X-Git-Url: https://err.no/cgi-bin/gitweb.cgi?a=blobdiff_plain;f=fs%2Finode.c;h=26cdb115ce67d5361222d39cf5e94039db654eec;hb=af60496f746596fdbc7a9ffa1a96f97e1bc59bcf;hp=bf6bec4e54ff648b4696c04909dcf2a5000c8748;hpb=6f3a28f7d1f0a65a78443c273b6e8ec01becf301;p=linux-2.6

diff --git a/fs/inode.c b/fs/inode.c
index bf6bec4e54..26cdb115ce 100644
--- a/fs/inode.c
+++ b/fs/inode.c
@@ -162,7 +162,7 @@ static struct inode *alloc_inode(struct super_block *sb)
 				bdi = sb->s_bdev->bd_inode->i_mapping->backing_dev_info;
 			mapping->backing_dev_info = bdi;
 		}
-		inode->i_private = 0;
+		inode->i_private = NULL;
 		inode->i_mapping = mapping;
 	}
 	return inode;
@@ -1306,6 +1306,42 @@ void wake_up_inode(struct inode *inode)
 	wake_up_bit(&inode->i_state, __I_LOCK);
 }
 
+/*
+ * We rarely want to lock two inodes that do not have a parent/child
+ * relationship (such as directory, child inode) simultaneously. The
+ * vast majority of file systems should be able to get along fine
+ * without this. Do not use these functions except as a last resort.
+ */
+void inode_double_lock(struct inode *inode1, struct inode *inode2)
+{
+	if (inode1 == NULL || inode2 == NULL || inode1 == inode2) {
+		if (inode1)
+			mutex_lock(&inode1->i_mutex);
+		else if (inode2)
+			mutex_lock(&inode2->i_mutex);
+		return;
+	}
+
+	if (inode1 < inode2) {
+		mutex_lock_nested(&inode1->i_mutex, I_MUTEX_PARENT);
+		mutex_lock_nested(&inode2->i_mutex, I_MUTEX_CHILD);
+	} else {
+		mutex_lock_nested(&inode2->i_mutex, I_MUTEX_PARENT);
+		mutex_lock_nested(&inode1->i_mutex, I_MUTEX_CHILD);
+	}
+}
+EXPORT_SYMBOL(inode_double_lock);
+
+void inode_double_unlock(struct inode *inode1, struct inode *inode2)
+{
+	if (inode1)
+		mutex_unlock(&inode1->i_mutex);
+
+	if (inode2 && inode2 != inode1)
+		mutex_unlock(&inode2->i_mutex);
+}
+EXPORT_SYMBOL(inode_double_unlock);
+
 static __initdata unsigned long ihash_entries;
 static int __init set_ihash_entries(char *str)
 {