[19/42] dm: set bi_op to REQ_OP
diff mbox

Message ID 1460576188-5751-20-git-send-email-mchristi@redhat.com
State New
Headers show

Commit Message

Mike Christie April 13, 2016, 7:36 p.m. UTC
From: Mike Christie <mchristi@redhat.com>

This patch has dm use bio->bi_op for REQ_OPs and rq_flag_bits
to bio->bi_rw.

Signed-off-by: Mike Christie <mchristi@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
---
 drivers/md/dm-bufio.c           |  8 +++---
 drivers/md/dm-crypt.c           |  1 +
 drivers/md/dm-io.c              | 57 ++++++++++++++++++++++-------------------
 drivers/md/dm-kcopyd.c          | 25 +++++++++---------
 drivers/md/dm-log-writes.c      |  6 ++---
 drivers/md/dm-log.c             |  5 ++--
 drivers/md/dm-raid1.c           | 11 +++++---
 drivers/md/dm-snap-persistent.c | 24 +++++++++--------
 drivers/md/dm-thin.c            |  7 ++---
 drivers/md/dm.c                 |  1 +
 include/linux/dm-io.h           |  3 ++-
 11 files changed, 82 insertions(+), 66 deletions(-)

Patch
diff mbox

diff --git a/drivers/md/dm-bufio.c b/drivers/md/dm-bufio.c
index 9d3ee7f..b6055f2 100644
--- a/drivers/md/dm-bufio.c
+++ b/drivers/md/dm-bufio.c
@@ -574,7 +574,8 @@  static void use_dmio(struct dm_buffer *b, int rw, sector_t block,
 {
 	int r;
 	struct dm_io_request io_req = {
-		.bi_rw = rw,
+		.bi_op = rw,
+		.bi_op_flags = 0,
 		.notify.fn = dmio_complete,
 		.notify.context = b,
 		.client = b->c->dm_io,
@@ -634,7 +635,7 @@  static void use_inline_bio(struct dm_buffer *b, int rw, sector_t block,
 	 * the dm_buffer's inline bio is local to bufio.
 	 */
 	b->bio.bi_private = end_io;
-	b->bio.bi_rw = rw;
+	b->bio.bi_op = rw;
 
 	/*
 	 * We assume that if len >= PAGE_SIZE ptr is page-aligned.
@@ -1327,7 +1328,8 @@  EXPORT_SYMBOL_GPL(dm_bufio_write_dirty_buffers);
 int dm_bufio_issue_flush(struct dm_bufio_client *c)
 {
 	struct dm_io_request io_req = {
-		.bi_rw = WRITE_FLUSH,
+		.bi_op = REQ_OP_WRITE,
+		.bi_op_flags = WRITE_FLUSH,
 		.mem.type = DM_IO_KMEM,
 		.mem.ptr.addr = NULL,
 		.client = c->dm_io,
diff --git a/drivers/md/dm-crypt.c b/drivers/md/dm-crypt.c
index 4f3cb35..70fbf11 100644
--- a/drivers/md/dm-crypt.c
+++ b/drivers/md/dm-crypt.c
@@ -1136,6 +1136,7 @@  static void clone_init(struct dm_crypt_io *io, struct bio *clone)
 	clone->bi_private = io;
 	clone->bi_end_io  = crypt_endio;
 	clone->bi_bdev    = cc->dev->bdev;
+	clone->bi_op      = io->base_bio->bi_op;
 	clone->bi_rw      = io->base_bio->bi_rw;
 }
 
