自学教程：C++ FUSE_ARGS函数代码示例

static int fuse_setxattr(struct dentry *entry, const char *name,			 const void *value, size_t size, int flags){	struct inode *inode = d_inode(entry);	struct fuse_conn *fc = get_fuse_conn(inode);	FUSE_ARGS(args);	struct fuse_setxattr_in inarg;	int err;	if (fc->no_setxattr)		return -EOPNOTSUPP;	memset(&inarg, 0, sizeof(inarg));	inarg.size = size;	inarg.flags = flags;	args.in.h.opcode = FUSE_SETXATTR;	args.in.h.nodeid = get_node_id(inode);	args.in.numargs = 3;	args.in.args[0].size = sizeof(inarg);	args.in.args[0].value = &inarg;	args.in.args[1].size = strlen(name) + 1;	args.in.args[1].value = name;	args.in.args[2].size = size;	args.in.args[2].value = value;	err = fuse_simple_request(fc, &args);	if (err == -ENOSYS) {		fc->no_setxattr = 1;		err = -EOPNOTSUPP;	}	if (!err) {		fuse_invalidate_attr(inode);		fuse_update_ctime(inode);	}	return err;}

static char *read_link(struct dentry *dentry){	struct inode *inode = dentry->d_inode;	struct fuse_conn *fc = get_fuse_conn(inode);	FUSE_ARGS(args);	char *link;	ssize_t ret;	link = (char *) __get_free_page(GFP_KERNEL);	if (!link)		return ERR_PTR(-ENOMEM);	args.in.h.opcode = FUSE_READLINK;	args.in.h.nodeid = get_node_id(inode);	args.out.argvar = 1;	args.out.numargs = 1;	args.out.args[0].size = PAGE_SIZE - 1;	args.out.args[0].value = link;	ret = fuse_simple_request(fc, &args);	if (ret < 0) {		free_page((unsigned long) link);		link = ERR_PTR(ret);	} else {		link[ret] = '/0';	}	fuse_invalidate_atime(inode);	return link;}

/* * Flush inode->i_mtime to the server */int fuse_flush_times(struct inode *inode, struct fuse_file *ff){	struct fuse_conn *fc = get_fuse_conn(inode);	FUSE_ARGS(args);	struct fuse_setattr_in inarg;	struct fuse_attr_out outarg;	memset(&inarg, 0, sizeof(inarg));	memset(&outarg, 0, sizeof(outarg));	inarg.valid = FATTR_MTIME;	inarg.mtime = inode->i_mtime.tv_sec;	inarg.mtimensec = inode->i_mtime.tv_nsec;	if (fc->minor >= 23) {		inarg.valid |= FATTR_CTIME;		inarg.ctime = inode->i_ctime.tv_sec;		inarg.ctimensec = inode->i_ctime.tv_nsec;	}	if (ff) {		inarg.valid |= FATTR_FH;		inarg.fh = ff->fh;	}	fuse_setattr_fill(fc, &args, inode, &inarg, &outarg);	return fuse_simple_request(fc, &args);}

static int fuse_access(struct inode *inode, int mask){	struct fuse_conn *fc = get_fuse_conn(inode);	FUSE_ARGS(args);	struct fuse_access_in inarg;	int err;	BUG_ON(mask & MAY_NOT_BLOCK);	if (fc->no_access)		return 0;	memset(&inarg, 0, sizeof(inarg));	inarg.mask = mask & (MAY_READ | MAY_WRITE | MAY_EXEC);	args.in.h.opcode = FUSE_ACCESS;	args.in.h.nodeid = get_node_id(inode);	args.in.numargs = 1;	args.in.args[0].size = sizeof(inarg);	args.in.args[0].value = &inarg;	err = fuse_simple_request(fc, &args);	if (err == -ENOSYS) {		fc->no_access = 1;		err = 0;	}	return err;}

