blockdev: don't set S_DAX for misaligned partitions

commit f0b2e563bc419df7c1b3d2f494574c25125f6aed upstream.

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

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/fs/block_dev.c b/fs/block_dev.c
index c7e4163..ccfd31f 100644 (file)
--- a/fs/block_dev.c
+++ b/fs/block_dev.c
@@ -1234,6 +1234,13 @@ 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) {