From: Jan Kara jack@suse.cz

DM was calling generic_fsdax_supported() to determine whether a device referenced in the DM table supports DAX. However this is a helper for "leaf" device drivers so that they don't have to duplicate common generic checks. High level code should call dax_supported() helper which that calls into appropriate helper for the particular device. This problem manifested itself as kernel messages:

dm-3: error: dax access failed (-95)

when lvm2-testsuite run in cases where a DM device was stacked on top of another DM device.

Fixes: 7bf7eac8d648 ("dax: Arrange for dax_supported check to span multiple devices") Cc: stable@vger.kernel.org Tested-by: Adrian Huang ahuang12@lenovo.com Signed-off-by: Jan Kara jack@suse.cz Acked-by: Mike Snitzer snitzer@redhat.com Reported-by: kernel test robot lkp@intel.com Signed-off-by: Dan Williams dan.j.williams@intel.com --- Changes since v2 [1]: - Add dummy definitions for dax_read_{lock,unlock} in the CONFIG_DAX=n case (0day robot)

[1]: http://lore.kernel.org/r/160040692945.25320.13233625491405115889.stgit@dwill...

drivers/dax/super.c | 4 ++++ drivers/md/dm-table.c | 10 +++++++--- include/linux/dax.h | 22 ++++++++++++++++++++-- 3 files changed, 31 insertions(+), 5 deletions(-)

diff --git a/drivers/dax/super.c b/drivers/dax/super.c index e5767c83ea23..b6284c5cae0a 100644 --- a/drivers/dax/super.c +++ b/drivers/dax/super.c @@ -325,11 +325,15 @@ EXPORT_SYMBOL_GPL(dax_direct_access); bool dax_supported(struct dax_device *dax_dev, struct block_device *bdev, int blocksize, sector_t start, sector_t len) { + if (!dax_dev) + return false; + if (!dax_alive(dax_dev)) return false;

return dax_dev->ops->dax_supported(dax_dev, bdev, blocksize, start, len); } +EXPORT_SYMBOL_GPL(dax_supported);

size_t dax_copy_from_iter(struct dax_device *dax_dev, pgoff_t pgoff, void *addr, size_t bytes, struct iov_iter *i) diff --git a/drivers/md/dm-table.c b/drivers/md/dm-table.c index 5edc3079e7c1..229f461e7def 100644 --- a/drivers/md/dm-table.c +++ b/drivers/md/dm-table.c @@ -860,10 +860,14 @@ EXPORT_SYMBOL_GPL(dm_table_set_type); int device_supports_dax(struct dm_target *ti, struct dm_dev *dev, sector_t start, sector_t len, void *data) { - int blocksize = *(int *) data; + int blocksize = *(int *) data, id; + bool rc;

- return generic_fsdax_supported(dev->dax_dev, dev->bdev, blocksize, - start, len); + id = dax_read_lock(); + rc = dax_supported(dev->dax_dev, dev->bdev, blocksize, start, len); + dax_read_unlock(id); + + return rc; }

/* Check devices support synchronous DAX */ diff --git a/include/linux/dax.h b/include/linux/dax.h index 6904d4e0b2e0..d0af16b23122 100644 --- a/include/linux/dax.h +++ b/include/linux/dax.h @@ -130,6 +130,8 @@ static inline bool generic_fsdax_supported(struct dax_device *dax_dev, return __generic_fsdax_supported(dax_dev, bdev, blocksize, start, sectors); } +bool dax_supported(struct dax_device *dax_dev, struct block_device *bdev, + int blocksize, sector_t start, sector_t len);

static inline void fs_put_dax(struct dax_device *dax_dev) { @@ -157,6 +159,13 @@ static inline bool generic_fsdax_supported(struct dax_device *dax_dev, return false; }

+static inline bool dax_supported(struct dax_device *dax_dev, + struct block_device *bdev, int blocksize, sector_t start, + sector_t len) +{ + return false; +} + static inline void fs_put_dax(struct dax_device *dax_dev) { } @@ -189,14 +198,23 @@ static inline void dax_unlock_page(struct page *page, dax_entry_t cookie) } #endif

+#ifdef CONFIG_DAX int dax_read_lock(void); void dax_read_unlock(int id); +#else +static inline int dax_read_lock(void) +{ + return 0; +} + +static inline void dax_read_unlock(int id) +{ +} +#endif /* CONFIG_DAX */ bool dax_alive(struct dax_device *dax_dev); void *dax_get_private(struct dax_device *dax_dev); long dax_direct_access(struct dax_device *dax_dev, pgoff_t pgoff, long nr_pages, void **kaddr, pfn_t *pfn); -bool dax_supported(struct dax_device *dax_dev, struct block_device *bdev, - int blocksize, sector_t start, sector_t len); size_t dax_copy_from_iter(struct dax_device *dax_dev, pgoff_t pgoff, void *addr, size_t bytes, struct iov_iter *i); size_t dax_copy_to_iter(struct dax_device *dax_dev, pgoff_t pgoff, void *addr,