On Thu, Apr 27, 2017 at 11:59:30AM +0300, Amir Goldstein wrote:
> Overlayfs would like to make use of underlying filesystem's
> sb->s_uuid, but not all filesytems fill this field.
>
> Define a flag to be set by filesystems that do fill the s_uuid
> field, so let consumers like overlayfs know that the content
> of this field is valid.
>
> Signed-off-by: Amir Goldstein <amir73il@xxxxxxxxx>
> ---
> include/linux/fs.h | 3 +++
> 1 file changed, 3 insertions(+)
>
> diff --git a/include/linux/fs.h b/include/linux/fs.h
> index 80daadf..de913b4 100644
> --- a/include/linux/fs.h
> +++ b/include/linux/fs.h
> @@ -1272,6 +1272,9 @@ struct mm_struct;
> /* sb->s_iflags to limit user namespace mounts */
> #define SB_I_USERNS_VISIBLE 0x00000010 /* fstype already mounted */
>
> +/* sb->s_iflags for optional information available in super_block struct */
> +#define SB_I_HAVE_UUID 0x00000100 /* s_uuid */
SB_I_CAN_HAZ_UUID, heh. :)
There seems to be demand for a "Yes I really filled this out" flag, so
for the vfs and xfs parts,
Reviewed-by: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
(I wonder why we can't just leave s_uuid as nil and to heck with anyone
who deliberately sets their fs to have a nil uuid (like we do now), but
whatever... :))
--D
> +
> /* Possible states of 'frozen' field */
> enum {
> SB_UNFROZEN = 0, /* FS is unfrozen */
> --
> 2.7.4
>
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