mount.c

微内核软实时操作系统

/*
 * Copyright (c) 2005-2007, Kohsuke Ohtani
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the name of the author nor the names of any co-contributors 
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

/*
 * mount.c - mount operations
 */

#include <prex/prex.h>

#include <sys/stat.h>
#include <sys/vnode.h>
#include <sys/file.h>
#include <sys/mount.h>
#include <sys/dirent.h>
#include <sys/list.h>
#include <sys/buf.h>

#include <limits.h>
#include <unistd.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include <fcntl.h>

#include "vfs.h"

/*
 * List for VFS mount points.
 */
static struct list mount_list = LIST_INIT(mount_list);

/*
 * Global lock to access mount point.
 */
#if NR_FS_THREADS > 1
static mutex_t mount_lock = MUTEX_INITIALIZER;
#define MOUNT_LOCK()	mutex_lock(&mount_lock)
#define MOUNT_UNLOCK()	mutex_unlock(&mount_lock)
#else
#define MOUNT_LOCK()
#define MOUNT_UNLOCK()
#endif

static const struct vfssw *fs_lookup(char *name)
{
	const struct vfssw *fs;

	for (fs = vfssw_table; fs->vs_name; fs++) {
		if (!strncmp(name, fs->vs_name, FSNAME_MAX))
			break;
	}
	if (!fs->vs_name)
		return NULL;
	return fs;
}

int sys_mount(char *dev, char *dir, char *fsname, int flags, void *data)
{
	const struct vfssw *fs;
	mount_t mp;
	list_t head, n;
	device_t device;
	vnode_t vp, vp_covered;
	int err;

	dprintf("Mounting fs=%s dir=%s dev=%s\n", fsname, dir, dev);

	if (!dir || *dir == '\0')
		return ENOENT;

	/* Find a file system. */
	if (!(fs = fs_lookup(fsname)))
		return ENODEV;	/* No such file system */

	/* Open device. NULL can be specified as a device. */
	device = NULL;
	if (*dev != '\0') {
		if (strncmp(dev, "/dev/", 5))
			return ENOTBLK;
		if ((err = device_open(dev + 5, DO_RDWR, &device)) != 0)
			return err;
	}

	MOUNT_LOCK();

	/* Check if device or directory has already been mounted. */
	head = &mount_list;
	for (n = list_first(head); n != head; n = list_next(n)) {
		mp = list_entry(n, struct mount, m_link);
		if (!strcmp(mp->m_path, dir) ||
		    (device && mp->m_dev == (dev_t)device)) {
			err = EBUSY;	/* Already mounted */
			goto err1;
		}
	}
	/*
	 * Create VFS mount entry
	 */
	if (!(mp = malloc(sizeof(struct mount)))) {
		err = ENOMEM;
		goto err1;
	}
	mp->m_count = 0;
	mp->m_op = fs->vs_op;
	mp->m_flags = flags;
	mp->m_dev = (dev_t)device;
	strlcpy(mp->m_path, dir, PATH_MAX);
	mp->m_path[PATH_MAX - 1] = '\0';

	/*
	 * Get vnode to be covered in the upper file system.
	 */
	if (*dir == '/' && *(dir + 1) == '\0') {
		/* Ignore if it mounts to global root directory. */
		vp_covered = NULL;
	} else {
		if ((err = namei(dir, &vp_covered)) != 0) {
			err = ENOENT;
			goto err2;
		}
		if (vp_covered->v_type != VDIR) {
			err = ENOTDIR;
			goto err3;
		}
	}
	mp->m_covered = vp_covered;

	/*
	 * Create a root vnode for this file system.
	 */
	if ((vp = vget(mp, "/")) == NULL) {
		err = ENOMEM;
		goto err3;
	}
	vp->v_type = VDIR;
	vp->v_flags = VROOT;
	vp->v_mode = (mode_t)(S_IFDIR | S_IRUSR | S_IRGRP | S_IROTH);
	mp->m_root = vp;

	/*
	 * Call a file system specific routine to mount.
	 */
	if ((err = VFS_MOUNT(mp, dev, flags, data)) != 0)
		goto err4;

	/*
	 * Keep reference count for root/covered vnode.
	 */
	vn_unlock(vp);
	if (vp_covered)
		vn_unlock(vp_covered);

