dm raid: add region_size parameter

Allow the user to specify the region_size.

Ensures that the supplied value meets md's constraints, viz. the number of
regions does not exceed 2^21.

Signed-off-by: Jonathan Brassow <jbrassow@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>

1 files changed, 79 insertions, 3 deletions

diff --git a/drivers/md/dm-raid.c b/drivers/md/dm-raid.c
index d4e95b2e39f6..a8a1915a450d 100644
--- a/drivers/md/dm-raid.c
+++ b/drivers/md/dm-raid.c
@@ -52,7 +52,7 @@ struct raid_dev {
 #define DMPF_MAX_RECOVERY_RATE 0x20
 #define DMPF_MAX_WRITE_BEHIND  0x40
 #define DMPF_STRIPE_CACHE      0x80
-
+#define DMPF_REGION_SIZE       0X100
 struct raid_set {
         struct dm_target *ti;
 
@@ -237,6 +237,67 @@ static int dev_parms(struct raid_set *rs, char **argv)
 }
 
 /*
+ * validate_region_size
+ * @rs
+ * @region_size:  region size in sectors.  If 0, pick a size (4MiB default).
+ *
+ * Set rs->md.bitmap_info.chunksize (which really refers to 'region size').
+ * Ensure that (ti->len/region_size < 2^21) - required by MD bitmap.
+ *
+ * Returns: 0 on success, -EINVAL on failure.
+ */
+static int validate_region_size(struct raid_set *rs, unsigned long region_size)
+{
+        unsigned long min_region_size = rs->ti->len / (1 << 21);
+
+        if (!region_size) {
+                /*
+                 * Choose a reasonable default.  All figures in sectors.
+                 */
+                if (min_region_size > (1 << 13)) {
+                        DMINFO("Choosing default region size of %lu sectors",
+                               region_size);
+                        region_size = min_region_size;
+                } else {
+                        DMINFO("Choosing default region size of 4MiB");
+                        region_size = 1 << 13; /* sectors */
+                }
+        } else {
+                /*
+                 * Validate user-supplied value.
+                 */
+                if (region_size > rs->ti->len) {
+                        rs->ti->error = "Supplied region size is too large";
+                        return -EINVAL;
+                }
+
+                if (region_size < min_region_size) {
+                        DMERR("Supplied region_size (%lu sectors) below minimum (%lu)",
+                              region_size, min_region_size);
+                        rs->ti->error = "Supplied region size is too small";
+                        return -EINVAL;
+                }
+
+                if (!is_power_of_2(region_size)) {
+                        rs->ti->error = "Region size is not a power of 2";
+                        return -EINVAL;
+                }
+
+                if (region_size < rs->md.chunk_sectors) {
+                        rs->ti->error = "Region size is smaller than the chunk size";
+                        return -EINVAL;
+                }
+        }
+
+        /*
+         * Convert sectors to bytes.
+         */
+        rs->md.bitmap_info.chunksize = (region_size << 9);
+
+        return 0;
+}
+
+/*
  * Possible arguments are...
  * RAID456:
  *      <chunk_size> [optional_args]
@@ -249,12 +310,13 @@ static int dev_parms(struct raid_set *rs, char **argv)
  *    [max_recovery_rate <kB/sec/disk>] Throttle RAID initialization
  *    [max_write_behind <sectors>]      See '-write-behind=' (man mdadm)
  *    [stripe_cache <sectors>]          Stripe cache size for higher RAIDs
+ *    [region_size <sectors>]           Defines granularity of bitmap
  */
 static int parse_raid_params(struct raid_set *rs, char **argv,
                              unsigned num_raid_params)
 {
         unsigned i, rebuild_cnt = 0;
-        unsigned long value;
+        unsigned long value, region_size = 0;
         char *key;
 
         /*
@@ -365,6 +427,9 @@ static int parse_raid_params(struct raid_set *rs, char **argv,
                                 return -EINVAL;
                         }
                         rs->md.sync_speed_max = (int)value;
+                } else if (!strcasecmp(key, "region_size")) {
+                        rs->print_flags |= DMPF_REGION_SIZE;
+                        region_size = value;
                 } else {
                         DMERR("Unable to parse RAID parameter: %s", key);
                         rs->ti->error = "Unable to parse RAID parameters";
@@ -372,6 +437,14 @@ static int parse_raid_params(struct raid_set *rs, char **argv,
                 }
         }
 
+        if (validate_region_size(rs, region_size))
+                return -EINVAL;
+
+        if (rs->md.chunk_sectors)
+                rs->ti->split_io = rs->md.chunk_sectors;
+        else
+                rs->ti->split_io = region_size;
+
         /* Assume there are no metadata devices until the drives are parsed */
         rs->md.persistent = 0;
         rs->md.external = 1;
@@ -469,7 +542,6 @@ static int raid_ctr(struct dm_target *ti, unsigned argc, char **argv)
                 goto bad;
 
         INIT_WORK(&rs->md.event_work, do_table_event);
-        ti->split_io = rs->md.chunk_sectors;
         ti->private = rs;
 
         mutex_lock(&rs->md.reconfig_mutex);
@@ -596,6 +668,10 @@ static int raid_status(struct dm_target *ti, status_type_t type,
                                conf ? conf->max_nr_stripes * 2 : 0);
                 }
 
+                if (rs->print_flags & DMPF_REGION_SIZE)
+                        DMEMIT(" region_size %lu",
+                               rs->md.bitmap_info.chunksize >> 9);
+
                 DMEMIT(" %d", rs->md.raid_disks);
                 for (i = 0; i < rs->md.raid_disks; i++) {
                         DMEMIT(" -"); /* metadata device */