[PATCH 43/73] union-mount: Process negative dentries in__lookup_union() [ver #2]

[David Howells]

From: Valerie Aurora <vaurora@xxxxxxxxxx>

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

Original-author: Valerie Aurora <vaurora@xxxxxxxxxx>
Signed-off-by: David Howells <dhowells@xxxxxxxxxx>
---

 fs/namei.c |   22 +++++++++++++++++++++-
 1 files changed, 21 insertions(+), 1 deletions(-)

diff --git a/fs/namei.c b/fs/namei.c
index 8caed86..009d9b5 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -1163,11 +1163,31 @@ 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);

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