Presently __bdev_dax_supported() checks if first sector of last page ( last_page ) on the block device is aligned to page boundary. However the code to compute 'last_page' assumes that there are 8 sectors/page assuming a 4K page-size.
This assumption breaks on architectures which use a different page size specifically PPC64 where page-size == 64K. Hence a warning is seen while trying to mount a xfs/ext4 file-system with dax enabled: $ sudo mount -o dax /dev/pmem0 /mnt/pmem XFS (pmem0): DAX enabled. Warning: EXPERIMENTAL, use at your own risk XFS (pmem0): DAX unsupported by block device. Turning off DAX. The patch fixes this issue by updating calculation of 'last_var' to take into account number-of-sectors/page instead of assuming it to be '8'. Fixes: ad428cdb525a ("dax: Check the end of the block-device capacity with dax_direct_access()") Signed-off-by: Chandan Rajendra <chan...@linux.ibm.com> Signed-off-by: Vaibhav Jain <vaib...@linux.ibm.com> --- drivers/dax/super.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/drivers/dax/super.c b/drivers/dax/super.c index bbd57ca0634a..6b50ed3673d3 100644 --- a/drivers/dax/super.c +++ b/drivers/dax/super.c @@ -116,7 +116,9 @@ bool __bdev_dax_supported(struct block_device *bdev, int blocksize) return false; } - last_page = PFN_DOWN(i_size_read(bdev->bd_inode) - 1) * 8; + /* Calculate the first sector of last page on the block device */ + last_page = PFN_DOWN(i_size_read(bdev->bd_inode) - 1) * + (PAGE_SIZE >> SECTOR_SHIFT); err = bdev_dax_pgoff(bdev, last_page, PAGE_SIZE, &pgoff_end); if (err) { pr_debug("%s: error: unaligned partition for dax\n", -- 2.21.0