static int fuse_unlink(struct inode *dir, struct dentry *entry){	int err;	struct fuse_conn *fc = get_fuse_conn(dir);	FUSE_ARGS(args);	args.in.h.opcode = FUSE_UNLINK;	args.in.h.nodeid = get_node_id(dir);	args.in.numargs = 1;	args.in.args[0].size = entry->d_name.len + 1;	args.in.args[0].value = entry->d_name.name;	err = fuse_simple_request(fc, &args);	if (!err) {		struct inode *inode = d_inode(entry);		struct fuse_inode *fi = get_fuse_inode(inode);		spin_lock(&fc->lock);		fi->attr_version = ++fc->attr_version;		/*		 * If i_nlink == 0 then unlink doesn't make sense, yet this can		 * happen if userspace filesystem is careless.  It would be		 * difficult to enforce correct nlink usage so just ignore this		 * condition here		 */		if (inode->i_nlink > 0)			drop_nlink(inode);		spin_unlock(&fc->lock);		fuse_invalidate_attr(inode);		fuse_invalidate_attr(dir);		fuse_invalidate_entry_cache(entry);		fuse_update_ctime(inode);	} else if (err == -EINTR)		fuse_invalidate_entry(entry);	return err;}

static int fuse_removexattr(struct dentry *entry, const char *name){	struct inode *inode = d_inode(entry);	struct fuse_conn *fc = get_fuse_conn(inode);	FUSE_ARGS(args);	int err;	if (fc->no_removexattr)		return -EOPNOTSUPP;	args.in.h.opcode = FUSE_REMOVEXATTR;	args.in.h.nodeid = get_node_id(inode);	args.in.numargs = 1;	args.in.args[0].size = strlen(name) + 1;	args.in.args[0].value = name;	err = fuse_simple_request(fc, &args);	if (err == -ENOSYS) {		fc->no_removexattr = 1;		err = -EOPNOTSUPP;	}	if (!err) {		fuse_invalidate_attr(inode);		fuse_update_ctime(inode);	}	return err;}

static const char *fuse_get_link(struct dentry *dentry,				 struct inode *inode,				 struct delayed_call *done){	struct fuse_conn *fc = get_fuse_conn(inode);	FUSE_ARGS(args);	char *link;	ssize_t ret;	if (!dentry)		return ERR_PTR(-ECHILD);	link = kmalloc(PAGE_SIZE, GFP_KERNEL);	if (!link)		return ERR_PTR(-ENOMEM);	args.in.h.opcode = FUSE_READLINK;	args.in.h.nodeid = get_node_id(inode);	args.out.argvar = 1;	args.out.numargs = 1;	args.out.args[0].size = PAGE_SIZE - 1;	args.out.args[0].value = link;	ret = fuse_simple_request(fc, &args);	if (ret < 0) {		kfree(link);		link = ERR_PTR(ret);	} else {		link[ret] = '/0';		set_delayed_call(done, kfree_link, link);	}	fuse_invalidate_atime(inode);	return link;}

static int fuse_rename_common(struct inode *olddir, struct dentry *oldent,			      struct inode *newdir, struct dentry *newent,			      unsigned int flags, int opcode, size_t argsize){	int err;	struct fuse_rename2_in inarg;	struct fuse_conn *fc = get_fuse_conn(olddir);	FUSE_ARGS(args);	memset(&inarg, 0, argsize);	inarg.newdir = get_node_id(newdir);	inarg.flags = flags;	args.in.h.opcode = opcode;	args.in.h.nodeid = get_node_id(olddir);	args.in.numargs = 3;	args.in.args[0].size = argsize;	args.in.args[0].value = &inarg;	args.in.args[1].size = oldent->d_name.len + 1;	args.in.args[1].value = oldent->d_name.name;	args.in.args[2].size = newent->d_name.len + 1;	args.in.args[2].value = newent->d_name.name;	err = fuse_simple_request(fc, &args);	if (!err) {		/* ctime changes */		fuse_invalidate_attr(d_inode(oldent));		fuse_update_ctime(d_inode(oldent));		if (flags & RENAME_EXCHANGE) {			fuse_invalidate_attr(d_inode(newent));			fuse_update_ctime(d_inode(newent));		}		fuse_invalidate_attr(olddir);		if (olddir != newdir)			fuse_invalidate_attr(newdir);		/* newent will end up negative */		if (!(flags & RENAME_EXCHANGE) && d_really_is_positive(newent)) {			fuse_invalidate_attr(d_inode(newent));			fuse_invalidate_entry_cache(newent);			fuse_update_ctime(d_inode(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 (d_really_is_positive(newent))			fuse_invalidate_entry(newent);	}	return err;}

