dir.c

linux 内核源代码

	if (S_ISDIR(inode->i_mode)) {
		struct dentry *alias;
		mutex_lock(&fc->inst_mutex);
		alias = d_find_alias(inode);
		if (alias) {
			/* New directory must have moved since mkdir */
			mutex_unlock(&fc->inst_mutex);
			dput(alias);
			iput(inode);
			return -EBUSY;
		}
		d_instantiate(entry, inode);
		mutex_unlock(&fc->inst_mutex);
	} else
		d_instantiate(entry, inode);

	fuse_change_entry_timeout(entry, &outarg);
	fuse_invalidate_attr(dir);
	return 0;

 out_put_forget_req:
	fuse_put_request(fc, forget_req);
	return err;
}

static int fuse_mknod(struct inode *dir, struct dentry *entry, int mode,
		      dev_t rdev)
{
	struct fuse_mknod_in inarg;
	struct fuse_conn *fc = get_fuse_conn(dir);
	struct fuse_req *req = fuse_get_req(fc);
	if (IS_ERR(req))
		return PTR_ERR(req);

	memset(&inarg, 0, sizeof(inarg));
	inarg.mode = mode;
	inarg.rdev = new_encode_dev(rdev);
	req->in.h.opcode = FUSE_MKNOD;
	req->in.numargs = 2;
	req->in.args[0].size = sizeof(inarg);
	req->in.args[0].value = &inarg;
	req->in.args[1].size = entry->d_name.len + 1;
	req->in.args[1].value = entry->d_name.name;
	return create_new_entry(fc, req, dir, entry, mode);
}

static int fuse_create(struct inode *dir, struct dentry *entry, int mode,
		       struct nameidata *nd)
{
	if (nd && (nd->flags & LOOKUP_OPEN)) {
		int err = fuse_create_open(dir, entry, mode, nd);
		if (err != -ENOSYS)
			return err;
		/* Fall back on mknod */
	}
	return fuse_mknod(dir, entry, mode, 0);
}

static int fuse_mkdir(struct inode *dir, struct dentry *entry, int mode)
{
	struct fuse_mkdir_in inarg;
	struct fuse_conn *fc = get_fuse_conn(dir);
	struct fuse_req *req = fuse_get_req(fc);
	if (IS_ERR(req))
		return PTR_ERR(req);

	memset(&inarg, 0, sizeof(inarg));
	inarg.mode = mode;
	req->in.h.opcode = FUSE_MKDIR;
	req->in.numargs = 2;
	req->in.args[0].size = sizeof(inarg);
	req->in.args[0].value = &inarg;
	req->in.args[1].size = entry->d_name.len + 1;
	req->in.args[1].value = entry->d_name.name;
	return create_new_entry(fc, req, dir, entry, S_IFDIR);
}

static int fuse_symlink(struct inode *dir, struct dentry *entry,
			const char *link)
{
	struct fuse_conn *fc = get_fuse_conn(dir);
	unsigned len = strlen(link) + 1;
	struct fuse_req *req = fuse_get_req(fc);
	if (IS_ERR(req))
		return PTR_ERR(req);

	req->in.h.opcode = FUSE_SYMLINK;
	req->in.numargs = 2;
	req->in.args[0].size = entry->d_name.len + 1;
	req->in.args[0].value = entry->d_name.name;
	req->in.args[1].size = len;
	req->in.args[1].value = link;
	return create_new_entry(fc, req, dir, entry, S_IFLNK);
}

static int fuse_unlink(struct inode *dir, struct dentry *entry)
{
	int err;
	struct fuse_conn *fc = get_fuse_conn(dir);
	struct fuse_req *req = fuse_get_req(fc);
	if (IS_ERR(req))
		return PTR_ERR(req);

	req->in.h.opcode = FUSE_UNLINK;
	req->in.h.nodeid = get_node_id(dir);
	req->in.numargs = 1;
	req->in.args[0].size = entry->d_name.len + 1;
	req->in.args[0].value = entry->d_name.name;
	request_send(fc, req);
	err = req->out.h.error;
	fuse_put_request(fc, req);
	if (!err) {
		struct inode *inode = entry->d_inode;

