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Linux 4.5 compat: xattr list handler
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The registered xattr .list handler was simplified in the 4.5 kernel
to only perform a permission check.  Given a dentry for the file it
must return a boolean indicating if the name is visible.  This
differs slightly from the previous APIs which also required the
function to copy the name in to the provided list and return its
size.  That is now all the responsibility of the caller.

This should be straight forward change to make to ZoL since we've
always required the caller to make the copy.  However, this was
slightly complicated by the need to support 3 older APIs.  Yes,
between 2.6.32 and 4.5 there are 4 versions of this interface!

Therefore, while the functional change in this patch is small it
includes significant cleanup to make the code understandable and
maintainable.  These changes include:

- Improved configure checks for .list, .get, and .set interfaces.
  - Interfaces checked from newest to oldest.
  - Strict checking for each possible known interface.
  - Configure fails when no known interface is available.
  - HAVE_*_XATTR_LIST renamed HAVE_XATTR_LIST_* for consistency
    with similar iops and fops configure checks.

- POSIX_ACL_XATTR_{DEFAULT|ACCESS} were removed forcing callers to
  move to their replacements, XATTR_NAME_POSIX_ACL_{DEFAULT|ACCESS}.
  Compatibility wrapper were added for old kernels.

- ZPL_XATTR_LIST_WRAPPER added which behaves the same as the existing
  ZPL_XATTR_{GET|SET} WRAPPERs.  Only the inode is guaranteed to be
  a valid pointer, passing NULL for the 'list' and 'name' variables
  is allowed and must be checked for.  All .list functions were
  updated to use the wrapper to aid readability.

- zpl_xattr_filldir() updated to use the .list function for its
  permission check which is consistent with the updated Linux 4.5
  interface.  If a .list function is registered it should return 0
  to indicate a name should be skipped, if there is no registered
  function the name will be added.

- Additional documentation from xattr(7) describing the correct
  behavior for each namespace was added before the relevant handlers.

Signed-off-by: Brian Behlendorf <[email protected]>
Signed-off-by: Tim Chase <[email protected]>
Signed-off-by: Chunwei Chen <[email protected]>
Issue #4228
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@behlendorf
behlendorf committed Jan 29, 2016
1 parent b3c9e2c commit 9842008
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Showing 3 changed files with 518 additions and 282 deletions.
228 changes: 170 additions & 58 deletions config/kernel-xattr-handler.m4
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Original file line number Diff line number Diff line change
Expand Up @@ -3,8 +3,8 @@ dnl # 2.6.35 API change,
dnl # The 'struct xattr_handler' was constified in the generic
dnl # super_block structure.
dnl #
AC_DEFUN([ZFS_AC_KERNEL_CONST_XATTR_HANDLER],
[AC_MSG_CHECKING([whether super_block uses const struct xattr_hander])
AC_DEFUN([ZFS_AC_KERNEL_CONST_XATTR_HANDLER], [
AC_MSG_CHECKING([whether super_block uses const struct xattr_handler])
ZFS_LINUX_TRY_COMPILE([
#include <linux/fs.h>
#include <linux/xattr.h>
Expand All @@ -26,157 +26,269 @@ AC_DEFUN([ZFS_AC_KERNEL_CONST_XATTR_HANDLER],
],[
AC_MSG_RESULT([yes])
AC_DEFINE(HAVE_CONST_XATTR_HANDLER, 1,
[super_block uses const struct xattr_hander])
[super_block uses const struct xattr_handler])
],[
AC_MSG_RESULT([no])
])
])

