dm thin: adjust max_sectors_kb based on thinp blocksize

Allows for filesystems to submit bios that are a factor of the thinp
blocksize, improving dm-thinp efficiency (particularly when the data
volume is RAID).

Also set io_min to max_sectors_kb if it is a factor of the thinp
blocksize.

Signed-off-by: Mike Snitzer <snitzer@redhat.com>

1 files changed, 31 insertions, 3 deletions

diff --git a/drivers/md/dm-thin.c b/drivers/md/dm-thin.c
index 91b430b883fd..de55ae9d4926 100644
--- a/drivers/md/dm-thin.c
+++ b/drivers/md/dm-thin.c
@@ -11,6 +11,7 @@
 #include <linux/device-mapper.h>
 #include <linux/dm-io.h>
 #include <linux/dm-kcopyd.h>
+#include <linux/log2.h>
 #include <linux/list.h>
 #include <linux/rculist.h>
 #include <linux/init.h>
@@ -3242,15 +3243,42 @@ static void pool_io_hints(struct dm_target *ti, struct queue_limits *limits)
 {
         struct pool_c *pt = ti->private;
         struct pool *pool = pt->pool;
-        uint64_t io_opt_sectors = limits->io_opt >> SECTOR_SHIFT;
+        sector_t io_opt_sectors = limits->io_opt >> SECTOR_SHIFT;
+
+        /*
+         * Adjust max_sectors_kb to highest possible power-of-2
+         * factor of pool->sectors_per_block.
+         */
+        if (limits->max_hw_sectors & (limits->max_hw_sectors - 1))
+                limits->max_sectors = rounddown_pow_of_two(limits->max_hw_sectors);
+        else
+                limits->max_sectors = limits->max_hw_sectors;
+
+        if (limits->max_sectors < pool->sectors_per_block) {
+                while (!is_factor(pool->sectors_per_block, limits->max_sectors)) {
+                        if ((limits->max_sectors & (limits->max_sectors - 1)) == 0)
+                                limits->max_sectors--;
+                        limits->max_sectors = rounddown_pow_of_two(limits->max_sectors);
+                }
+        } else if (block_size_is_power_of_two(pool)) {
+                /* max_sectors_kb is >= power-of-2 thinp blocksize */
+                while (!is_factor(limits->max_sectors, pool->sectors_per_block)) {
+                        if ((limits->max_sectors & (limits->max_sectors - 1)) == 0)
+                                limits->max_sectors--;
+                        limits->max_sectors = rounddown_pow_of_two(limits->max_sectors);
+                }
+        }
 
         /*
          * If the system-determined stacked limits are compatible with the
          * pool's blocksize (io_opt is a factor) do not override them.
          */
         if (io_opt_sectors < pool->sectors_per_block ||
-            do_div(io_opt_sectors, pool->sectors_per_block)) {
-                blk_limits_io_min(limits, pool->sectors_per_block << SECTOR_SHIFT);
+            !is_factor(io_opt_sectors, pool->sectors_per_block)) {
+                if (is_factor(pool->sectors_per_block, limits->max_sectors))
+                        blk_limits_io_min(limits, limits->max_sectors << SECTOR_SHIFT);
+                else
+                        blk_limits_io_min(limits, pool->sectors_per_block << SECTOR_SHIFT);
                 blk_limits_io_opt(limits, pool->sectors_per_block << SECTOR_SHIFT);
         }