diff --git a/drivers/md/dm-io.c b/drivers/md/dm-io.c
index 50f17e3..0f723ca 100644
--- a/drivers/md/dm-io.c
+++ b/drivers/md/dm-io.c
@@ -278,8 +278,9 @@  static void km_dp_init(struct dpages *dp, void *data)
 /*-----------------------------------------------------------------
  * IO routines that accept a list of pages.
  *---------------------------------------------------------------*/
-static void do_region(int rw, unsigned region, struct dm_io_region *where,
-		      struct dpages *dp, struct io *io)
+static void do_region(int op, int op_flags, unsigned region,
+		      struct dm_io_region *where, struct dpages *dp,
+		      struct io *io)
 {
 	struct bio *bio;
 	struct page *page;
@@ -295,24 +296,25 @@  static void do_region(int rw, unsigned region, struct dm_io_region *where,
 	/*
 	 * Reject unsupported discard and write same requests.
 	 */
-	if (rw & REQ_DISCARD)
+	if (op == REQ_OP_DISCARD)
 		special_cmd_max_sectors = q->limits.max_discard_sectors;
-	else if (rw & REQ_WRITE_SAME)
+	else if (op == REQ_OP_WRITE_SAME)
 		special_cmd_max_sectors = q->limits.max_write_same_sectors;
-	if ((rw & (REQ_DISCARD | REQ_WRITE_SAME)) && special_cmd_max_sectors == 0) {
+	if ((op == REQ_OP_DISCARD || op == REQ_OP_WRITE_SAME) &&
+	    special_cmd_max_sectors == 0) {
 		dec_count(io, region, -EOPNOTSUPP);
 		return;
 	}
 
 	/*
-	 * where->count may be zero if rw holds a flush and we need to
+	 * where->count may be zero if op holds a flush and we need to
 	 * send a zero-sized flush.
 	 */
 	do {
 		/*
 		 * Allocate a suitably sized-bio.
 		 */
-		if ((rw & REQ_DISCARD) || (rw & REQ_WRITE_SAME))
+		if ((op == REQ_OP_DISCARD) || (op == REQ_OP_WRITE_SAME))
 			num_bvecs = 1;
 		else
 			num_bvecs = min_t(int, BIO_MAX_PAGES,
@@ -322,14 +324,15 @@  static void do_region(int rw, unsigned region, struct dm_io_region *where,
 		bio->bi_iter.bi_sector = where->sector + (where->count - remaining);
 		bio->bi_bdev = where->bdev;
 		bio->bi_end_io = endio;
-		bio->bi_rw = rw;
+		bio->bi_op = op;
+		bio->bi_rw = op_flags;
 		store_io_and_region_in_bio(bio, io, region);
 
-		if (rw & REQ_DISCARD) {
+		if (op == REQ_OP_DISCARD) {
 			num_sectors = min_t(sector_t, special_cmd_max_sectors, remaining);
 			bio->bi_iter.bi_size = num_sectors << SECTOR_SHIFT;
 			remaining -= num_sectors;
-		} else if (rw & REQ_WRITE_SAME) {
+		} else if (op == REQ_OP_WRITE_SAME) {
 			/*
 			 * WRITE SAME only uses a single page.
 			 */
@@ -360,7 +363,7 @@  static void do_region(int rw, unsigned region, struct dm_io_region *where,
 	} while (remaining);
 }
 
-static void dispatch_io(int rw, unsigned int num_regions,
+static void dispatch_io(int op, int op_flags, unsigned int num_regions,
 			struct dm_io_region *where, struct dpages *dp,
 			struct io *io, int sync)
 {
@@ -370,7 +373,7 @@  static void dispatch_io(int rw, unsigned int num_regions,
 	BUG_ON(num_regions > DM_IO_MAX_REGIONS);
 
 	if (sync)
-		rw |= REQ_SYNC;
+		op_flags |= REQ_SYNC;
 
 	/*
 	 * For multiple regions we need to be careful to rewind
@@ -378,8 +381,8 @@  static void dispatch_io(int rw, unsigned int num_regions,
 	 */
 	for (i = 0; i < num_regions; i++) {
 		*dp = old_pages;
-		if (where[i].count || (rw & REQ_FLUSH))
-			do_region(rw, i, where + i, dp, io);
+		if (where[i].count || (op_flags & REQ_FLUSH))
+			do_region(op, op_flags, i, where + i, dp, io);
 	}
 
 	/*
@@ -403,13 +406,13 @@  static void sync_io_complete(unsigned long error, void *context)
 }
 
 static int sync_io(struct dm_io_client *client, unsigned int num_regions,
-		   struct dm_io_region *where, int rw, struct dpages *dp,
-		   unsigned long *error_bits)
+		   struct dm_io_region *where, int op, int op_flags,
+		   struct dpages *dp, unsigned long *error_bits)
 {
 	struct io *io;
 	struct sync_io sio;
 
