linux-kernel - [PATCH 44/73] union-mount: Return files found in lower layers in __lookup

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Message-ID: <20120221180300.25235.63345.stgit@warthog.procyon.org.uk>
Date:	Tue, 21 Feb 2012 18:03:00 +0000
From:	David Howells <dhowells@...hat.com>
To:	linux-fsdevel@...r.kernel.org, viro@...IV.linux.org.uk,
	valerie.aurora@...il.com
Cc:	linux-kernel@...r.kernel.org, David Howells <dhowells@...hat.com>
Subject: [PATCH 44/73] union-mount: Return files found in lower layers in
 __lookup_union() [ver #2]

From: Valerie Aurora <vaurora@...hat.com>

If we find a file during union lookup, don't look in any lower layers
and replace the topmost path with the file's path.

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

 fs/namei.c |   20 ++++++++++++++++++++
 1 files changed, 20 insertions(+), 0 deletions(-)

diff --git a/fs/namei.c b/fs/namei.c
index 009d9b5..f81f24e 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -1179,11 +1179,31 @@ static int __lookup_union(struct nameidata *nd, struct qstr *name,
 			continue;
 		}
 
+		/* Files block everything below them.  Special case: If we find
+		 * a file below a directory (which makes no sense), just ignore
+		 * the file and return the directory above it.
+		 */
+		if (!S_ISDIR(lower.dentry->d_inode->i_mode)) {
+			if (topmost->dentry->d_inode &&
+			    S_ISDIR(topmost->dentry->d_inode->i_mode))
+				goto out_lookup_done;
+			goto out_found_file;
+		}
+
 		/* XXX - do nothing, more in later patches */
 		path_put(&lower);
 	}
 	return 0;
 
+out_found_file:
+	/* Swap out the positive lower dentry with the negative upper
+	 * dentry for this file.  Note that the matching mntput() is done
+	 * in link_path_walk().
+	 */
+	dput(topmost->dentry);
+	*topmost = lower;
+	return 0;
+
 out_lookup_done:
 	path_put(&lower);
 	return 0;

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