[v6,05/10] block: Add core atomic write support

diff --git a/Documentation/ABI/stable/sysfs-block b/Documentation/ABI/stable/sysfs-block
index 1fe9a553c37b..4c775f4bdefe 100644
--- a/Documentation/ABI/stable/sysfs-block
+++ b/Documentation/ABI/stable/sysfs-block
@@ -21,6 +21,58 @@  Description:
 		device is offset from the internal allocation unit's
 		natural alignment.
 
+What:		/sys/block/<disk>/atomic_write_max_bytes
+Date:		February 2024
+Contact:	Himanshu Madhani <himanshu.madhani@oracle.com>
+Description:
+		[RO] This parameter specifies the maximum atomic write
+		size reported by the device. This parameter is relevant
+		for merging of writes, where a merged atomic write
+		operation must not exceed this number of bytes.
+		This parameter may be greater to the value in
+		atomic_write_unit_max_bytes as
+		atomic_write_unit_max_bytes will be rounded down to a
+		power-of-two and atomic_write_unit_max_bytes may also be
+		limited by some other queue limits, such as max_segments.
+		This parameter - along with atomic_write_unit_min_bytes
+		and atomic_write_unit_max_bytes - will not be larger than
+		max_hw_sectors_kb, but may be larger than max_sectors_kb.
+
+
+What:		/sys/block/<disk>/atomic_write_unit_min_bytes
+Date:		February 2024
+Contact:	Himanshu Madhani <himanshu.madhani@oracle.com>
+Description:
+		[RO] This parameter specifies the smallest block which can
+		be written atomically with an atomic write operation. All
+		atomic write operations must begin at a
+		atomic_write_unit_min boundary and must be multiples of
+		atomic_write_unit_min. This value must be a power-of-two.
+
+
+What:		/sys/block/<disk>/atomic_write_unit_max_bytes
+Date:		February 2024
+Contact:	Himanshu Madhani <himanshu.madhani@oracle.com>
+Description:
+		[RO] This parameter defines the largest block which can be
+		written atomically with an atomic write operation. This
+		value must be a multiple of atomic_write_unit_min and must
+		be a power-of-two. This value will not be larger than
+		atomic_write_max_bytes.
+
+
+What:		/sys/block/<disk>/atomic_write_boundary_bytes
+Date:		February 2024
+Contact:	Himanshu Madhani <himanshu.madhani@oracle.com>
+Description:
+		[RO] A device may need to internally split I/Os which
+		straddle a given logical block address boundary. In that
+		case a single atomic write operation will be processed as
+		one of more sub-operations which each complete atomically.
+		This parameter specifies the size in bytes of the atomic
+		boundary if one is reported by the device. This value must
+		be a power-of-two.
+
 
 What:		/sys/block/<disk>/diskseq
 Date:		February 2021
diff --git a/block/blk-core.c b/block/blk-core.c
index a16b5abdbbf5..de868c91a295 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -174,6 +174,8 @@  static const struct {
 	/* Command duration limit device-side timeout */
 	[BLK_STS_DURATION_LIMIT]	= { -ETIME, "duration limit exceeded" },
 
+	[BLK_STS_INVAL]		= { -EINVAL,	"invalid" },
+
 	/* everything else not covered above: */
 	[BLK_STS_IOERR]		= { -EIO,	"I/O" },
 };
@@ -729,6 +731,18 @@  void submit_bio_noacct_nocheck(struct bio *bio)
 		__submit_bio_noacct(bio);
 }
 
+static blk_status_t blk_validate_atomic_write_op_size(struct request_queue *q,
+						 struct bio *bio)
+{
+	if (bio->bi_iter.bi_size > queue_atomic_write_unit_max_bytes(q))
+		return BLK_STS_INVAL;
+
+	if (bio->bi_iter.bi_size % queue_atomic_write_unit_min_bytes(q))
+		return BLK_STS_INVAL;
+
+	return BLK_STS_OK;
+}
+
 /**
  * submit_bio_noacct - re-submit a bio to the block device layer for I/O
  * @bio:  The bio describing the location in memory and on the device.
@@ -786,6 +800,11 @@  void submit_bio_noacct(struct bio *bio)
 	switch (bio_op(bio)) {
 	case REQ_OP_READ:
 	case REQ_OP_WRITE:
+		if (bio->bi_opf & REQ_ATOMIC) {
+			status = blk_validate_atomic_write_op_size(q, bio);
+			if (status != BLK_STS_OK)
+				goto end_io;
+		}
 		break;
 	case REQ_OP_FLUSH:
 		/*
diff --git a/block/blk-merge.c b/block/blk-merge.c
index 6f9d9ca7922b..34a68e131168 100644
--- a/block/blk-merge.c
+++ b/block/blk-merge.c
@@ -18,6 +18,46 @@ 
 #include "blk-rq-qos.h"
 #include "blk-throttle.h"
 
