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dm table: fix iterate_devices based device capability checks
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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.

Fixes: c3c4555 ("dm table: clear add_random unless all devices have it set")
Fixes: 4693c96 ("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>
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Jeffle Xu authored and Mike Snitzer committed Feb 9, 2021
1 parent 054bee1 commit a4c8dd9
Showing 1 changed file with 51 additions and 46 deletions.
97 changes: 51 additions & 46 deletions drivers/md/dm-table.c
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Original file line number Diff line number Diff line change
Expand Up @@ -1295,6 +1295,46 @@ struct dm_target *dm_table_find_target(struct dm_table *t, sector_t sector)
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)
{
Expand Down Expand Up @@ -1595,12 +1635,12 @@ static int dm_table_supports_dax_write_cache(struct dm_table *t)
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,
Expand All @@ -1611,23 +1651,6 @@ static int device_is_not_random(struct dm_target *ti, struct dm_dev *dev,
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;
}

static int device_not_write_same_capable(struct dm_target *ti, struct dm_dev *dev,
sector_t start, sector_t len, void *data)
{
Expand Down Expand Up @@ -1779,27 +1802,6 @@ static int device_requires_stable_pages(struct dm_target *ti,
return q && 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.
*/
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)
{
Expand Down Expand Up @@ -1849,10 +1851,10 @@ void dm_table_set_restrictions(struct dm_table *t, struct request_queue *q,
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_rotational))
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;
Expand All @@ -1864,8 +1866,11 @@ 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))
blk_queue_flag_set(QUEUE_FLAG_STABLE_WRITES, q);
else
blk_queue_flag_clear(QUEUE_FLAG_STABLE_WRITES, q);
Expand All @@ -1876,7 +1881,7 @@ 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 (blk_queue_add_random(q) && dm_table_any_dev_attr(t, device_is_not_random))
blk_queue_flag_clear(QUEUE_FLAG_ADD_RANDOM, q);

/*
Expand Down

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