-	if (num_regions > 1 && (rw & RW_MASK) != WRITE) {
+	if (num_regions > 1 && !op_is_write(op)) {
 		WARN_ON(1);
 		return -EIO;
 	}
@@ -426,7 +429,7 @@  static int sync_io(struct dm_io_client *client, unsigned int num_regions,
 	io->vma_invalidate_address = dp->vma_invalidate_address;
 	io->vma_invalidate_size = dp->vma_invalidate_size;
 
-	dispatch_io(rw, num_regions, where, dp, io, 1);
+	dispatch_io(op, op_flags, num_regions, where, dp, io, 1);
 
 	wait_for_completion_io(&sio.wait);
 
@@ -437,12 +440,12 @@  static int sync_io(struct dm_io_client *client, unsigned int num_regions,
 }
 
 static int async_io(struct dm_io_client *client, unsigned int num_regions,
-		    struct dm_io_region *where, int rw, struct dpages *dp,
-		    io_notify_fn fn, void *context)
+		    struct dm_io_region *where, int op, int op_flags,
+		    struct dpages *dp, io_notify_fn fn, void *context)
 {
 	struct io *io;
 
-	if (num_regions > 1 && (rw & RW_MASK) != WRITE) {
+	if (num_regions > 1 && !op_is_write(op)) {
 		WARN_ON(1);
 		fn(1, context);
 		return -EIO;
@@ -458,7 +461,7 @@  static int async_io(struct dm_io_client *client, unsigned int num_regions,
 	io->vma_invalidate_address = dp->vma_invalidate_address;
 	io->vma_invalidate_size = dp->vma_invalidate_size;
 
-	dispatch_io(rw, num_regions, where, dp, io, 0);
+	dispatch_io(op, op_flags, num_regions, where, dp, io, 0);
 	return 0;
 }
 
@@ -481,7 +484,7 @@  static int dp_init(struct dm_io_request *io_req, struct dpages *dp,
 
 	case DM_IO_VMA:
 		flush_kernel_vmap_range(io_req->mem.ptr.vma, size);
-		if ((io_req->bi_rw & RW_MASK) == READ) {
+		if (io_req->bi_op == REQ_OP_READ) {
 			dp->vma_invalidate_address = io_req->mem.ptr.vma;
 			dp->vma_invalidate_size = size;
 		}
@@ -519,10 +522,12 @@  int dm_io(struct dm_io_request *io_req, unsigned num_regions,
 
 	if (!io_req->notify.fn)
 		return sync_io(io_req->client, num_regions, where,
-			       io_req->bi_rw, &dp, sync_error_bits);
+			       io_req->bi_op, io_req->bi_op_flags, &dp,
+			       sync_error_bits);
 
-	return async_io(io_req->client, num_regions, where, io_req->bi_rw,
-			&dp, io_req->notify.fn, io_req->notify.context);
+	return async_io(io_req->client, num_regions, where, io_req->bi_op,
+			io_req->bi_op_flags, &dp, io_req->notify.fn,
+			io_req->notify.context);
 }
 EXPORT_SYMBOL(dm_io);
 
diff --git a/drivers/md/dm-kcopyd.c b/drivers/md/dm-kcopyd.c
index 1452ed9..4182bc7d 100644
--- a/drivers/md/dm-kcopyd.c
+++ b/drivers/md/dm-kcopyd.c
@@ -465,10 +465,10 @@  static void complete_io(unsigned long error, void *context)
 	io_job_finish(kc->throttle);
 
 	if (error) {
-		if (job->rw & WRITE)
-			job->write_err |= error;
-		else
+		if (job->rw == READ)
 			job->read_err = 1;
+		else
+			job->write_err |= error;
 
 		if (!test_bit(DM_KCOPYD_IGNORE_ERROR, &job->flags)) {
 			push(&kc->complete_jobs, job);
@@ -477,13 +477,11 @@  static void complete_io(unsigned long error, void *context)
 		}
 	}
 
