[PATCH v3 08/11] dm: fix iterate_device sanity check

[Jeffle Xu <jefflexu@linux.alibaba.com>]

According to the definition of dm_iterate_devices_fn:
 * This function must iterate through each section of device used by the
 * target until it encounters a non-zero return code, which it then returns.
 * Returns zero if no callout returned non-zero.

For some target type (e.g., dm-stripe), one call of iterate_devices()
may iterate multiple underlying devices internally, in which case a
non-zero return code returned by iterate_devices_callout_fn will stop
the iteration in advance.

Thus if we want to ensure that _all_ underlying devices support some
kind of attribute, the iteration structure like
dm_table_supports_nowait() should be used, while the input
iterate_devices_callout_fn should handle the 'not support' semantics.
On the opposite, the iteration structure like dm_table_any_dev_attr()
should be used if _any_ underlying device supporting this attibute is
sufficient. In this case, the input iterate_devices_callout_fn should
handle the 'support' semantics.

Besides, remove the unnecessary NULL pointer check for request_queue,
since the request_queue pointer returned from bdev_get_queue() shall
never be NULL according to commit ff9ea323816d ("block, bdi: an active
gendisk always has a request_queue associated with it").

Fixes: 545ed20e6df6 ("dm: add infrastructure for DAX support")
Fixes: c3c4555edd10 ("dm table: clear add_random unless all devices have it set")
Fixes: 4693c9668fdc ("dm table: propagate non rotational flag")
Cc: stable@vger.kernel.org
Signed-off-by: Jeffle Xu <jefflexu@linux.alibaba.com>
---
 drivers/md/dm-table.c | 195 +++++++++++++++++++-----------------------
 drivers/md/dm.c       |   2 +-
 drivers/md/dm.h       |   2 +-
 3 files changed, 91 insertions(+), 108 deletions(-)

diff --git a/drivers/md/dm-table.c b/drivers/md/dm-table.c
index 4acf2342f7ad..aa37f3e82238 100644
--- a/drivers/md/dm-table.c
+++ b/drivers/md/dm-table.c
@@ -820,24 +820,24 @@ void dm_table_set_type(struct dm_table *t, enum dm_queue_mode type)
 EXPORT_SYMBOL_GPL(dm_table_set_type);
 
 /* validate the dax capability of the target device span */
-int device_supports_dax(struct dm_target *ti, struct dm_dev *dev,
-			sector_t start, sector_t len, void *data)
+int device_not_dax_capable(struct dm_target *ti, struct dm_dev *dev,
+			   sector_t start, sector_t len, void *data)
 {
 	int blocksize = *(int *) data, id;
 	bool rc;
 
 	id = dax_read_lock();
-	rc = dax_supported(dev->dax_dev, dev->bdev, blocksize, start, len);
+	rc = !dax_supported(dev->dax_dev, dev->bdev, blocksize, start, len);
 	dax_read_unlock(id);
 
 	return rc;
 }
 
 /* Check devices support synchronous DAX */
-static int device_dax_synchronous(struct dm_target *ti, struct dm_dev *dev,
-				  sector_t start, sector_t len, void *data)
+static int device_not_dax_sync_capable(struct dm_target *ti, struct dm_dev *dev,
+				       sector_t start, sector_t len, void *data)
 {
-	return dev->dax_dev && dax_synchronous(dev->dax_dev);
+	return !dev->dax_dev || !dax_synchronous(dev->dax_dev);
 }
 
 bool dm_table_supports_dax(struct dm_table *t,
@@ -854,7 +854,7 @@ bool dm_table_supports_dax(struct dm_table *t,
 			return false;
 
 		if (!ti->type->iterate_devices ||
-		    !ti->type->iterate_devices(ti, iterate_fn, blocksize))
+		    ti->type->iterate_devices(ti, iterate_fn, blocksize))
 			return false;
 	}
 
@@ -925,7 +925,7 @@ static int dm_table_determine_type(struct dm_table *t)
 verify_bio_based:
 		/* We must use this table as bio-based */
 		t->type = DM_TYPE_BIO_BASED;
-		if (dm_table_supports_dax(t, device_supports_dax, &page_size) ||
+		if (dm_table_supports_dax(t, device_not_dax_capable, &page_size) ||
 		    (list_empty(devices) && live_md_type == DM_TYPE_DAX_BIO_BASED)) {
 			t->type = DM_TYPE_DAX_BIO_BASED;
 		}
@@ -1331,13 +1331,49 @@ bool dm_table_has_no_data_devices(struct dm_table *table)
 	return true;
 }
 
