From: Jeff Moyer <jmoyer@redhat.com>
Date: Fri, 14 Aug 2015 20:15:32 +0000 (-0400)
Subject: blockdev: don't set S_DAX for misaligned partitions
X-Git-Tag: v4.2.4~209
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=5704348dfc130c1482ac41da0c635ad157b43f4c;p=thirdparty%2Fkernel%2Fstable.git

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 198243717da56..1170f8ce5e7f5 100644
--- a/fs/block_dev.c
+++ b/fs/block_dev.c
@@ -1241,6 +1241,13 @@ 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) {