9p: fix ignored return value in v9fs_dir_release

retval from filemap_fdatawrite was immediately overwritten by the
following p9_fid_put: preserve any error in fdatawrite if there
was any first.

This fixes the following scan-build warning:
fs/9p/vfs_dir.c:220:4: warning: Value stored to 'retval' is never read [deadcode.DeadStores]
                        retval = filemap_fdatawrite(inode->i_mapping);
                        ^        ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Fixes: 89c58cb ("fs/9p: fix error reporting in v9fs_dir_release")
Cc: stable@vger.kernel.org
Reviewed-by: Simon Horman <simon.horman@corigine.com>
Signed-off-by: Dominique Martinet <asmadeus@codewreck.org>
Signed-off-by: Eric Van Hensbergen <ericvh@kernel.org>

Author: martinetd

fs/9p/vfs_dir.c

@@ -208,7 +208,7 @@ int v9fs_dir_release(struct inode *inode, struct file *filp)
 	struct p9_fid *fid;
 	__le32 version;
 	loff_t i_size;
-	int retval = 0;
+	int retval = 0, put_err;
 
 	fid = filp->private_data;
 	p9_debug(P9_DEBUG_VFS, "inode: %p filp: %p fid: %d\n",
@@ -221,7 +221,8 @@ int v9fs_dir_release(struct inode *inode, struct file *filp)
 		spin_lock(&inode->i_lock);
 		hlist_del(&fid->ilist);
 		spin_unlock(&inode->i_lock);
-		retval = p9_fid_put(fid);
+		put_err = p9_fid_put(fid);
+		retval = retval < 0 ? retval : put_err;
 	}
 
 	if ((filp->f_mode & FMODE_WRITE)) {