dm: support non power of two target max_io_len

Remove the restriction that limits a target's specified maximum incoming
I/O size to be a power of 2.

Rename this setting from 'split_io' to the less-ambiguous 'max_io_len'.
Change it from sector_t to uint32_t, which is plenty big enough, and
introduce a wrapper function dm_set_target_max_io_len() to set it.
Use sector_div() to process it now that it is not necessarily a power of 2.

Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>

6 files changed, 60 insertions, 29 deletions

diff --git a/drivers/md/dm-raid.c b/drivers/md/dm-raid.c
index 017c34d78d61..858a8b70811c 100644
--- a/drivers/md/dm-raid.c
+++ b/drivers/md/dm-raid.c
@@ -353,6 +353,7 @@ static int parse_raid_params(struct raid_set *rs, char **argv,
 {
         unsigned i, rebuild_cnt = 0;
         unsigned long value, region_size = 0;
+        sector_t max_io_len;
         char *key;
 
         /*
@@ -522,14 +523,12 @@ static int parse_raid_params(struct raid_set *rs, char **argv,
                 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;
+                max_io_len = region_size;
 
-        if (rs->md.chunk_sectors)
-                rs->ti->split_io = rs->md.chunk_sectors;
-        else
-                rs->ti->split_io = region_size;
+        if (dm_set_target_max_io_len(rs->ti, max_io_len))
+                return -EINVAL;
 
         /* Assume there are no metadata devices until the drives are parsed */
         rs->md.persistent = 0;
diff --git a/drivers/md/dm-raid1.c b/drivers/md/dm-raid1.c
index b58b7a33914a..819ccba65912 100644
--- a/drivers/md/dm-raid1.c
+++ b/drivers/md/dm-raid1.c
@@ -1081,7 +1081,11 @@ static int mirror_ctr(struct dm_target *ti, unsigned int argc, char **argv)
         }
 
         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)
+                goto err_free_context;
+
         ti->num_flush_requests = 1;
         ti->num_discard_requests = 1;
         ti->discard_zeroes_data_unsupported = 1;
diff --git a/drivers/md/dm-snap.c b/drivers/md/dm-snap.c
index a228c20e40b3..6c0f3e33923a 100644
--- a/drivers/md/dm-snap.c
+++ b/drivers/md/dm-snap.c
@@ -691,7 +691,7 @@ static int dm_add_exception(void *context, chunk_t old, chunk_t new)
  * Return a minimum chunk size of all snapshots that have the specified origin.
  * Return zero if the origin has no snapshots.
  */
-static sector_t __minimum_chunk_size(struct origin *o)
+static uint32_t __minimum_chunk_size(struct origin *o)
 {
         struct dm_snapshot *snap;
         unsigned chunk_size = 0;
@@ -701,7 +701,7 @@ static sector_t __minimum_chunk_size(struct origin *o)
                         chunk_size = min_not_zero(chunk_size,
                                                   snap->store->chunk_size);
 
-        return chunk_size;
+        return (uint32_t) chunk_size;
 }
 
 /*
@@ -1172,7 +1172,10 @@ static int snapshot_ctr(struct dm_target *ti, unsigned int argc, char **argv)
                 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)
+                goto bad_read_metadata;
 
         return 0;
 
@@ -1239,7 +1242,7 @@ static void __handover_exceptions(struct dm_snapshot *snap_src,
         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;
 
         /*
@@ -1817,9 +1820,9 @@ static void snapshot_resume(struct dm_target *ti)
         up_write(&s->lock);
 }
 
-static sector_t get_origin_minimum_chunksize(struct block_device *bdev)
+static uint32_t get_origin_minimum_chunksize(struct block_device *bdev)
 {
-        sector_t min_chunksize;
+        uint32_t min_chunksize;
 
         down_read(&_origins_lock);
         min_chunksize = __minimum_chunk_size(__lookup_origin(bdev));
@@ -1838,9 +1841,9 @@ static void snapshot_merge_resume(struct dm_target *ti)
         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_snapshot *merging_snap,
         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 *ti, struct bio *bio,
 }
 
 /*
- * 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,
diff --git a/drivers/md/dm-stripe.c b/drivers/md/dm-stripe.c
index 6931bd18b615..992c9d4c3bd9 100644
--- a/drivers/md/dm-stripe.c
+++ b/drivers/md/dm-stripe.c
@@ -165,7 +165,10 @@ static int stripe_ctr(struct dm_target *ti, unsigned int argc, char **argv)
         else
                 sc->stripes_shift = __ffs(stripes);
 
-        ti->split_io = chunk_size;
+        r = dm_set_target_max_io_len(ti, chunk_size);
+        if (r)
+                return r;
+
         ti->num_flush_requests = stripes;
         ti->num_discard_requests = stripes;
 
diff --git a/drivers/md/dm-thin.c b/drivers/md/dm-thin.c
index e89f8e7d8a33..350bcf40485e 100644
--- a/drivers/md/dm-thin.c
+++ b/drivers/md/dm-thin.c
@@ -2628,7 +2628,10 @@ static int thin_ctr(struct dm_target *ti, unsigned argc, char **argv)
                 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)
+                goto bad_thin_open;
+
         ti->num_flush_requests = 1;
 
         /* In case the pool supports discards, pass them on. */
diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index e24143cc2040..415c2803c0c9 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -968,22 +968,41 @@ static sector_t max_io_len_target_boundary(sector_t sector, struct dm_target *ti
 static sector_t max_io_len(sector_t sector, struct dm_target *ti)
 {
         sector_t len = max_io_len_target_boundary(sector, ti);
+        sector_t offset, max_len;
 
         /*
-         * Does the target need to split even further ?
+         * Does the target need to split even further?
          */
-        if (ti->split_io) {
-                sector_t boundary;
-                sector_t offset = dm_target_offset(ti, sector);
-                boundary = ((offset + ti->split_io) & ~(ti->split_io - 1))
-                           - offset;
-                if (len > boundary)
-                        len = boundary;
+        if (ti->max_io_len) {
+                offset = dm_target_offset(ti, sector);
+                if (unlikely(ti->max_io_len & (ti->max_io_len - 1)))
+                        max_len = sector_div(offset, ti->max_io_len);
+                else
+                        max_len = offset & (ti->max_io_len - 1);
+                max_len = ti->max_io_len - max_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)
 {