dm thin: support for non power of 2 pool blocksize

Non power of 2 blocksize support is needed to properly align thinp IO
on storage that has non power of 2 optimal IO sizes (e.g. RAID6 10+2).

Use sector_div to support non power of 2 blocksize for the pool's
data device.  This provides comparable performance to the power of 2
math that was performed until now (as tested on modern x86_64 hardware).

The kernel currently assumes that limits->discard_granularity is a power
of two so the thin target only enables discard support if the block
size is a power of two.

Eliminate pool structure's 'block_shift', 'offset_mask' and
remaining 4 byte holes.

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

1 files changed, 37 insertions, 22 deletions

diff --git a/drivers/md/dm-thin.c b/drivers/md/dm-thin.c
index 350bcf40485e..f21d318d98f0 100644
--- a/drivers/md/dm-thin.c
+++ b/drivers/md/dm-thin.c
@@ -510,10 +510,8 @@ struct pool {
         struct block_device *md_dev;
         struct dm_pool_metadata *pmd;
 
-        uint32_t sectors_per_block;
-        unsigned block_shift;
-        dm_block_t offset_mask;
         dm_block_t low_water_blocks;
+        uint32_t sectors_per_block;
 
         struct pool_features pf;
         unsigned low_water_triggered:1; /* A dm event has been sent */
@@ -526,8 +524,8 @@ struct pool {
         struct work_struct worker;
         struct delayed_work waker;
 
-        unsigned ref_count;
         unsigned long last_commit_jiffies;
+        unsigned ref_count;
 
         spinlock_t lock;
         struct bio_list deferred_bios;
@@ -679,16 +677,21 @@ static void requeue_io(struct thin_c *tc)
 
 static dm_block_t get_bio_block(struct thin_c *tc, struct bio *bio)
 {
-        return bio->bi_sector >> tc->pool->block_shift;
+        sector_t block_nr = bio->bi_sector;
+
+        (void) sector_div(block_nr, tc->pool->sectors_per_block);
+
+        return block_nr;
 }
 
 static void remap(struct thin_c *tc, struct bio *bio, dm_block_t block)
 {
         struct pool *pool = tc->pool;
+        sector_t bi_sector = bio->bi_sector;
 
         bio->bi_bdev = tc->pool_dev->bdev;
-        bio->bi_sector = (block << pool->block_shift) +
-                (bio->bi_sector & pool->offset_mask);
+        bio->bi_sector = (block * pool->sectors_per_block) +
+                         sector_div(bi_sector, pool->sectors_per_block);
 }
 
 static void remap_to_origin(struct thin_c *tc, struct bio *bio)
@@ -933,9 +936,10 @@ static void process_prepared(struct pool *pool, struct list_head *head,
  */
 static int io_overlaps_block(struct pool *pool, struct bio *bio)
 {
-        return !(bio->bi_sector & pool->offset_mask) &&
-                (bio->bi_size == (pool->sectors_per_block << SECTOR_SHIFT));
+        sector_t bi_sector = bio->bi_sector;
 
+        return !sector_div(bi_sector, pool->sectors_per_block) &&
+                (bio->bi_size == (pool->sectors_per_block << SECTOR_SHIFT));
 }
 
 static int io_overwrites_block(struct pool *pool, struct bio *bio)
@@ -1239,8 +1243,8 @@ static void process_discard(struct thin_c *tc, struct bio *bio)
                          * part of the discard that is in a subsequent
                          * block.
                          */
-                        sector_t offset = bio->bi_sector - (block << pool->block_shift);
-                        unsigned remaining = (pool->sectors_per_block - offset) << 9;
+                        sector_t offset = bio->bi_sector - (block * pool->sectors_per_block);
+                        unsigned remaining = (pool->sectors_per_block - offset) << SECTOR_SHIFT;
                         bio->bi_size = min(bio->bi_size, remaining);
 
