blockdev: don't set S_DAX for misaligned partitions

The dax code doesn't currently support misaligned partitions,
so disable O_DIRECT via dax until such time as that support
materializes.

Cc: <stable@vger.kernel.org>
Suggested-by: Boaz Harrosh <boaz@plexistor.com>
Signed-off-by: Jeff Moyer <jmoyer@redhat.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

1 files changed, 7 insertions, 0 deletions

diff --git a/fs/block_dev.c b/fs/block_dev.c
index 22ea424ee741..073bb57adab1 100644
--- a/fs/block_dev.c
+++ b/fs/block_dev.c
@@ -1242,6 +1242,13 @@ static int __blkdev_get(struct block_device *bdev, fmode_t mode, int for_part)
                                 goto out_clear;
                         }
                         bd_set_size(bdev, (loff_t)bdev->bd_part->nr_sects << 9);
+                        /*
+                         * If the partition is not aligned on a page
+                         * boundary, we can't do dax I/O to it.
+                         */
+                        if ((bdev->bd_part->start_sect % (PAGE_SIZE / 512)) ||
+                            (bdev->bd_part->nr_sects % (PAGE_SIZE / 512)))
+                                bdev->bd_inode->i_flags &= ~S_DAX;
                 }
         } else {
                 if (bdev->bd_contains == bdev) {