hv_vss_daemon.c 6.13 KB
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/*
 * An implementation of the host initiated guest snapshot for Hyper-V.
 *
 *
 * Copyright (C) 2013, Microsoft, Inc.
 * Author : K. Y. Srinivasan <kys@microsoft.com>
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 as published
 * by the Free Software Foundation.
 *
 * This program 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, GOOD TITLE or
 * NON INFRINGEMENT.  See the GNU General Public License for more
 * details.
 *
 */


#include <sys/types.h>
#include <sys/poll.h>
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#include <sys/ioctl.h>
#include <fcntl.h>
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#include <stdio.h>
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#include <mntent.h>
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#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <ctype.h>
#include <errno.h>
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#include <linux/fs.h>
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#include <linux/hyperv.h>
#include <syslog.h>
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#include <getopt.h>
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/* Don't use syslog() in the function since that can cause write to disk */
static int vss_do_freeze(char *dir, unsigned int cmd)
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{
	int ret, fd = open(dir, O_RDONLY);

	if (fd < 0)
		return 1;
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	ret = ioctl(fd, cmd, 0);
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	/*
	 * If a partition is mounted more than once, only the first
	 * FREEZE/THAW can succeed and the later ones will get
	 * EBUSY/EINVAL respectively: there could be 2 cases:
	 * 1) a user may mount the same partition to differnt directories
	 *  by mistake or on purpose;
	 * 2) The subvolume of btrfs appears to have the same partition
	 * mounted more than once.
	 */
	if (ret) {
		if ((cmd == FIFREEZE && errno == EBUSY) ||
		    (cmd == FITHAW && errno == EINVAL)) {
			close(fd);
			return 0;
		}
	}

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	close(fd);
	return !!ret;
}

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static int vss_operate(int operation)
{
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	char match[] = "/dev/";
	FILE *mounts;
	struct mntent *ent;
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	char errdir[1024] = {0};
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	unsigned int cmd;
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	int error = 0, root_seen = 0, save_errno = 0;
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	switch (operation) {
	case VSS_OP_FREEZE:
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		cmd = FIFREEZE;
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		break;
	case VSS_OP_THAW:
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		cmd = FITHAW;
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		break;
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	default:
		return -1;
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	}

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	mounts = setmntent("/proc/mounts", "r");
	if (mounts == NULL)
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		return -1;
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	while ((ent = getmntent(mounts))) {
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		if (strncmp(ent->mnt_fsname, match, strlen(match)))
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			continue;
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		if (hasmntopt(ent, MNTOPT_RO) != NULL)
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			continue;
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		if (strcmp(ent->mnt_type, "vfat") == 0)
			continue;
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		if (strcmp(ent->mnt_dir, "/") == 0) {
			root_seen = 1;
			continue;
		}
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		error |= vss_do_freeze(ent->mnt_dir, cmd);
		if (error && operation == VSS_OP_FREEZE)
			goto err;
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	}

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	endmntent(mounts);

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	if (root_seen) {
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		error |= vss_do_freeze("/", cmd);
		if (error && operation == VSS_OP_FREEZE)
			goto err;
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	}
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	goto out;
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err:
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	save_errno = errno;
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	if (ent) {
		strncpy(errdir, ent->mnt_dir, sizeof(errdir)-1);
		endmntent(mounts);
	}
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	vss_operate(VSS_OP_THAW);
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	/* Call syslog after we thaw all filesystems */
	if (ent)
		syslog(LOG_ERR, "FREEZE of %s failed; error:%d %s",
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		       errdir, save_errno, strerror(save_errno));
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	else
		syslog(LOG_ERR, "FREEZE of / failed; error:%d %s", save_errno,
		       strerror(save_errno));
out:
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	return error;
}

