[PATCH] (4/) BKL removal in d_move()

	... is finally done.

Documentation/filesystems/porting

@@ -198,3 +198,20 @@ e.g.
 ->revalidate() is gone.  If your filesystem had it - provide ->getattr()
 and let it call whatever you had as ->revlidate() + (for symlinks that
 had ->revalidate()) add calls in ->follow_link()/->readlink().
+
+---
+[mandatory]
+
+->d_parent changes are not protected by BKL anymore.  Read access is safe
+if at least one of the following is true:
+	* filesystem has no cross-directory rename()
+	* dcache_lock is held
+	* dparent_lock is held (shared)
+	* we know that parent had been locked (e.g. we are looking at
+->d_parent of ->lookup() argument).
+	* we are called from ->rename().
+Audit your code and add locking if needed.  Notice that any place that is
+not protected by the conditions above is risky even in the old tree - you
+had been relying on BKL and that's prone to screwups.  Old tree had quite
+a few holes of that kind - unprotected access to ->d_parent leading to
+anything from oops to silent memory corruption.

fs/dcache.c

@@ -32,9 +32,6 @@
 spinlock_t dcache_lock __cacheline_aligned_in_smp = SPIN_LOCK_UNLOCKED;
 rwlock_t dparent_lock __cacheline_aligned_in_smp = RW_LOCK_UNLOCKED;
 
-/* Right now the dcache depends on the kernel lock */
-#define check_lock()	if (!kernel_locked()) BUG()
-
 static kmem_cache_t *dentry_cache; 
 
 /*
@@ -812,7 +809,6 @@ struct dentry *d_splice_alias(struct inode *inode, struct dentry *dentry)
 	struct dentry *new = NULL;
 
 	if (inode && S_ISDIR(inode->i_mode)) {
-		lock_kernel(); /* for d_move */
 		spin_lock(&dcache_lock);
 		if (!list_empty(&inode->i_dentry)) {
 			new = list_entry(inode->i_dentry.next, struct dentry, d_alias);
@@ -828,7 +824,6 @@ struct dentry *d_splice_alias(struct inode *inode, struct dentry *dentry)
 			spin_unlock(&dcache_lock);
 			d_rehash(dentry);
 		}
-		unlock_kernel();
 	} else
 		d_add(dentry, inode);
 	return new;
@@ -1012,7 +1007,6 @@ static inline void switch_names(struct dentry * dentry, struct dentry * target)
 {
 	const unsigned char *old_name, *new_name;
 
-	check_lock();
 	memcpy(dentry->d_iname, target->d_iname, DNAME_INLINE_LEN); 
 	old_name = target->d_name.name;
 	new_name = dentry->d_name.name;
@@ -1051,8 +1045,6 @@ static inline void switch_names(struct dentry * dentry, struct dentry * target)
   
 void d_move(struct dentry * dentry, struct dentry * target)
 {
-	check_lock();
-
 	if (!dentry->d_inode)
 		printk(KERN_WARNING "VFS: moving negative dcache entry\n");
 

fs/namei.c

@@ -1866,11 +1866,8 @@ int vfs_rename_dir(struct inode *old_dir, struct dentry *old_dentry,
 			d_rehash(new_dentry);
 		dput(new_dentry);
 	}
-	if (!error) {
-		lock_kernel();
+	if (!error)
 		d_move(old_dentry,new_dentry);
-		unlock_kernel();
-	}
 	return error;
 }
 
@@ -1890,11 +1887,8 @@ int vfs_rename_other(struct inode *old_dir, struct dentry *old_dentry,
 		error = old_dir->i_op->rename(old_dir, old_dentry, new_dir, new_dentry);
 	if (!error) {
 		/* The following d_move() should become unconditional */
-		if (!(old_dir->i_sb->s_type->fs_flags & FS_ODD_RENAME)) {
-			lock_kernel();
+		if (!(old_dir->i_sb->s_type->fs_flags & FS_ODD_RENAME))
 			d_move(old_dentry, new_dentry);
-			unlock_kernel();
-		}
 	}
 	if (target)
 		up(&target->i_sem);