REQ_OP_DISCARD)
+		else if (bio_op(bio) == REQ_OP_WRITE_ZEROES ||
+			 bio_op(bio) == REQ_OP_DISCARD)
 			drbd_process_discard_req(req);
 		else
 			generic_make_request(bio);
@@ -1234,7 +1236,8 @@ drbd_request_prepare(struct drbd_device *device, struct bio *bio, unsigned long
 	_drbd_start_io_acct(device, req);
 
 	/* process discards always from our submitter thread */
-	if (bio_op(bio) & REQ_OP_DISCARD)
+	if ((bio_op(bio) & REQ_OP_WRITE_ZEROES) ||
+	    (bio_op(bio) & REQ_OP_DISCARD))
 		goto queue_for_submitter_thread;
 
 	if (rw == WRITE && req->private_bio && req->i.size
diff --git a/drivers/block/drbd/drbd_worker.c b/drivers/block/drbd/drbd_worker.c
index 3bff33f21435..1afcb4e02d8d 100644
--- a/drivers/block/drbd/drbd_worker.c
+++ b/drivers/block/drbd/drbd_worker.c
@@ -174,7 +174,8 @@ void drbd_peer_request_endio(struct bio *bio)
 	struct drbd_peer_request *peer_req = bio->bi_private;
 	struct drbd_device *device = peer_req->peer_device->device;
 	bool is_write = bio_data_dir(bio) == WRITE;
-	bool is_discard = !!(bio_op(bio) == REQ_OP_DISCARD);
+	bool is_discard = bio_op(bio) == REQ_OP_WRITE_ZEROES ||
+			  bio_op(bio) == REQ_OP_DISCARD;
 
 	if (bio->bi_error && __ratelimit(&drbd_ratelimit_state))
 		drbd_warn(device, "%s: error=%d s=%llus\n",
@@ -249,6 +250,7 @@ void drbd_request_endio(struct bio *bio)
 	/* to avoid recursion in __req_mod */
 	if (unlikely(bio->bi_error)) {
 		switch (bio_op(bio)) {
+		case REQ_OP_WRITE_ZEROES:
 		case REQ_OP_DISCARD:
 			if (bio->bi_error == -EOPNOTSUPP)
 				what = DISCARD_COMPLETED_NOTSUPP;
-- 
2.11.0

[PATCH 25/25] block: remove the discard_zeroes_data flag

[Christoph Hellwig]

Now that we use the proper REQ_OP_WRITE_ZEROES operation everywhere we can
kill this hack.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 Documentation/ABI/testing/sysfs-block | 10 ++-----
 Documentation/block/queue-sysfs.txt   |  5 ----
 block/blk-lib.c                       |  7 +----
 block/blk-settings.c                  |  3 ---
 block/blk-sysfs.c                     |  2 +-
 block/compat_ioctl.c                  |  2 +-
 block/ioctl.c                         |  2 +-
 drivers/block/drbd/drbd_main.c        |  2 --
 drivers/block/drbd/drbd_nl.c          |  7 +----
 drivers/block/loop.c                  |  2 --
 drivers/block/mtip32xx/mtip32xx.c     |  1 -
 drivers/block/nbd.c                   |  1 -
 drivers/md/dm-cache-target.c          |  1 -
 drivers/md/dm-crypt.c                 |  1 -
 drivers/md/dm-raid.c                  |  6 ++---
 drivers/md/dm-raid1.c                 |  1 -
 drivers/md/dm-table.c                 | 19 -------------
 drivers/md/dm-thin.c                  |  2 --
 drivers/md/raid5.c                    | 50 +++++++++++------------------------
 drivers/scsi/sd.c                     |  5 ----
 drivers/target/target_core_device.c   |  2 +-
 include/linux/blkdev.h                | 15 -----------
 include/linux/device-mapper.h         |  5 ----
 23 files changed, 27 insertions(+), 124 deletions(-)

