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dm: Call proper helper to determine dax support
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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: 7bf7eac ("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>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
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jankara authored and intel-lab-lkp committed Sep 18, 2020
1 parent 3a653b2 commit 3600076
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Showing 3 changed files with 20 additions and 5 deletions.
4 changes: 4 additions & 0 deletions drivers/dax/super.c
Original file line number Diff line number Diff line change
Expand Up @@ -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)
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10 changes: 7 additions & 3 deletions drivers/md/dm-table.c
Original file line number Diff line number Diff line change
Expand Up @@ -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 */
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11 changes: 9 additions & 2 deletions include/linux/dax.h
Original file line number Diff line number Diff line change
Expand Up @@ -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)
{
Expand Down Expand Up @@ -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)
{
}
Expand Down Expand Up @@ -195,8 +204,6 @@ 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,
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