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block: Implement support for WRITE SAME

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@oracle.com>
Acked-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
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commit 4363ac7c13a9a4b763c6e8d9fdbfc2468f3b8ca4 1 parent f31dc1c
Martin K. Petersen authored axboe committed
View
14 Documentation/ABI/testing/sysfs-block
@@ -206,3 +206,17 @@ 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/write_same_max_bytes
+Date: January 2012
+Contact: Martin K. Petersen <martin.petersen@oracle.com>
+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. write_same_max_bytes indicates how many
+ bytes can be written in a single write same command. If
+ write_same_max_bytes is 0, write same is not supported
+ by the device.
+
View
14 block/blk-core.c
@@ -1704,6 +1704,11 @@ 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;
+ }
+
/*
* Various block parts want %current->io_context and lazy ioc
* allocation ends up trading a lot of pain for a small amount of
@@ -1809,8 +1814,6 @@ EXPORT_SYMBOL(generic_make_request);
*/
void submit_bio(int rw, struct bio *bio)
{
- int count = bio_sectors(bio);
-
bio->bi_rw |= rw;
/*
@@ -1818,6 +1821,13 @@ void submit_bio(int rw, struct bio *bio)
* go through the normal accounting stuff before submission.
*/
if (bio_has_data(bio)) {
+ unsigned int count;
+
+ if (unlikely(rw & REQ_WRITE_SAME))
+ count = bdev_logical_block_size(bio->bi_bdev) >> 9;
+ else
+ count = bio_sectors(bio);
+
if (rw & WRITE) {
count_vm_events(PGPGOUT, count);
} else {
View
74 block/blk-lib.c
@@ -130,6 +130,80 @@ 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)
+ * @page: page containing data to write
+ *
+ * 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,
+ struct page *page)
+{
+ 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;
+
+ 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_io_vec->bv_page = page;
+ bio->bi_io_vec->bv_offset = 0;
+ bio->bi_io_vec->bv_len = bdev_logical_block_size(bdev);
+
+ 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
View
9 block/blk-merge.c
@@ -419,6 +419,10 @@ static int attempt_merge(struct request_queue *q, struct request *req,
|| next->special)
return 0;
+ if (req->cmd_flags & REQ_WRITE_SAME &&
+ !blk_write_same_mergeable(req->bio, next->bio))
+ return 0;
+
/*
* If we are allowed to merge, then append bio list
* from next to rq and release next. merge_requests_fn
@@ -518,6 +522,11 @@ bool blk_rq_merge_ok(struct request *rq, struct bio *bio)
if (bio_integrity(bio) != blk_integrity_rq(rq))
return false;
+ /* must be using the same buffer */
+ if (rq->cmd_flags & REQ_WRITE_SAME &&
+ !blk_write_same_mergeable(rq->bio, bio))
+ return false;
+
return true;
}
View
16 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;
@@ -144,6 +145,7 @@ void blk_set_stacking_limits(struct queue_limits *lim)
lim->max_segments = USHRT_MAX;
lim->max_hw_sectors = UINT_MAX;
lim->max_sectors = UINT_MAX;
+ lim->max_write_same_sectors = UINT_MAX;
}
EXPORT_SYMBOL(blk_set_stacking_limits);
@@ -286,6 +288,18 @@ 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
@@ -510,6 +524,8 @@ 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,
View
13 block/blk-sysfs.c
@@ -180,6 +180,13 @@ 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_write_same_max_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)
{
