[AIO] add thread based fallback for aio_{read,write}v

Add thread based fallbacks for aio readv and writev operations.

Signed-off-by: Benjamin LaHaise <bcrl@linux.intel.com>
diff -purN --exclude=description 83_fix_refcounting/fs/aio.c 85_vectored_fallback/fs/aio.c
--- 83_fix_refcounting/fs/aio.c	2005-08-17 13:46:57.000000000 -0400
+++ 85_vectored_fallback/fs/aio.c	2005-08-17 13:46:58.000000000 -0400
@@ -1537,6 +1537,30 @@ static int aio_thread_write_fn(void *arg
 	return 0;
 }
 
+static int aio_thread_rw_v_fn(void *arg)
+{
+	struct kiocb *iocb = arg;
+	long ret;
+
+	set_fs(USER_DS);
+	use_mm(iocb->ki_ctx->mm);
+
+	if (iocb->ki_opcode == IOCB_CMD_PREADV)
+		ret = vfs_readv(iocb->ki_filp,
+				&iocb->ki_iovec[iocb->ki_cur_seg],
+				iocb->ki_nr_segs - iocb->ki_cur_seg,
+				&iocb->ki_pos);
+	else
+		ret = vfs_writev(iocb->ki_filp,
+				 &iocb->ki_iovec[iocb->ki_cur_seg],
+				 iocb->ki_nr_segs - iocb->ki_cur_seg,
+				 &iocb->ki_pos);
+	unuse_mm(iocb->ki_ctx->mm);
+	aio_complete(iocb, ret, 0);
+
+	return 0;
+}
+
 static int aio_thread_fsync_fn(void *arg)
 {
 	struct kiocb *iocb = arg;
@@ -1578,11 +1602,21 @@ static ssize_t aio_thread_pread(struct k
 	return aio_kernel_thread(iocb, aio_thread_read_fn);
 }
 
+static ssize_t aio_thread_preadv(struct kiocb *iocb)
+{
+	return aio_kernel_thread(iocb, aio_thread_rw_v_fn);
+}
+
 static ssize_t aio_thread_pwrite(struct kiocb *iocb)
 {
 	return aio_kernel_thread(iocb, aio_thread_write_fn);
 }
 
+static ssize_t aio_thread_pwritev(struct kiocb *iocb)
+{
+	return aio_kernel_thread(iocb, aio_thread_rw_v_fn);
+}
+
 static ssize_t aio_thread_fsync(struct kiocb *iocb)
 {
 	return aio_kernel_thread(iocb, aio_thread_fsync_fn);
@@ -1683,6 +1717,8 @@ static ssize_t aio_setup_iocb(struct kio
 		ret = EINVAL;
 		if (file->f_op->aio_readv)
 			kiocb->ki_retry = aio_rw_vect_retry;
+		else if (file->f_op->readv || file->f_op->read)
+			kiocb->ki_retry = aio_thread_preadv;
 		break;
 	case IOCB_CMD_PWRITEV:
 		ret = -EBADF;
@@ -1694,6 +1730,8 @@ static ssize_t aio_setup_iocb(struct kio
 		ret = EINVAL;
 		if (file->f_op->aio_writev)
 			kiocb->ki_retry = aio_rw_vect_retry;
+		else if (file->f_op->writev || file->f_op->write)
+			kiocb->ki_retry = aio_thread_pwritev;
 		break;
 	case IOCB_CMD_FDSYNC:
 		ret = -EINVAL;