[PATCH v4 3/6] ext4: Add alignment check for DAX mount

Toshi Kani
2016-05-10T16:34:46Z

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.

Call bdev_dax_supported() to perform proper precondition checks
which includes this partition alignment check.

Reported-by: Micah Parrish <micah.parrish@hpe.com>
Signed-off-by: Toshi Kani <toshi.kani@hpe.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Cc: "Theodore Ts'o" <tytso@mit.edu>
Cc: Andreas Dilger <adilger.kernel@dilger.ca>
Cc: Jan Kara <jack@suse.cz>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Ross Zwisler <ross.zwisler@linux.intel.com>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Boaz Harrosh <boaz@plexistor.com>
---
fs/ext4/super.c | 11 ++---------
1 file changed, 2 insertions(+), 9 deletions(-)

diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index 304c712..6925e86 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -3416,16 +3416,9 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent)
}

if (sbi->s_mount_opt & EXT4_MOUNT_DAX) {
- if (blocksize != PAGE_SIZE) {
- ext4_msg(sb, KERN_ERR,
- "error: unsupported blocksize 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");
+ err = bdev_dax_supported(sb, blocksize);
+ if (err)
goto failed_mount;
- }
}

if (ext4_has_feature_encrypt(sb) && es->s_encryption_level) {