+/*
+ * rq_straddles_atomic_write_boundary - check for boundary violation
+ * @rq: request to check
+ * @front: data size to be appended to front
+ * @back: data size to be appended to back
+ *
+ * Determine whether merging a request or bio into another request will result
+ * in a merged request which straddles an atomic write boundary.
+ *
+ * The value @front_adjust is the data which would be appended to the front of
+ * @rq, while the value @back_adjust is the data which would be appended to the
+ * back of @rq. Callers will typically only have either @front_adjust or
+ * @back_adjust as non-zero.
+ *
+ */
+static bool rq_straddles_atomic_write_boundary(struct request *rq,
+					unsigned int front_adjust,
+					unsigned int back_adjust)
+{
+	unsigned int boundary = queue_atomic_write_boundary_bytes(rq->q);
+	u64 mask, start_rq_pos, end_rq_pos;
+
+	if (!boundary)
+		return false;
+
+	start_rq_pos = blk_rq_pos(rq) << SECTOR_SHIFT;
+	end_rq_pos = start_rq_pos + blk_rq_bytes(rq) - 1;
+
+	start_rq_pos -= front_adjust;
+	end_rq_pos += back_adjust;
+
+	mask = ~(boundary - 1);
+
+	/* Top bits are different, so crossed a boundary */
+	if ((start_rq_pos & mask) != (end_rq_pos & mask))
+		return true;
+
+	return false;
+}
+
 static inline void bio_get_first_bvec(struct bio *bio, struct bio_vec *bv)
 {
 	*bv = mp_bvec_iter_bvec(bio->bi_io_vec, bio->bi_iter);
@@ -167,7 +207,16 @@  static inline unsigned get_max_io_size(struct bio *bio,
 {
 	unsigned pbs = lim->physical_block_size >> SECTOR_SHIFT;
 	unsigned lbs = lim->logical_block_size >> SECTOR_SHIFT;
-	unsigned max_sectors = lim->max_sectors, start, end;
+	unsigned max_sectors, start, end;
+
+	/*
+	 * We ignore lim->max_sectors for atomic writes simply because
+	 * it may less than the bio size, which we cannot tolerate.
+	 */
+	if (bio->bi_opf & REQ_ATOMIC)
+		max_sectors = lim->atomic_write_max_sectors;
+	else
+		max_sectors = lim->max_sectors;
 
 	if (lim->chunk_sectors) {
 		max_sectors = min(max_sectors,
@@ -305,6 +354,11 @@  struct bio *bio_split_rw(struct bio *bio, const struct queue_limits *lim,
 	*segs = nsegs;
 	return NULL;
 split:
+	if (bio->bi_opf & REQ_ATOMIC) {
+		bio->bi_status = BLK_STS_INVAL;
+		bio_endio(bio);
+		return ERR_PTR(-EINVAL);
+	}
 	/*
 	 * We can't sanely support splitting for a REQ_NOWAIT bio. End it
 	 * with EAGAIN if splitting is required and return an error pointer.
@@ -645,6 +699,13 @@  int ll_back_merge_fn(struct request *req, struct bio *bio, unsigned int nr_segs)
 		return 0;
 	}
 
+	if (req->cmd_flags & REQ_ATOMIC) {
+		if (rq_straddles_atomic_write_boundary(req,
+				0, bio->bi_iter.bi_size)) {
+			return 0;
+		}
+	}
+
 	return ll_new_hw_segment(req, bio, nr_segs);
 }
 
@@ -664,6 +725,13 @@  static int ll_front_merge_fn(struct request *req, struct bio *bio,
 		return 0;
 	}
 
