linux-kernel - [PATCH 2/2] blockdev: don't set S

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Date:	Fri, 14 Aug 2015 16:15:32 -0400
From:	Jeff Moyer <jmoyer@...hat.com>
To:	matthew.r.wilcox@...el.com
Cc:	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-nvdimm@...1.01.org
Subject: [PATCH 2/2] 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.

Suggested-by: Boaz Harrosh <boaz@...xistor.com>
Signed-off-by: Jeff Moyer <jmoyer@...hat.com>
---
 fs/block_dev.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/fs/block_dev.c b/fs/block_dev.c
index 1982437..1170f8c 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) {
-- 
1.8.3.1

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