-static int device_is_zoned_model(struct dm_target *ti, struct dm_dev *dev,
-				 sector_t start, sector_t len, void *data)
+/*
+ * Cases requiring _any_ underlying device supporting some kind of attribute,
+ * should use the iteration structure like dm_table_any_dev_attr(), or call
+ * it directly. @func should handle semantics of positive examples, e.g.,
+ * capable of something.
+ */
+static bool dm_table_any_dev_attr(struct dm_table *t,
+				  iterate_devices_callout_fn func, void *data)
+{
+	struct dm_target *ti;
+	unsigned int i;
+
+	for (i = 0; i < dm_table_get_num_targets(t); i++) {
+		ti = dm_table_get_target(t, i);
+
+		if (ti->type->iterate_devices &&
+		    ti->type->iterate_devices(ti, func, data))
+			return true;
+	}
+
+	return false;
+}
+
+/*
+ * Cases requiring _all_ underlying devices supporting some kind of attribute,
+ * should use the iteration structure like dm_table_supports_nowait(), or call
+ * dm_table_all_devs_attr() directly. @anti_func should handle semantics of
+ * counter examples, e.g., not capable of something.
+ */
+static inline bool dm_table_all_devs_attr(struct dm_table *t,
+					  iterate_devices_callout_fn anti_func,
+					  void *data)
+{
+	return !dm_table_any_dev_attr(t, anti_func, data);
+}
+
+static int device_not_zoned_model(struct dm_target *ti, struct dm_dev *dev,
+				  sector_t start, sector_t len, void *data)
 {
 	struct request_queue *q = bdev_get_queue(dev->bdev);
 	enum blk_zoned_model *zoned_model = data;
 
-	return q && blk_queue_zoned_model(q) == *zoned_model;
+	return blk_queue_zoned_model(q) != *zoned_model;
 }
 
 static bool dm_table_supports_zoned_model(struct dm_table *t,
@@ -1354,37 +1390,20 @@ static bool dm_table_supports_zoned_model(struct dm_table *t,
 			return false;
 
 		if (!ti->type->iterate_devices ||
-		    !ti->type->iterate_devices(ti, device_is_zoned_model, &zoned_model))
+		    ti->type->iterate_devices(ti, device_not_zoned_model, &zoned_model))
 			return false;
 	}
 
 	return true;
 }
 
-static int device_matches_zone_sectors(struct dm_target *ti, struct dm_dev *dev,
-				       sector_t start, sector_t len, void *data)
+static int device_not_matches_zone_sectors(struct dm_target *ti, struct dm_dev *dev,
+					   sector_t start, sector_t len, void *data)
 {
 	struct request_queue *q = bdev_get_queue(dev->bdev);
 	unsigned int *zone_sectors = data;
 
-	return q && blk_queue_zone_sectors(q) == *zone_sectors;
-}
-
-static bool dm_table_matches_zone_sectors(struct dm_table *t,
-					  unsigned int zone_sectors)
-{
-	struct dm_target *ti;
-	unsigned i;
-
-	for (i = 0; i < dm_table_get_num_targets(t); i++) {
-		ti = dm_table_get_target(t, i);
-
-		if (!ti->type->iterate_devices ||
-		    !ti->type->iterate_devices(ti, device_matches_zone_sectors, &zone_sectors))
-			return false;
-	}
-
-	return true;
+	return blk_queue_zone_sectors(q) != *zone_sectors;
 }
 
 static int validate_hardware_zoned_model(struct dm_table *table,
@@ -1404,7 +1423,7 @@ static int validate_hardware_zoned_model(struct dm_table *table,
 	if (!zone_sectors || !is_power_of_2(zone_sectors))
 		return -EINVAL;
 
-	if (!dm_table_matches_zone_sectors(table, zone_sectors)) {
+	if (dm_table_any_dev_attr(table, device_not_matches_zone_sectors, &zone_sectors)) {
 		DMERR("%s: zone sectors is not consistent across all devices",
 		      dm_device_name(table->md));
 		return -EINVAL;
@@ -1533,7 +1552,7 @@ static int device_flush_capable(struct dm_target *ti, struct dm_dev *dev,
 	unsigned long flush = (unsigned long) data;
 	struct request_queue *q = bdev_get_queue(dev->bdev);
 
-	return q && (q->queue_flags & flush);
+	return (q->queue_flags & flush);
 }
 
 static bool dm_table_supports_flush(struct dm_table *t, unsigned long flush)
@@ -1578,54 +1597,20 @@ static int device_dax_write_cache_enabled(struct dm_target *ti,
 	return false;
 }
 
