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

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