	/*
	 * Insert to mount list
	 */
	list_insert(&mount_list, &mp->m_link);
	MOUNT_UNLOCK();
	return 0;
 err4:
	vput(vp);
 err3:
	if (vp_covered)
		vput(vp_covered);
 err2:
	free(mp);
 err1:
	device_close(device);
	MOUNT_UNLOCK();
	return err;
}

int sys_umount(char *path)
{
	mount_t mp;
	list_t head, n;
	int err;

	dprintf("sys_umount: path=%s\n", path);

	MOUNT_LOCK();

	/* Get mount entry */
	head = &mount_list;
	for (n = list_first(head); n != head; n = list_next(n)) {
		mp = list_entry(n, struct mount, m_link);
		if (!strcmp(path, mp->m_path))
			break;
	}
	if (n == head) {
		err = EINVAL;
		goto out;
	}
	/*
	 * Root fs can not be unmounted.
	 */
	if (mp->m_covered == NULL) {
		err = EINVAL;
		goto out;
	}
	if ((err = VFS_UNMOUNT(mp)) != 0)
		goto out;
	list_remove(&mp->m_link);

	/* Decrement referece count of root vnode */
	vrele(mp->m_covered);

	if (mp->m_dev)
		device_close((device_t)mp->m_dev);
	free(mp);
 out:
	MOUNT_UNLOCK();
	return err;
}

int sys_sync(void)
{
	mount_t mp;
	list_t head, n;

	/* Call each mounted file system. */
	MOUNT_LOCK();
	head = &mount_list;
	for (n = list_first(head); n != head; n = list_next(n)) {
		mp = list_entry(n, struct mount, m_link);
		VFS_SYNC(mp);
	}
	MOUNT_UNLOCK();
	return 0;
}

/*
 * Compare two path strings. Return matched length.
 *
 * @path: target path.
 * @root: vfs root path as mount point.
 */
static size_t count_match(char *path, char *mount_root)
{
	size_t len = 0;

	while (*path && *mount_root) {
		if (*path++ != *mount_root++)
			break;
		len++;
	}
	if (*mount_root != '\0')
		return 0;

	if (len == 1 && *(path - 1) == '/')
		return 1;

	if (*path == '\0' || *path == '/')
		return len;
	return 0;
}

/*
 * Get the root directory and mount point for specified path.
 *
 * @path: full path.
 * @mp: mount point to return.
 * @root: pointer to root directory in path.
 */
int vfs_findroot(char *path, mount_t *mp, char **root)
{
	mount_t m, tmp;
	list_t head, n;
	size_t len, max_len = 0;

	if (!path)
		return -1;

	/* Find mount point from nearest path */
	MOUNT_LOCK();
	m = NULL;
	head = &mount_list;
	for (n = list_first(head); n != head; n = list_next(n)) {
		tmp = list_entry(n, struct mount, m_link);
		len = count_match(path, tmp->m_path);
		if (len > max_len) {
			max_len = len;
			m = tmp;
		}
	}
	MOUNT_UNLOCK();
	if (m == NULL)
		return -1;
	*root = (char *)(path + max_len);
	if (**root == '/')
		(*root)++;
	*mp = m;
	return 0;
}

/*
 * Mark a mount point as busy.
 */
void vfs_busy(mount_t mp)
{
	MOUNT_LOCK();
	mp->m_count++;
	MOUNT_UNLOCK();
}


/*
 * Mark a mount point as busy.
 */
void vfs_unbusy(mount_t mp)
{
	MOUNT_LOCK();
	mp->m_count--;
	MOUNT_UNLOCK();
}

#ifdef DEBUG
void mount_dump(void)
{
	list_t head, n;
	mount_t mp;

	MOUNT_LOCK();

	printf("mount_dump\n");
	printf("dev      count root\n");
	printf("-------- ----- --------\n");
	head = &mount_list;
	for (n = list_first(head); n != head; n = list_next(n)) {
		mp = list_entry(n, struct mount, m_link);
		printf("%8x %5d %s\n", mp->m_dev, mp->m_count, mp->m_path);
	}
	MOUNT_UNLOCK();
}
#endif