[PATCH] dcache: Add helper d_hash_and_lookup

It is very common to hash a dentry and then to call lookup.  If we take fs
specific hash functions into account the full hash logic can get ugly.
Further full_name_hash as an inline function is almost 100 bytes on x86 so
having a non-inline choice in some cases can measurably decrease code size.

Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

2 files changed, 29 insertions, 16 deletions

diff --git a/fs/dcache.c b/fs/dcache.c
index 21dffeec755b..940d188e5d14 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -1101,6 +1101,32 @@ next:
 }
 
 /**
+ * d_hash_and_lookup - hash the qstr then search for a dentry
+ * @dir: Directory to search in
+ * @name: qstr of name we wish to find
+ *
+ * On hash failure or on lookup failure NULL is returned.
+ */
+struct dentry *d_hash_and_lookup(struct dentry *dir, struct qstr *name)
+{
+        struct dentry *dentry = NULL;
+
+        /*
+         * Check for a fs-specific hash function. Note that we must
+         * calculate the standard hash first, as the d_op->d_hash()
+         * routine may choose to leave the hash value unchanged.
+         */
+        name->hash = full_name_hash(name->name, name->len);
+        if (dir->d_op && dir->d_op->d_hash) {
+                if (dir->d_op->d_hash(dir, name) < 0)
+                        goto out;
+        }
+        dentry = d_lookup(dir, name);
+out:
+        return dentry;
+}
+
+/**
  * d_validate - verify dentry provided from insecure source
  * @dentry: The dentry alleged to be valid child of @dparent
  * @dparent: The parent dentry (known to be valid)
@@ -1616,26 +1642,12 @@ ino_t find_inode_number(struct dentry *dir, struct qstr *name)
         struct dentry * dentry;
         ino_t ino = 0;
 
-        /*
-         * Check for a fs-specific hash function. Note that we must
-         * calculate the standard hash first, as the d_op->d_hash()
-         * routine may choose to leave the hash value unchanged.
-         */
-        name->hash = full_name_hash(name->name, name->len);
-        if (dir->d_op && dir->d_op->d_hash)
-        {
-                if (dir->d_op->d_hash(dir, name) != 0)
-                        goto out;
-        }
-
-        dentry = d_lookup(dir, name);
-        if (dentry)
-        {
+        dentry = d_hash_and_lookup(dir, name);
+        if (dentry) {
                 if (dentry->d_inode)
                         ino = dentry->d_inode->i_ino;
                 dput(dentry);
         }
-out:
         return ino;
 }
 
diff --git a/include/linux/dcache.h b/include/linux/dcache.h
index d10bd30c337e..836325ee0931 100644
--- a/include/linux/dcache.h
+++ b/include/linux/dcache.h
@@ -275,6 +275,7 @@ extern void d_move(struct dentry *, struct dentry *);
 /* appendix may either be NULL or be used for transname suffixes */
 extern struct dentry * d_lookup(struct dentry *, struct qstr *);
 extern struct dentry * __d_lookup(struct dentry *, struct qstr *);
+extern struct dentry * d_hash_and_lookup(struct dentry *, struct qstr *);
 
 /* validate "insecure" dentry pointer */
 extern int d_validate(struct dentry *, struct dentry *);