[dm-devel] [PATCH] dm: fix iterate_device sanity check
JeffleXu
jefflexu at linux.alibaba.com
Tue Feb 2 04:40:33 UTC 2021
dm_table_supports_dax_write_cache() is remained untouched, since I'm not
sure if the semantics requires that 'any underlying device' or 'all
underlying devices' supporting dax_write_cache. At least it seems that
'any underlying device' is sufficient from the current code.
On 2/2/21 11:35 AM, Jeffle Xu wrote:
> 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_device_attribute() 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.
>
> 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 at vger.kernel.org
> Signed-off-by: Jeffle Xu <jefflexu at linux.alibaba.com>
> ---
> drivers/md/dm-table.c | 84 ++++++++++++++++++++++---------------------
> drivers/md/dm.c | 2 +-
> drivers/md/dm.h | 2 +-
> 3 files changed, 46 insertions(+), 42 deletions(-)
>
> diff --git a/drivers/md/dm-table.c b/drivers/md/dm-table.c
> index 4acf2342f7ad..53dcbf75eda9 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,
> +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,
> +static int device_not_dax_synchronous_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;
> }
> @@ -1595,12 +1595,12 @@ 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,
> +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 q && !blk_queue_nonrot(q);
> }
>
> static int device_is_not_random(struct dm_target *ti, struct dm_dev *dev,
> @@ -1611,8 +1611,8 @@ 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)
> +static bool dm_table_any_device_attribute(struct dm_table *t,
> + iterate_devices_callout_fn func)
> {
> struct dm_target *ti;
> unsigned i;
> @@ -1620,12 +1620,12 @@ static bool dm_table_all_devices_attribute(struct dm_table *t,
> 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;
> + if (ti->type->iterate_devices &&
> + ti->type->iterate_devices(ti, func, NULL))
> + return true;
> }
>
> - return true;
> + return false;
> }
>
> static int device_not_write_same_capable(struct dm_target *ti, struct dm_dev *dev,
> @@ -1780,26 +1780,25 @@ static int device_requires_stable_pages(struct dm_target *ti,
> }
>
> /*
> - * 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 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_device_attribute() 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.
> */
> -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)
> {
> @@ -1837,9 +1836,9 @@ 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_synchronous_capable, NULL))
> set_dax_synchronous(t->md->dax_dev);
> }
> else
> @@ -1849,10 +1848,10 @@ 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_device_attribute(t, device_is_rot))
> 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 +1863,11 @@ 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_device_attribute(t, device_requires_stable_pages))
> blk_queue_flag_set(QUEUE_FLAG_STABLE_WRITES, q);
> else
> blk_queue_flag_clear(QUEUE_FLAG_STABLE_WRITES, q);
> @@ -1876,8 +1878,10 @@ 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_device_attribute(t, device_is_not_random))
> 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 7bac564f3faa..8a3d73efb9dd 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);
>
--
Thanks,
Jeffle
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