diff --git a/Documentation/ABI/testing/sysfs-block b/Documentation/ABI/testing/sysfs-block
index 2da04ce6aeef..dea212db9df3 100644
--- a/Documentation/ABI/testing/sysfs-block
+++ b/Documentation/ABI/testing/sysfs-block
@@ -213,14 +213,8 @@ What:		/sys/block/<disk>/queue/discard_zeroes_data
 Date:		May 2011
 Contact:	Martin K. Petersen <martin.petersen@oracle.com>
 Description:
-		Devices that support discard functionality may return
-		stale or random data when a previously discarded block
-		is read back. This can cause problems if the filesystem
-		expects discarded blocks to be explicitly cleared. If a
-		device reports that it deterministically returns zeroes
-		when a discarded area is read the discard_zeroes_data
-		parameter will be set to one. Otherwise it will be 0 and
-		the result of reading a discarded area is undefined.
+		Will always return 0.  Don't rely on any specific behavior
+		for discards, and don't read this file.
 
 What:		/sys/block/<disk>/queue/write_same_max_bytes
 Date:		January 2012
diff --git a/Documentation/block/queue-sysfs.txt b/Documentation/block/queue-sysfs.txt
index b7f6bdc96d73..2c1e67058fd3 100644
--- a/Documentation/block/queue-sysfs.txt
+++ b/Documentation/block/queue-sysfs.txt
@@ -43,11 +43,6 @@ large discards are issued, setting this value lower will make Linux issue
 smaller discards and potentially help reduce latencies induced by large
 discard operations.
 
-discard_zeroes_data (RO)
-------------------------
-When read, this file will show if the discarded block are zeroed by the
-device or not. If its value is '1' the blocks are zeroed otherwise not.
-
 hw_sector_size (RO)
 -------------------
 This is the hardware sector size of the device, in bytes.
diff --git a/block/blk-lib.c b/block/blk-lib.c
index 7c27211570fa..268bc9e054c0 100644
--- a/block/blk-lib.c
+++ b/block/blk-lib.c
@@ -37,17 +37,12 @@ int __blkdev_issue_discard(struct block_device *bdev, sector_t sector,
 		return -ENXIO;
 
 	if (flags & BLKDEV_DISCARD_SECURE) {
-		if (flags & BLKDEV_DISCARD_ZERO)
-			return -EOPNOTSUPP;
 		if (!blk_queue_secure_erase(q))
 			return -EOPNOTSUPP;
 		op = REQ_OP_SECURE_ERASE;
 	} else {
 		if (!blk_queue_discard(q))
 			return -EOPNOTSUPP;
-		if ((flags & BLKDEV_DISCARD_ZERO) &&
-		    !q->limits.discard_zeroes_data)
-			return -EOPNOTSUPP;
 		op = REQ_OP_DISCARD;
 	}
 
@@ -126,7 +121,7 @@ int blkdev_issue_discard(struct block_device *bdev, sector_t sector,
 			&bio);
 	if (!ret && bio) {
 		ret = submit_bio_wait(bio);
-		if (ret == -EOPNOTSUPP && !(flags & BLKDEV_DISCARD_ZERO))
+		if (ret == -EOPNOTSUPP)
 			ret = 0;
 		bio_put(bio);
 	}
diff --git a/block/blk-settings.c b/block/blk-settings.c
index 1e7174ffc9d4..4fa81ed383ca 100644
--- a/block/blk-settings.c
+++ b/block/blk-settings.c
@@ -103,7 +103,6 @@ void blk_set_default_limits(struct queue_limits *lim)
 	lim->discard_granularity = 0;
 	lim->discard_alignment = 0;
 	lim->discard_misaligned = 0;
-	lim->discard_zeroes_data = 0;
 	lim->logical_block_size = lim->physical_block_size = lim->io_min = 512;
 	lim->bounce_pfn = (unsigned long)(BLK_BOUNCE_ANY >> PAGE_SHIFT);
 	lim->alignment_offset = 0;
@@ -127,7 +126,6 @@ void blk_set_stacking_limits(struct queue_limits *lim)
 	blk_set_default_limits(lim);
 
 	/* Inherit limits from component devices */
-	lim->discard_zeroes_data = 1;
 	lim->max_segments = USHRT_MAX;
 	lim->max_discard_segments = 1;
 	lim->max_hw_sectors = UINT_MAX;
@@ -609,7 +607,6 @@ int blk_stack_limits(struct queue_limits *t, struct queue_limits *b,
 	t->io_opt = lcm_not_zero(t->io_opt, b->io_opt);
 
 	t->cluster &= b->cluster;
-	t->discard_zeroes_data &= b->discard_zeroes_data;
 
