[PATCH 28/34] union-mount: Process negative dentries in __union_lookup()

[Valerie Aurora]

Whiteouts end a union lookup.  So do opaque directories, unless
specific fallthru entry exists for this name.

Signed-off-by: Valerie Aurora <vaurora@xxxxxxxxxx>
---
 fs/namei.c |   23 ++++++++++++++++++++++-
 1 files changed, 22 insertions(+), 1 deletions(-)

diff --git a/fs/namei.c b/fs/namei.c
index 8373463..f6ad8b3 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -781,11 +781,32 @@ static int __lookup_union(struct nameidata *nd, struct qstr *name,
 			err = PTR_ERR(lower.dentry);
 			goto out_err;
 		}
-		/* XXX - do nothing, lookup rule processing in later patches */
+
+		/*
+		 * A negative dentry can mean several things.  A plain
+		 * negative dentry is ignored and lookup continues to
+		 * the next layer.  But a whiteout or a non-fallthru
+		 * in an opaque dir covers everything below it.
+		 */
+		if (!lower.dentry->d_inode) {
+			if (d_is_whiteout(lower.dentry))
+				goto out_lookup_done;
+			if (IS_OPAQUE(nd->path.dentry->d_inode) &&
+			    !d_is_fallthru(lower.dentry))
+				goto out_lookup_done;
+			path_put(&lower);
+			continue;
+		}
+
+		/* XXX - do nothing, more in later patches */
 		path_put(&lower);
 	}
 	return 0;
 
+out_lookup_done:
+	path_put(&lower);
+	return 0;
+
 out_err:
 	d_free_unions(topmost->dentry);
 	path_put(&lower);
-- 
1.6.3.3

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