NFS: Refactor nfs_instantiate() for dentry referencing callers

Since commit b0c6108ecf64 ("nfs_instantiate(): prevent multiple aliases for
directory inode"), nfs_instantiate() may succeed without actually
instantiating the dentry that was passed in.  That can be problematic for
some callers in NFSv3, so this patch breaks things up so we can get the
actual dentry obtained.

Signed-off-by: Benjamin Coddington <bcodding@redhat.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>

1 files changed, 27 insertions, 14 deletions

diff --git a/fs/nfs/dir.c b/fs/nfs/dir.c
index 8d501093660f..d1bbf2fb6ac7 100644
--- a/fs/nfs/dir.c
+++ b/fs/nfs/dir.c
@@ -1669,24 +1669,23 @@ static int nfs4_lookup_revalidate(struct dentry *dentry, unsigned int flags)
 
 #endif /* CONFIG_NFSV4 */
 
-/*
- * Code common to create, mkdir, and mknod.
- */
-int nfs_instantiate(struct dentry *dentry, struct nfs_fh *fhandle,
+struct dentry *
+nfs_add_or_obtain(struct dentry *dentry, struct nfs_fh *fhandle,
 				struct nfs_fattr *fattr,
 				struct nfs4_label *label)
 {
 	struct dentry *parent = dget_parent(dentry);
 	struct inode *dir = d_inode(parent);
 	struct inode *inode;
-	struct dentry *d;
-	int error = -EACCES;
+	struct dentry *d = NULL;
+	int error;
 
 	d_drop(dentry);
 
 	/* We may have been initialized further down */
 	if (d_really_is_positive(dentry))
 		goto out;
+
 	if (fhandle->size == 0) {
 		error = NFS_PROTO(dir)->lookup(dir, &dentry->d_name, fhandle, fattr, NULL);
 		if (error)
@@ -1702,18 +1701,32 @@ int nfs_instantiate(struct dentry *dentry, struct nfs_fh *fhandle,
 	}
 	inode = nfs_fhget(dentry->d_sb, fhandle, fattr, label);
 	d = d_splice_alias(inode, dentry);
-	if (IS_ERR(d)) {
-		error = PTR_ERR(d);
-		goto out_error;
-	}
-	dput(d);
 out:
 	dput(parent);
-	return 0;
+	return d;
 out_error:
 	nfs_mark_for_revalidate(dir);
-	dput(parent);
-	return error;
+	d = ERR_PTR(error);
+	goto out;
+}
+EXPORT_SYMBOL_GPL(nfs_add_or_obtain);
+
+/*
+ * Code common to create, mkdir, and mknod.
+ */
+int nfs_instantiate(struct dentry *dentry, struct nfs_fh *fhandle,
+				struct nfs_fattr *fattr,
+				struct nfs4_label *label)
+{
+	struct dentry *d;
+
+	d = nfs_add_or_obtain(dentry, fhandle, fattr, label);
+	if (IS_ERR(d))
+		return PTR_ERR(d);
+
+	/* Callers don't care */
+	dput(d);
+	return 0;
 }
 EXPORT_SYMBOL_GPL(nfs_instantiate);