 	/* Physical block size a multiple of the logical block size? */
 	if (t->physical_block_size & (t->logical_block_size - 1)) {
diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c
index 45854266e398..b65ce3c65ae8 100644
--- a/block/blk-sysfs.c
+++ b/block/blk-sysfs.c
@@ -208,7 +208,7 @@ static ssize_t queue_discard_max_store(struct request_queue *q,
 
 static ssize_t queue_discard_zeroes_data_show(struct request_queue *q, char *page)
 {
-	return queue_var_show(queue_discard_zeroes_data(q), page);
+	return queue_var_show(0, page);
 }
 
 static ssize_t queue_write_same_max_show(struct request_queue *q, char *page)
diff --git a/block/compat_ioctl.c b/block/compat_ioctl.c
index 570021a0dc1c..04325b81c2b4 100644
--- a/block/compat_ioctl.c
+++ b/block/compat_ioctl.c
@@ -685,7 +685,7 @@ long compat_blkdev_ioctl(struct file *file, unsigned cmd, unsigned long arg)
 	case BLKALIGNOFF:
 		return compat_put_int(arg, bdev_alignment_offset(bdev));
 	case BLKDISCARDZEROES:
-		return compat_put_uint(arg, bdev_discard_zeroes_data(bdev));
+		return compat_put_uint(arg, 0);
 	case BLKFLSBUF:
 	case BLKROSET:
 	case BLKDISCARD:
diff --git a/block/ioctl.c b/block/ioctl.c
index 8ea00a41be01..0de02ee67eed 100644
--- a/block/ioctl.c
+++ b/block/ioctl.c
@@ -547,7 +547,7 @@ int blkdev_ioctl(struct block_device *bdev, fmode_t mode, unsigned cmd,
 	case BLKALIGNOFF:
 		return put_int(arg, bdev_alignment_offset(bdev));
 	case BLKDISCARDZEROES:
-		return put_uint(arg, bdev_discard_zeroes_data(bdev));
+		return put_uint(arg, 0);
 	case BLKSECTGET:
 		max_sectors = min_t(unsigned int, USHRT_MAX,
 				    queue_max_sectors(bdev_get_queue(bdev)));
diff --git a/drivers/block/drbd/drbd_main.c b/drivers/block/drbd/drbd_main.c
index 8e62d9f65510..84455c365f57 100644
--- a/drivers/block/drbd/drbd_main.c
+++ b/drivers/block/drbd/drbd_main.c
@@ -931,7 +931,6 @@ void assign_p_sizes_qlim(struct drbd_device *device, struct p_sizes *p, struct r
 		p->qlim->io_min = cpu_to_be32(queue_io_min(q));
 		p->qlim->io_opt = cpu_to_be32(queue_io_opt(q));
 		p->qlim->discard_enabled = blk_queue_discard(q);
-		p->qlim->discard_zeroes_data = queue_discard_zeroes_data(q);
 		p->qlim->write_same_capable = !!q->limits.max_write_same_sectors;
 	} else {
 		q = device->rq_queue;
@@ -941,7 +940,6 @@ void assign_p_sizes_qlim(struct drbd_device *device, struct p_sizes *p, struct r
 		p->qlim->io_min = cpu_to_be32(queue_io_min(q));
 		p->qlim->io_opt = cpu_to_be32(queue_io_opt(q));
 		p->qlim->discard_enabled = 0;
-		p->qlim->discard_zeroes_data = 0;
 		p->qlim->write_same_capable = 0;
 	}
 }
diff --git a/drivers/block/drbd/drbd_nl.c b/drivers/block/drbd/drbd_nl.c
index e4516d3b971d..02255a0d68b9 100644
--- a/drivers/block/drbd/drbd_nl.c
+++ b/drivers/block/drbd/drbd_nl.c
@@ -1199,10 +1199,6 @@ static void decide_on_discard_support(struct drbd_device *device,
 	struct drbd_connection *connection = first_peer_device(device)->connection;
 	bool can_do = b ? blk_queue_discard(b) : true;
 
