dm bio prison v1: add dm_cell_key_has_valid_range

Don't have bio_detain() BUG_ON if a dm_cell_key is beyond
BIO_PRISON_MAX_RANGE or spans a boundary.

Update dm-thin.c:build_key() to use dm_cell_key_has_valid_range() which
will do this checking without using BUG_ON. Also update
process_discard_bio() to check the discard bio that DM core passes in
(having first imposed max_discard_granularity based splitting).

dm_cell_key_has_valid_range() will merely WARN_ON_ONCE if it returns
false because if it does: it is programmer error that should be caught
with proper testing. So relax the BUG_ONs to be WARN_ON_ONCE.

Signed-off-by: Mike Snitzer <snitzer@kernel.org>

1 files changed, 9 insertions, 5 deletions

diff --git a/drivers/md/dm-bio-prison-v1.c b/drivers/md/dm-bio-prison-v1.c
index 2b8af861e5f6..78bb559b521c 100644
--- a/drivers/md/dm-bio-prison-v1.c
+++ b/drivers/md/dm-bio-prison-v1.c
@@ -120,12 +120,17 @@ static unsigned lock_nr(struct dm_cell_key *key)
 	return (key->block_begin >> BIO_PRISON_MAX_RANGE_SHIFT) & LOCK_MASK;
 }
 
-static void check_range(struct dm_cell_key *key)
+bool dm_cell_key_has_valid_range(struct dm_cell_key *key)
 {
-	BUG_ON(key->block_end - key->block_begin > BIO_PRISON_MAX_RANGE);
-	BUG_ON((key->block_begin >> BIO_PRISON_MAX_RANGE_SHIFT) !=
-	       ((key->block_end - 1) >> BIO_PRISON_MAX_RANGE_SHIFT));
+	if (WARN_ON_ONCE(key->block_end - key->block_begin > BIO_PRISON_MAX_RANGE))
+		return false;
+	if (WARN_ON_ONCE((key->block_begin >> BIO_PRISON_MAX_RANGE_SHIFT) !=
+			 (key->block_end - 1) >> BIO_PRISON_MAX_RANGE_SHIFT))
+		return false;
+
+	return true;
 }
+EXPORT_SYMBOL(dm_cell_key_has_valid_range);
 
 static int __bio_detain(struct rb_root *root,
 			struct dm_cell_key *key,
@@ -172,7 +177,6 @@ static int bio_detain(struct dm_bio_prison *prison,
 {
 	int r;
 	unsigned l = lock_nr(key);
-	check_range(key);
 
 	spin_lock_irq(&prison->regions[l].lock);
 	r = __bio_detain(&prison->regions[l].cell, key, inmate, cell_prealloc, cell_result);