vfs: split __lookup_hash
Miklos Szeredi [Mon, 26 Mar 2012 10:54:24 +0000 (12:54 +0200)]
Split __lookup_hash into two component functions:

 lookup_dcache - tries cached lookup, returns whether real lookup is needed
 lookup_real - calls i_op->lookup

This eliminates code duplication between d_alloc_and_lookup() and
d_inode_lookup().

Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

fs/namei.c

index 5eeec56..fef80bf 100644 (file)
@@ -1054,53 +1054,65 @@ static void follow_dotdot(struct nameidata *nd)
 }
 
 /*
- * Allocate a dentry with name and parent, and perform a parent
- * directory ->lookup on it. Returns the new dentry, or ERR_PTR
- * on error. parent->d_inode->i_mutex must be held. d_lookup must
- * have verified that no child exists while under i_mutex.
+ * This looks up the name in dcache, possibly revalidates the old dentry and
+ * allocates a new one if not found or not valid.  In the need_lookup argument
+ * returns whether i_op->lookup is necessary.
+ *
+ * dir->d_inode->i_mutex must be held
  */
-static struct dentry *d_alloc_and_lookup(struct dentry *parent,
-                               struct qstr *name, struct nameidata *nd)
+static struct dentry *lookup_dcache(struct qstr *name, struct dentry *dir,
+                                   struct nameidata *nd, bool *need_lookup)
 {
-       struct inode *inode = parent->d_inode;
        struct dentry *dentry;
-       struct dentry *old;
+       int error;
 
-       /* Don't create child dentry for a dead directory. */
-       if (unlikely(IS_DEADDIR(inode)))
-               return ERR_PTR(-ENOENT);
+       *need_lookup = false;
+       dentry = d_lookup(dir, name);
+       if (dentry) {
+               if (d_need_lookup(dentry)) {
+                       *need_lookup = true;
+               } else if (dentry->d_flags & DCACHE_OP_REVALIDATE) {
+                       error = d_revalidate(dentry, nd);
+                       if (unlikely(error <= 0)) {
+                               if (error < 0) {
+                                       dput(dentry);
+                                       return ERR_PTR(error);
+                               } else if (!d_invalidate(dentry)) {
+                                       dput(dentry);
+                                       dentry = NULL;
+                               }
+                       }
+               }
+       }
 
-       dentry = d_alloc(parent, name);
-       if (unlikely(!dentry))
-               return ERR_PTR(-ENOMEM);
+       if (!dentry) {
+               dentry = d_alloc(dir, name);
+               if (unlikely(!dentry))
+                       return ERR_PTR(-ENOMEM);
 
-       old = inode->i_op->lookup(inode, dentry, nd);
-       if (unlikely(old)) {
-               dput(dentry);
-               dentry = old;
+               *need_lookup = true;
        }
        return dentry;
 }
 
 /*
- * We already have a dentry, but require a lookup to be performed on the parent
- * directory to fill in d_inode. Returns the new dentry, or ERR_PTR on error.
- * parent->d_inode->i_mutex must be held. d_lookup must have verified that no
- * child exists while under i_mutex.
+ * Call i_op->lookup on the dentry.  The dentry must be negative but may be
+ * hashed if it was pouplated with DCACHE_NEED_LOOKUP.
+ *
+ * dir->d_inode->i_mutex must be held
  */
-static struct dentry *d_inode_lookup(struct dentry *parent, struct dentry *dentry,
-                                    struct nameidata *nd)
+static struct dentry *lookup_real(struct inode *dir, struct dentry *dentry,
+                                 struct nameidata *nd)
 {
-       struct inode *inode = parent->d_inode;
        struct dentry *old;
 
        /* Don't create child dentry for a dead directory. */
-       if (unlikely(IS_DEADDIR(inode))) {
+       if (unlikely(IS_DEADDIR(dir))) {
                dput(dentry);
                return ERR_PTR(-ENOENT);
        }
 
-       old = inode->i_op->lookup(inode, dentry, nd);
+       old = dir->i_op->lookup(dir, dentry, nd);
        if (unlikely(old)) {
                dput(dentry);
                dentry = old;
@@ -1111,46 +1123,14 @@ static struct dentry *d_inode_lookup(struct dentry *parent, struct dentry *dentr
 static struct dentry *__lookup_hash(struct qstr *name,
                struct dentry *base, struct nameidata *nd)
 {
+       bool need_lookup;
        struct dentry *dentry;
 
-       /*
-        * Don't bother with __d_lookup: callers are for creat as
-        * well as unlink, so a lot of the time it would cost
-        * a double lookup.
-        */
-       dentry = d_lookup(base, name);
+       dentry = lookup_dcache(name, base, nd, &need_lookup);
+       if (!need_lookup)
+               return dentry;
 
-       if (dentry && d_need_lookup(dentry)) {
-               /*
-                * __lookup_hash is called with the parent dir's i_mutex already
-                * held, so we are good to go here.
-                */
-               return d_inode_lookup(base, dentry, nd);
-       }
-
-       if (dentry && (dentry->d_flags & DCACHE_OP_REVALIDATE)) {
-               int status = d_revalidate(dentry, nd);
-               if (unlikely(status <= 0)) {
-                       /*
-                        * The dentry failed validation.
-                        * If d_revalidate returned 0 attempt to invalidate
-                        * the dentry otherwise d_revalidate is asking us
-                        * to return a fail status.
-                        */
-                       if (status < 0) {
-                               dput(dentry);
-                               return ERR_PTR(status);
-                       } else if (!d_invalidate(dentry)) {
-                               dput(dentry);
-                               dentry = NULL;
-                       }
-               }
-       }
-
-       if (!dentry)
-               dentry = d_alloc_and_lookup(base, name, nd);
-
-       return dentry;
+       return lookup_real(base->d_inode, dentry, nd);
 }
 
 /*