-	if (can_do && b && !b->limits.discard_zeroes_data && !discard_zeroes_if_aligned) {
-		can_do = false;
-		drbd_info(device, "discard_zeroes_data=0 and discard_zeroes_if_aligned=no: disabling discards\n");
-	}
 	if (can_do && connection->cstate >= C_CONNECTED && !(connection->agreed_features & DRBD_FF_TRIM)) {
 		can_do = false;
 		drbd_info(connection, "peer DRBD too old, does not support TRIM: disabling discards\n");
@@ -1484,8 +1480,7 @@ static void sanitize_disk_conf(struct drbd_device *device, struct disk_conf *dis
 	if (disk_conf->al_extents > drbd_al_extents_max(nbc))
 		disk_conf->al_extents = drbd_al_extents_max(nbc);
 
-	if (!blk_queue_discard(q)
-	    || (!q->limits.discard_zeroes_data && !disk_conf->discard_zeroes_if_aligned)) {
+	if (!blk_queue_discard(q)) {
 		if (disk_conf->rs_discard_granularity) {
 			disk_conf->rs_discard_granularity = 0; /* disable feature */
 			drbd_info(device, "rs_discard_granularity feature disabled\n");
diff --git a/drivers/block/loop.c b/drivers/block/loop.c
index 265cd2e33ff0..57f68f4ee886 100644
--- a/drivers/block/loop.c
+++ b/drivers/block/loop.c
@@ -828,7 +828,6 @@ static void loop_config_discard(struct loop_device *lo)
 		q->limits.discard_alignment = 0;
 		blk_queue_max_discard_sectors(q, 0);
 		blk_queue_max_write_zeroes_sectors(q, 0);
-		q->limits.discard_zeroes_data = 0;
 		queue_flag_clear_unlocked(QUEUE_FLAG_DISCARD, q);
 		return;
 	}
@@ -837,7 +836,6 @@ static void loop_config_discard(struct loop_device *lo)
 	q->limits.discard_alignment = 0;
 	blk_queue_max_discard_sectors(q, UINT_MAX >> 9);
 	blk_queue_max_write_zeroes_sectors(q, UINT_MAX >> 9);
-	q->limits.discard_zeroes_data = 1;
 	queue_flag_set_unlocked(QUEUE_FLAG_DISCARD, q);
 }
 
diff --git a/drivers/block/mtip32xx/mtip32xx.c b/drivers/block/mtip32xx/mtip32xx.c
index c96c35ab39df..0aaf8077bd19 100644
--- a/drivers/block/mtip32xx/mtip32xx.c
+++ b/drivers/block/mtip32xx/mtip32xx.c
@@ -4025,7 +4025,6 @@ static int mtip_block_initialize(struct driver_data *dd)
 		dd->queue->limits.discard_granularity = 4096;
 		blk_queue_max_discard_sectors(dd->queue,
 			MTIP_MAX_TRIM_ENTRY_LEN * MTIP_MAX_TRIM_ENTRIES);
-		dd->queue->limits.discard_zeroes_data = 0;
 	}
 
 	/* Set the capacity of the device in 512 byte sectors. */
diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c
index 7e4287bc19e5..616e5c6d3ebd 100644
--- a/drivers/block/nbd.c
+++ b/drivers/block/nbd.c
@@ -1040,7 +1040,6 @@ static int nbd_dev_add(int index)
 	queue_flag_clear_unlocked(QUEUE_FLAG_ADD_RANDOM, disk->queue);
 	disk->queue->limits.discard_granularity = 512;
 	blk_queue_max_discard_sectors(disk->queue, UINT_MAX);
-	disk->queue->limits.discard_zeroes_data = 0;
 	blk_queue_max_hw_sectors(disk->queue, 65536);
 	disk->queue->limits.max_sectors = 256;
 
diff --git a/drivers/md/dm-cache-target.c b/drivers/md/dm-cache-target.c
index 9c689b34e6e7..975922c8f231 100644
--- a/drivers/md/dm-cache-target.c
+++ b/drivers/md/dm-cache-target.c
@@ -2773,7 +2773,6 @@ static int cache_create(struct cache_args *ca, struct cache **result)
 