+	if (req->cmd_flags & REQ_ATOMIC) {
+		if (rq_straddles_atomic_write_boundary(req,
+				bio->bi_iter.bi_size, 0)) {
+			return 0;
+		}
+	}
+
 	return ll_new_hw_segment(req, bio, nr_segs);
 }
 
@@ -700,6 +768,13 @@  static int ll_merge_requests_fn(struct request_queue *q, struct request *req,
 	    blk_rq_get_max_sectors(req, blk_rq_pos(req)))
 		return 0;
 
+	if (req->cmd_flags & REQ_ATOMIC) {
+		if (rq_straddles_atomic_write_boundary(req,
+				0, blk_rq_bytes(next))) {
+			return 0;
+		}
+	}
+
 	total_phys_segments = req->nr_phys_segments + next->nr_phys_segments;
 	if (total_phys_segments > blk_rq_get_max_segments(req))
 		return 0;
@@ -795,6 +870,18 @@  static enum elv_merge blk_try_req_merge(struct request *req,
 	return ELEVATOR_NO_MERGE;
 }
 
+static bool blk_atomic_write_mergeable_rq_bio(struct request *rq,
+					      struct bio *bio)
+{
+	return (rq->cmd_flags & REQ_ATOMIC) == (bio->bi_opf & REQ_ATOMIC);
+}
+
+static bool blk_atomic_write_mergeable_rqs(struct request *rq,
+					   struct request *next)
+{
+	return (rq->cmd_flags & REQ_ATOMIC) == (next->cmd_flags & REQ_ATOMIC);
+}
+
 /*
  * For non-mq, this has to be called with the request spinlock acquired.
  * For mq with scheduling, the appropriate queue wide lock should be held.
@@ -818,6 +905,9 @@  static struct request *attempt_merge(struct request_queue *q,
 	if (req->ioprio != next->ioprio)
 		return NULL;
 
+	if (!blk_atomic_write_mergeable_rqs(req, next))
+		return NULL;
+
 	/*
 	 * If we are allowed to merge, then append bio list
 	 * from next to rq and release next. merge_requests_fn
@@ -949,6 +1039,9 @@  bool blk_rq_merge_ok(struct request *rq, struct bio *bio)
 	if (rq->ioprio != bio_prio(bio))
 		return false;
 
+	if (blk_atomic_write_mergeable_rq_bio(rq, bio) == false)
+		return false;
+
 	return true;
 }
 
diff --git a/block/blk-settings.c b/block/blk-settings.c
index 3c7d8d638ab5..98d6c2f59ccf 100644
--- a/block/blk-settings.c
+++ b/block/blk-settings.c
@@ -97,6 +97,41 @@  static int blk_validate_zoned_limits(struct queue_limits *lim)
 	return 0;
 }
 
+/*
+ * Returns max guaranteed bytes which we can fit in a bio.
+ *
+ * We always assume that we can fit in at least PAGE_SIZE in a segment, apart
+ * from first and last segments.
+ */
+static
+unsigned int blk_queue_max_guaranteed_bio(struct queue_limits *limits)
+{
+	unsigned int max_segments = min(BIO_MAX_VECS, limits->max_segments);
+	unsigned int length;
+
+	length = min(max_segments, 2) * limits->logical_block_size;
+	if (max_segments > 2)
+		length += (max_segments - 2) * PAGE_SIZE;
+
+	return length;
+}
+
+static void blk_atomic_writes_update_limits(struct queue_limits *limits)
+{
+	unsigned int unit_limit = min(limits->max_hw_sectors << SECTOR_SHIFT,
+					blk_queue_max_guaranteed_bio(limits));
+
+	unit_limit = rounddown_pow_of_two(unit_limit);
+
+	limits->atomic_write_max_sectors =
+		min(limits->atomic_write_hw_max >> SECTOR_SHIFT,
+			limits->max_hw_sectors);
+	limits->atomic_write_unit_min =
+		min(limits->atomic_write_hw_unit_min, unit_limit);
+	limits->atomic_write_unit_max =
+		min(limits->atomic_write_hw_unit_max, unit_limit);
+}
+
 /*
  * Check that the limits in lim are valid, initialize defaults for unset
  * values, and cap values based on others where needed.
@@ -221,6 +256,23 @@  static int blk_validate_limits(struct queue_limits *lim)
 		lim->misaligned = 0;
 	}
 
