On Thu 21-05-20 12:13:12, ira.we...@intel.com wrote:
> From: Ira Weiny <ira.we...@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.we...@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 <j...@suse.com>
SUSE Labs, CR

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