 	ti->num_discard_bios = 1;
 	ti->discards_supported = true;
-	ti->discard_zeroes_data_unsupported = true;
 	ti->split_discard_bios = false;
 
 	cache->features = ca->features;
diff --git a/drivers/md/dm-crypt.c b/drivers/md/dm-crypt.c
index 389a3637ffcc..ef1d836bd81b 100644
--- a/drivers/md/dm-crypt.c
+++ b/drivers/md/dm-crypt.c
@@ -2030,7 +2030,6 @@ static int crypt_ctr(struct dm_target *ti, unsigned int argc, char **argv)
 	wake_up_process(cc->write_thread);
 
 	ti->num_flush_bios = 1;
-	ti->discard_zeroes_data_unsupported = true;
 
 	return 0;
 
diff --git a/drivers/md/dm-raid.c b/drivers/md/dm-raid.c
index f8564d63982f..468f1380de1d 100644
--- a/drivers/md/dm-raid.c
+++ b/drivers/md/dm-raid.c
@@ -2813,7 +2813,9 @@ static void configure_discard_support(struct raid_set *rs)
 	/* Assume discards not supported until after checks below. */
 	ti->discards_supported = false;
 
-	/* RAID level 4,5,6 require discard_zeroes_data for data integrity! */
+	/*
+	 * XXX: RAID level 4,5,6 require zeroing for safety.
+	 */
 	raid456 = (rs->md.level == 4 || rs->md.level == 5 || rs->md.level == 6);
 
 	for (i = 0; i < rs->raid_disks; i++) {
@@ -2827,8 +2829,6 @@ static void configure_discard_support(struct raid_set *rs)
 			return;
 
 		if (raid456) {
-			if (!q->limits.discard_zeroes_data)
-				return;
 			if (!devices_handle_discard_safely) {
 				DMERR("raid456 discard support disabled due to discard_zeroes_data uncertainty.");
 				DMERR("Set dm-raid.devices_handle_discard_safely=Y to override.");
diff --git a/drivers/md/dm-raid1.c b/drivers/md/dm-raid1.c
index 2ddc2d20e62d..a95cbb80fb34 100644
--- a/drivers/md/dm-raid1.c
+++ b/drivers/md/dm-raid1.c
@@ -1124,7 +1124,6 @@ static int mirror_ctr(struct dm_target *ti, unsigned int argc, char **argv)
 	ti->num_flush_bios = 1;
 	ti->num_discard_bios = 1;
 	ti->per_io_data_size = sizeof(struct dm_raid1_bio_record);
-	ti->discard_zeroes_data_unsupported = true;
 
 	ms->kmirrord_wq = alloc_workqueue("kmirrord", WQ_MEM_RECLAIM, 0);
 	if (!ms->kmirrord_wq) {
diff --git a/drivers/md/dm-table.c b/drivers/md/dm-table.c
index 5cd665c91ead..958275aca008 100644
--- a/drivers/md/dm-table.c
+++ b/drivers/md/dm-table.c
@@ -1449,22 +1449,6 @@ static bool dm_table_supports_flush(struct dm_table *t, unsigned long flush)
 	return false;
 }
 
-static bool dm_table_discard_zeroes_data(struct dm_table *t)
-{
-	struct dm_target *ti;
-	unsigned i = 0;
-
-	/* Ensure that all targets supports discard_zeroes_data. */
-	while (i < dm_table_get_num_targets(t)) {
-		ti = dm_table_get_target(t, i++);
-
-		if (ti->discard_zeroes_data_unsupported)
-			return false;
-	}
-
-	return true;
-}
-
 static int device_is_nonrot(struct dm_target *ti, struct dm_dev *dev,
 			    sector_t start, sector_t len, void *data)
 {
@@ -1620,9 +1604,6 @@ void dm_table_set_restrictions(struct dm_table *t, struct request_queue *q,
 	}
 	blk_queue_write_cache(q, wc, fua);
 
