[PATCH 35/74] union-mount: Create needs_lookup_union()

[Valerie Aurora <valerie.aurora@gmail.com>]

From: Valerie Aurora <vaurora@redhat.com>

needs_lookup_union() tests if a path could possibly require a union
lookup.

Signed-off-by: Valerie Aurora <valerie.aurora@gmail.com>
---
 fs/union.h             |   16 ++++++++++++++++
 include/linux/dcache.h |    1 +
 2 files changed, 17 insertions(+), 0 deletions(-)

diff --git a/fs/union.h b/fs/union.h
index c496823..9efb177 100644
--- a/fs/union.h
+++ b/fs/union.h
@@ -57,6 +57,21 @@ extern int union_add_dir(struct path *, struct path *, unsigned int);
 extern int union_create_topmost_dir(struct path *, struct qstr *, struct path *,
 				    struct path *);
 
+static inline int needs_lookup_union(struct path *parent_path, struct path *path)
+{
+	if (!IS_DIR_UNIONED(parent_path->dentry))
+		return 0;
+
+	/* Either already built or crossed a mountpoint to not-unioned mnt */
+	/* XXX are bind mounts root? think not */
+	if (IS_ROOT(path->dentry))
+		return 0;
+
+	/* It's okay not to have the lock; will recheck in lookup_union() */
+	/* XXX set for root dentry at mount? */
+	return !(path->dentry->d_flags & DCACHE_UNION_LOOKUP_DONE);
+}
+
 static inline struct path *union_find_dir(struct dentry *dentry,
 					  unsigned int layer) {
 	BUG_ON(layer >= dentry->d_sb->s_union_count);
@@ -72,6 +87,7 @@ static inline struct path *union_find_dir(struct dentry *dentry,
 #define union_add_dir(x, y, z)		({ BUG(); (0); })
 #define union_find_dir(x, y)		({ BUG(); (NULL); })
 #define union_create_topmost_dir(w, x, y, z)	({ BUG(); (0); })
+#define needs_lookup_union(x, y)	({ (0); })
 
 #endif	/* CONFIG_UNION_MOUNT */
 #endif	/* __KERNEL__ */
diff --git a/include/linux/dcache.h b/include/linux/dcache.h
index ddf3d2d..c37b621 100644
--- a/include/linux/dcache.h
+++ b/include/linux/dcache.h
@@ -209,6 +209,7 @@ d_iput:		no		no		no       yes
 #define DCACHE_WHITEOUT		0x0200	/* Stop lookup in a unioned file system */
 
 #define DCACHE_FALLTHRU		0x0400	/* Continue lookup below an opaque dir */
+#define DCACHE_UNION_LOOKUP_DONE	0x0800	/* Union lookup was called on this dentry */
 
 extern spinlock_t dcache_lock;
 extern seqlock_t rename_lock;
-- 
1.7.0.4