int fuse_lookup_name(struct super_block *sb, u64 nodeid, const struct qstr *name,		     struct fuse_entry_out *outarg, struct inode **inode){	struct fuse_conn *fc = get_fuse_conn_super(sb);	FUSE_ARGS(args);	struct fuse_forget_link *forget;	u64 attr_version;	int err;	*inode = NULL;	err = -ENAMETOOLONG;	if (name->len > FUSE_NAME_MAX)		goto out;	forget = fuse_alloc_forget();	err = -ENOMEM;	if (!forget)		goto out;	attr_version = fuse_get_attr_version(fc);	fuse_lookup_init(fc, &args, nodeid, name, outarg);	err = fuse_simple_request(fc, &args);	/* Zero nodeid is same as -ENOENT, but with valid timeout */	if (err || !outarg->nodeid)		goto out_put_forget;	err = -EIO;	if (!outarg->nodeid)		goto out_put_forget;	if (!fuse_valid_type(outarg->attr.mode))		goto out_put_forget;	*inode = fuse_iget(sb, outarg->nodeid, outarg->generation,			   &outarg->attr, entry_attr_timeout(outarg),			   attr_version);	err = -ENOMEM;	if (!*inode) {		fuse_queue_forget(fc, forget, outarg->nodeid, 1);		goto out;	}	err = 0; out_put_forget:	kfree(forget); out:	return err;}

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

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);	FUSE_ARGS(args);	u64 attr_version;	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;	}	args.in.h.opcode = FUSE_GETATTR;	args.in.h.nodeid = get_node_id(inode);	args.in.numargs = 1;	args.in.args[0].size = sizeof(inarg);	args.in.args[0].value = &inarg;	args.out.numargs = 1;	args.out.args[0].size = sizeof(outarg);	args.out.args[0].value = &outarg;	err = fuse_simple_request(fc, &args);	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;}

static int fuse_rmdir(struct inode *dir, struct dentry *entry){	int err;	struct fuse_conn *fc = get_fuse_conn(dir);	FUSE_ARGS(args);	args.in.h.opcode = FUSE_RMDIR;	args.in.h.nodeid = get_node_id(dir);	args.in.numargs = 1;	args.in.args[0].size = entry->d_name.len + 1;	args.in.args[0].value = entry->d_name.name;	err = fuse_simple_request(fc, &args);	if (!err) {		clear_nlink(d_inode(entry));		fuse_invalidate_attr(dir);		fuse_invalidate_entry_cache(entry);	} else if (err == -EINTR)		fuse_invalidate_entry(entry);	return err;}

static int fuse_mkdir(struct inode *dir, struct dentry *entry, umode_t mode){	struct fuse_mkdir_in inarg;	struct fuse_conn *fc = get_fuse_conn(dir);	FUSE_ARGS(args);	if (!fc->dont_mask)		mode &= ~current_umask();	memset(&inarg, 0, sizeof(inarg));	inarg.mode = mode;	inarg.umask = current_umask();	args.in.h.opcode = FUSE_MKDIR;	args.in.numargs = 2;	args.in.args[0].size = sizeof(inarg);	args.in.args[0].value = &inarg;	args.in.args[1].size = entry->d_name.len + 1;	args.in.args[1].value = entry->d_name.name;	return create_new_entry(fc, &args, dir, entry, S_IFDIR);}

static int fuse_link(struct dentry *entry, struct inode *newdir,		     struct dentry *newent){	int err;	struct fuse_link_in inarg;	struct inode *inode = d_inode(entry);	struct fuse_conn *fc = get_fuse_conn(inode);	FUSE_ARGS(args);	memset(&inarg, 0, sizeof(inarg));	inarg.oldnodeid = get_node_id(inode);	args.in.h.opcode = FUSE_LINK;	args.in.numargs = 2;	args.in.args[0].size = sizeof(inarg);	args.in.args[0].value = &inarg;	args.in.args[1].size = newent->d_name.len + 1;	args.in.args[1].value = newent->d_name.name;	err = create_new_entry(fc, &args, 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) {		struct fuse_inode *fi = get_fuse_inode(inode);		spin_lock(&fc->lock);		fi->attr_version = ++fc->attr_version;		inc_nlink(inode);		spin_unlock(&fc->lock);		fuse_invalidate_attr(inode);		fuse_update_ctime(inode);	} else if (err == -EINTR) {		fuse_invalidate_attr(inode);	}	return err;}