-	if (!dm_table_discard_zeroes_data(t))
-		q->limits.discard_zeroes_data = 0;
-
 	/* Ensure that all underlying devices are non-rotational. */
 	if (dm_table_all_devices_attribute(t, device_is_nonrot))
 		queue_flag_set_unlocked(QUEUE_FLAG_NONROT, q);
diff --git a/drivers/md/dm-thin.c b/drivers/md/dm-thin.c
index 2b266a2b5035..a5f1916f621a 100644
--- a/drivers/md/dm-thin.c
+++ b/drivers/md/dm-thin.c
@@ -3263,7 +3263,6 @@ static int pool_ctr(struct dm_target *ti, unsigned argc, char **argv)
 	 * them down to the data device.  The thin device's discard
 	 * processing will cause mappings to be removed from the btree.
 	 */
-	ti->discard_zeroes_data_unsupported = true;
 	if (pf.discard_enabled && pf.discard_passdown) {
 		ti->num_discard_bios = 1;
 
@@ -4119,7 +4118,6 @@ static int thin_ctr(struct dm_target *ti, unsigned argc, char **argv)
 	ti->per_io_data_size = sizeof(struct dm_thin_endio_hook);
 
 	/* In case the pool supports discards, pass them on. */
-	ti->discard_zeroes_data_unsupported = true;
 	if (tc->pool->pf.discard_enabled) {
 		ti->discards_supported = true;
 		ti->num_discard_bios = 1;
diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index 8cf1f86dcd05..d6ae8d22d461 100644
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -7229,7 +7229,6 @@ static int raid5_run(struct mddev *mddev)
 
 	if (mddev->queue) {
 		int chunk_size;
-		bool discard_supported = true;
 		/* read-ahead size must cover two whole stripes, which
 		 * is 2 * (datadisks) * chunksize where 'n' is the
 		 * number of raid devices
@@ -7265,12 +7264,6 @@ static int raid5_run(struct mddev *mddev)
 		blk_queue_max_discard_sectors(mddev->queue,
 					      0xfffe * STRIPE_SECTORS);
 
-		/*
-		 * unaligned part of discard request will be ignored, so can't
-		 * guarantee discard_zeroes_data
-		 */
-		mddev->queue->limits.discard_zeroes_data = 0;
-
 		blk_queue_max_write_same_sectors(mddev->queue, 0);
 		blk_queue_max_write_zeroes_sectors(mddev->queue, 0);
 
@@ -7279,35 +7272,24 @@ static int raid5_run(struct mddev *mddev)
 					  rdev->data_offset << 9);
 			disk_stack_limits(mddev->gendisk, rdev->bdev,
 					  rdev->new_data_offset << 9);
-			/*
-			 * discard_zeroes_data is required, otherwise data
-			 * could be lost. Consider a scenario: discard a stripe
-			 * (the stripe could be inconsistent if
-			 * discard_zeroes_data is 0); write one disk of the
-			 * stripe (the stripe could be inconsistent again
-			 * depending on which disks are used to calculate
-			 * parity); the disk is broken; The stripe data of this
-			 * disk is lost.
-			 */
-			if (!blk_queue_discard(bdev_get_queue(rdev->bdev)) ||
-			    !bdev_get_queue(rdev->bdev)->
-						limits.discard_zeroes_data)
-				discard_supported = false;
-			/* Unfortunately, discard_zeroes_data is not currently
-			 * a guarantee - just a hint.  So we only allow DISCARD
-			 * if the sysadmin has confirmed that only safe devices
-			 * are in use by setting a module parameter.
-			 */
-			if (!devices_handle_discard_safely) {
-				if (discard_supported) {
-					pr_info("md/raid456: discard support disabled due to uncertainty.\n");
-					pr_info("Set raid456.devices_handle_discard_safely=Y to override.\n");
-				}
-				discard_supported = false;
-			}
 		}
 
