Re: [PATCH] fs: fold _d_rehash into d_rehash

[Al Viro <viro@ZenIV.linux.org.uk>]

On Thu, Oct 02, 2014 at 07:34:24PM +0200, Christoph Hellwig wrote:

FWIW, I already have something stronger in my tree.  Look: the only reason
to have separate __d_rehash() is doing it early in __d_move().  Move that
past the place where we change names and locations and you get this:

diff --git a/fs/dcache.c b/fs/dcache.c
index e605b6d..2041261 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -2345,8 +2345,9 @@ again:
 }
 EXPORT_SYMBOL(d_delete);
 
-static void __d_rehash(struct dentry * entry, struct hlist_bl_head *b)
+static void __d_rehash(struct dentry *entry)
 {
+	struct hlist_bl_head *b = d_hash(entry->d_parent, entry->d_name.hash);
 	BUG_ON(!d_unhashed(entry));
 	hlist_bl_lock(b);
 	entry->d_flags |= DCACHE_RCUACCESS;
@@ -2354,11 +2355,6 @@ static void __d_rehash(struct dentry * entry, struct hlist_bl_head *b)
 	hlist_bl_unlock(b);
 }
 
-static void _d_rehash(struct dentry * entry)
-{
-	__d_rehash(entry, d_hash(entry->d_parent, entry->d_name.hash));
-}
-
 /**
  * d_rehash	- add an entry back to the hash
  * @entry: dentry to add to the hash
@@ -2369,7 +2365,7 @@ static void _d_rehash(struct dentry * entry)
 void d_rehash(struct dentry * entry)
 {
 	spin_lock(&entry->d_lock);
-	_d_rehash(entry);
+	__d_rehash(entry);
 	spin_unlock(&entry->d_lock);
 }
 EXPORT_SYMBOL(d_rehash);
@@ -2545,17 +2541,12 @@ static void __d_move(struct dentry *dentry, struct dentry *target,
 	 * for the same hash queue because of how unlikely it is.
 	 */
 	__d_drop(dentry);
-	__d_rehash(dentry, d_hash(target->d_parent, target->d_name.hash));
 
 	/*
 	 * Unhash the target (d_delete() is not usable here).  If exchanging
 	 * the two dentries, then rehash onto the other's hash queue.
 	 */
 	__d_drop(target);
-	if (exchange) {
-		__d_rehash(target,
-			   d_hash(dentry->d_parent, dentry->d_name.hash));
-	}
 
 	/* Switch the names.. */
 	if (exchange)
@@ -2579,6 +2570,9 @@ static void __d_move(struct dentry *dentry, struct dentry *target,
 			fsnotify_d_move(target);
 		fsnotify_d_move(dentry);
 	}
+	__d_rehash(dentry);
+	if (exchange)
+		__d_rehash(target);
 
 	write_seqcount_end(&target->d_seq);
 	write_seqcount_end(&dentry->d_seq);