NFSv4: Save the owner/group name string when doing open

...so that we can do the uid/gid mapping outside the asynchronous RPC
context.
This fixes a bug in the current NFSv4 atomic open code where the client
isn't able to determine what the true uid/gid fields of the file are,
(because the asynchronous nature of the OPEN call denies it the ability
to do an upcall) and so fills them with default values, marking the
inode as needing revalidation.
Unfortunately, in some cases, the VFS will do some additional sanity
checks on the file, and may override the server's decision to allow
the open because it sees the wrong owner/group fields.

Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

1 files changed, 83 insertions, 0 deletions

diff --git a/fs/nfs/idmap.c b/fs/nfs/idmap.c
index 47d1c6f..2c05f19 100644
--- a/fs/nfs/idmap.c
+++ b/fs/nfs/idmap.c
@@ -38,6 +38,89 @@
 #include <linux/kernel.h>
 #include <linux/slab.h>
 #include <linux/nfs_idmap.h>
+#include <linux/nfs_fs.h>
+
+/**
+ * nfs_fattr_init_names - initialise the nfs_fattr owner_name/group_name fields
+ * @fattr: fully initialised struct nfs_fattr
+ * @owner_name: owner name string cache
+ * @group_name: group name string cache
+ */
+void nfs_fattr_init_names(struct nfs_fattr *fattr,
+		struct nfs4_string *owner_name,
+		struct nfs4_string *group_name)
+{
+	fattr->owner_name = owner_name;
+	fattr->group_name = group_name;
+}
+
+static void nfs_fattr_free_owner_name(struct nfs_fattr *fattr)
+{
+	fattr->valid &= ~NFS_ATTR_FATTR_OWNER_NAME;
+	kfree(fattr->owner_name->data);
+}
+
+static void nfs_fattr_free_group_name(struct nfs_fattr *fattr)
+{
+	fattr->valid &= ~NFS_ATTR_FATTR_GROUP_NAME;
+	kfree(fattr->group_name->data);
+}
+
+static bool nfs_fattr_map_owner_name(struct nfs_server *server, struct nfs_fattr *fattr)
+{
+	struct nfs4_string *owner = fattr->owner_name;
+	__u32 uid;
+
+	if (!(fattr->valid & NFS_ATTR_FATTR_OWNER_NAME))
+		return false;
+	if (nfs_map_name_to_uid(server, owner->data, owner->len, &uid) == 0) {
+		fattr->uid = uid;
+		fattr->valid |= NFS_ATTR_FATTR_OWNER;
+	}
+	return true;
+}
+
+static bool nfs_fattr_map_group_name(struct nfs_server *server, struct nfs_fattr *fattr)
+{
+	struct nfs4_string *group = fattr->group_name;
+	__u32 gid;
+
+	if (!(fattr->valid & NFS_ATTR_FATTR_GROUP_NAME))
+		return false;
+	if (nfs_map_group_to_gid(server, group->data, group->len, &gid) == 0) {
+		fattr->gid = gid;
+		fattr->valid |= NFS_ATTR_FATTR_GROUP;
+	}
+	return true;
+}
+
+/**
+ * nfs_fattr_free_names - free up the NFSv4 owner and group strings
+ * @fattr: a fully initialised nfs_fattr structure
+ */
+void nfs_fattr_free_names(struct nfs_fattr *fattr)
+{
+	if (fattr->valid & NFS_ATTR_FATTR_OWNER_NAME)
+		nfs_fattr_free_owner_name(fattr);
+	if (fattr->valid & NFS_ATTR_FATTR_GROUP_NAME)
+		nfs_fattr_free_group_name(fattr);
+}
+
+/**
+ * nfs_fattr_map_and_free_names - map owner/group strings into uid/gid and free
+ * @server: pointer to the filesystem nfs_server structure
+ * @fattr: a fully initialised nfs_fattr structure
+ *
+ * This helper maps the cached NFSv4 owner/group strings in fattr into
+ * their numeric uid/gid equivalents, and then frees the cached strings.
+ */
+void nfs_fattr_map_and_free_names(struct nfs_server *server, struct nfs_fattr *fattr)
+{
+	if (nfs_fattr_map_owner_name(server, fattr))
+		nfs_fattr_free_owner_name(fattr);
+	if (nfs_fattr_map_group_name(server, fattr))
+		nfs_fattr_free_group_name(fattr);
+}
 
 static int nfs_map_string_to_numeric(const char *name, size_t namelen, __u32 *res)
 {