[PATCH 4.14 07/20] dm table: fix iterate_devices based device capability checks

gregkh
2021-03-10T13:28:54Z

From: Jeffle Xu <jefflexu@linux.alibaba.com>

commit a4c8dd9c2d0987cf542a2a0c42684c9c6d78a04e upstream.

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. No iterate_devices_callout_fn should return non-zero unless
device iteration should stop.

Rename dm_table_requires_stable_pages() to dm_table_any_dev_attr() and
elevate it for reuse to stop iterating (and return non-zero) on the
first device that causes iterate_devices_callout_fn to return non-zero.
Use dm_table_any_dev_attr() to properly iterate through devices.

Rename device_is_nonrot() to device_is_rotational() and invert logic
accordingly to fix improper disposition.

[jeffle: backport notes]
Also convert the no_sg_merge capability check, which is introduced by
commit 200612ec33e5 ("dm table: propagate QUEUE_FLAG_NO_SG_MERGE"), and
removed since commit 2705c93742e9 ("block: kill QUEUE_FLAG_NO_SG_MERGE")
in v5.1.

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>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/md/dm-table.c | 109 ++++++++++++++++++++++++++------------------------
1 file changed, 57 insertions(+), 52 deletions(-)

--- a/drivers/md/dm-table.c
+++ b/drivers/md/dm-table.c
@@ -1351,6 +1351,46 @@ struct dm_target *dm_table_find_target(s
return &t->targets[(KEYS_PER_NODE * n) + k];
}

+/*
+ * 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.
+ *
+ * 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.
+ *
+ * Cases requiring _all_ underlying devices supporting some kind of attribute,
+ * should use the iteration structure like dm_table_supports_nowait() or
+ * dm_table_supports_discards(). Or introduce dm_table_all_devs_attr() that
+ * uses an @anti_func that handle semantics of counter examples, e.g. not
+ * capable of something. So: return !dm_table_any_dev_attr(t, anti_func);
+ */
+static bool dm_table_any_dev_attr(struct dm_table *t,
+ iterate_devices_callout_fn func)
+{
+ 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, NULL))
+ return true;
+ }
+
+ return false;
+}
+
static int count_device(struct dm_target *ti, struct dm_dev *dev,
sector_t start, sector_t len, void *data)
{
@@ -1667,12 +1707,12 @@ static int dm_table_supports_dax_write_c
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_rotational(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 q && !blk_queue_nonrot(q);
}

static int device_is_not_random(struct dm_target *ti, struct dm_dev *dev,
@@ -1683,29 +1723,12 @@ static int device_is_not_random(struct d
return q && !blk_queue_add_random(q);
}

-static int queue_supports_sg_merge(struct dm_target *ti, struct dm_dev *dev,
- sector_t start, sector_t len, void *data)
+static int queue_no_sg_merge(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 && !test_bit(QUEUE_FLAG_NO_SG_MERGE, &q->queue_flags);
-}
-
-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 q && test_bit(QUEUE_FLAG_NO_SG_MERGE, &q->queue_flags);
}

static int device_not_write_same_capable(struct dm_target *ti, struct dm_dev *dev,
@@ -1804,27 +1827,6 @@ static int device_requires_stable_pages(
return q && bdi_cap_stable_pages_required(q->backing_dev_info);
}

-/*
- * 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.
- */
-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)
{
@@ -1856,28 +1858,31 @@ void dm_table_set_restrictions(struct dm
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))
- queue_flag_set_unlocked(QUEUE_FLAG_NONROT, q);
- else
+ if (dm_table_any_dev_attr(t, device_is_rotational))
queue_flag_clear_unlocked(QUEUE_FLAG_NONROT, q);
+ else
+ queue_flag_set_unlocked(QUEUE_FLAG_NONROT, q);

if (!dm_table_supports_write_same(t))
q->limits.max_write_same_sectors = 0;
if (!dm_table_supports_write_zeroes(t))
q->limits.max_write_zeroes_sectors = 0;

- if (dm_table_all_devices_attribute(t, queue_supports_sg_merge))
- queue_flag_clear_unlocked(QUEUE_FLAG_NO_SG_MERGE, q);
- else
+ if (dm_table_any_dev_attr(t, queue_no_sg_merge))
queue_flag_set_unlocked(QUEUE_FLAG_NO_SG_MERGE, q);
+ else
+ queue_flag_clear_unlocked(QUEUE_FLAG_NO_SG_MERGE, q);

dm_table_verify_integrity(t);

/*
* 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))
q->backing_dev_info->capabilities |= BDI_CAP_STABLE_WRITES;
else
q->backing_dev_info->capabilities &= ~BDI_CAP_STABLE_WRITES;
@@ -1888,7 +1893,7 @@ void dm_table_set_restrictions(struct dm
* 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 (blk_queue_add_random(q) && dm_table_any_dev_attr(t, device_is_not_random))
queue_flag_clear_unlocked(QUEUE_FLAG_ADD_RANDOM, q);

/*