From: "Martin K. Petersen" <martin.petersen@xxxxxxxxxx>
The WRITE SAME command supported on some SCSI devices allows the same
block to be efficiently replicated throughout a block range. Only a
single logical block is transferred from the host and the storage device
writes the same data to all blocks described by the I/O.
This patch implements support for WRITE SAME in the block layer. The
blkdev_issue_write_same() function can be used by filesystems and block
drivers to replicate a buffer across a block range. This can be used to
efficiently initialize software RAID devices, etc.
Signed-off-by: Martin K. Petersen <martin.petersen@xxxxxxxxxx>
---
Documentation/ABI/testing/sysfs-block | 13 +++++
block/blk-core.c | 10 +++-
block/blk-lib.c | 79 +++++++++++++++++++++++++++++++++
block/blk-settings.c | 16 +++++++
block/blk-sysfs.c | 13 +++++
block/elevator.c | 9 +++-
include/linux/blk_types.h | 5 ++-
include/linux/blkdev.h | 21 ++++++++-
8 files changed, 160 insertions(+), 6 deletions(-)
diff --git a/Documentation/ABI/testing/sysfs-block b/Documentation/ABI/testing/sysfs-block
index c1eb41c..e5f4194 100644
--- a/Documentation/ABI/testing/sysfs-block
+++ b/Documentation/ABI/testing/sysfs-block
@@ -206,3 +206,16 @@ Description:
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.
+
+What: /sys/block/<disk>/queue/max_write_same_bytes
+Date: January 2012
+Contact: Martin K. Petersen <martin.petersen@xxxxxxxxxx>
+Description:
+ Some devices support a write same operation in which a
+ single data block can be written to a range of several
+ contiguous blocks on storage. This can be used to wipe
+ areas on disk or to initialize drives in a RAID
+ configuration. max_write_same_bytes indicates how many
+ bytes can be written in a single write same command. If
+ max_write_same_bytes is 0, write same is not supported
+ by the device.
diff --git a/block/blk-core.c b/block/blk-core.c
index e6c05a9..373ed52 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -1592,6 +1592,11 @@ generic_make_request_checks(struct bio *bio)
goto end_io;
}
+ if (bio->bi_rw & REQ_WRITE_SAME && !bdev_write_same(bio->bi_bdev)) {
+ err = -EOPNOTSUPP;
+ goto end_io;
+ }
+
if (blk_throtl_bio(q, bio))
return false; /* throttled, will be resubmitted later */
@@ -1743,7 +1748,7 @@ EXPORT_SYMBOL(submit_bio);
*/
int blk_rq_check_limits(struct request_queue *q, struct request *rq)
{
- if (rq->cmd_flags & REQ_DISCARD)
+ if ((rq->cmd_flags & REQ_DISCARD) || (rq->cmd_flags & REQ_WRITE_SAME))
return 0;
if (blk_rq_sectors(rq) > queue_max_sectors(q) ||
@@ -2217,7 +2222,8 @@ bool blk_update_request(struct request *req, int error, unsigned int nr_bytes)
req->buffer = bio_data(req->bio);
/* update sector only for requests with clear definition of sector */
- if (req->cmd_type == REQ_TYPE_FS || (req->cmd_flags & REQ_DISCARD))
+ if (req->cmd_type == REQ_TYPE_FS || (req->cmd_flags & REQ_DISCARD) ||
+ (req->cmd_flags & REQ_WRITE_SAME))
req->__sector += total_bytes >> 9;
/* mixed attributes always follow the first bio */
diff --git a/block/blk-lib.c b/block/blk-lib.c
index 2b461b4..19f4754 100644
--- a/block/blk-lib.c
+++ b/block/blk-lib.c
@@ -115,6 +115,85 @@ int blkdev_issue_discard(struct block_device *bdev, sector_t sector,
EXPORT_SYMBOL(blkdev_issue_discard);
/**
+ * blkdev_issue_write_same - queue a write same operation
+ * @bdev: target blockdev
+ * @sector: start sector
+ * @nr_sects: number of sectors to write
+ * @gfp_mask: memory allocation flags (for bio_alloc)
+ * @buffer: pointer to buffer containing data to write
+ * @length: buffer length. Must be equal to bdev logical block size.
