linux-kernel - Re: [PATCH v2 1/3] ext4: Add alignment check for DAX mount

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Date:	Tue, 3 May 2016 09:58:11 +0200
From:	Jan Kara <jack@...e.cz>
To:	Toshi Kani <toshi.kani@....com>
Cc:	dan.j.williams@...el.com, jack@...e.cz, david@...morbit.com,
	hch@...radead.org, boaz@...xistor.com, tytso@....edu,
	adilger.kernel@...ger.ca, ross.zwisler@...ux.intel.com,
	micah.parrish@....com, linux-nvdimm@...ts.01.org,
	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 1/3] ext4: Add alignment check for DAX mount

On Mon 02-05-16 12:42:56, 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.
> 
> 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>
> Cc: Christoph Hellwig <hch@...radead.org>
> Cc: Boaz Harrosh <boaz@...xistor.com>

Looks good to me. You can add:

Reviewed-by: Jan Kara <jack@...e.cz>

								Honza
> ---
>  fs/ext4/super.c |   20 ++++++++++++++++++--
>  1 file changed, 18 insertions(+), 2 deletions(-)
> 
> diff --git a/fs/ext4/super.c b/fs/ext4/super.c
> index 304c712..51ac78e 100644
> --- a/fs/ext4/super.c
> +++ b/fs/ext4/super.c
> @@ -3416,14 +3416,30 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent)
>  	}
>  
>  	if (sbi->s_mount_opt & EXT4_MOUNT_DAX) {
> +		struct blk_dax_ctl dax = {
> +			.sector = 0,
> +			.size = PAGE_SIZE,
> +		};
>  		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,
> +		err = bdev_direct_access(sb->s_bdev, &dax);
> +		if (err < 0) {
> +			switch (err) {
> +			case -EOPNOTSUPP:
> +				ext4_msg(sb, KERN_ERR,
>  					"error: device does not support dax");
> +				break;
> +			case -EINVAL:
> +				ext4_msg(sb, KERN_ERR,
> +					"error: unaligned partition for dax");
> +				break;
> +			default:
> +				ext4_msg(sb, KERN_ERR,
> +					"error: dax access failed (%d)", err);
> +			}
>  			goto failed_mount;
>  		}
>  	}
-- 
Jan Kara <jack@...e.com>
SUSE Labs, CR