btrfs: add const function attribute

For some reason the attribute is called __attribute_const__ and not
__const, marks functions that have no observable effects on program
state, IOW not reading pointers, just the arguments and calculating a
value. Allows the compiler to do some optimizations, based on
-Wsuggest-attribute=const . The effects are rather small, though, about
60 bytes decrese of btrfs.ko.

Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

1 files changed, 1 insertions, 1 deletions

diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index 173427731a69..d09371b0cdf9 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -297,7 +297,7 @@ static int __btrfs_map_block(struct btrfs_fs_info *fs_info,
 
 DEFINE_MUTEX(uuid_mutex);
 static LIST_HEAD(fs_uuids);
-struct list_head *btrfs_get_fs_uuids(void)
+struct list_head * __attribute_const__ btrfs_get_fs_uuids(void)
 {
 	return &fs_uuids;
 }