+ *
+ * Description:
+ * Issue a write same request for the sectors in question.
+ */
+int blkdev_issue_write_same(struct block_device *bdev, sector_t sector,
+ sector_t nr_sects, gfp_t gfp_mask, void *buffer,
+ unsigned int length)
+{
+ DECLARE_COMPLETION_ONSTACK(wait);
+ struct request_queue *q = bdev_get_queue(bdev);
+ unsigned int max_write_same_sectors;
+ struct bio_batch bb;
+ struct bio *bio;
+ int ret = 0;
+
+ if (!q)
+ return -ENXIO;
+
+ max_write_same_sectors = q->limits.max_write_same_sectors;
+
+ if (max_write_same_sectors == 0)
+ return -EOPNOTSUPP;
+
+ BUG_ON(length != bdev_logical_block_size(bdev));
+ BUG_ON(offset_in_page(buffer) + length > PAGE_CACHE_SIZE);
+
+ atomic_set(&bb.done, 1);
+ bb.flags = 1 << BIO_UPTODATE;
+ bb.wait = &wait;
+
+ while (nr_sects) {
+ bio = bio_alloc(gfp_mask, 1);
+ if (!bio) {
+ ret = -ENOMEM;
+ break;
+ }
+
+ bio->bi_sector = sector;
+ bio->bi_end_io = bio_batch_end_io;
+ bio->bi_bdev = bdev;
+ bio->bi_private = &bb;
+ bio->bi_vcnt = 1;
+ bio->bi_phys_segments = 1;
+ bio->bi_io_vec->bv_page = virt_to_page(buffer);
+ bio->bi_io_vec->bv_offset = offset_in_page(buffer);
+ bio->bi_io_vec->bv_len = length;
+
+ if (nr_sects > max_write_same_sectors) {
+ bio->bi_size = max_write_same_sectors << 9;
+ nr_sects -= max_write_same_sectors;
+ sector += max_write_same_sectors;
+ } else {
+ bio->bi_size = nr_sects << 9;
+ nr_sects = 0;
+ }
+
+ atomic_inc(&bb.done);
+ submit_bio(REQ_WRITE | REQ_WRITE_SAME, bio);
+ }
+
+ /* Wait for bios in-flight */
+ if (!atomic_dec_and_test(&bb.done))
+ wait_for_completion(&wait);
+
+ if (!test_bit(BIO_UPTODATE, &bb.flags))
+ ret = -ENOTSUPP;
+
+ return ret;
+}
+EXPORT_SYMBOL(blkdev_issue_write_same);
+
+/**
* blkdev_issue_zeroout - generate number of zero filed write bios
* @bdev: blockdev to issue
* @sector: start sector
diff --git a/block/blk-settings.c b/block/blk-settings.c
index d3234fc..5680b91 100644
--- a/block/blk-settings.c
+++ b/block/blk-settings.c
@@ -113,6 +113,7 @@ void blk_set_default_limits(struct queue_limits *lim)
lim->seg_boundary_mask = BLK_SEG_BOUNDARY_MASK;
lim->max_segment_size = BLK_MAX_SEGMENT_SIZE;
lim->max_sectors = lim->max_hw_sectors = BLK_SAFE_MAX_SECTORS;
+ lim->max_write_same_sectors = 0;
lim->max_discard_sectors = 0;
lim->discard_granularity = 0;
lim->discard_alignment = 0;
@@ -143,6 +144,7 @@ void blk_set_stacking_limits(struct queue_limits *lim)
lim->discard_zeroes_data = 1;
lim->max_segments = USHRT_MAX;
lim->max_hw_sectors = UINT_MAX;
+ lim->max_write_same_sectors = UINT_MAX;
lim->max_sectors = BLK_DEF_MAX_SECTORS;
}
@@ -287,6 +289,18 @@ void blk_queue_max_discard_sectors(struct request_queue *q,
EXPORT_SYMBOL(blk_queue_max_discard_sectors);
/**
+ * blk_queue_max_write_same_sectors - set max sectors for a single write same
+ * @q: the request queue for the device
+ * @max_write_same_sectors: maximum number of sectors to write per command
+ **/
+void blk_queue_max_write_same_sectors(struct request_queue *q,
+ unsigned int max_write_same_sectors)
+{
+ q->limits.max_write_same_sectors = max_write_same_sectors;
+}