+	/*
+	 * The atomic write boundary size just needs to be a multiple of
+	 * unit_max (and not necessarily a power-of-2), so this following check
+	 * could be relaxed in future.
+	 * Furthermore, if needed, unit_max could be reduced so that the
+	 * boundary size was compliant (with a !power-of-2 boundary).
+	 */
+	if (lim->atomic_write_hw_boundary &&
+	    !is_power_of_2(lim->atomic_write_hw_boundary)) {
+
+		lim->atomic_write_hw_max = 0;
+		lim->atomic_write_hw_boundary = 0;
+		lim->atomic_write_hw_unit_min = 0;
+		lim->atomic_write_hw_unit_max = 0;
+	}
+	blk_atomic_writes_update_limits(lim);
+
 	return blk_validate_zoned_limits(lim);
 }
 
@@ -344,6 +396,8 @@  void blk_queue_max_hw_sectors(struct request_queue *q, unsigned int max_hw_secto
 				 limits->logical_block_size >> SECTOR_SHIFT);
 	limits->max_sectors = max_sectors;
 
+	blk_atomic_writes_update_limits(limits);
+
 	if (!q->disk)
 		return;
 	q->disk->bdi->io_pages = max_sectors >> (PAGE_SHIFT - 9);
@@ -384,6 +438,61 @@  void blk_queue_max_discard_sectors(struct request_queue *q,
 }
 EXPORT_SYMBOL(blk_queue_max_discard_sectors);
 
+/**
+ * blk_queue_atomic_write_max_bytes - set max bytes supported by
+ * the device for atomic write operations.
+ * @q:  the request queue for the device
+ * @bytes: maximum bytes supported
+ */
+void blk_queue_atomic_write_max_bytes(struct request_queue *q,
+				      unsigned int bytes)
+{
+	q->limits.atomic_write_hw_max = bytes;
+	blk_atomic_writes_update_limits(&q->limits);
+}
+EXPORT_SYMBOL(blk_queue_atomic_write_max_bytes);
+
+/**
+ * blk_queue_atomic_write_boundary_bytes - Device's logical block address space
+ * which an atomic write should not cross.
+ * @q:  the request queue for the device
+ * @bytes: must be a power-of-two.
+ */
+void blk_queue_atomic_write_boundary_bytes(struct request_queue *q,
+					   unsigned int bytes)
+{
+	q->limits.atomic_write_hw_boundary = bytes;
+}
+EXPORT_SYMBOL(blk_queue_atomic_write_boundary_bytes);
+
+/**
+ * blk_queue_atomic_write_unit_min_bytes - smallest unit that can be written
+ * atomically to the device.
+ * @q:  the request queue for the device
+ * @bytes: must be a power-of-two.
+ */
+void blk_queue_atomic_write_unit_min_bytes(struct request_queue *q,
+					     unsigned int bytes)
+{
+	q->limits.atomic_write_hw_unit_min = bytes;
+	blk_atomic_writes_update_limits(&q->limits);
+}
+EXPORT_SYMBOL(blk_queue_atomic_write_unit_min_bytes);
+
+/*
+ * blk_queue_atomic_write_unit_max_bytes - largest unit that can be written
+ * atomically to the device.
+ * @q: the request queue for the device
+ * @bytes: must be a power-of-two.
+ */
+void blk_queue_atomic_write_unit_max_bytes(struct request_queue *q,
+					     unsigned int bytes)
+{
+	q->limits.atomic_write_hw_unit_max = bytes;
+	blk_atomic_writes_update_limits(&q->limits);
+}
+EXPORT_SYMBOL(blk_queue_atomic_write_unit_max_bytes);
+
 /**
  * blk_queue_max_secure_erase_sectors - set max sectors for a secure erase
  * @q:  the request queue for the device
diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c
index 8c8f69d8ba48..e2ff824ce02f 100644
--- a/block/blk-sysfs.c
+++ b/block/blk-sysfs.c
@@ -118,6 +118,30 @@  static ssize_t queue_max_discard_segments_show(struct request_queue *q,
 	return queue_var_show(queue_max_discard_segments(q), page);
 }
 