/* * Set attributes, and at the same time refresh them. * * Truncation is slightly complicated, because the 'truncate' request * may fail, in which case we don't want to touch the mapping. * vmtruncate() doesn't allow for this case, so do the rlimit checking * and the actual truncation by hand. */int fuse_do_setattr(struct dentry *dentry, struct iattr *attr,		    struct file *file){	struct inode *inode = d_inode(dentry);	struct fuse_conn *fc = get_fuse_conn(inode);	struct fuse_inode *fi = get_fuse_inode(inode);	FUSE_ARGS(args);	struct fuse_setattr_in inarg;	struct fuse_attr_out outarg;	bool is_truncate = false;	bool is_wb = fc->writeback_cache;	loff_t oldsize;	int err;	bool trust_local_cmtime = is_wb && S_ISREG(inode->i_mode);	if (!fc->default_permissions)		attr->ia_valid |= ATTR_FORCE;	err = setattr_prepare(dentry, attr);	if (err)		return err;	if (attr->ia_valid & ATTR_OPEN) {		if (fc->atomic_o_trunc)			return 0;		file = NULL;	}	if (attr->ia_valid & ATTR_SIZE)		is_truncate = true;	if (is_truncate) {		fuse_set_nowrite(inode);		set_bit(FUSE_I_SIZE_UNSTABLE, &fi->state);		if (trust_local_cmtime && attr->ia_size != inode->i_size)			attr->ia_valid |= ATTR_MTIME | ATTR_CTIME;	}	memset(&inarg, 0, sizeof(inarg));	memset(&outarg, 0, sizeof(outarg));	iattr_to_fattr(attr, &inarg, trust_local_cmtime);	if (file) {		struct fuse_file *ff = file->private_data;		inarg.valid |= FATTR_FH;		inarg.fh = ff->fh;	}	if (attr->ia_valid & ATTR_SIZE) {		/* For mandatory locking in truncate */		inarg.valid |= FATTR_LOCKOWNER;		inarg.lock_owner = fuse_lock_owner_id(fc, current->files);	}	fuse_setattr_fill(fc, &args, inode, &inarg, &outarg);	err = fuse_simple_request(fc, &args);	if (err) {		if (err == -EINTR)			fuse_invalidate_attr(inode);		goto error;	}	if ((inode->i_mode ^ outarg.attr.mode) & S_IFMT) {		make_bad_inode(inode);		err = -EIO;		goto error;	}	spin_lock(&fc->lock);	/* the kernel maintains i_mtime locally */	if (trust_local_cmtime) {		if (attr->ia_valid & ATTR_MTIME)			inode->i_mtime = attr->ia_mtime;		if (attr->ia_valid & ATTR_CTIME)			inode->i_ctime = attr->ia_ctime;		/* FIXME: clear I_DIRTY_SYNC? */	}	fuse_change_attributes_common(inode, &outarg.attr,				      attr_timeout(&outarg));	oldsize = inode->i_size;	/* see the comment in fuse_change_attributes() */	if (!is_wb || is_truncate || !S_ISREG(inode->i_mode))		i_size_write(inode, outarg.attr.size);	if (is_truncate) {		/* NOTE: this may release/reacquire fc->lock */		__fuse_release_nowrite(inode);	}	spin_unlock(&fc->lock);	/*	 * Only call invalidate_inode_pages2() after removing	 * FUSE_NOWRITE, otherwise fuse_launder_page() would deadlock.	 *///.........这里部分代码省略.........

