Re: [PATCH V4 7/8] fs/ext4: Introduce DAX inode flag

[Jan Kara <jack@suse.cz>]

On Thu 21-05-20 12:13:12, ira.weiny@intel.com wrote:
> From: Ira Weiny <ira.weiny@intel.com>
> 
> Add a flag to preserve FS_XFLAG_DAX in the ext4 inode.
> 
> Set the flag to be user visible and changeable.  Set the flag to be
> inherited.  Allow applications to change the flag at any time with the
> exception of if VERITY or ENCRYPT is set.
> 
> Disallow setting VERITY or ENCRYPT if DAX is set.
> 
> Finally, on regular files, flag the inode to not be cached to facilitate
> changing S_DAX on the next creation of the inode.
> 
> Signed-off-by: Ira Weiny <ira.weiny@intel.com>

...

> @@ -303,6 +318,16 @@ static int ext4_ioctl_setflags(struct inode *inode,
>  	unsigned int jflag;
>  	struct super_block *sb = inode->i_sb;
>  
> +	if (ext4_test_inode_flag(inode, EXT4_INODE_DAX)) {
> +		if (ext4_test_inode_flag(inode, EXT4_INODE_VERITY) ||
> +		    ext4_test_inode_flag(inode, EXT4_INODE_ENCRYPT) ||
> +		    ext4_test_inode_state(inode,
> +					  EXT4_STATE_VERITY_IN_PROGRESS)) {
> +			err = -EOPNOTSUPP;
> +			goto flags_out;
> +		}
> +	}

The way this check is implemented wouldn't IMO do what we need... It
doesn't check the flags that are being set but just the current inode
state. I think it should rather be:

	if ((flags ^ oldflags) & EXT4_INODE_DAX_FL) {
		...
	}

And perhaps move this to a place in ext4_ioctl_setflags() where we check
other similar conflicts.

And then we should check conflicts with the journal flag as well, as I
mentioned in reply to the first patch. There it is more complicated by the
fact that we should disallow setting of both EXT4_INODE_DAX_FL and
EXT4_JOURNAL_DATA_FL at the same time so the checks will be somewhat more
complicated.

								Honza

> +
>  	/* Is it quota file? Do not allow user to mess with it */
>  	if (ext4_is_quota_file(inode))
>  		goto flags_out;
-- 
Jan Kara <jack@suse.com>
SUSE Labs, CR