-	if (job->rw & WRITE)
-		push(&kc->complete_jobs, job);
-
-	else {
+	if (job->rw == READ) {
 		job->rw = WRITE;
 		push(&kc->io_jobs, job);
-	}
+	} else
+		push(&kc->complete_jobs, job);
 
 	wake(kc);
 }
@@ -496,7 +494,8 @@  static int run_io_job(struct kcopyd_job *job)
 {
 	int r;
 	struct dm_io_request io_req = {
-		.bi_rw = job->rw,
+		.bi_op = job->rw,
+		.bi_op_flags = 0,
 		.mem.type = DM_IO_PAGE_LIST,
 		.mem.ptr.pl = job->pages,
 		.mem.offset = 0,
@@ -550,10 +549,10 @@  static int process_jobs(struct list_head *jobs, struct dm_kcopyd_client *kc,
 
 		if (r < 0) {
 			/* error this rogue job */
-			if (job->rw & WRITE)
-				job->write_err = (unsigned long) -1L;
-			else
+			if (job->rw == READ)
 				job->read_err = 1;
+			else
+				job->write_err = (unsigned long) -1L;
 			push(&kc->complete_jobs, job);
 			break;
 		}
@@ -734,7 +733,7 @@  int dm_kcopyd_copy(struct dm_kcopyd_client *kc, struct dm_io_region *from,
 		/*
 		 * Use WRITE SAME to optimize zeroing if all dests support it.
 		 */
-		job->rw = WRITE | REQ_WRITE_SAME;
+		job->rw = REQ_OP_WRITE_SAME;
 		for (i = 0; i < job->num_dests; i++)
 			if (!bdev_write_same(job->dests[i].bdev)) {
 				job->rw = WRITE;
diff --git a/drivers/md/dm-log-writes.c b/drivers/md/dm-log-writes.c
index addcc4b..27630c5 100644
--- a/drivers/md/dm-log-writes.c
+++ b/drivers/md/dm-log-writes.c
@@ -205,7 +205,7 @@  static int write_metadata(struct log_writes_c *lc, void *entry,
 	bio->bi_bdev = lc->logdev->bdev;
 	bio->bi_end_io = log_end_io;
 	bio->bi_private = lc;
-	bio->bi_rw = WRITE;
+	bio->bi_op = REQ_OP_WRITE;
 
 	page = alloc_page(GFP_KERNEL);
 	if (!page) {
@@ -270,7 +270,7 @@  static int log_one_block(struct log_writes_c *lc,
 	bio->bi_bdev = lc->logdev->bdev;
 	bio->bi_end_io = log_end_io;
 	bio->bi_private = lc;
-	bio->bi_rw = WRITE;
+	bio->bi_op = REQ_OP_WRITE;
 
 	for (i = 0; i < block->vec_cnt; i++) {
 		/*
@@ -292,7 +292,7 @@  static int log_one_block(struct log_writes_c *lc,
 			bio->bi_bdev = lc->logdev->bdev;
 			bio->bi_end_io = log_end_io;
 			bio->bi_private = lc;
-			bio->bi_rw = WRITE;
+			bio->bi_op = REQ_OP_WRITE;
 
 			ret = bio_add_page(bio, block->vecs[i].bv_page,
 					   block->vecs[i].bv_len, 0);
diff --git a/drivers/md/dm-log.c b/drivers/md/dm-log.c
index 627d191..4ca2d1d 100644
--- a/drivers/md/dm-log.c
+++ b/drivers/md/dm-log.c
@@ -293,7 +293,7 @@  static void header_from_disk(struct log_header_core *core, struct log_header_dis
 
 static int rw_header(struct log_c *lc, int rw)
 {
-	lc->io_req.bi_rw = rw;
+	lc->io_req.bi_op = rw;
 
 	return dm_io(&lc->io_req, 1, &lc->header_location, NULL);
 }
@@ -306,7 +306,8 @@  static int flush_header(struct log_c *lc)
 		.count = 0,
 	};
 
-	lc->io_req.bi_rw = WRITE_FLUSH;
+	lc->io_req.bi_op = REQ_OP_WRITE;
+	lc->io_req.bi_op_flags = WRITE_FLUSH;
 
