1. 根目录:
2. include
3. linux
4. posix_acl_xattr.h

/*
  File: linux/posix_acl_xattr.h

  Extended attribute system call representation of Access Control Lists.

  Copyright (C) 2000 by Andreas Gruenbacher <a.gruenbacher@computer.org>
  Copyright (C) 2002 SGI - Silicon Graphics, Inc <linux-xfs@oss.sgi.com>
 */
#ifndef _POSIX_ACL_XATTR_H
#define _POSIX_ACL_XATTR_H

#include <linux/posix_acl.h>

/* Extended attribute names */
#define POSIX_ACL_XATTR_ACCESS	"system.posix_acl_access"
#define POSIX_ACL_XATTR_DEFAULT	"system.posix_acl_default"

/* Supported ACL a_version fields */
#define POSIX_ACL_XATTR_VERSION	0x0002


/* An undefined entry e_id value */
#define ACL_UNDEFINED_ID	(-1)

typedef struct {
	__le16			e_tag;
	__le16			e_perm;
	__le32			e_id;
} posix_acl_xattr_entry;

typedef struct {
	__le32			a_version;
	posix_acl_xattr_entry	a_entries[0];
} posix_acl_xattr_header;


static inline size_t
posix_acl_xattr_size(int count)
{
	return (sizeof(posix_acl_xattr_header) +
		(count * sizeof(posix_acl_xattr_entry)));
}

static inline int
posix_acl_xattr_count(size_t size)
{
	if (size < sizeof(posix_acl_xattr_header))
		return -1;
	size -= sizeof(posix_acl_xattr_header);
	if (size % sizeof(posix_acl_xattr_entry))
		return -1;
	return size / sizeof(posix_acl_xattr_entry);
}

#ifdef CONFIG_FS_POSIX_ACL
void posix_acl_fix_xattr_from_user(void *value, size_t size);
void posix_acl_fix_xattr_to_user(void *value, size_t size);
#else
static inline void posix_acl_fix_xattr_from_user(void *value, size_t size)
{
}
static inline void posix_acl_fix_xattr_to_user(void *value, size_t size)
{
}
#endif

struct posix_acl *posix_acl_from_xattr(struct user_namespace *user_ns, 
				       const void *value, size_t size);
int posix_acl_to_xattr(struct user_namespace *user_ns,
		       const struct posix_acl *acl, void *buffer, size_t size);

extern const struct xattr_handler posix_acl_access_xattr_handler;
extern const struct xattr_handler posix_acl_default_xattr_handler;

#endif	/* _POSIX_ACL_XATTR_H */