-		if (discard_supported &&
+		/*
+		 * zeroing is required, otherwise data
+		 * could be lost. Consider a scenario: discard a stripe
+		 * (the stripe could be inconsistent if
+		 * discard_zeroes_data is 0); write one disk of the
+		 * stripe (the stripe could be inconsistent again
+		 * depending on which disks are used to calculate
+		 * parity); the disk is broken; The stripe data of this
+		 * disk is lost.
+		 *
+		 * We only allow DISCARD if the sysadmin has confirmed that
+		 * only safe devices are in use by setting a module parameter.
+		 * A better idea might be to turn DISCARD into WRITE_ZEROES
+		 * requests, as that is required to be safe.
+		 */
+		if (devices_handle_discard_safely &&
 		    mddev->queue->limits.max_discard_sectors >= (stripe >> 9) &&
 		    mddev->queue->limits.discard_granularity >= stripe)
 			queue_flag_set_unlocked(QUEUE_FLAG_DISCARD,
diff --git a/drivers/scsi/sd.c b/drivers/scsi/sd.c
index 001593ed0444..bcb0cb020fd2 100644
--- a/drivers/scsi/sd.c
+++ b/drivers/scsi/sd.c
@@ -644,8 +644,6 @@ static void sd_config_discard(struct scsi_disk *sdkp, unsigned int mode)
 	unsigned int logical_block_size = sdkp->device->sector_size;
 	unsigned int max_blocks = 0;
 
-	q->limits.discard_zeroes_data = 0;
-
 	/*
 	 * When LBPRZ is reported, discard alignment and granularity
 	 * must be fixed to the logical block size. Otherwise the block
@@ -681,19 +679,16 @@ static void sd_config_discard(struct scsi_disk *sdkp, unsigned int mode)
 	case SD_LBP_WS16:
 		max_blocks = min_not_zero(sdkp->max_ws_blocks,
 					  (u32)SD_MAX_WS16_BLOCKS);
-		q->limits.discard_zeroes_data = sdkp->lbprz;
 		break;
 
 	case SD_LBP_WS10:
 		max_blocks = min_not_zero(sdkp->max_ws_blocks,
 					  (u32)SD_MAX_WS10_BLOCKS);
-		q->limits.discard_zeroes_data = sdkp->lbprz;
 		break;
 
 	case SD_LBP_ZERO:
 		max_blocks = min_not_zero(sdkp->max_ws_blocks,
 					  (u32)SD_MAX_WS10_BLOCKS);
-		q->limits.discard_zeroes_data = 1;
 		break;
 	}
 
diff --git a/drivers/target/target_core_device.c b/drivers/target/target_core_device.c
index c754ae33bf7b..d2f089cfa9ae 100644
--- a/drivers/target/target_core_device.c
+++ b/drivers/target/target_core_device.c
@@ -851,7 +851,7 @@ bool target_configure_unmap_from_queue(struct se_dev_attrib *attrib,
 	attrib->unmap_granularity = q->limits.discard_granularity / block_size;
 	attrib->unmap_granularity_alignment = q->limits.discard_alignment /
 								block_size;
-	attrib->unmap_zeroes_data = q->limits.discard_zeroes_data;
+	attrib->unmap_zeroes_data = 0;
 	return true;
 }
 EXPORT_SYMBOL(target_configure_unmap_from_queue);
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index a5055d760661..d5d9dd72418a 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -339,7 +339,6 @@ struct queue_limits {
 	unsigned char		misaligned;
 	unsigned char		discard_misaligned;
 	unsigned char		cluster;
-	unsigned char		discard_zeroes_data;
 	unsigned char		raid_partial_stripes_expensive;
 	enum blk_zoned_model	zoned;
 };
@@ -1342,7 +1341,6 @@ extern int blkdev_issue_write_same(struct block_device *bdev, sector_t sector,
 		sector_t nr_sects, gfp_t gfp_mask, struct page *page);
 
 #define BLKDEV_DISCARD_SECURE	(1 << 0)	/* issue a secure erase */
-#define BLKDEV_DISCARD_ZERO	(1 << 1)	/* must reliably zero data */
 
 extern int blkdev_issue_discard(struct block_device *bdev, sector_t sector,
 		sector_t nr_sects, gfp_t gfp_mask, unsigned long flags);
@@ -1542,19 +1540,6 @@ static inline int bdev_discard_alignment(struct block_device *bdev)
 	return q->limits.discard_alignment;
 }
 
