Add function activate_super() for grabbing an active reference on a
super block. Fails if the filesystem is already shutting down.
Signed-off-by: Andreas Gruenbacher <agruenba@xxxxxxxxxx>
---
fs/super.c | 19 +++++++++++++++++++
include/linux/fs.h | 1 +
2 files changed, 20 insertions(+)
diff --git a/fs/super.c b/fs/super.c
index 8d39e4f11cfa..051241cf408b 100644
--- a/fs/super.c
+++ b/fs/super.c
@@ -393,6 +393,25 @@ static int grab_super(struct super_block *s) __releases(sb_lock)
return 0;
}
+/**
+ * activate_super - try to grab an active reference on the superblock
+ * @sb: reference we are trying to grab
+ *
+ * Try to grab an active reference on the superblock to prevent filesystem
+ * shutdown. Fails if the filesystem is already shutting down (see
+ * deactivate_locked_super()).
+ */
+bool activate_super(struct super_block *sb)
+{
+ if (atomic_inc_not_zero(&sb->s_active)) {
+ smp_mb__after_atomic();
+ BUG_ON(!(sb->s_flags & SB_BORN));
+ return true;
+ }
+ return false;
+}
+EXPORT_SYMBOL(activate_super);
+
/*
* trylock_super - try to grab ->s_umount shared
* @sb: reference we are trying to grab
diff --git a/include/linux/fs.h b/include/linux/fs.h
index e654435f1651..84c609123a25 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -2573,6 +2573,7 @@ void generic_shutdown_super(struct super_block *sb);
void kill_block_super(struct super_block *sb);
void kill_anon_super(struct super_block *sb);
void kill_litter_super(struct super_block *sb);
+bool activate_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);
--
2.38.1
