On Tue, Jun 26 2018 at 1:59pm -0400,
Ross Zwisler <ross.zwisler@xxxxxxxxxxxxxxx> 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@xxxxxxxxxxxxxxx>
> Fixes: commit 545ed20e6df6 ("dm: add infrastructure for DAX support")
> Cc: stable@xxxxxxxxxxxxxxx
> ---
> 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