+static ssize_t queue_atomic_write_max_bytes_show(struct request_queue *q,
+						char *page)
+{
+	return queue_var_show(queue_atomic_write_max_bytes(q), page);
+}
+
+static ssize_t queue_atomic_write_boundary_show(struct request_queue *q,
+						char *page)
+{
+	return queue_var_show(queue_atomic_write_boundary_bytes(q), page);
+}
+
+static ssize_t queue_atomic_write_unit_min_show(struct request_queue *q,
+						char *page)
+{
+	return queue_var_show(queue_atomic_write_unit_min_bytes(q), page);
+}
+
+static ssize_t queue_atomic_write_unit_max_show(struct request_queue *q,
+						char *page)
+{
+	return queue_var_show(queue_atomic_write_unit_max_bytes(q), page);
+}
+
 static ssize_t queue_max_integrity_segments_show(struct request_queue *q, char *page)
 {
 	return queue_var_show(q->limits.max_integrity_segments, page);
@@ -495,6 +519,11 @@  QUEUE_RO_ENTRY(queue_discard_max_hw, "discard_max_hw_bytes");
 QUEUE_RW_ENTRY(queue_discard_max, "discard_max_bytes");
 QUEUE_RO_ENTRY(queue_discard_zeroes_data, "discard_zeroes_data");
 
+QUEUE_RO_ENTRY(queue_atomic_write_max_bytes, "atomic_write_max_bytes");
+QUEUE_RO_ENTRY(queue_atomic_write_boundary, "atomic_write_boundary_bytes");
+QUEUE_RO_ENTRY(queue_atomic_write_unit_max, "atomic_write_unit_max_bytes");
+QUEUE_RO_ENTRY(queue_atomic_write_unit_min, "atomic_write_unit_min_bytes");
+
 QUEUE_RO_ENTRY(queue_write_same_max, "write_same_max_bytes");
 QUEUE_RO_ENTRY(queue_write_zeroes_max, "write_zeroes_max_bytes");
 QUEUE_RO_ENTRY(queue_zone_append_max, "zone_append_max_bytes");
@@ -622,6 +651,10 @@  static struct attribute *queue_attrs[] = {
 	&queue_discard_max_entry.attr,
 	&queue_discard_max_hw_entry.attr,
 	&queue_discard_zeroes_data_entry.attr,
+	&queue_atomic_write_max_bytes_entry.attr,
+	&queue_atomic_write_boundary_entry.attr,
+	&queue_atomic_write_unit_min_entry.attr,
+	&queue_atomic_write_unit_max_entry.attr,
 	&queue_write_same_max_entry.attr,
 	&queue_write_zeroes_max_entry.attr,
 	&queue_zone_append_max_entry.attr,
diff --git a/block/blk.h b/block/blk.h
index dc2fa6f88adc..5e49c14525df 100644
--- a/block/blk.h
+++ b/block/blk.h
@@ -192,6 +192,9 @@  static inline unsigned int blk_queue_get_max_sectors(struct request *rq)
 	if (unlikely(op == REQ_OP_WRITE_ZEROES))
 		return q->limits.max_write_zeroes_sectors;
 
+	if (rq->cmd_flags & REQ_ATOMIC)
+		return q->limits.atomic_write_max_sectors;
+
 	return q->limits.max_sectors;
 }
 
diff --git a/include/linux/blk_types.h b/include/linux/blk_types.h
index cb1526ec44b5..b7d35ead4d1b 100644
--- a/include/linux/blk_types.h
+++ b/include/linux/blk_types.h
@@ -179,6 +179,11 @@  typedef u16 blk_short_t;
  */
 #define BLK_STS_DURATION_LIMIT	((__force blk_status_t)18)
 
+/*
+ * Invalid size or alignment.
+ */
+#define BLK_STS_INVAL	((__force blk_status_t)19)
+
 /**
  * blk_path_error - returns true if error may be path related
  * @error: status the request was completed with
@@ -381,7 +386,7 @@  enum req_flag_bits {
 	__REQ_SWAP,		/* swap I/O */
 	__REQ_DRV,		/* for driver use */
 	__REQ_FS_PRIVATE,	/* for file system (submitter) use */
-
+	__REQ_ATOMIC,		/* for atomic write operations */
 	/*
 	 * Command specific flags, keep last:
 	 */
@@ -413,6 +418,7 @@  enum req_flag_bits {
 #define REQ_SWAP	(__force blk_opf_t)(1ULL << __REQ_SWAP)
 #define REQ_DRV		(__force blk_opf_t)(1ULL << __REQ_DRV)
 #define REQ_FS_PRIVATE	(__force blk_opf_t)(1ULL << __REQ_FS_PRIVATE)
+#define REQ_ATOMIC	(__force blk_opf_t)(1ULL << __REQ_ATOMIC)
 