-static int dm_table_supports_dax_write_cache(struct dm_table *t)
-{
-	struct dm_target *ti;
-	unsigned i;
-
-	for (i = 0; i < dm_table_get_num_targets(t); i++) {
-		ti = dm_table_get_target(t, i);
-
-		if (ti->type->iterate_devices &&
-		    ti->type->iterate_devices(ti,
-				device_dax_write_cache_enabled, NULL))
-			return true;
-	}
-
-	return false;
-}
-
-static int device_is_nonrot(struct dm_target *ti, struct dm_dev *dev,
-			    sector_t start, sector_t len, void *data)
+static int device_is_rot(struct dm_target *ti, struct dm_dev *dev,
+			 sector_t start, sector_t len, void *data)
 {
 	struct request_queue *q = bdev_get_queue(dev->bdev);
 
-	return q && blk_queue_nonrot(q);
+	return !blk_queue_nonrot(q);
 }
 
 static int device_is_not_random(struct dm_target *ti, struct dm_dev *dev,
-			     sector_t start, sector_t len, void *data)
+				sector_t start, sector_t len, void *data)
 {
 	struct request_queue *q = bdev_get_queue(dev->bdev);
 
-	return q && !blk_queue_add_random(q);
-}
-
-static bool dm_table_all_devices_attribute(struct dm_table *t,
-					   iterate_devices_callout_fn func)
-{
-	struct dm_target *ti;
-	unsigned i;
-
-	for (i = 0; i < dm_table_get_num_targets(t); i++) {
-		ti = dm_table_get_target(t, i);
-
-		if (!ti->type->iterate_devices ||
-		    !ti->type->iterate_devices(ti, func, NULL))
-			return false;
-	}
-
-	return true;
+	return !blk_queue_add_random(q);
 }
 
 static int device_not_write_same_capable(struct dm_target *ti, struct dm_dev *dev,
@@ -1633,7 +1618,7 @@ static int device_not_write_same_capable(struct dm_target *ti, struct dm_dev *de
 {
 	struct request_queue *q = bdev_get_queue(dev->bdev);
 
-	return q && !q->limits.max_write_same_sectors;
+	return !q->limits.max_write_same_sectors;
 }
 
 static bool dm_table_supports_write_same(struct dm_table *t)
@@ -1660,7 +1645,7 @@ static int device_not_write_zeroes_capable(struct dm_target *ti, struct dm_dev *
 {
 	struct request_queue *q = bdev_get_queue(dev->bdev);
 
-	return q && !q->limits.max_write_zeroes_sectors;
+	return !q->limits.max_write_zeroes_sectors;
 }
 
 static bool dm_table_supports_write_zeroes(struct dm_table *t)
@@ -1687,7 +1672,7 @@ static int device_not_nowait_capable(struct dm_target *ti, struct dm_dev *dev,
 {
 	struct request_queue *q = bdev_get_queue(dev->bdev);
 
-	return q && !blk_queue_nowait(q);
+	return !blk_queue_nowait(q);
 }
 
 static bool dm_table_supports_nowait(struct dm_table *t)
@@ -1714,7 +1699,7 @@ static int device_not_discard_capable(struct dm_target *ti, struct dm_dev *dev,
 {
 	struct request_queue *q = bdev_get_queue(dev->bdev);
 
-	return q && !blk_queue_discard(q);
+	return !blk_queue_discard(q);
 }
 
 static bool dm_table_supports_discards(struct dm_table *t)
@@ -1748,7 +1733,7 @@ static int device_not_secure_erase_capable(struct dm_target *ti,
 {
 	struct request_queue *q = bdev_get_queue(dev->bdev);
 
-	return q && !blk_queue_secure_erase(q);
+	return !blk_queue_secure_erase(q);
 }
 
 static bool dm_table_supports_secure_erase(struct dm_table *t)
@@ -1776,30 +1761,23 @@ static int device_requires_stable_pages(struct dm_target *ti,
 {
 	struct request_queue *q = bdev_get_queue(dev->bdev);
 
-	return q && blk_queue_stable_writes(q);
+	return blk_queue_stable_writes(q);
 }
 
 /*
- * If any underlying device requires stable pages, a table must require
- * them as well.  Only targets that support iterate_devices are considered:
- * don't want error, zero, etc to require stable pages.
+ * type->iterate_devices() should be called when the sanity check needs to
+ * iterate and check all underlying data devices. iterate_devices() will
+ * iterate all underlying data devices until it encounters a non-zero return
+ * code, returned by whether the input iterate_devices_callout_fn, or
+ * iterate_devices() itself internally.
+ *
+ * For some target type (e.g., dm-stripe), one call of iterate_devices() may
+ * iterate multiple underlying devices internally, in which case a non-zero
+ * return code returned by iterate_devices_callout_fn will stop the iteration
+ * in advance.
+ * Thus users should call dm_table_any_dev_attr() or dm_table_all_devs_attr()
+ * directly if possible. See comments of these two functions for more details.
  */
-static bool dm_table_requires_stable_pages(struct dm_table *t)
-{
-	struct dm_target *ti;
-	unsigned i;
-
-	for (i = 0; i < dm_table_get_num_targets(t); i++) {
-		ti = dm_table_get_target(t, i);
-
-		if (ti->type->iterate_devices &&
-		    ti->type->iterate_devices(ti, device_requires_stable_pages, NULL))
-			return true;
-	}
-
-	return false;
-}
-
 void dm_table_set_restrictions(struct dm_table *t, struct request_queue *q,
 			       struct queue_limits *limits)
 {
@@ -1837,22 +1815,22 @@ void dm_table_set_restrictions(struct dm_table *t, struct request_queue *q,
 	}
 	blk_queue_write_cache(q, wc, fua);
 
