New helper: deactivate_locked_super()
Does equivalent of up_write(&s->s_umount); deactivate_super(s);
However, it does not does not unlock it until it's all over.
As the result, it's safe to use to dispose of new superblock on ->get_sb()
failure exits - nobody will see the sucker until it's all over.
Equivalent using up_write/deactivate_super is safe for that purpose
if superblock is either safe to use or has NULL ->s_root when we unlock.
Normally filesystems take the required precautions, but
a) we do have bugs in that area in some of them.
b) up_write/deactivate_super sequence is extremely common,
so the helper makes sense anyway.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 5bed436..11484d0 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -1775,6 +1775,7 @@
void kill_anon_super(struct super_block *sb);
void kill_litter_super(struct super_block *sb);
void deactivate_super(struct super_block *sb);
+void deactivate_locked_super(struct super_block *sb);
int set_anon_super(struct super_block *s, void *data);
struct super_block *sget(struct file_system_type *type,
int (*test)(struct super_block *,void *),