@@ -385,6 +392,11 @@ static struct queue_sysfs_entry queue_discard_zeroes_data_entry = {
.show = queue_discard_zeroes_data_show,
};
+static struct queue_sysfs_entry queue_write_same_max_entry = {
+ .attr = {.name = "write_same_max_bytes", .mode = S_IRUGO },
+ .show = queue_write_same_max_show,
+};
+
static struct queue_sysfs_entry queue_nonrot_entry = {
.attr = {.name = "rotational", .mode = S_IRUGO | S_IWUSR },
.show = queue_show_nonrot,
@@ -432,6 +444,7 @@ static struct attribute *default_attrs[] = {
&queue_discard_granularity_entry.attr,
&queue_discard_max_entry.attr,
&queue_discard_zeroes_data_entry.attr,
+ &queue_write_same_max_entry.attr,
&queue_nonrot_entry.attr,
&queue_nomerges_entry.attr,
&queue_rq_affinity_entry.attr,
View
1  drivers/md/raid0.c
@@ -422,6 +422,7 @@ static int raid0_run(struct mddev *mddev)
if (md_check_no_bitmap(mddev))
return -EINVAL;
blk_queue_max_hw_sectors(mddev->queue, mddev->chunk_sectors);
+ blk_queue_max_write_same_sectors(mddev->queue, mddev->chunk_sectors);
/* if private is not null, we are here after takeover */
if (mddev->private == NULL) {
View
9 fs/bio.c
@@ -1487,9 +1487,12 @@ struct bio_pair *bio_split(struct bio *bi, int first_sectors)
bp->bv1 = bi->bi_io_vec[0];
bp->bv2 = bi->bi_io_vec[0];
- bp->bv2.bv_offset += first_sectors << 9;
- bp->bv2.bv_len -= first_sectors << 9;
- bp->bv1.bv_len = first_sectors << 9;
+
+ if (bio_is_rw(bi)) {
+ bp->bv2.bv_offset += first_sectors << 9;
+ bp->bv2.bv_len -= first_sectors << 9;
+ bp->bv1.bv_len = first_sectors << 9;
+ }
bp->bio1.bi_io_vec = &bp->bv1;
bp->bio2.bi_io_vec = &bp->bv2;
View
3  include/linux/bio.h
@@ -399,6 +399,9 @@ static inline bool bio_is_rw(struct bio *bio)
if (!bio_has_data(bio))
return false;
+ if (bio->bi_rw & REQ_WRITE_SAME)
+ return false;
+
return true;
}
View
5 include/linux/blk_types.h
@@ -147,6 +147,7 @@ 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 */
@@ -185,13 +186,15 @@ enum rq_flag_bits {
#define REQ_META (1 << __REQ_META)
#define REQ_PRIO (1 << __REQ_PRIO)
#define REQ_DISCARD (1 << __REQ_DISCARD)
+#define REQ_WRITE_SAME (1 << __REQ_WRITE_SAME)
#define REQ_NOIDLE (1 << __REQ_NOIDLE)
#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
/* This mask is used for both bio and request merge checking */
View
29 include/linux/blkdev.h
@@ -270,6 +270,7 @@ 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;
@@ -614,9 +615,20 @@ static inline bool blk_check_merge_flags(unsigned int flags1,
if ((flags1 & REQ_SECURE) != (flags2 & REQ_SECURE))
return false;
+ if ((flags1 & REQ_WRITE_SAME) != (flags2 & REQ_WRITE_SAME))
+ return false;
+
return true;
}
+static inline bool blk_write_same_mergeable(struct bio *a, struct bio *b)
+{
+ if (bio_data(a) == bio_data(b))
+ return true;
+
+ return false;
+}
+
/*
* q->prep_rq_fn return values
*/
@@ -818,6 +830,9 @@ static inline unsigned int blk_queue_get_max_sectors(struct request_queue *q,
if (unlikely(cmd_flags & REQ_DISCARD))
return q->limits.max_discard_sectors;
+ if (unlikely(cmd_flags & REQ_WRITE_SAME))
+ return q->limits.max_write_same_sectors;
+
return q->limits.max_sectors;
}
@@ -886,6 +901,8 @@ 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,
@@ -1016,6 +1033,8 @@ 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, struct page *page);
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,
@@ -1193,6 +1212,16 @@ 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;
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