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/* NBD client library in userspace
* Copyright Red Hat
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2 of the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*/
#include <config.h>
#include <stdio.h>
#include <stdlib.h>
#include <stdbool.h>
#include <errno.h>
#include <poll.h>
#include "internal.h"
/* A simple main loop implementation using poll(2). */
static int
do_poll (struct nbd_handle *h, int extra_fd, int timeout)
{
struct pollfd fds[2];
int r;
/* fd might be negative, and poll will ignore it. */
fds[0].fd = nbd_unlocked_aio_get_fd (h);
fds[1].fd = extra_fd;
fds[1].events = POLLIN;
fds[1].revents = 0;
switch (nbd_internal_aio_get_direction (get_next_state (h))) {
case LIBNBD_AIO_DIRECTION_READ:
fds[0].events = POLLIN;
break;
case LIBNBD_AIO_DIRECTION_WRITE:
fds[0].events = POLLOUT;
break;
case LIBNBD_AIO_DIRECTION_BOTH:
fds[0].events = POLLIN|POLLOUT;
break;
default:
set_error (EINVAL, "nothing to poll for in state %s",
nbd_internal_state_short_string (get_next_state (h)));
return -1;
}
fds[0].revents = 0;
debug (h, "poll start: events=%x", fds[0].events);
/* Note that it's not safe to release the handle lock here, as it
* would allow other threads to close file descriptors which we have
* passed to poll.
*/
do {
r = poll (fds, 2, timeout);
debug (h, "poll end: r=%d revents=%x", r, fds[0].revents);
} while (r == -1 && errno == EINTR);
if (r == -1) {
set_error (errno, "poll");
return -1;
}
if (r == 0)
return 0;
/* POLLIN and POLLOUT might both be set. However we shouldn't call
* both nbd_aio_notify_read and nbd_aio_notify_write at this time
* since the first might change the handle state, making the second
* notification invalid. Nothing bad happens by ignoring one of the
* notifications since if it's still valid it will be picked up by a
* subsequent poll. Prefer notifying on read, since the reply is
* for a command older than what we are trying to write.
*/
r = 0;
if ((fds[0].revents & (POLLIN | POLLHUP)) != 0)
r = nbd_unlocked_aio_notify_read (h);
else if ((fds[0].revents & POLLOUT) != 0)
r = nbd_unlocked_aio_notify_write (h);
else if ((fds[0].revents & (POLLERR | POLLNVAL)) != 0) {
set_error (ENOTCONN, "server closed socket unexpectedly");
return -1;
}
if (r == -1)
return -1;
return 1;
}
int
nbd_unlocked_poll (struct nbd_handle *h, int timeout)
{
return do_poll (h, -1, timeout);
}
int
nbd_unlocked_poll2 (struct nbd_handle *h, int fd, int timeout)
{
return do_poll (h, fd, timeout);
}
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