		/* Set nlink to zero so the inode can be cleared, if
                   the inode does have more links this will be
                   discovered at the next lookup/getattr */
		clear_nlink(inode);
		fuse_invalidate_attr(inode);
		fuse_invalidate_attr(dir);
		fuse_invalidate_entry_cache(entry);
	} else if (err == -EINTR)
		fuse_invalidate_entry(entry);
	return err;
}

static int fuse_rmdir(struct inode *dir, struct dentry *entry)
{
	int err;
	struct fuse_conn *fc = get_fuse_conn(dir);
	struct fuse_req *req = fuse_get_req(fc);
	if (IS_ERR(req))
		return PTR_ERR(req);

	req->in.h.opcode = FUSE_RMDIR;
	req->in.h.nodeid = get_node_id(dir);
	req->in.numargs = 1;
	req->in.args[0].size = entry->d_name.len + 1;
	req->in.args[0].value = entry->d_name.name;
	request_send(fc, req);
	err = req->out.h.error;
	fuse_put_request(fc, req);
	if (!err) {
		clear_nlink(entry->d_inode);
		fuse_invalidate_attr(dir);
		fuse_invalidate_entry_cache(entry);
	} else if (err == -EINTR)
		fuse_invalidate_entry(entry);
	return err;
}

static int fuse_rename(struct inode *olddir, struct dentry *oldent,
		       struct inode *newdir, struct dentry *newent)
{
	int err;
	struct fuse_rename_in inarg;
	struct fuse_conn *fc = get_fuse_conn(olddir);
	struct fuse_req *req = fuse_get_req(fc);
	if (IS_ERR(req))
		return PTR_ERR(req);

	memset(&inarg, 0, sizeof(inarg));
	inarg.newdir = get_node_id(newdir);
	req->in.h.opcode = FUSE_RENAME;
	req->in.h.nodeid = get_node_id(olddir);
	req->in.numargs = 3;
	req->in.args[0].size = sizeof(inarg);
	req->in.args[0].value = &inarg;
	req->in.args[1].size = oldent->d_name.len + 1;
	req->in.args[1].value = oldent->d_name.name;
	req->in.args[2].size = newent->d_name.len + 1;
	req->in.args[2].value = newent->d_name.name;
	request_send(fc, req);
	err = req->out.h.error;
	fuse_put_request(fc, req);
	if (!err) {
		/* ctime changes */
		fuse_invalidate_attr(oldent->d_inode);

		fuse_invalidate_attr(olddir);
		if (olddir != newdir)
			fuse_invalidate_attr(newdir);

		/* newent will end up negative */
		if (newent->d_inode)
			fuse_invalidate_entry_cache(newent);
	} else if (err == -EINTR) {
		/* If request was interrupted, DEITY only knows if the
		   rename actually took place.  If the invalidation
		   fails (e.g. some process has CWD under the renamed
		   directory), then there can be inconsistency between
		   the dcache and the real filesystem.  Tough luck. */
		fuse_invalidate_entry(oldent);
		if (newent->d_inode)
			fuse_invalidate_entry(newent);
	}

	return err;
}

static int fuse_link(struct dentry *entry, struct inode *newdir,
		     struct dentry *newent)
{
	int err;
	struct fuse_link_in inarg;
	struct inode *inode = entry->d_inode;
	struct fuse_conn *fc = get_fuse_conn(inode);
	struct fuse_req *req = fuse_get_req(fc);
	if (IS_ERR(req))
		return PTR_ERR(req);

	memset(&inarg, 0, sizeof(inarg));
	inarg.oldnodeid = get_node_id(inode);
	req->in.h.opcode = FUSE_LINK;
	req->in.numargs = 2;
	req->in.args[0].size = sizeof(inarg);
	req->in.args[0].value = &inarg;
	req->in.args[1].size = newent->d_name.len + 1;
	req->in.args[1].value = newent->d_name.name;
	err = create_new_entry(fc, req, newdir, newent, inode->i_mode);
	/* Contrary to "normal" filesystems it can happen that link
	   makes two "logical" inodes point to the same "physical"
	   inode.  We invalidate the attributes of the old one, so it
	   will reflect changes in the backing inode (link count,
	   etc.)
	*/
	if (!err || err == -EINTR)
		fuse_invalidate_attr(inode);
	return err;
}

