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Go Back   Linux Archive > Redhat > Device-mapper Development

 
 
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Old 05-05-2012, 03:57 AM
Mike Snitzer
 
Default dm: support for non power of 2 target IO sizes

Update DM core's max_io_len() to use sector_div() to support a target's
use of a non power of 2 blocksize.

Rename split_io to max_io_len in the dm_target structure and change data
type from sector_t to uint32_t. Introduce dm_set_target_max_io_len() to
check that each target's max_io_len does not exceed UINT_MAX.

Add do_div wrappers (dm_do_div and dm_do_mod) that don't modify the
dividend; these will be used by thin-pool and striped targets.

Signed-off-by: Mike Snitzer <snitzer@redhat.com>
---
drivers/md/dm-raid.c | 12 +++++-------
drivers/md/dm-raid1.c | 4 +++-
drivers/md/dm-snap.c | 19 +++++++++++--------
drivers/md/dm-stripe.c | 4 +++-
drivers/md/dm-thin.c | 4 +++-
drivers/md/dm.c | 28 +++++++++++++++++++++-------
include/linux/device-mapper.h | 20 ++++++++++++++++++--
7 files changed, 64 insertions(+), 27 deletions(-)

Index: linux/drivers/md/dm-raid.c
================================================== =================
--- linux.orig/drivers/md/dm-raid.c
+++ linux/drivers/md/dm-raid.c
@@ -356,6 +356,7 @@ static int parse_raid_params(struct raid
{
unsigned i, rebuild_cnt = 0;
unsigned long value, region_size = 0;
+ sector_t max_io_len;
char *key;

/*
@@ -525,14 +526,11 @@ static int parse_raid_params(struct raid
return -EINVAL;

if (rs->md.chunk_sectors)
- rs->ti->split_io = rs->md.chunk_sectors;
+ max_io_len = rs->md.chunk_sectors;
else
- rs->ti->split_io = region_size;
-
- if (rs->md.chunk_sectors)
- rs->ti->split_io = rs->md.chunk_sectors;
- else
- rs->ti->split_io = region_size;
+ max_io_len = region_size;
+ if (dm_set_target_max_io_len(rs->ti, max_io_len) < 0)
+ return -EINVAL;

/* Assume there are no metadata devices until the drives are parsed */
rs->md.persistent = 0;
Index: linux/drivers/md/dm-raid1.c
================================================== =================
--- linux.orig/drivers/md/dm-raid1.c
+++ linux/drivers/md/dm-raid1.c
@@ -1081,7 +1081,9 @@ static int mirror_ctr(struct dm_target *
}

ti->private = ms;
- ti->split_io = dm_rh_get_region_size(ms->rh);
+ r = dm_set_target_max_io_len(ti, dm_rh_get_region_size(ms->rh));
+ if (r < 0)
+ goto err_free_context;
ti->num_flush_requests = 1;
ti->num_discard_requests = 1;

Index: linux/drivers/md/dm-snap.c
================================================== =================
--- linux.orig/drivers/md/dm-snap.c
+++ linux/drivers/md/dm-snap.c
@@ -1172,7 +1172,10 @@ static int snapshot_ctr(struct dm_target
ti->error = "Chunk size not set";
goto bad_read_metadata;
}
- ti->split_io = s->store->chunk_size;
+
+ r = dm_set_target_max_io_len(ti, s->store->chunk_size);
+ if (r < 0)
+ goto bad_read_metadata;

return 0;

@@ -1239,7 +1242,7 @@ static void __handover_exceptions(struct
snap_dest->store->snap = snap_dest;
snap_src->store->snap = snap_src;

- snap_dest->ti->split_io = snap_dest->store->chunk_size;
+ snap_dest->ti->max_io_len = snap_dest->store->chunk_size;
snap_dest->valid = snap_src->valid;

/*
@@ -1838,9 +1841,9 @@ static void snapshot_merge_resume(struct
snapshot_resume(ti);

/*
- * snapshot-merge acts as an origin, so set ti->split_io
+ * snapshot-merge acts as an origin, so set ti->max_io_len
*/
- ti->split_io = get_origin_minimum_chunksize(s->origin->bdev);
+ ti->max_io_len = get_origin_minimum_chunksize(s->origin->bdev);

start_merge(s);
}
@@ -2073,12 +2076,12 @@ static int origin_write_extent(struct dm
struct origin *o;

/*
- * The origin's __minimum_chunk_size() got stored in split_io
+ * The origin's __minimum_chunk_size() got stored in max_io_len
* by snapshot_merge_resume().
*/
down_read(&_origins_lock);
o = __lookup_origin(merging_snap->origin->bdev);
- for (n = 0; n < size; n += merging_snap->ti->split_io)
+ for (n = 0; n < size; n += merging_snap->ti->max_io_len)
if (__origin_write(&o->snapshots, sector + n, NULL) ==
DM_MAPIO_SUBMITTED)
must_wait = 1;
@@ -2138,14 +2141,14 @@ static int origin_map(struct dm_target *
}

