1 files changed, 39 insertions, 7 deletions

diff --git a/fs/dcache.c b/fs/dcache.c
index a88948b..a901c69 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -225,7 +225,7 @@ static void dentry_unlink_inode(struct dentry * dentry)
 }
 
 /*
- * dentry_lru_(add|del|move_tail) must be called with d_lock held.
+ * dentry_lru_(add|del|prune|move_tail) must be called with d_lock held.
  */
 static void dentry_lru_add(struct dentry *dentry)
 {
@@ -245,6 +245,9 @@ static void __dentry_lru_del(struct dentry *dentry)
 	dentry_stat.nr_unused--;
 }
 
+/*
+ * Remove a dentry with references from the LRU.
+ */
 static void dentry_lru_del(struct dentry *dentry)
 {
 	if (!list_empty(&dentry->d_lru)) {
@@ -254,6 +257,23 @@ static void dentry_lru_del(struct dentry *dentry)
 	}
 }
 
+/*
+ * Remove a dentry that is unreferenced and about to be pruned
+ * (unhashed and destroyed) from the LRU, and inform the file system.
+ * This wrapper should be called _prior_ to unhashing a victim dentry.
+ */
+static void dentry_lru_prune(struct dentry *dentry)
+{
+	if (!list_empty(&dentry->d_lru)) {
+		if (dentry->d_flags & DCACHE_OP_PRUNE)
+			dentry->d_op->d_prune(dentry);
+
+		spin_lock(&dcache_lru_lock);
+		__dentry_lru_del(dentry);
+		spin_unlock(&dcache_lru_lock);
+	}
+}
+
 static void dentry_lru_move_tail(struct dentry *dentry)
 {
 	spin_lock(&dcache_lru_lock);
@@ -403,8 +423,12 @@ relock:
 
 	if (ref)
 		dentry->d_count--;
-	/* if dentry was on the d_lru list delete it from there */
-	dentry_lru_del(dentry);
+	/*
+	 * if dentry was on the d_lru list delete it from there.
+	 * inform the fs via d_prune that this dentry is about to be
+	 * unhashed and destroyed.
+	 */
+	dentry_lru_prune(dentry);
 	/* if it was on the hash then remove it */
 	__d_drop(dentry);
 	return d_kill(dentry, parent);
@@ -522,9 +546,11 @@ int d_invalidate(struct dentry * dentry)
 	 * would make it unreachable from the root,
 	 * we might still populate it if it was a
 	 * working directory or similar).
+	 * We also need to leave mountpoints alone,
+	 * directory or not.
 	 */
-	if (dentry->d_count > 1) {
-		if (dentry->d_inode && S_ISDIR(dentry->d_inode->i_mode)) {
+	if (dentry->d_count > 1 && dentry->d_inode) {
+		if (S_ISDIR(dentry->d_inode->i_mode) || d_mountpoint(dentry)) {
 			spin_unlock(&dentry->d_lock);
 			return -EBUSY;
 		}
@@ -854,8 +880,12 @@ static void shrink_dcache_for_umount_subtree(struct dentry *dentry)
 		do {
 			struct inode *inode;
 
-			/* detach from the system */
-			dentry_lru_del(dentry);
+			/*
+			 * remove the dentry from the lru, and inform
+			 * the fs that this dentry is about to be
+			 * unhashed and destroyed.
+			 */
+			dentry_lru_prune(dentry);
 			__d_shrink(dentry);
 
 			if (dentry->d_count != 0) {
@@ -1283,6 +1313,8 @@ void d_set_d_op(struct dentry *dentry, const struct dentry_operations *op)
 		dentry->d_flags |= DCACHE_OP_REVALIDATE;
 	if (op->d_delete)
 		dentry->d_flags |= DCACHE_OP_DELETE;
+	if (op->d_prune)
+		dentry->d_flags |= DCACHE_OP_PRUNE;
 
 }
 EXPORT_SYMBOL(d_set_d_op);