static void fuse_fillattr(struct inode *inode, struct fuse_attr *attr,
			  struct kstat *stat)
{
	stat->dev = inode->i_sb->s_dev;
	stat->ino = attr->ino;
	stat->mode = (inode->i_mode & S_IFMT) | (attr->mode & 07777);
	stat->nlink = attr->nlink;
	stat->uid = attr->uid;
	stat->gid = attr->gid;
	stat->rdev = inode->i_rdev;
	stat->atime.tv_sec = attr->atime;
	stat->atime.tv_nsec = attr->atimensec;
	stat->mtime.tv_sec = attr->mtime;
	stat->mtime.tv_nsec = attr->mtimensec;
	stat->ctime.tv_sec = attr->ctime;
	stat->ctime.tv_nsec = attr->ctimensec;
	stat->size = attr->size;
	stat->blocks = attr->blocks;
	stat->blksize = (1 << inode->i_blkbits);
}

static int fuse_do_getattr(struct inode *inode, struct kstat *stat,
			   struct file *file)
{
	int err;
	struct fuse_getattr_in inarg;
	struct fuse_attr_out outarg;
	struct fuse_conn *fc = get_fuse_conn(inode);
	struct fuse_req *req;
	u64 attr_version;

	req = fuse_get_req(fc);
	if (IS_ERR(req))
		return PTR_ERR(req);

	attr_version = fuse_get_attr_version(fc);

	memset(&inarg, 0, sizeof(inarg));
	memset(&outarg, 0, sizeof(outarg));
	/* Directories have separate file-handle space */
	if (file && S_ISREG(inode->i_mode)) {
		struct fuse_file *ff = file->private_data;

		inarg.getattr_flags |= FUSE_GETATTR_FH;
		inarg.fh = ff->fh;
	}
	req->in.h.opcode = FUSE_GETATTR;
	req->in.h.nodeid = get_node_id(inode);
	req->in.numargs = 1;
	req->in.args[0].size = sizeof(inarg);
	req->in.args[0].value = &inarg;
	req->out.numargs = 1;
	if (fc->minor < 9)
		req->out.args[0].size = FUSE_COMPAT_ATTR_OUT_SIZE;
	else
		req->out.args[0].size = sizeof(outarg);
	req->out.args[0].value = &outarg;
	request_send(fc, req);
	err = req->out.h.error;
	fuse_put_request(fc, req);
	if (!err) {
		if ((inode->i_mode ^ outarg.attr.mode) & S_IFMT) {
			make_bad_inode(inode);
			err = -EIO;
		} else {
			fuse_change_attributes(inode, &outarg.attr,
					       attr_timeout(&outarg),
					       attr_version);
			if (stat)
				fuse_fillattr(inode, &outarg.attr, stat);
		}
	}
	return err;
}

int fuse_update_attributes(struct inode *inode, struct kstat *stat,
			   struct file *file, bool *refreshed)
{
	struct fuse_inode *fi = get_fuse_inode(inode);
	int err;
	bool r;

	if (fi->i_time < get_jiffies_64()) {
		r = true;
		err = fuse_do_getattr(inode, stat, file);
	} else {
		r = false;
		err = 0;
		if (stat) {
			generic_fillattr(inode, stat);
			stat->mode = fi->orig_i_mode;
		}
	}

	if (refreshed != NULL)
		*refreshed = r;

	return err;
}

/*
 * Calling into a user-controlled filesystem gives the filesystem
 * daemon ptrace-like capabilities over the requester process.  This
 * means, that the filesystem daemon is able to record the exact
 * filesystem operations performed, and can also control the behavior
 * of the requester process in otherwise impossible ways.  For example
 * it can delay the operation for arbitrary length of time allowing
 * DoS against the requester.
 *
 * For this reason only those processes can call into the filesystem,
 * for which the owner of the mount has ptrace privilege.  This
 * excludes processes started by other users, suid or sgid processes.
 */
int fuse_allow_task(struct fuse_conn *fc, struct task_struct *task)
{
	if (fc->flags & FUSE_ALLOW_OTHER)
		return 1;