                         cell_release_singleton(cell, bio);
@@ -1722,8 +1726,6 @@ static struct pool *pool_create(struct mapped_device *pool_md,
 
         pool->pmd = pmd;
         pool->sectors_per_block = block_size;
-        pool->block_shift = ffs(block_size) - 1;
-        pool->offset_mask = block_size - 1;
         pool->low_water_blocks = 0;
         pool_features_init(&pool->pf);
         pool->prison = prison_create(PRISON_CELLS);
@@ -1971,7 +1973,7 @@ static int pool_ctr(struct dm_target *ti, unsigned argc, char **argv)
         if (kstrtoul(argv[2], 10, &block_size) || !block_size ||
             block_size < DATA_DEV_BLOCK_SIZE_MIN_SECTORS ||
             block_size > DATA_DEV_BLOCK_SIZE_MAX_SECTORS ||
-            !is_power_of_2(block_size)) {
+            block_size & (DATA_DEV_BLOCK_SIZE_MIN_SECTORS - 1)) {
                 ti->error = "Invalid block size";
                 r = -EINVAL;
                 goto out;
@@ -2018,6 +2020,15 @@ static int pool_ctr(struct dm_target *ti, unsigned argc, char **argv)
                 goto out_flags_changed;
         }
 
+        /*
+         * The block layer requires discard_granularity to be a power of 2.
+         */
+        if (pf.discard_enabled && !is_power_of_2(block_size)) {
+                ti->error = "Discard support must be disabled when the block size is not a power of 2";
+                r = -EINVAL;
+                goto out_flags_changed;
+        }
+
         pt->pool = pool;
         pt->ti = ti;
         pt->metadata_dev = metadata_dev;
@@ -2097,7 +2108,8 @@ static int pool_preresume(struct dm_target *ti)
         int r;
         struct pool_c *pt = ti->private;
         struct pool *pool = pt->pool;
-        dm_block_t data_size, sb_data_size;
+        sector_t data_size = ti->len;
+        dm_block_t sb_data_size;
 
         /*
          * Take control of the pool object.
@@ -2106,7 +2118,8 @@ static int pool_preresume(struct dm_target *ti)
         if (r)
                 return r;
 
-        data_size = ti->len >> pool->block_shift;
+        (void) sector_div(data_size, pool->sectors_per_block);
+
         r = dm_pool_get_data_dev_size(pool->pmd, &sb_data_size);
         if (r) {
                 DMERR("failed to retrieve data device size");
@@ -2115,7 +2128,7 @@ static int pool_preresume(struct dm_target *ti)
 
         if (data_size < sb_data_size) {
                 DMERR("pool target too small, is %llu blocks (expected %llu)",
-                      data_size, sb_data_size);
+                      (unsigned long long)data_size, sb_data_size);
                 return -EINVAL;
 
         } else if (data_size > sb_data_size) {
@@ -2764,19 +2777,21 @@ static int thin_status(struct dm_target *ti, status_type_t type,
 static int thin_iterate_devices(struct dm_target *ti,
                                 iterate_devices_callout_fn fn, void *data)
 {
-        dm_block_t blocks;
+        sector_t blocks;
         struct thin_c *tc = ti->private;
+        struct pool *pool = tc->pool;
 
         /*
          * We can't call dm_pool_get_data_dev_size() since that blocks.  So
          * we follow a more convoluted path through to the pool's target.
          */
-        if (!tc->pool->ti)
+        if (!pool->ti)
                 return 0;       /* nothing is bound */
 
-        blocks = tc->pool->ti->len >> tc->pool->block_shift;
+        blocks = pool->ti->len;
+        (void) sector_div(blocks, pool->sectors_per_block);
         if (blocks)
-                return fn(ti, tc->pool_dev, 0, tc->pool->sectors_per_block * blocks, data);
+                return fn(ti, tc->pool_dev, 0, pool->sectors_per_block * blocks, data);
 
         return 0;
 }
@@ -2793,7 +2808,7 @@ static void thin_io_hints(struct dm_target *ti, struct queue_limits *limits)
 
 static struct target_type thin_target = {
         .name = "thin",
-        .version = {1, 1, 0},
+        .version = {1, 2, 0},
         .module = THIS_MODULE,
         .ctr = thin_ctr,
         .dtr = thin_dtr,