[PATCH 1/6] fs: super_block->s_uuid_len

[Kent Overstreet <kent.overstreet@linux.dev>]

Some weird old filesytems have UUID-like things that we wish to expose
as UUIDs, but are smaller; add a length field so that the new
FS_IOC_(GET|SET)UUID ioctls can handle them in generic code.

Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
---
 fs/super.c         | 1 +
 include/linux/fs.h | 1 +
 2 files changed, 2 insertions(+)

diff --git a/fs/super.c b/fs/super.c
index d35e85295489..ed688d2a58a7 100644
--- a/fs/super.c
+++ b/fs/super.c
@@ -375,6 +375,7 @@ static struct super_block *alloc_super(struct file_system_type *type, int flags,
 	s->s_time_gran = 1000000000;
 	s->s_time_min = TIME64_MIN;
 	s->s_time_max = TIME64_MAX;
+	s->s_uuid_len = sizeof(s->s_uuid);
 
 	s->s_shrink = shrinker_alloc(SHRINKER_NUMA_AWARE | SHRINKER_MEMCG_AWARE,
 				     "sb-%s", type->name);
diff --git a/include/linux/fs.h b/include/linux/fs.h
index ed5966a70495..ff41ea6c3a9c 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -1257,6 +1257,7 @@ struct super_block {
 
 	char			s_id[32];	/* Informational name */
 	uuid_t			s_uuid;		/* UUID */
+	u8			s_uuid_len;	/* Default 16, possibly smaller for weird filesystems */
 
 	unsigned int		s_max_links;
 
-- 
2.43.0