	if (task->euid == fc->user_id &&
	    task->suid == fc->user_id &&
	    task->uid == fc->user_id &&
	    task->egid == fc->group_id &&
	    task->sgid == fc->group_id &&
	    task->gid == fc->group_id)
		return 1;

	return 0;
}

static int fuse_access(struct inode *inode, int mask)
{
	struct fuse_conn *fc = get_fuse_conn(inode);
	struct fuse_req *req;
	struct fuse_access_in inarg;
	int err;

	if (fc->no_access)
		return 0;

	req = fuse_get_req(fc);
	if (IS_ERR(req))
		return PTR_ERR(req);

	memset(&inarg, 0, sizeof(inarg));
	inarg.mask = mask;
	req->in.h.opcode = FUSE_ACCESS;
	req->in.h.nodeid = get_node_id(inode);
	req->in.numargs = 1;
	req->in.args[0].size = sizeof(inarg);
	req->in.args[0].value = &inarg;
	request_send(fc, req);
	err = req->out.h.error;
	fuse_put_request(fc, req);
	if (err == -ENOSYS) {
		fc->no_access = 1;
		err = 0;
	}
	return err;
}

/*
 * Check permission.  The two basic access models of FUSE are:
 *
 * 1) Local access checking ('default_permissions' mount option) based
 * on file mode.  This is the plain old disk filesystem permission
 * modell.
 *
 * 2) "Remote" access checking, where server is responsible for
 * checking permission in each inode operation.  An exception to this
 * is if ->permission() was invoked from sys_access() in which case an
 * access request is sent.  Execute permission is still checked
 * locally based on file mode.
 */
static int fuse_permission(struct inode *inode, int mask, struct nameidata *nd)
{
	struct fuse_conn *fc = get_fuse_conn(inode);
	bool refreshed = false;
	int err = 0;

	if (!fuse_allow_task(fc, current))
		return -EACCES;

	/*
	 * If attributes are needed, refresh them before proceeding
	 */
	if ((fc->flags & FUSE_DEFAULT_PERMISSIONS) ||
	    ((mask & MAY_EXEC) && S_ISREG(inode->i_mode))) {
		err = fuse_update_attributes(inode, NULL, NULL, &refreshed);
		if (err)
			return err;
	}

	if (fc->flags & FUSE_DEFAULT_PERMISSIONS) {
		int err = generic_permission(inode, mask, NULL);

		/* If permission is denied, try to refresh file
		   attributes.  This is also needed, because the root
		   node will at first have no permissions */
		if (err == -EACCES && !refreshed) {
			err = fuse_do_getattr(inode, NULL, NULL);
			if (!err)
				err = generic_permission(inode, mask, NULL);
		}

		/* Note: the opposite of the above test does not
		   exist.  So if permissions are revoked this won't be
		   noticed immediately, only after the attribute
		   timeout has expired */
	} else if (nd && (nd->flags & (LOOKUP_ACCESS | LOOKUP_CHDIR))) {
		err = fuse_access(inode, mask);
	} else if ((mask & MAY_EXEC) && S_ISREG(inode->i_mode)) {
		if (!(inode->i_mode & S_IXUGO)) {
			if (refreshed)
				return -EACCES;

			err = fuse_do_getattr(inode, NULL, NULL);
			if (!err && !(inode->i_mode & S_IXUGO))
				return -EACCES;
		}
	}
	return err;
}

static int parse_dirfile(char *buf, size_t nbytes, struct file *file,
			 void *dstbuf, filldir_t filldir)
{
	while (nbytes >= FUSE_NAME_OFFSET) {
		struct fuse_dirent *dirent = (struct fuse_dirent *) buf;
		size_t reclen = FUSE_DIRENT_SIZE(dirent);
		int over;
		if (!dirent->namelen || dirent->namelen > FUSE_NAME_MAX)
			return -EIO;
		if (reclen > nbytes)
			break;

		over = filldir(dstbuf, dirent->name, dirent->namelen,
			       file->f_pos, dirent->ino, dirent->type);
		if (over)
			break;

		buf += reclen;
		nbytes -= reclen;
		file->f_pos = dirent->off;
	}

	return 0;
}

static int fuse_readdir(struct file *file, void *dstbuf, filldir_t filldir)
{
	int err;
	size_t nbytes;