[PATCH] new helper: d_obtain_alias
The calling conventions of d_alloc_anon are rather unfortunate for all
users, and it's name is not very descriptive either.
Add d_obtain_alias as a new exported helper that drops the inode
reference in the failure case, too and allows to pass-through NULL
pointers and inodes to allow for tail-calls in the export operations.
Incidentally this helper already existed as a private function in
libfs.c as exportfs_d_alloc so kill that one and switch the callers
to d_obtain_alias.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/fs/dcache.c b/fs/dcache.c
index e7a1a99..46fc782 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -1174,6 +1174,41 @@
return res;
}
+/**
+ * d_obtain_alias - find or allocate a dentry for a given inode
+ * @inode: inode to allocate the dentry for
+ *
+ * Obtain a dentry for an inode resulting from NFS filehandle conversion or
+ * similar open by handle operations. The returned dentry may be anonymous,
+ * or may have a full name (if the inode was already in the cache).
+ *
+ * When called on a directory inode, we must ensure that the inode only ever
+ * has one dentry. If a dentry is found, that is returned instead of
+ * allocating a new one.
+ *
+ * On successful return, the reference to the inode has been transferred
+ * to the dentry. If %NULL is returned (indicating kmalloc failure),
+ * the reference on the inode has been released. To make it easier
+ * to use in export operations a NULL or IS_ERR inode may be passed in
+ * and will be casted to the corresponding NULL or IS_ERR dentry.
+ */
+struct dentry *d_obtain_alias(struct inode *inode)
+{
+ struct dentry *dentry;
+
+ if (!inode)
+ return NULL;
+ if (IS_ERR(inode))
+ return ERR_CAST(inode);
+
+ dentry = d_alloc_anon(inode);
+ if (!dentry) {
+ iput(inode);
+ dentry = ERR_PTR(-ENOMEM);
+ }
+ return dentry;
+}
+EXPORT_SYMBOL_GPL(d_obtain_alias);
/**
* d_splice_alias - splice a disconnected dentry into the tree if one exists