fix do_emergency_remount()/umount() races

need list_for_each_entry_safe() here.  Original didn't even
have restart logics, so if you race with umount() it blew up.

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

diff --git a/fs/super.c b/fs/super.c
index ccb2b5f..4df8233 100644 (file)
--- a/fs/super.c
+++ b/fs/super.c
@@ -602,10 +602,10 @@ int do_remount_sb(struct super_block *sb, int flags, void *data, int force)
 
 static void do_emergency_remount(struct work_struct *work)
 {
-       struct super_block *sb;
+       struct super_block *sb, *n;
 
        spin_lock(&sb_lock);
-       list_for_each_entry(sb, &super_blocks, s_list) {
+       list_for_each_entry_safe(sb, n, &super_blocks, s_list) {
                if (list_empty(&sb->s_instances))
                        continue;
                sb->s_count++;
@@ -618,8 +618,8 @@ static void do_emergency_remount(struct work_struct *work)
                        do_remount_sb(sb, MS_RDONLY, NULL, 1);
                }
                up_write(&sb->s_umount);
-               put_super(sb);
                spin_lock(&sb_lock);
+               __put_super(sb);
        }
        spin_unlock(&sb_lock);
        kfree(work);