On Tue, Jun 26 2018 at 1:59pm -0400, Ross Zwisler ross.zwisler@linux.intel.com wrote:

Currently device_supports_dax() just checks to see if the QUEUE_FLAG_DAX flag is set on the device's request queue to decide whether or not the device supports filesystem DAX. Really we should be using bdev_dax_supported() like filesystems do at mount time. This performs other tests like checking to make sure the dax_direct_access() path works.

Conditionally set QUEUE_FLAG_DAX on the DM device's request queue based on whether all underlying devices support DAX. Now that bdev_dax_supported() explicitly checks for this flag, this will ensure that filesystems built upon DM devices will only be able to mount with DAX if all underlying devices also support DAX.

Signed-off-by: Ross Zwisler ross.zwisler@linux.intel.com Fixes: commit 545ed20e6df6 ("dm: add infrastructure for DAX support") Cc: stable@vger.kernel.org

---

drivers/md/dm-ioctl.c | 5 +++++ drivers/md/dm-table.c | 7 +++---- drivers/md/dm.c | 3 +-- include/linux/device-mapper.h | 5 +++++ 4 files changed, 14 insertions(+), 6 deletions(-)

diff --git a/drivers/md/dm-ioctl.c b/drivers/md/dm-ioctl.c index b810ea77e6b1..0055bdbee5b1 100644 --- a/drivers/md/dm-ioctl.c +++ b/drivers/md/dm-ioctl.c @@ -1350,6 +1350,11 @@ static int table_load(struct file *filp, struct dm_ioctl *param, size_t param_si goto err_unlock_md_type; }

• if (dm_table_supports_dax(t))

• blk_queue_flag_set(QUEUE_FLAG_DAX, md->queue);
  

• else

• blk_queue_flag_clear(QUEUE_FLAG_DAX, md->queue);
  

• dm_unlock_md_type(md);

/* stage inactive table */

This should occur in drivers/md/dm-table.c:dm_table_set_restrictions(). Which already has: if (dm_table_supports_dax(t)) blk_queue_flag_set(QUEUE_FLAG_DAX, q);

So it just needs tweaking.

diff --git a/drivers/md/dm-table.c b/drivers/md/dm-table.c index 938766794c2e..c673b4a51fb2 100644 --- a/drivers/md/dm-table.c +++ b/drivers/md/dm-table.c @@ -885,12 +885,10 @@ EXPORT_SYMBOL_GPL(dm_table_set_type); static int device_supports_dax(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_dax(q);

• return bdev_dax_supported(dev->bdev, PAGE_SIZE);

} -static bool dm_table_supports_dax(struct dm_table *t) +bool dm_table_supports_dax(struct dm_table *t) { struct dm_target *ti; unsigned i; @@ -909,6 +907,7 @@ static bool dm_table_supports_dax(struct dm_table *t) return true; } +EXPORT_SYMBOL_GPL(dm_table_supports_dax); static bool dm_table_does_not_support_partial_completion(struct dm_table *t);

Which would mean you don't need to export dm_table_supports_dax().

diff --git a/drivers/md/dm.c b/drivers/md/dm.c index e65429a29c06..bef5a3f243ed 100644 --- a/drivers/md/dm.c +++ b/drivers/md/dm.c @@ -1056,8 +1056,7 @@ static long dm_dax_direct_access(struct dax_device *dax_dev, pgoff_t pgoff, if (len < 1) goto out; nr_pages = min(len, nr_pages);

• if (ti->type->direct_access)

• ret = ti->type->direct_access(ti, pgoff, nr_pages, kaddr, pfn);
  

• ret = ti->type->direct_access(ti, pgoff, nr_pages, kaddr, pfn);

out: dm_put_live_table(md, srcu_idx); diff --git a/include/linux/device-mapper.h b/include/linux/device-mapper.h index 6fb0808e87c8..45ea9e1f9af9 100644 --- a/include/linux/device-mapper.h +++ b/include/linux/device-mapper.h @@ -461,6 +461,11 @@ void dm_table_add_target_callbacks(struct dm_table *t, struct dm_target_callback */ void dm_table_set_type(struct dm_table *t, enum dm_queue_mode type); +/*

• • Check to see if this target type and all table devices support DAX.
• */

+bool dm_table_supports_dax(struct dm_table *t);

/*

• Finally call this to make the table ready for use.

*/

Nor do you need to publish the dm_table_supports_dax() interface via include/linux/device-mapper.h