replace d_add_unique() with saner primitive

new primitive: d_exact_alias(dentry, inode).  If there is an unhashed
dentry with the same name/parent and given inode, rehash, grab and
return it.  Otherwise, return NULL.  The only caller of d_add_unique()
switched to d_exact_alias() + d_splice_alias().

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

1 files changed, 50 insertions, 75 deletions

diff --git a/fs/dcache.c b/fs/dcache.c
index 2398f9f94337..4d20bf5c609b 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -1782,81 +1782,6 @@ void d_instantiate(struct dentry *entry, struct inode * inode)
 EXPORT_SYMBOL(d_instantiate);
 
 /**
- * d_instantiate_unique - instantiate a non-aliased dentry
- * @entry: dentry to instantiate
- * @inode: inode to attach to this dentry
- *
- * Fill in inode information in the entry. On success, it returns NULL.
- * If an unhashed alias of "entry" already exists, then we return the
- * aliased dentry instead and drop one reference to inode.
- *
- * Note that in order to avoid conflicts with rename() etc, the caller
- * had better be holding the parent directory semaphore.
- *
- * This also assumes that the inode count has been incremented
- * (or otherwise set) by the caller to indicate that it is now
- * in use by the dcache.
- */
-static struct dentry *__d_instantiate_unique(struct dentry *entry,
-                                             struct inode *inode)
-{
-        struct dentry *alias;
-        int len = entry->d_name.len;
-        const char *name = entry->d_name.name;
-        unsigned int hash = entry->d_name.hash;
-
-        if (!inode) {
-                __d_instantiate(entry, NULL);
-                return NULL;
-        }
-
-        hlist_for_each_entry(alias, &inode->i_dentry, d_u.d_alias) {
-                /*
-                 * Don't need alias->d_lock here, because aliases with
-                 * d_parent == entry->d_parent are not subject to name or
-                 * parent changes, because the parent inode i_mutex is held.
-                 */
-                if (alias->d_name.hash != hash)
-                        continue;
-                if (alias->d_parent != entry->d_parent)
-                        continue;
-                if (alias->d_name.len != len)
-                        continue;
-                if (dentry_cmp(alias, name, len))
-                        continue;
-                __dget(alias);
-                return alias;
-        }
-
-        __d_instantiate(entry, inode);
-        return NULL;
-}
-
-struct dentry *d_instantiate_unique(struct dentry *entry, struct inode *inode)
-{
-        struct dentry *result;
-
-        BUG_ON(!hlist_unhashed(&entry->d_u.d_alias));
-
-        if (inode)
-                spin_lock(&inode->i_lock);
-        result = __d_instantiate_unique(entry, inode);
-        if (inode)
-                spin_unlock(&inode->i_lock);
-
-        if (!result) {
-                security_d_instantiate(entry, inode);
-                return NULL;
-        }
-
-        BUG_ON(!d_unhashed(result));
-        iput(inode);
-        return result;
-}
-
-EXPORT_SYMBOL(d_instantiate_unique);
-
-/**
  * d_instantiate_no_diralias - instantiate a non-aliased dentry
  * @entry: dentry to complete
  * @inode: inode to attach to this dentry
@@ -2437,6 +2362,56 @@ void d_rehash(struct dentry * entry)
 EXPORT_SYMBOL(d_rehash);
 
 /**
+ * d_exact_alias - find and hash an exact unhashed alias
+ * @entry: dentry to add
+ * @inode: The inode to go with this dentry
+ *
+ * If an unhashed dentry with the same name/parent and desired
+ * inode already exists, hash and return it.  Otherwise, return
+ * NULL.
+ *
+ * Parent directory should be locked.
+ */
+struct dentry *d_exact_alias(struct dentry *entry, struct inode *inode)
+{
+        struct dentry *alias;
+        int len = entry->d_name.len;
+        const char *name = entry->d_name.name;
+        unsigned int hash = entry->d_name.hash;
+
+        spin_lock(&inode->i_lock);
+        hlist_for_each_entry(alias, &inode->i_dentry, d_u.d_alias) {
+                /*
+                 * Don't need alias->d_lock here, because aliases with
+                 * d_parent == entry->d_parent are not subject to name or
+                 * parent changes, because the parent inode i_mutex is held.
+                 */
+                if (alias->d_name.hash != hash)
+                        continue;
+                if (alias->d_parent != entry->d_parent)
+                        continue;
+                if (alias->d_name.len != len)
+                        continue;
+                if (dentry_cmp(alias, name, len))
+                        continue;
+                spin_lock(&alias->d_lock);
+                if (!d_unhashed(alias)) {
+                        spin_unlock(&alias->d_lock);
+                        alias = NULL;
+                } else {
+                        __dget_dlock(alias);
+                        _d_rehash(alias);
+                        spin_unlock(&alias->d_lock);
+                }
+                spin_unlock(&inode->i_lock);
+                return alias;
+        }
+        spin_unlock(&inode->i_lock);
+        return NULL;
+}
+EXPORT_SYMBOL(d_exact_alias);
+
+/**
  * dentry_update_name_case - update case insensitive dentry with a new name
  * @dentry: dentry to be updated
  * @name: new name