Re: [PATCH v2 2/3] ext2: Add alignment check for DAX mount

[Jan Kara]

On Mon 02-05-16 12:42:57, Toshi Kani wrote:
> 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_direct_access to check the alignment when -o dax is
> specified.
> 
> Signed-off-by: Toshi Kani <toshi.kani@xxxxxxx>
> Cc: Jan Kara <jack@xxxxxxx>
> Cc: Dan Williams <dan.j.williams@xxxxxxxxx>
> Cc: Ross Zwisler <ross.zwisler@xxxxxxxxxxxxxxx>
> Cc: Christoph Hellwig <hch@xxxxxxxxxxxxx>
> Cc: Boaz Harrosh <boaz@xxxxxxxxxxxxx>

The patch looks good. I've added it to my tree and will push it to Linus in
the coming merge window.

								Honza

> ---
>  fs/ext2/super.c |   21 +++++++++++++++++++--
>  1 file changed, 19 insertions(+), 2 deletions(-)
> 
> diff --git a/fs/ext2/super.c b/fs/ext2/super.c
> index b78caf2..e636b56 100644
> --- a/fs/ext2/super.c
> +++ b/fs/ext2/super.c
> @@ -922,14 +922,31 @@ static int ext2_fill_super(struct super_block *sb, void *data, int silent)
>  	blocksize = BLOCK_SIZE << le32_to_cpu(sbi->s_es->s_log_block_size);
>  
>  	if (sbi->s_mount_opt & EXT2_MOUNT_DAX) {
> +		struct blk_dax_ctl dax = {
> +			.sector = 0,
> +			.size = PAGE_SIZE,
> +		};
>  		if (blocksize != PAGE_SIZE) {
>  			ext2_msg(sb, KERN_ERR,
>  					"error: unsupported blocksize for dax");
>  			goto failed_mount;
>  		}
> -		if (!sb->s_bdev->bd_disk->fops->direct_access) {
> -			ext2_msg(sb, KERN_ERR,
> +		err = bdev_direct_access(sb->s_bdev, &dax);
> +		if (err < 0) {
> +			switch (err) {
> +			case -EOPNOTSUPP:
> +				ext2_msg(sb, KERN_ERR,
>  					"error: device does not support dax");
> +				break;
> +			case -EINVAL:
> +				ext2_msg(sb, KERN_ERR,
> +					"error: unaligned partition for dax");
> +				break;
> +			default:
> +				ext2_msg(sb, KERN_ERR,
> +					"error: dax access failed (%d)", err);
> +				break;
> +			}
>  			goto failed_mount;
>  		}
>  	}
-- 
Jan Kara <jack@xxxxxxxx>
SUSE Labs, CR