+EXPORT_SYMBOL(blk_queue_max_write_same_sectors);
+
+/**
* blk_queue_max_segments - set max hw segments for a request for this queue
* @q: the request queue for the device
* @max_segments: max number of segments
@@ -511,6 +525,8 @@ int blk_stack_limits(struct queue_limits *t, struct queue_limits *b,
t->max_sectors = min_not_zero(t->max_sectors, b->max_sectors);
t->max_hw_sectors = min_not_zero(t->max_hw_sectors, b->max_hw_sectors);
+ t->max_write_same_sectors = min(t->max_write_same_sectors,
+ b->max_write_same_sectors);
t->bounce_pfn = min_not_zero(t->bounce_pfn, b->bounce_pfn);
t->seg_boundary_mask = min_not_zero(t->seg_boundary_mask,
diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c
index cf15001..e0b38d2 100644
--- a/block/blk-sysfs.c
+++ b/block/blk-sysfs.c
@@ -161,6 +161,13 @@ static ssize_t queue_discard_zeroes_data_show(struct request_queue *q, char *pag
return queue_var_show(queue_discard_zeroes_data(q), page);
}
+static ssize_t queue_max_write_same_show(struct request_queue *q, char *page)
+{
+ return sprintf(page, "%llu\n",
+ (unsigned long long)q->limits.max_write_same_sectors << 9);
+}
+
+
static ssize_t
queue_max_sectors_store(struct request_queue *q, const char *page, size_t count)
{
@@ -357,6 +364,11 @@ static struct queue_sysfs_entry queue_discard_zeroes_data_entry = {
.show = queue_discard_zeroes_data_show,
};
+static struct queue_sysfs_entry queue_max_write_same_entry = {
+ .attr = {.name = "max_write_same_bytes", .mode = S_IRUGO },
+ .show = queue_max_write_same_show,
+};
+
static struct queue_sysfs_entry queue_nonrot_entry = {
.attr = {.name = "rotational", .mode = S_IRUGO | S_IWUSR },
.show = queue_show_nonrot,
@@ -404,6 +416,7 @@ static struct attribute *default_attrs[] = {
&queue_discard_granularity_entry.attr,
&queue_discard_max_entry.attr,
&queue_discard_zeroes_data_entry.attr,
+ &queue_max_write_same_entry.attr,
&queue_nonrot_entry.attr,
&queue_nomerges_entry.attr,
&queue_rq_affinity_entry.attr,
diff --git a/block/elevator.c b/block/elevator.c
index 91e18f8..d6f7703 100644
--- a/block/elevator.c
+++ b/block/elevator.c
@@ -82,6 +82,12 @@ int elv_rq_merge_ok(struct request *rq, struct bio *bio)
return 0;
/*
+ * Don't merge write same requests
+ */
+ if ((bio->bi_rw & REQ_WRITE_SAME) || (rq->bio->bi_rw & REQ_WRITE_SAME))
+ return 0;
+
+ /*
* Don't merge discard requests and secure discard requests
*/
if ((bio->bi_rw & REQ_SECURE) != (rq->bio->bi_rw & REQ_SECURE))
@@ -639,7 +645,8 @@ void __elv_add_request(struct request_queue *q, struct request *rq, int where)
if (rq->cmd_flags & REQ_SOFTBARRIER) {
/* barriers are scheduling boundary, update end_sector */
if (rq->cmd_type == REQ_TYPE_FS ||
- (rq->cmd_flags & REQ_DISCARD)) {
+ (rq->cmd_flags & REQ_DISCARD) ||
+ (rq->cmd_flags & REQ_WRITE_SAME)) {
q->end_sector = rq_end_sector(rq);
q->boundary_rq = rq;
}
diff --git a/include/linux/blk_types.h b/include/linux/blk_types.h
index 4053cbd..b312ac8 100644
--- a/include/linux/blk_types.h
+++ b/include/linux/blk_types.h
@@ -124,6 +124,7 @@ enum rq_flag_bits {
