linux-kernel - [PATCH 33/34] union-mount: Add do_lookup_union() wrapper for __lookup

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Date:	Thu, 16 Sep 2010 15:12:24 -0700
From:	Valerie Aurora <vaurora@...hat.com>
To:	Alexander Viro <viro@...iv.linux.org.uk>
Cc:	Miklos Szeredi <miklos@...redi.hu>,
	Christoph Hellwig <hch@...radead.org>,
	Andreas Gruenbacher <agruen@...e.de>,
	Nick Piggin <npiggin@...nel.dk>, linux-kernel@...r.kernel.org,
	linux-fsdevel@...r.kernel.org, Valerie Aurora <vaurora@...hat.com>
Subject: [PATCH 33/34] union-mount: Add do_lookup_union() wrapper for __lookup_union()

do_lookup_union() locks the parent directory and follows the mount
after lookup.  It is appropriate for calling from do_lookup().

Signed-off-by: Valerie Aurora <vaurora@...hat.com>
---
 fs/namei.c |   22 ++++++++++++++++++++++
 1 files changed, 22 insertions(+), 0 deletions(-)

diff --git a/fs/namei.c b/fs/namei.c
index ecb1796..7656442 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -880,6 +880,28 @@ static int lookup_union(struct nameidata *nd, struct qstr *name,
 }
 
 /*
+ * do_union_lookup - union mount-aware part of do_lookup
+ *
+ * do_lookup()-style wrapper for lookup_union().  Follows mounts.
+ */
+
+static int do_lookup_union(struct nameidata *nd, struct qstr *name,
+			   struct path *topmost)
+{
+	struct dentry *parent = nd->path.dentry;
+	struct inode *dir = parent->d_inode;
+	int err;
+
+	mutex_lock(&dir->i_mutex);
+	err = lookup_union(nd, name, topmost);
+	mutex_unlock(&dir->i_mutex);
+
+	__follow_mount(topmost);
+
+	return err;
+}
+
+/*
  *  It's more convoluted than I'd like it to be, but... it's still fairly
  *  small and for now I'd prefer to have fast path as straight as possible.
  *  It _is_ time-critical.
-- 
1.6.3.3

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