linux-kernel - [PATCH 1/3] ext4: Add alignment check for DAX mount

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Message-Id: <1461962375-3720-2-git-send-email-toshi.kani@hpe.com>
Date:	Fri, 29 Apr 2016 14:39:33 -0600
From:	Toshi Kani <toshi.kani@....com>
To:	dan.j.williams@...el.com, david@...morbit.com, jack@...e.cz
Cc:	tytso@....edu, adilger.kernel@...ger.ca,
	ross.zwisler@...ux.intel.com, toshi.kani@....com,
	linux-nvdimm@...ts.01.org, linux-fsdevel@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH 1/3] ext4: Add alignment check for DAX mount

When a partition is not aligned by 4KB, mount -o dax succeeds,
but any read/write access to the filesystem fails, except for
metadata update.

Add alignment check to ext4_fill_super() when -o dax is specified.

Reported-by: Micah Parrish <micah.parrish@....com>
Signed-off-by: Toshi Kani <toshi.kani@....com>
Cc: "Theodore Ts'o" <tytso@....edu>
Cc: Andreas Dilger <adilger.kernel@...ger.ca>
Cc: Jan Kara <jack@...e.cz>
Cc: Dan Williams <dan.j.williams@...el.com>
Cc: Ross Zwisler <ross.zwisler@...ux.intel.com>
---
 fs/ext4/super.c |    6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index 304c712..90a8670 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -3421,6 +3421,12 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent)
 					"error: unsupported blocksize for dax");
 			goto failed_mount;
 		}
+		if (sb->s_bdev->bd_part->start_sect % (PAGE_SIZE / 512) ||
+		    sb->s_bdev->bd_part->nr_sects % (PAGE_SIZE / 512)) {
+			ext4_msg(sb, KERN_ERR,
+					"error: unaligned partition for dax");
+			goto failed_mount;
+		}
 		if (!sb->s_bdev->bd_disk->fops->direct_access) {
 			ext4_msg(sb, KERN_ERR,
 					"error: device does not support dax");