[CIFS] clean up page array when uncached write send fails

In the event that a send fails in an uncached write, or we end up
needing to reissue it (-EAGAIN case), we'll kfree the wdata but
the pages currently leak.

Fix this by adding a new kref release routine for uncached writedata
that releases the pages, and have the uncached codepaths use that.

[original patch by Jeff modified to fix minor formatting problems]

Signed-off-by: Jeff Layton <jlayton@redhat.com>
Reviewed-by: Pavel Shilovsky <piastry@etersoft.ru>
Signed-off-by: Steve French <smfrench@gmail.com>
diff --git a/fs/cifs/cifsglob.h b/fs/cifs/cifsglob.h
index d6a031e..86dc28c 100644
--- a/fs/cifs/cifsglob.h
+++ b/fs/cifs/cifsglob.h
@@ -323,7 +323,8 @@
 	/* async read from the server */
 	int (*async_readv)(struct cifs_readdata *);
 	/* async write to the server */
-	int (*async_writev)(struct cifs_writedata *);
+	int (*async_writev)(struct cifs_writedata *,
+			    void (*release)(struct kref *));
 	/* sync read from the server */
 	int (*sync_read)(const unsigned int, struct cifsFileInfo *,
 			 struct cifs_io_parms *, unsigned int *, char **,