dm thin: tidy discard support

A little thin discard code refactoring to make the next patch (dm thin:
fix discard support for data devices) more readable.
Pull out a couple of functions (and uses bools instead of unsigned for
features).

No functional changes.

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

1 files changed, 39 insertions, 25 deletions

diff --git a/drivers/md/dm-thin.c b/drivers/md/dm-thin.c
index d4209231069d..e99f4134dbd7 100644
--- a/drivers/md/dm-thin.c
+++ b/drivers/md/dm-thin.c
@@ -509,9 +509,9 @@ enum pool_mode {
 struct pool_features {
         enum pool_mode mode;
 
-        unsigned zero_new_blocks:1;
-        unsigned discard_enabled:1;
-        unsigned discard_passdown:1;
+        bool zero_new_blocks:1;
+        bool discard_enabled:1;
+        bool discard_passdown:1;
 };
 
 struct thin_c;
@@ -1839,6 +1839,32 @@ static void __requeue_bios(struct pool *pool)
 /*----------------------------------------------------------------
  * Binding of control targets to a pool object
  *--------------------------------------------------------------*/
+static bool data_dev_supports_discard(struct pool_c *pt)
+{
+        struct request_queue *q = bdev_get_queue(pt->data_dev->bdev);
+
+        return q && blk_queue_discard(q);
+}
+
+/*
+ * If discard_passdown was enabled verify that the data device
+ * supports discards.  Disable discard_passdown if not; otherwise
+ * -EOPNOTSUPP will be returned.
+ */
+static void disable_passdown_if_not_supported(struct pool_c *pt,
+                                              struct pool_features *pf)
+{
+        char buf[BDEVNAME_SIZE];
+
+        if (!pf->discard_passdown || data_dev_supports_discard(pt))
+                return;
+
+        DMWARN("Discard unsupported by data device (%s): Disabling discard passdown.",
+               bdevname(pt->data_dev->bdev, buf));
+
+        pf->discard_passdown = false;
+}
+
 static int bind_control_target(struct pool *pool, struct dm_target *ti)
 {
         struct pool_c *pt = ti->private;
@@ -1855,23 +1881,9 @@ static int bind_control_target(struct pool *pool, struct dm_target *ti)
         pool->ti = ti;
         pool->low_water_blocks = pt->low_water_blocks;
         pool->pf = pt->pf;
-        set_pool_mode(pool, new_mode);
 
-        /*
-         * If discard_passdown was enabled verify that the data device
-         * supports discards.  Disable discard_passdown if not; otherwise
-         * -EOPNOTSUPP will be returned.
-         */
-        /* FIXME: pull this out into a sep fn. */
-        if (pt->pf.discard_passdown) {
-                struct request_queue *q = bdev_get_queue(pt->data_dev->bdev);
-                if (!q || !blk_queue_discard(q)) {
-                        char buf[BDEVNAME_SIZE];
-                        DMWARN("Discard unsupported by data device (%s): Disabling discard passdown.",
-                               bdevname(pt->data_dev->bdev, buf));
-                        pool->pf.discard_passdown = 0;
-                }
-        }
+        disable_passdown_if_not_supported(pt, &pool->pf);
+        set_pool_mode(pool, new_mode);
 
         return 0;
 }
@@ -1889,9 +1901,9 @@ static void unbind_control_target(struct pool *pool, struct dm_target *ti)
 static void pool_features_init(struct pool_features *pf)
 {
         pf->mode = PM_WRITE;
-        pf->zero_new_blocks = 1;
-        pf->discard_enabled = 1;
-        pf->discard_passdown = 1;
+        pf->zero_new_blocks = true;
+        pf->discard_enabled = true;
+        pf->discard_passdown = true;
 }
 
 static void __pool_destroy(struct pool *pool)
@@ -2119,13 +2131,13 @@ static int parse_pool_features(struct dm_arg_set *as, struct pool_features *pf,
                 argc--;
 
                 if (!strcasecmp(arg_name, "skip_block_zeroing"))
-                        pf->zero_new_blocks = 0;
+                        pf->zero_new_blocks = false;
 
                 else if (!strcasecmp(arg_name, "ignore_discard"))
-                        pf->discard_enabled = 0;
+                        pf->discard_enabled = false;
 
                 else if (!strcasecmp(arg_name, "no_discard_passdown"))
-                        pf->discard_passdown = 0;
+                        pf->discard_passdown = false;
 
                 else if (!strcasecmp(arg_name, "read_only"))
                         pf->mode = PM_READ_ONLY;
@@ -2261,6 +2273,7 @@ static int pool_ctr(struct dm_target *ti, unsigned argc, char **argv)
         pt->low_water_blocks = low_water_blocks;
         pt->pf = pf;
         ti->num_flush_requests = 1;
+
         /*
          * Only need to enable discards if the pool should pass
          * them down to the data device.  The thin device's discard
@@ -2268,6 +2281,7 @@ static int pool_ctr(struct dm_target *ti, unsigned argc, char **argv)
          */
         if (pf.discard_enabled && pf.discard_passdown) {
                 ti->num_discard_requests = 1;
+
                 /*
                  * Setting 'discards_supported' circumvents the normal
                  * stacking of discard limits (this keeps the pool and