sysfs: implement SYSFS_FLAG_REMOVED flag

Implement SYSFS_FLAG_REMOVED flag which currently is used only to
improve sanity check in sysfs_deactivate().  The flag will be used to
make directory entries reclamiable.
Signed-off-by: Tejun Heo <htejun@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

fs/sysfs/dir.c

@@ -171,7 +171,7 @@ void sysfs_deactivate(struct sysfs_dirent *sd)
 	DECLARE_COMPLETION_ONSTACK(wait);
 	int v;
 
-	BUG_ON(sd->s_sibling);
+	BUG_ON(sd->s_sibling || !(sd->s_flags & SYSFS_FLAG_REMOVED));
 	sd->s_sibling = (void *)&wait;
 
 	/* atomic_add_return() is a mb(), put_active() will always see
@@ -506,6 +506,7 @@ static void remove_dir(struct dentry * d)
 	mutex_lock(&parent->d_inode->i_mutex);
 
 	sysfs_unlink_sibling(sd);
+	sd->s_flags |= SYSFS_FLAG_REMOVED;
 
 	pr_debug(" o %s removing done (%d)\n",d->d_name.name,
 		 atomic_read(&d->d_count));
@@ -540,6 +541,7 @@ static void __sysfs_remove_dir(struct dentry *dentry)
 		struct sysfs_dirent *sd = *pos;
 
 		if (sysfs_type(sd) && (sysfs_type(sd) & SYSFS_NOT_PINNED)) {
+			sd->s_flags |= SYSFS_FLAG_REMOVED;
 			*pos = sd->s_sibling;
 			sd->s_sibling = removed;
 			removed = sd;

fs/sysfs/inode.c

@@ -296,6 +296,7 @@ int sysfs_hash_and_remove(struct dentry * dir, const char * name)
 		if (!sysfs_type(sd))
 			continue;
 		if (!strcmp(sd->s_name, name)) {
+			sd->s_flags |= SYSFS_FLAG_REMOVED;
 			*pos = sd->s_sibling;
 			sd->s_sibling = NULL;
 			found = 1;

include/linux/sysfs.h

@@ -84,6 +84,7 @@ struct sysfs_ops {
 #define SYSFS_COPY_NAME		(SYSFS_DIR | SYSFS_KOBJ_LINK)
 
 #define SYSFS_FLAG_MASK		~SYSFS_TYPE_MASK
+#define SYSFS_FLAG_REMOVED	0x0100
 
 #ifdef CONFIG_SYSFS