[PATCH] filesystem-dax: fix broken __dax_zero_page_range() conversion

[Dan Williams]

The conversion of __dax_zero_page_range() to 'struct dax_operations'
caused it to frequently fail. The mistake was treating the @size
parameter as a dax mapping length rather than just a length of the
clear_pmem() operation. The dax mapping length is assumed to be hard
coded as PAGE_SIZE.

Without this fix any page unaligned zeroing request will trigger a
-EINVAL return from bdev_dax_pgoff().

Cc: Jan Kara <j...@suse.com>
Cc: Christoph Hellwig <h...@lst.de>
Reported-by: Ross Zwisler <ross.zwis...@linux.intel.com>
Fixes: cccbce671582 ("filesystem-dax: convert to dax_direct_access()")
Signed-off-by: Dan Williams <dan.j.willi...@intel.com>
---
 fs/dax.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/fs/dax.c b/fs/dax.c
index ce9dc9c3e829..5ee1d212d81f 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -971,12 +971,12 @@ int __dax_zero_page_range(struct block_device *bdev,
                void *kaddr;
                pfn_t pfn;
 
-               rc = bdev_dax_pgoff(bdev, sector, size, &pgoff);
+               rc = bdev_dax_pgoff(bdev, sector, PAGE_SIZE, &pgoff);
                if (rc)
                        return rc;
 
                id = dax_read_lock();
-               rc = dax_direct_access(dax_dev, pgoff, PHYS_PFN(size), &kaddr,
+               rc = dax_direct_access(dax_dev, pgoff, 1, &kaddr,
                                &pfn);
                if (rc < 0) {
                        dax_read_unlock(id);