 	return dm_io(&lc->io_req, 1, &null_location, NULL);
 }
diff --git a/drivers/md/dm-raid1.c b/drivers/md/dm-raid1.c
index b3ccf1e..8a86bc3 100644
--- a/drivers/md/dm-raid1.c
+++ b/drivers/md/dm-raid1.c
@@ -260,7 +260,8 @@  static int mirror_flush(struct dm_target *ti)
 	struct dm_io_region io[ms->nr_mirrors];
 	struct mirror *m;
 	struct dm_io_request io_req = {
-		.bi_rw = WRITE_FLUSH,
+		.bi_op = REQ_OP_WRITE,
+		.bi_op_flags = WRITE_FLUSH,
 		.mem.type = DM_IO_KMEM,
 		.mem.ptr.addr = NULL,
 		.client = ms->io_client,
@@ -541,7 +542,8 @@  static void read_async_bio(struct mirror *m, struct bio *bio)
 {
 	struct dm_io_region io;
 	struct dm_io_request io_req = {
-		.bi_rw = READ,
+		.bi_op = REQ_OP_READ,
+		.bi_op_flags = 0,
 		.mem.type = DM_IO_BIO,
 		.mem.ptr.bio = bio,
 		.notify.fn = read_callback,
@@ -654,7 +656,8 @@  static void do_write(struct mirror_set *ms, struct bio *bio)
 	struct dm_io_region io[ms->nr_mirrors], *dest = io;
 	struct mirror *m;
 	struct dm_io_request io_req = {
-		.bi_rw = WRITE | (bio->bi_rw & WRITE_FLUSH_FUA),
+		.bi_op = REQ_OP_WRITE,
+		.bi_op_flags = bio->bi_rw & WRITE_FLUSH_FUA,
 		.mem.type = DM_IO_BIO,
 		.mem.ptr.bio = bio,
 		.notify.fn = write_callback,
@@ -663,7 +666,7 @@  static void do_write(struct mirror_set *ms, struct bio *bio)
 	};
 
 	if (bio->bi_rw & REQ_DISCARD) {
-		io_req.bi_rw |= REQ_DISCARD;
+		io_req.bi_op = REQ_OP_DISCARD;
 		io_req.mem.type = DM_IO_KMEM;
 		io_req.mem.ptr.addr = NULL;
 	}
diff --git a/drivers/md/dm-snap-persistent.c b/drivers/md/dm-snap-persistent.c
index 4d39093..b8cf956 100644
--- a/drivers/md/dm-snap-persistent.c
+++ b/drivers/md/dm-snap-persistent.c
@@ -226,8 +226,8 @@  static void do_metadata(struct work_struct *work)
 /*
  * Read or write a chunk aligned and sized block of data from a device.
  */
-static int chunk_io(struct pstore *ps, void *area, chunk_t chunk, int rw,
-		    int metadata)
+static int chunk_io(struct pstore *ps, void *area, chunk_t chunk, int op,
+		    int op_flags, int metadata)
 {
 	struct dm_io_region where = {
 		.bdev = dm_snap_cow(ps->store->snap)->bdev,
@@ -235,7 +235,8 @@  static int chunk_io(struct pstore *ps, void *area, chunk_t chunk, int rw,
 		.count = ps->store->chunk_size,
 	};
 	struct dm_io_request io_req = {
-		.bi_rw = rw,
+		.bi_op = op,
+		.bi_op_flags = op_flags,
 		.mem.type = DM_IO_VMA,
 		.mem.ptr.vma = area,
 		.client = ps->io_client,
@@ -281,14 +282,14 @@  static void skip_metadata(struct pstore *ps)
  * Read or write a metadata area.  Remembering to skip the first
  * chunk which holds the header.
  */
-static int area_io(struct pstore *ps, int rw)
+static int area_io(struct pstore *ps, int op, int op_flags)
 {
 	int r;
 	chunk_t chunk;
 
 	chunk = area_location(ps, ps->current_area);
 
-	r = chunk_io(ps, ps->area, chunk, rw, 0);
+	r = chunk_io(ps, ps->area, chunk, op, op_flags, 0);
 	if (r)
 		return r;
 
@@ -302,7 +303,8 @@  static void zero_memory_area(struct pstore *ps)
 
 static int zero_disk_area(struct pstore *ps, chunk_t area)
 {
-	return chunk_io(ps, ps->zero_area, area_location(ps, area), WRITE, 0);
+	return chunk_io(ps, ps->zero_area, area_location(ps, area),
+			REQ_OP_WRITE, 0, 0);
 }
 
 static int read_header(struct pstore *ps, int *new_snapshot)
@@ -334,7 +336,7 @@  static int read_header(struct pstore *ps, int *new_snapshot)
 	if (r)
 		return r;
 
-	r = chunk_io(ps, ps->header_area, 0, READ, 1);
+	r = chunk_io(ps, ps->header_area, 0, REQ_OP_READ, 0, 1);
 	if (r)
 		goto bad;
 