 #define REQ_NOUNMAP	(__force blk_opf_t)(1ULL << __REQ_NOUNMAP)
 
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index c3e8f7cf96be..07145b0acbc8 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -300,6 +300,15 @@  struct queue_limits {
 	unsigned int		discard_alignment;
 	unsigned int		zone_write_granularity;
 
+	/* atomic write limits */
+	unsigned int		atomic_write_hw_max;
+	unsigned int		atomic_write_max_sectors;
+	unsigned int		atomic_write_hw_boundary;
+	unsigned int		atomic_write_hw_unit_min;
+	unsigned int		atomic_write_unit_min;
+	unsigned int		atomic_write_hw_unit_max;
+	unsigned int		atomic_write_unit_max;
+
 	unsigned short		max_segments;
 	unsigned short		max_integrity_segments;
 	unsigned short		max_discard_segments;
@@ -916,6 +925,14 @@  void blk_queue_zone_write_granularity(struct request_queue *q,
 				      unsigned int size);
 extern void blk_queue_alignment_offset(struct request_queue *q,
 				       unsigned int alignment);
+void blk_queue_atomic_write_max_bytes(struct request_queue *q,
+				unsigned int bytes);
+void blk_queue_atomic_write_boundary_bytes(struct request_queue *q,
+				unsigned int bytes);
+void blk_queue_atomic_write_unit_max_bytes(struct request_queue *q,
+				unsigned int bytes);
+void blk_queue_atomic_write_unit_min_bytes(struct request_queue *q,
+				unsigned int bytes);
 void disk_update_readahead(struct gendisk *disk);
 extern void blk_limits_io_min(struct queue_limits *limits, unsigned int min);
 extern void blk_queue_io_min(struct request_queue *q, unsigned int min);
@@ -1339,6 +1356,30 @@  static inline int queue_dma_alignment(const struct request_queue *q)
 	return q ? q->limits.dma_alignment : 511;
 }
 
+static inline unsigned int
+queue_atomic_write_unit_max_bytes(const struct request_queue *q)
+{
+	return q->limits.atomic_write_unit_max;
+}
+
+static inline unsigned int
+queue_atomic_write_unit_min_bytes(const struct request_queue *q)
+{
+	return q->limits.atomic_write_unit_min;
+}
+
+static inline unsigned int
+queue_atomic_write_boundary_bytes(const struct request_queue *q)
+{
+	return q->limits.atomic_write_hw_boundary;
+}
+
+static inline unsigned int
+queue_atomic_write_max_bytes(const struct request_queue *q)
+{
+	return q->limits.atomic_write_max_sectors << SECTOR_SHIFT;
+}
+
 static inline unsigned int bdev_dma_alignment(struct block_device *bdev)
 {
 	return queue_dma_alignment(bdev_get_queue(bdev));
@@ -1592,6 +1633,26 @@  struct io_comp_batch {
 	void (*complete)(struct io_comp_batch *);
 };
 
+static inline bool bdev_can_atomic_write(struct block_device *bdev)
+{
+	struct request_queue *bd_queue = bdev->bd_queue;
+	struct queue_limits *limits = &bd_queue->limits;
+
+	if (!limits->atomic_write_unit_min)
+		return false;
+
+	if (bdev_is_partition(bdev)) {
+		sector_t bd_start_sect = bdev->bd_start_sect;
+		unsigned int alignment =
+			max(limits->atomic_write_unit_min,
+			    limits->atomic_write_hw_boundary);
+		if (!IS_ALIGNED(bd_start_sect, alignment))
+			return false;
+	}
+
+	return true;
+}
+
 #define DEFINE_IO_COMP_BATCH(name)	struct io_comp_batch name = { }
 
 #endif /* _LINUX_BLKDEV_H */