/*
- * Set the target "split_io" field to the minimum of all the snapshots'
+ * Set the target "max_io_len" field to the minimum of all the snapshots'
* chunk sizes.
*/
static void origin_resume(struct dm_target *ti)
{
struct dm_dev *dev = ti->private;

- ti->split_io = get_origin_minimum_chunksize(dev->bdev);
+ ti->max_io_len = get_origin_minimum_chunksize(dev->bdev);
}

static int origin_status(struct dm_target *ti, status_type_t type, char *result,
Index: linux/drivers/md/dm-stripe.c
================================================== =================
--- linux.orig/drivers/md/dm-stripe.c
+++ linux/drivers/md/dm-stripe.c
@@ -172,7 +172,9 @@ static int stripe_ctr(struct dm_target *
sc->stripes_mask = ((sector_t) stripes) - 1;
}

- ti->split_io = chunk_size;
+ r = dm_set_target_max_io_len(ti, chunk_size);
+ if (r < 0)
+ return r;
ti->num_flush_requests = stripes;
ti->num_discard_requests = stripes;

Index: linux/drivers/md/dm-thin.c
================================================== =================
--- linux.orig/drivers/md/dm-thin.c
+++ linux/drivers/md/dm-thin.c
@@ -2575,7 +2575,9 @@ static int thin_ctr(struct dm_target *ti
goto bad_thin_open;
}

- ti->split_io = tc->pool->sectors_per_block;
+ r = dm_set_target_max_io_len(ti, tc->pool->sectors_per_block);
+ if (r < 0)
+ goto bad_thin_open;
ti->num_flush_requests = 1;

/* In case the pool supports discards, pass them on. */
Index: linux/drivers/md/dm.c
================================================== =================
--- linux.orig/drivers/md/dm.c
+++ linux/drivers/md/dm.c
@@ -970,20 +970,34 @@ static sector_t max_io_len(sector_t sect
sector_t len = max_io_len_target_boundary(sector, ti);

/*
- * Does the target need to split even further ?
+ * Does the target need to split even further?
*/
- if (ti->split_io) {
- sector_t boundary;
+ if (ti->max_io_len) {
sector_t offset = dm_target_offset(ti, sector);
- boundary = ((offset + ti->split_io) & ~(ti->split_io - 1))
- - offset;
- if (len > boundary)
- len = boundary;
+ sector_t boundary = offset + ti->max_io_len;
+ sector_t max_len = ti->max_io_len - sector_div(boundary, ti->max_io_len);
+
+ if (len > max_len)
+ len = max_len;
}

return len;
}

+int dm_set_target_max_io_len(struct dm_target *ti, sector_t len)
+{
+ if (len > UINT_MAX) {
+ DMERR("Specified maximum size of target IO (%llu) exceeds limit (%u)",
+ (unsigned long long)len, UINT_MAX);
+ ti->error = "Maximum size of target IO is too large";
+ return -EINVAL;
+ }
+
+ ti->max_io_len = (uint32_t) len;
+ return 0;
+}
+EXPORT_SYMBOL_GPL(dm_set_target_max_io_len);
+
static void __map_bio(struct dm_target *ti, struct bio *clone,
struct dm_target_io *tio)
{
Index: linux/include/linux/device-mapper.h
================================================== =================
--- linux.orig/include/linux/device-mapper.h
+++ linux/include/linux/device-mapper.h
@@ -188,8 +188,8 @@ struct dm_target {
sector_t begin;
sector_t len;

- /* Always a power of 2 */
- sector_t split_io;
+ /* If non-zero, maximum size of I/O submitted to a target. */
+ uint32_t max_io_len;

/*
* A number of zero-length barrier requests that will be submitted
@@ -503,6 +503,20 @@ static inline unsigned long to_bytes(sec
return (n << SECTOR_SHIFT);
}

+/*
+ * do_div wrappers that don't modify the dividend
+ */
+static inline sector_t dm_do_div(sector_t a, uint32_t b)
+{
+ do_div(a, b);
+ return a;
+}
+
+static inline uint32_t dm_do_mod(sector_t a, uint32_t b)
+{
+ return do_div(a, b);
+}
+
/*-----------------------------------------------------------------
* Helper for block layer and dm core operations
*---------------------------------------------------------------*/
@@ -511,4 +525,6 @@ void dm_requeue_unmapped_request(struct
void dm_kill_unmapped_request(struct request *rq, int error);
int dm_underlying_device_busy(struct request_queue *q);

+int __must_check dm_set_target_max_io_len(struct dm_target *ti, sector_t len);
+
#endif /* _LINUX_DEVICE_MAPPER_H */

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