__REQ_PRIO, /* boost priority in cfq */
__REQ_DISCARD, /* request to discard sectors */
__REQ_SECURE, /* secure discard (used with __REQ_DISCARD) */
+ __REQ_WRITE_SAME, /* write same block many times */
__REQ_NOIDLE, /* don't anticipate more IO after this one */
__REQ_FUA, /* forced unit access */
@@ -162,12 +163,14 @@ enum rq_flag_bits {
#define REQ_PRIO (1 << __REQ_PRIO)
#define REQ_DISCARD (1 << __REQ_DISCARD)
#define REQ_NOIDLE (1 << __REQ_NOIDLE)
+#define REQ_WRITE_SAME (1 << __REQ_WRITE_SAME)
#define REQ_FAILFAST_MASK \
(REQ_FAILFAST_DEV | REQ_FAILFAST_TRANSPORT | REQ_FAILFAST_DRIVER)
#define REQ_COMMON_MASK \
(REQ_WRITE | REQ_FAILFAST_MASK | REQ_SYNC | REQ_META | REQ_PRIO | \
- REQ_DISCARD | REQ_NOIDLE | REQ_FLUSH | REQ_FUA | REQ_SECURE)
+ REQ_DISCARD | REQ_WRITE_SAME | REQ_NOIDLE | REQ_FLUSH | REQ_FUA | \
+ REQ_SECURE)
#define REQ_CLONE_MASK REQ_COMMON_MASK
#define REQ_RAHEAD (1 << __REQ_RAHEAD)
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 6c6a1f0..4e2f049 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -254,6 +254,7 @@ struct queue_limits {
unsigned int io_min;
unsigned int io_opt;
unsigned int max_discard_sectors;
+ unsigned int max_write_same_sectors;
unsigned int discard_granularity;
unsigned int discard_alignment;
@@ -581,8 +582,9 @@ static inline void blk_clear_queue_full(struct request_queue *q, int sync)
(REQ_NOMERGE | REQ_STARTED | REQ_SOFTBARRIER | REQ_FLUSH | REQ_FUA)
#define rq_mergeable(rq) \
(!((rq)->cmd_flags & RQ_NOMERGE_FLAGS) && \
- (((rq)->cmd_flags & REQ_DISCARD) || \
- (rq)->cmd_type == REQ_TYPE_FS))
+ (((rq)->cmd_flags & REQ_DISCARD || \
+ (rq)->cmd_flags & REQ_WRITE_SAME || \
+ (rq)->cmd_type == REQ_TYPE_FS)))
/*
* q->prep_rq_fn return values
@@ -835,6 +837,8 @@ extern void blk_queue_max_segments(struct request_queue *, unsigned short);
extern void blk_queue_max_segment_size(struct request_queue *, unsigned int);
extern void blk_queue_max_discard_sectors(struct request_queue *q,
unsigned int max_discard_sectors);
+extern void blk_queue_max_write_same_sectors(struct request_queue *q,
+ unsigned int max_write_same_sectors);
extern void blk_queue_logical_block_size(struct request_queue *, unsigned short);
extern void blk_queue_physical_block_size(struct request_queue *, unsigned int);
extern void blk_queue_alignment_offset(struct request_queue *q,
@@ -959,6 +963,9 @@ static inline struct request *blk_map_queue_find_tag(struct blk_queue_tag *bqt,
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_write_same(struct block_device *bdev, sector_t sector,
+ sector_t nr_sects, gfp_t gfp_mask, void *buffer,
+ unsigned int length);
extern int blkdev_issue_zeroout(struct block_device *bdev, sector_t sector,
sector_t nr_sects, gfp_t gfp_mask);
static inline int sb_issue_discard(struct super_block *sb, sector_t block,
@@ -1126,6 +1133,16 @@ 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);
+
+ if (q)
+ return q->limits.max_write_same_sectors;
+
+ return 0;
+}
+
static inline int queue_dma_alignment(struct request_queue *q)
{
return q ? q->dma_alignment : 511;
--
1.7.8.3.21.gab8a7
--
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