dm thin: do not expose non-zero discard limits if discards disabled

Fix issue where the block layer would stack the discard limits of the pool's data device even if the "ignore_discard" pool feature was specified. The pool and thin device(s) still had discards disabled because the QUEUE_FLAG_DISCARD request_queue flag wasn't set. But to avoid user confusion when "ignore_discard" is used: both the pool device and the thin device(s) have zeroes for all discard limits. Also, always set discard_zeroes_data_unsupported in targets because they should never advertise the 'discard_zeroes_data' capability (even if the pool's data device supports it). Signed-off-by: Mike Snitzer <snitzer@redhat.com> Acked-by: Joe Thornber <ejt@redhat.com>

dm thin: do not expose non-zero discard limits if discards disabled
Fix issue where the block layer would stack the discard limits of the pool's data device even if the "ignore_discard" pool feature was specified. The pool and thin device(s) still had discards disabled because the QUEUE_FLAG_DISCARD request_queue flag wasn't set. But to avoid user confusion when "ignore_discard" is used: both the pool device and the thin device(s) have zeroes for all discard limits. Also, always set discard_zeroes_data_unsupported in targets because they should never advertise the 'discard_zeroes_data' capability (even if the pool's data device supports it). Signed-off-by: Mike Snitzer <snitzer@redhat.com> Acked-by: Joe Thornber <ejt@redhat.com>
Mike Snitzer
1 parent f84cb8a46a
Showing 1 changed file with 11 additions and 3 deletions Side-by-side Diff
drivers/md/dm-thin.c
@@ -2095,6 +2095,7 @@
 	 * them down to the data device.  The thin device's discard
 	 * processing will cause mappings to be removed from the btree.
 	 */
+	ti->discard_zeroes_data_unsupported = true;
 	if (pf.discard_enabled && pf.discard_passdown) {
 		ti->num_discard_bios = 1;
  
@@ -2104,7 +2105,6 @@
 		 * thin devices' discard limits consistent).
 		 */
 		ti->discards_supported = true;
-		ti->discard_zeroes_data_unsupported = true;
 	}
 	ti->private = pt;
  
  
@@ -2689,8 +2689,16 @@
 	 * They get transferred to the live pool in bind_control_target()
 	 * called from pool_preresume().
 	 */
-	if (!pt->adjusted_pf.discard_enabled)
+	if (!pt->adjusted_pf.discard_enabled) {
+		/*
+		 * Must explicitly disallow stacking discard limits otherwise the
+		 * block layer will stack them if pool's data device has support.
+		 * QUEUE_FLAG_DISCARD wouldn't be set but there is no way for the
+		 * user to see that, so make sure to set all discard limits to 0.
+		 */
+		limits->discard_granularity = 0;
 		return;
+	}
  
 	disable_passdown_if_not_supported(pt);
  
  
@@ -2826,10 +2834,10 @@
 	ti->per_bio_data_size = sizeof(struct dm_thin_endio_hook);
  
 	/* In case the pool supports discards, pass them on. */
+	ti->discard_zeroes_data_unsupported = true;
 	if (tc->pool->pf.discard_enabled) {
 		ti->discards_supported = true;
 		ti->num_discard_bios = 1;
-		ti->discard_zeroes_data_unsupported = true;
 		/* Discard bios must be split on a block boundary */
 		ti->split_discard_bios = true;
 	}
...	...	@@ -2095,6 +2095,7 @@
2095	2095	* them down to the data device. The thin device's discard
2096	2096	* processing will cause mappings to be removed from the btree.
2097	2097	*/
	2098	+ ti->discard_zeroes_data_unsupported = true;
2098	2099	if (pf.discard_enabled && pf.discard_passdown) {
2099	2100	ti->num_discard_bios = 1;
2100	2101
...	...	@@ -2104,7 +2105,6 @@
2104	2105	* thin devices' discard limits consistent).
2105	2106	*/
2106	2107	ti->discards_supported = true;
2107		- ti->discard_zeroes_data_unsupported = true;
2108	2108	}
2109	2109	ti->private = pt;
2110	2110
2111	2111
...	...	@@ -2689,8 +2689,16 @@
2689	2689	* They get transferred to the live pool in bind_control_target()
2690	2690	* called from pool_preresume().
2691	2691	*/
2692		- if (!pt->adjusted_pf.discard_enabled)
	2692	+ if (!pt->adjusted_pf.discard_enabled) {
	2693	+ /*
	2694	+ * Must explicitly disallow stacking discard limits otherwise the
	2695	+ * block layer will stack them if pool's data device has support.
	2696	+ * QUEUE_FLAG_DISCARD wouldn't be set but there is no way for the
	2697	+ * user to see that, so make sure to set all discard limits to 0.
	2698	+ */
	2699	+ limits->discard_granularity = 0;
2693	2700	return;
	2701	+ }
2694	2702
2695	2703	disable_passdown_if_not_supported(pt);
2696	2704
2697	2705
...	...	@@ -2826,10 +2834,10 @@
2826	2834	ti->per_bio_data_size = sizeof(struct dm_thin_endio_hook);
2827	2835
2828	2836	/* In case the pool supports discards, pass them on. */
	2837	+ ti->discard_zeroes_data_unsupported = true;
2829	2838	if (tc->pool->pf.discard_enabled) {
2830	2839	ti->discards_supported = true;
2831	2840	ti->num_discard_bios = 1;
2832		- ti->discard_zeroes_data_unsupported = true;
2833	2841	/* Discard bios must be split on a block boundary */
2834	2842	ti->split_discard_bios = true;
2835	2843	}