-	if (dm_table_supports_dax(t, device_supports_dax, &page_size)) {
+	if (dm_table_supports_dax(t, device_not_dax_capable, &page_size)) {
 		blk_queue_flag_set(QUEUE_FLAG_DAX, q);
-		if (dm_table_supports_dax(t, device_dax_synchronous, NULL))
+		if (dm_table_supports_dax(t, device_not_dax_sync_capable, NULL))
 			set_dax_synchronous(t->md->dax_dev);
 	}
 	else
 		blk_queue_flag_clear(QUEUE_FLAG_DAX, q);
 
-	if (dm_table_supports_dax_write_cache(t))
+	if (dm_table_any_dev_attr(t, device_dax_write_cache_enabled, NULL))
 		dax_write_cache(t->md->dax_dev, true);
 
 	/* Ensure that all underlying devices are non-rotational. */
-	if (dm_table_all_devices_attribute(t, device_is_nonrot))
-		blk_queue_flag_set(QUEUE_FLAG_NONROT, q);
-	else
+	if (dm_table_any_dev_attr(t, device_is_rot, NULL))
 		blk_queue_flag_clear(QUEUE_FLAG_NONROT, q);
+	else
+		blk_queue_flag_set(QUEUE_FLAG_NONROT, q);
 
 	if (!dm_table_supports_write_same(t))
 		q->limits.max_write_same_sectors = 0;
@@ -1864,8 +1842,11 @@ void dm_table_set_restrictions(struct dm_table *t, struct request_queue *q,
 	/*
 	 * Some devices don't use blk_integrity but still want stable pages
 	 * because they do their own checksumming.
+	 * If any underlying device requires stable pages, a table must require
+	 * them as well.  Only targets that support iterate_devices are considered:
+	 * don't want error, zero, etc to require stable pages.
 	 */
-	if (dm_table_requires_stable_pages(t))
+	if (dm_table_any_dev_attr(t, device_requires_stable_pages, NULL))
 		blk_queue_flag_set(QUEUE_FLAG_STABLE_WRITES, q);
 	else
 		blk_queue_flag_clear(QUEUE_FLAG_STABLE_WRITES, q);
@@ -1876,8 +1857,10 @@ void dm_table_set_restrictions(struct dm_table *t, struct request_queue *q,
 	 * Clear QUEUE_FLAG_ADD_RANDOM if any underlying device does not
 	 * have it set.
 	 */
-	if (blk_queue_add_random(q) && dm_table_all_devices_attribute(t, device_is_not_random))
+	if (dm_table_any_dev_attr(t, device_is_not_random, NULL))
 		blk_queue_flag_clear(QUEUE_FLAG_ADD_RANDOM, q);
+	else
+		blk_queue_flag_set(QUEUE_FLAG_ADD_RANDOM, q);
 
 	/*
 	 * For a zoned target, the number of zones should be updated for the
diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index 46ca3b739396..c2945c90745e 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -1128,7 +1128,7 @@ static bool dm_dax_supported(struct dax_device *dax_dev, struct block_device *bd
 	if (!map)
 		goto out;
 
-	ret = dm_table_supports_dax(map, device_supports_dax, &blocksize);
+	ret = dm_table_supports_dax(map, device_not_dax_capable, &blocksize);
 
 out:
 	dm_put_live_table(md, srcu_idx);
diff --git a/drivers/md/dm.h b/drivers/md/dm.h
index fffe1e289c53..b441ad772c18 100644
--- a/drivers/md/dm.h
+++ b/drivers/md/dm.h
@@ -73,7 +73,7 @@ void dm_table_free_md_mempools(struct dm_table *t);
 struct dm_md_mempools *dm_table_get_md_mempools(struct dm_table *t);
 bool dm_table_supports_dax(struct dm_table *t, iterate_devices_callout_fn fn,
 			   int *blocksize);
-int device_supports_dax(struct dm_target *ti, struct dm_dev *dev,
+int device_not_dax_capable(struct dm_target *ti, struct dm_dev *dev,
 			   sector_t start, sector_t len, void *data);
 
 void dm_lock_md_type(struct mapped_device *md);
-- 
2.27.0