/* * Atomic create+open operation * * If the filesystem doesn't support this, then fall back to separate * 'mknod' + 'open' requests. */static int fuse_create_open(struct inode *dir, struct dentry *entry,			    struct file *file, unsigned flags,			    umode_t mode, int *opened){	int err;	struct inode *inode;	struct fuse_conn *fc = get_fuse_conn(dir);	FUSE_ARGS(args);	struct fuse_forget_link *forget;	struct fuse_create_in inarg;	struct fuse_open_out outopen;	struct fuse_entry_out outentry;	struct fuse_file *ff;	/* Userspace expects S_IFREG in create mode */	BUG_ON((mode & S_IFMT) != S_IFREG);	forget = fuse_alloc_forget();	err = -ENOMEM;	if (!forget)		goto out_err;	err = -ENOMEM;	ff = fuse_file_alloc(fc);	if (!ff)		goto out_put_forget_req;	if (!fc->dont_mask)		mode &= ~current_umask();	flags &= ~O_NOCTTY;	memset(&inarg, 0, sizeof(inarg));	memset(&outentry, 0, sizeof(outentry));	inarg.flags = flags;	inarg.mode = mode;	inarg.umask = current_umask();	args.in.h.opcode = FUSE_CREATE;	args.in.h.nodeid = get_node_id(dir);	args.in.numargs = 2;	args.in.args[0].size = sizeof(inarg);	args.in.args[0].value = &inarg;	args.in.args[1].size = entry->d_name.len + 1;	args.in.args[1].value = entry->d_name.name;	args.out.numargs = 2;	args.out.args[0].size = sizeof(outentry);	args.out.args[0].value = &outentry;	args.out.args[1].size = sizeof(outopen);	args.out.args[1].value = &outopen;	err = fuse_simple_request(fc, &args);	if (err)		goto out_free_ff;	err = -EIO;	if (!S_ISREG(outentry.attr.mode) || invalid_nodeid(outentry.nodeid))		goto out_free_ff;	ff->fh = outopen.fh;	ff->nodeid = outentry.nodeid;	ff->open_flags = outopen.open_flags;	inode = fuse_iget(dir->i_sb, outentry.nodeid, outentry.generation,			  &outentry.attr, entry_attr_timeout(&outentry), 0);	if (!inode) {		flags &= ~(O_CREAT | O_EXCL | O_TRUNC);		fuse_sync_release(ff, flags);		fuse_queue_forget(fc, forget, outentry.nodeid, 1);		err = -ENOMEM;		goto out_err;	}	kfree(forget);	d_instantiate(entry, inode);	fuse_change_entry_timeout(entry, &outentry);	fuse_invalidate_attr(dir);	err = finish_open(file, entry, generic_file_open, opened);	if (err) {		fuse_sync_release(ff, flags);	} else {		file->private_data = ff;		fuse_finish_open(inode, file);	}	return err;out_free_ff:	fuse_file_free(ff);out_put_forget_req:	kfree(forget);out_err:	return err;}

/* * Check whether the dentry is still valid * * If the entry validity timeout has expired and the dentry is * positive, try to redo the lookup.  If the lookup results in a * different inode, then let the VFS invalidate the dentry and redo * the lookup once more.  If the lookup results in the same inode, * then refresh the attributes, timeouts and mark the dentry valid. */static int fuse_dentry_revalidate(struct dentry *entry, unsigned int flags){	struct inode *inode;	struct dentry *parent;	struct fuse_conn *fc;	struct fuse_inode *fi;	int ret;	inode = d_inode_rcu(entry);	if (inode && is_bad_inode(inode))		goto invalid;	else if (time_before64(fuse_dentry_time(entry), get_jiffies_64()) ||		 (flags & LOOKUP_REVAL)) {		struct fuse_entry_out outarg;		FUSE_ARGS(args);		struct fuse_forget_link *forget;		u64 attr_version;		/* For negative dentries, always do a fresh lookup */		if (!inode)			goto invalid;		ret = -ECHILD;		if (flags & LOOKUP_RCU)			goto out;		fc = get_fuse_conn(inode);		forget = fuse_alloc_forget();		ret = -ENOMEM;		if (!forget)			goto out;		attr_version = fuse_get_attr_version(fc);		parent = dget_parent(entry);		fuse_lookup_init(fc, &args, get_node_id(d_inode(parent)),				 &entry->d_name, &outarg);		ret = fuse_simple_request(fc, &args);		dput(parent);		/* Zero nodeid is same as -ENOENT */		if (!ret && !outarg.nodeid)			ret = -ENOENT;		if (!ret) {			fi = get_fuse_inode(inode);			if (outarg.nodeid != get_node_id(inode)) {				fuse_queue_forget(fc, forget, outarg.nodeid, 1);				goto invalid;			}			spin_lock(&fc->lock);			fi->nlookup++;			spin_unlock(&fc->lock);		}		kfree(forget);		if (ret == -ENOMEM)			goto out;		if (ret || (outarg.attr.mode ^ inode->i_mode) & S_IFMT)			goto invalid;		forget_all_cached_acls(inode);		fuse_change_attributes(inode, &outarg.attr,				       entry_attr_timeout(&outarg),				       attr_version);		fuse_change_entry_timeout(entry, &outarg);	} else if (inode) {		fi = get_fuse_inode(inode);		if (flags & LOOKUP_RCU) {			if (test_bit(FUSE_I_INIT_RDPLUS, &fi->state))				return -ECHILD;		} else if (test_and_clear_bit(FUSE_I_INIT_RDPLUS, &fi->state)) {			parent = dget_parent(entry);			fuse_advise_use_readdirplus(d_inode(parent));			dput(parent);		}	}	ret = 1;out:	return ret;invalid:	ret = 0;	goto out;}