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void print_usage(char *argv[])
{
	fprintf(stderr, "Usage: %s [options]\n"
		"Options are:\n"
		"  -n, --no-daemon        stay in foreground, don't daemonize\n"
		"  -h, --help             print this help\n", argv[0]);
}

int main(int argc, char *argv[])
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{
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	int vss_fd, len;
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	int error;
	struct pollfd pfd;
	int	op;
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	struct hv_vss_msg vss_msg[1];
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	int daemonize = 1, long_index = 0, opt;
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	int in_handshake = 1;
	__u32 kernel_modver;
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	static struct option long_options[] = {
		{"help",	no_argument,	   0,  'h' },
		{"no-daemon",	no_argument,	   0,  'n' },
		{0,		0,		   0,  0   }
	};

	while ((opt = getopt_long(argc, argv, "hn", long_options,
				  &long_index)) != -1) {
		switch (opt) {
		case 'n':
			daemonize = 0;
			break;
		case 'h':
		default:
			print_usage(argv);
			exit(EXIT_FAILURE);
		}
	}
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	if (daemonize && daemon(1, 0))
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		return 1;

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	openlog("Hyper-V VSS", 0, LOG_USER);
	syslog(LOG_INFO, "VSS starting; pid is:%d", getpid());

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	vss_fd = open("/dev/vmbus/hv_vss", O_RDWR);
	if (vss_fd < 0) {
		syslog(LOG_ERR, "open /dev/vmbus/hv_vss failed; error: %d %s",
		       errno, strerror(errno));
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		exit(EXIT_FAILURE);
	}
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	/*
	 * Register ourselves with the kernel.
	 */
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	vss_msg->vss_hdr.operation = VSS_OP_REGISTER1;
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	len = write(vss_fd, vss_msg, sizeof(struct hv_vss_msg));
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	if (len < 0) {
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		syslog(LOG_ERR, "registration to kernel failed; error: %d %s",
		       errno, strerror(errno));
		close(vss_fd);
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		exit(EXIT_FAILURE);
	}

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	pfd.fd = vss_fd;
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	while (1) {
		pfd.events = POLLIN;
		pfd.revents = 0;
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		if (poll(&pfd, 1, -1) < 0) {
			syslog(LOG_ERR, "poll failed; error:%d %s", errno, strerror(errno));
			if (errno == EINVAL) {
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				close(vss_fd);
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				exit(EXIT_FAILURE);
			}
			else
				continue;
		}
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		len = read(vss_fd, vss_msg, sizeof(struct hv_vss_msg));
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		if (in_handshake) {
			if (len != sizeof(kernel_modver)) {
				syslog(LOG_ERR, "invalid version negotiation");
				exit(EXIT_FAILURE);
			}
			kernel_modver = *(__u32 *)vss_msg;
			in_handshake = 0;
			syslog(LOG_INFO, "VSS: kernel module version: %d",
			       kernel_modver);
			continue;
		}

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		if (len != sizeof(struct hv_vss_msg)) {
			syslog(LOG_ERR, "read failed; error:%d %s",
			       errno, strerror(errno));
			close(vss_fd);
			return EXIT_FAILURE;
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		}

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		op = vss_msg->vss_hdr.operation;
		error =  HV_S_OK;

		switch (op) {
		case VSS_OP_FREEZE:
		case VSS_OP_THAW:
			error = vss_operate(op);
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			syslog(LOG_INFO, "VSS: op=%s: %s\n",
				op == VSS_OP_FREEZE ? "FREEZE" : "THAW",
				error ? "failed" : "succeeded");

			if (error) {
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				error = HV_E_FAIL;
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				syslog(LOG_ERR, "op=%d failed!", op);
				syslog(LOG_ERR, "report it with these files:");
				syslog(LOG_ERR, "/etc/fstab and /proc/mounts");
			}
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			break;
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		case VSS_OP_HOT_BACKUP:
			syslog(LOG_INFO, "VSS: op=CHECK HOT BACKUP\n");
			break;
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		default:
			syslog(LOG_ERR, "Illegal op:%d\n", op);
		}
		vss_msg->error = error;
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		len = write(vss_fd, vss_msg, sizeof(struct hv_vss_msg));
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		if (len != sizeof(struct hv_vss_msg)) {
			syslog(LOG_ERR, "write failed; error: %d %s", errno,
			       strerror(errno));
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			if (op == VSS_OP_FREEZE)
				vss_operate(VSS_OP_THAW);
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		}
	}

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	close(vss_fd);
	exit(0);
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}