new helper: iterate_supers()

... and switch the simple "loop over superblocks and do something"
loops to it.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

1 files changed, 30 insertions, 0 deletions

diff --git a/fs/super.c b/fs/super.c
index 95adbb3d8e5..2c3e370c60d 100644
--- a/fs/super.c
+++ b/fs/super.c
@@ -392,6 +392,36 @@ void sync_supers(void)
 }
 
 /**
+ *      iterate_supers - call function for all active superblocks
+ *      @f: function to call
+ *      @arg: argument to pass to it
+ *
+ *      Scans the superblock list and calls given function, passing it
+ *      locked superblock and given argument.
+ */
+void iterate_supers(void (*f)(struct super_block *, void *), void *arg)
+{
+        struct super_block *sb, *n;
+
+        spin_lock(&sb_lock);
+        list_for_each_entry_safe(sb, n, &super_blocks, s_list) {
+                if (list_empty(&sb->s_instances))
+                        continue;
+                sb->s_count++;
+                spin_unlock(&sb_lock);
+
+                down_read(&sb->s_umount);
+                if (sb->s_root)
+                        f(sb, arg);
+                up_read(&sb->s_umount);
+
+                spin_lock(&sb_lock);
+                __put_super(sb);
+        }
+        spin_unlock(&sb_lock);
+}
+
+/**
  *      get_super - get the superblock of a device
  *      @bdev: device to get the superblock for
  *