[PATCH] 2.2.18: d_move() with self-root dentries

From: Chip Salzenberg <chip@valinux.com>
To: Linux Kernel <linux-kernel@vger.kernel.org>
Cc: nfs@lists.sourceforge.net
Subject: [PATCH] 2.2.18: d_move() with self-root dentries
Date: Tue, 21 Nov 2000 01:17:45 -0800	[thread overview]
Message-ID: <20001121011744.A2147@valinux.com> (raw)

The d_move() function doesn't correctly handle dentries that have no
parents (i.e. 'x->d_parent==x').  This patch lets it do so.

Normally, the only parentless dentries are filesystem roots.  However,
the NFS server creates (temporary) parentless dentries whenever dentry
pruning has deleted the dentries referring to clients' open files.

Making nfsd's d_splice() compensate for d_move's limitations is not
only a kludge, but also it harder to keep nfsd correct.  Besides,
someday, nfsd may not be the only creator of this kind of dentry.

Thus, this patch.  If you apply this, you'll also want to patch
fs/nfsd/nfsfh.c to stop compensating for d_move's old limitations.
(Alan, this is 2.2.19 material [if then].)

Index: fs/dcache.c

--- fs/dcache.c.prev
+++ fs/dcache.c	Mon Nov 20 22:31:09 2000
@@ -749,16 +749,28 @@ void d_move(struct dentry * dentry, stru
 	INIT_LIST_HEAD(&target->d_hash);
 
+	/* Switch the names */
+	switch_names(dentry, target);
+	do_switch(dentry->d_name.len, target->d_name.len);
+	do_switch(dentry->d_name.hash, target->d_name.hash);
+
+	/* Switch parentage, allowing for self-parents */
+
 	list_del(&dentry->d_child);
 	list_del(&target->d_child);
 
-	/* Switch the parents and the names.. */
-	switch_names(dentry, target);
 	do_switch(dentry->d_parent, target->d_parent);
-	do_switch(dentry->d_name.len, target->d_name.len);
-	do_switch(dentry->d_name.hash, target->d_name.hash);
 
-	/* And add them back to the (new) parent lists */
-	list_add(&target->d_child, &target->d_parent->d_subdirs);
-	list_add(&dentry->d_child, &dentry->d_parent->d_subdirs);
+	if (dentry->d_parent != target)
+		list_add(&dentry->d_child, &dentry->d_parent->d_subdirs);
+	else {
+		INIT_LIST_HEAD(&dentry->d_child);
+		dentry->d_parent = dentry;
+	}
+	if (target->d_parent != dentry)
+		list_add(&target->d_child, &target->d_parent->d_subdirs);
+	else {
+		INIT_LIST_HEAD(&target->d_child);
+		target->d_parent = target;
+	}
 }
 

-- 
Chip Salzenberg            - a.k.a. -            <chip@valinux.com>
   "Give me immortality, or give me death!"  // Firesign Theatre
-
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