@@ -395,7 +397,7 @@  static int write_header(struct pstore *ps)
 	dh->version = cpu_to_le32(ps->version);
 	dh->chunk_size = cpu_to_le32(ps->store->chunk_size);
 
-	return chunk_io(ps, ps->header_area, 0, WRITE, 1);
+	return chunk_io(ps, ps->header_area, 0, REQ_OP_WRITE, 0, 1);
 }
 
 /*
@@ -739,7 +741,7 @@  static void persistent_commit_exception(struct dm_exception_store *store,
 	/*
 	 * Commit exceptions to disk.
 	 */
-	if (ps->valid && area_io(ps, WRITE_FLUSH_FUA))
+	if (ps->valid && area_io(ps, REQ_OP_WRITE, WRITE_FLUSH_FUA))
 		ps->valid = 0;
 
 	/*
@@ -779,7 +781,7 @@  static int persistent_prepare_merge(struct dm_exception_store *store,
 			return 0;
 
 		ps->current_area--;
-		r = area_io(ps, READ);
+		r = area_io(ps, REQ_OP_READ, 0);
 		if (r < 0)
 			return r;
 		ps->current_committed = ps->exceptions_per_area;
@@ -816,7 +818,7 @@  static int persistent_commit_merge(struct dm_exception_store *store,
 	for (i = 0; i < nr_merged; i++)
 		clear_exception(ps, ps->current_committed - 1 - i);
 
-	r = area_io(ps, WRITE_FLUSH_FUA);
+	r = area_io(ps, REQ_OP_WRITE, WRITE_FLUSH_FUA);
 	if (r < 0)
 		return r;
 
diff --git a/drivers/md/dm-thin.c b/drivers/md/dm-thin.c
index 69d86e1..6049078 100644
--- a/drivers/md/dm-thin.c
+++ b/drivers/md/dm-thin.c
@@ -339,7 +339,7 @@  static int __blkdev_issue_discard_async(struct block_device *bdev, sector_t sect
 					struct bio *parent_bio)
 {
 	struct request_queue *q = bdev_get_queue(bdev);
-	int type = REQ_WRITE | REQ_DISCARD;
+	int op_flags = 0;
 	struct bio *bio;
 
 	if (!q || !nr_sects)
@@ -351,7 +351,7 @@  static int __blkdev_issue_discard_async(struct block_device *bdev, sector_t sect
 	if (flags & BLKDEV_DISCARD_SECURE) {
 		if (!blk_queue_secdiscard(q))
 			return -EOPNOTSUPP;
-		type |= REQ_SECURE;
+		op_flags |= REQ_SECURE;
 	}
 
 	/*
@@ -366,7 +366,8 @@  static int __blkdev_issue_discard_async(struct block_device *bdev, sector_t sect
 	bio->bi_iter.bi_sector = sector;
 	bio->bi_bdev = bdev;
 	bio->bi_iter.bi_size = nr_sects << 9;
-	bio->bi_rw = type;
+	bio->bi_op = REQ_OP_DISCARD;
+	bio->bi_rw = op_flags;
 
 	submit_bio(bio);
 
diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index 1b2f962..5432da7 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -2412,6 +2412,7 @@  static struct mapped_device *alloc_dev(int minor)
 
 	bio_init(&md->flush_bio);
 	md->flush_bio.bi_bdev = md->bdev;
+	md->flush_bio.bi_op = REQ_OP_WRITE;
 	md->flush_bio.bi_rw = WRITE_FLUSH;
 
 	dm_stats_init(&md->stats);
diff --git a/include/linux/dm-io.h b/include/linux/dm-io.h
index a68cbe5..b91b023 100644
--- a/include/linux/dm-io.h
+++ b/include/linux/dm-io.h
@@ -57,7 +57,8 @@  struct dm_io_notify {
  */
 struct dm_io_client;
 struct dm_io_request {
-	int bi_rw;			/* READ|WRITE - not READA */
+	int bi_op;			/* REQ_OP */
+	int bi_op_flags;		/* rq_flag_bits */
 	struct dm_io_memory mem;	/* Memory to use for io */
 	struct dm_io_notify notify;	/* Synchronous if notify.fn is NULL */
 	struct dm_io_client *client;	/* Client memory handler */