-static inline unsigned int queue_discard_zeroes_data(struct request_queue *q)
-{
-	if (q->limits.max_discard_sectors && q->limits.discard_zeroes_data == 1)
-		return 1;
-
-	return 0;
-}
-
-static inline unsigned int bdev_discard_zeroes_data(struct block_device *bdev)
-{
-	return queue_discard_zeroes_data(bdev_get_queue(bdev));
-}
-
 static inline unsigned int bdev_write_same(struct block_device *bdev)
 {
 	struct request_queue *q = bdev_get_queue(bdev);
diff --git a/include/linux/device-mapper.h b/include/linux/device-mapper.h
index 3829bee2302a..c7ea33e38fb9 100644
--- a/include/linux/device-mapper.h
+++ b/include/linux/device-mapper.h
@@ -296,11 +296,6 @@ struct dm_target {
 	 * on max_io_len boundary.
 	 */
 	bool split_discard_bios:1;
-
-	/*
-	 * Set if this target does not return zeroes on discarded blocks.
-	 */
-	bool discard_zeroes_data_unsupported:1;
 };
 
 /* Each target can link one of these into the table */
-- 
2.11.0

Re: [PATCH 25/25] block: remove the discard_zeroes_data flag

[Martin K. Petersen]

Christoph Hellwig <hch@lst.de> writes:

> Now that we use the proper REQ_OP_WRITE_ZEROES operation everywhere we
> can kill this hack.

Oh yeah!

Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>

-- 
Martin K. Petersen	Oracle Linux Engineering

Re: always use REQ_OP_WRITE_ZEROES for zeroing offload

[Hannes Reinecke]

On 03/31/2017 06:32 PM, Christoph Hellwig wrote:
> This series makes REQ_OP_WRITE_ZEROES the only zeroing offload
> supported by the block layer, and switches existing implementations
> of REQ_OP_DISCARD that correctly set discard_zeroes_data to it,
> removes incorrect discard_zeroes_data, and also switches WRITE SAME
> based zeroing in SCSI to this new method.
> 
> The series is against the block for-next tree.
> 
> A git tree is also avaiable at:
> 
>     git://git.infradead.org/users/hch/block.git discard-rework
> 
> Gitweb:
> 
>     http://git.infradead.org/users/hch/block.git/shortlog/refs/heads/discard-rework
Thank you for doing this.

For this series:

Reviewed-by: Hannes Reinecke <hare@suse.com>

Cheers,

Hannes
-- 
Dr. Hannes Reinecke		   Teamlead Storage & Networking
hare@suse.de			               +49 911 74053 688
SUSE LINUX GmbH, Maxfeldstr. 5, 90409 N�rnberg
GF: F. Imend�rffer, J. Smithard, J. Guild, D. Upmanyu, G. Norton
HRB 21284 (AG N�rnberg)

Re: always use REQ_OP_WRITE_ZEROES for zeroing offload

[Martin K. Petersen]

Christoph Hellwig <hch@lst.de> writes:

Christoph,

> This series makes REQ_OP_WRITE_ZEROES the only zeroing offload
> supported by the block layer, and switches existing implementations
> of REQ_OP_DISCARD that correctly set discard_zeroes_data to it,
> removes incorrect discard_zeroes_data, and also switches WRITE SAME
> based zeroing in SCSI to this new method.

Very, very nice. I think this is the correct approach.

I'm going to send two follow-up patches that allow us to use UNMAP for
discards and WRITE SAME w/ UNMAP for zeroout. That appears to be the
preferred configuration for most storage devices.

-- 
Martin K. Petersen	Oracle Linux Engineering

Re: always use REQ_OP_WRITE_ZEROES for zeroing offload

[Christoph Hellwig]

On Wed, Apr 05, 2017 at 07:40:36AM -0400, Martin K. Petersen wrote:
> > This series makes REQ_OP_WRITE_ZEROES the only zeroing offload
> > supported by the block layer, and switches existing implementations
> > of REQ_OP_DISCARD that correctly set discard_zeroes_data to it,
> > removes incorrect discard_zeroes_data, and also switches WRITE SAME
> > based zeroing in SCSI to this new method.
> 
> Very, very nice. I think this is the correct approach.
> 
> I'm going to send two follow-up patches that allow us to use UNMAP for
> discards and WRITE SAME w/ UNMAP for zeroout. That appears to be the
> preferred configuration for most storage devices.

Thanks, I'll resend it with your nitpicks fixed, your follow on
patches tacked on and the various reviewed-by tags in a bit.