dnl #
dnl # 2.6.33 API change,
dnl # The xattr_hander->get() callback was changed to take a dentry
dnl # instead of an inode, and a handler_flags argument was added.
dnl #
dnl # 4.4 API change,
dnl # The xattr_hander->get() callback was changed to take a xattr_handler,
dnl # and handler_flags argument was removed and should be accessed by
dnl # handler->flags.
dnl # Supported xattr handler get() interfaces checked newest to oldest.
dnl #
AC_DEFUN([ZFS_AC_KERNEL_XATTR_HANDLER_GET], [
AC_MSG_CHECKING([whether xattr_handler->get() wants dentry])
dnl #
dnl # 4.4 API change,
dnl # The xattr_handler->get() callback was changed to take a
dnl # attr_handler, and handler_flags argument was removed and
dnl # should be accessed by handler->flags.
dnl #
AC_MSG_CHECKING([whether xattr_handler->get() wants xattr_handler])
ZFS_LINUX_TRY_COMPILE([
#include <linux/xattr.h>
int get(struct dentry *dentry, const char *name,
void *buffer, size_t size, int handler_flags) { return 0; }
int get(const struct xattr_handler *handler,
struct dentry *dentry, const char *name,
void *buffer, size_t size) { return 0; }
static const struct xattr_handler
xops __attribute__ ((unused)) = {
.get = get,
};
],[
],[
AC_MSG_RESULT(yes)
AC_DEFINE(HAVE_DENTRY_XATTR_GET, 1,
[xattr_handler->get() wants dentry])
AC_DEFINE(HAVE_XATTR_GET_HANDLER, 1,
[xattr_handler->get() wants xattr_handler])
],[
dnl #
dnl # 2.6.33 API change,
dnl # The xattr_handler->get() callback was changed to take
dnl # a dentry instead of an inode, and a handler_flags
dnl # argument was added.
dnl #
AC_MSG_RESULT(no)
AC_MSG_CHECKING([whether xattr_handler->get() wants xattr_handler])
AC_MSG_CHECKING([whether xattr_handler->get() wants dentry])
ZFS_LINUX_TRY_COMPILE([
#include <linux/xattr.h>
int get(const struct xattr_handler *handler, struct dentry *dentry,
const char *name, void *buffer, size_t size) { return 0; }
int get(struct dentry *dentry, const char *name,
void *buffer, size_t size, int handler_flags)
{ return 0; }
static const struct xattr_handler
xops __attribute__ ((unused)) = {
.get = get,
};
],[
],[
AC_MSG_RESULT(yes)
AC_DEFINE(HAVE_HANDLER_XATTR_GET, 1,
[xattr_handler->get() wants xattr_handler])
AC_DEFINE(HAVE_XATTR_GET_DENTRY, 1,
[xattr_handler->get() wants dentry])
],[
dnl #
dnl # 2.6.32 API
dnl #
AC_MSG_RESULT(no)
AC_MSG_CHECKING(
[whether xattr_handler->get() wants inode])
ZFS_LINUX_TRY_COMPILE([
#include <linux/xattr.h>
int get(struct inode *ip, const char *name,
void *buffer, size_t size) { return 0; }
static const struct xattr_handler
xops __attribute__ ((unused)) = {
.get = get,
};
],[
],[
AC_MSG_RESULT(yes)
AC_DEFINE(HAVE_XATTR_GET_INODE, 1,
[xattr_handler->get() wants inode])
],[
AC_MSG_ERROR([no; please file a bug report])
])
])
])
])

dnl #
dnl # 2.6.33 API change,
dnl # The xattr_hander->set() callback was changed to take a dentry
dnl # instead of an inode, and a handler_flags argument was added.
dnl #
dnl # 4.4 API change,
dnl # The xattr_hander->set() callback was changed to take a xattr_handler,
dnl # and handler_flags argument was removed and should be accessed by
dnl # handler->flags.
dnl # Supported xattr handler set() interfaces checked newest to oldest.
dnl #
AC_DEFUN([ZFS_AC_KERNEL_XATTR_HANDLER_SET], [
AC_MSG_CHECKING([whether xattr_handler->set() wants dentry])
dnl #
dnl # 4.4 API change,
dnl # The xattr_handler->set() callback was changed to take a
dnl # xattr_handler, and handler_flags argument was removed and
dnl # should be accessed by handler->flags.
dnl #
AC_MSG_CHECKING([whether xattr_handler->set() wants xattr_handler])
ZFS_LINUX_TRY_COMPILE([
#include <linux/xattr.h>
int set(struct dentry *dentry, const char *name,
const void *buffer, size_t size, int flags,
int handler_flags) { return 0; }
int set(const struct xattr_handler *handler,
struct dentry *dentry, const char *name,
const void *buffer, size_t size, int flags)
{ return 0; }
static const struct xattr_handler
xops __attribute__ ((unused)) = {
.set = set,
};
],[
],[
AC_MSG_RESULT(yes)
AC_DEFINE(HAVE_DENTRY_XATTR_SET, 1,
[xattr_handler->set() wants dentry])
AC_DEFINE(HAVE_XATTR_SET_HANDLER, 1,
[xattr_handler->set() wants xattr_handler])
],[
dnl #
dnl # 2.6.33 API change,
dnl # The xattr_handler->set() callback was changed to take a
dnl # dentry instead of an inode, and a handler_flags
dnl # argument was added.
dnl #
AC_MSG_RESULT(no)
AC_MSG_CHECKING([whether xattr_handler->set() wants xattr_handler])
AC_MSG_CHECKING([whether xattr_handler->set() wants dentry])
ZFS_LINUX_TRY_COMPILE([
#include <linux/xattr.h>
int set(const struct xattr_handler *handler, struct dentry *dentry,
const char *name, const void *buffer, size_t size, int flags) { return 0; }
int set(struct dentry *dentry, const char *name,
const void *buffer, size_t size, int flags,
int handler_flags) { return 0; }
static const struct xattr_handler
xops __attribute__ ((unused)) = {
.set = set,
};
],[
],[
AC_MSG_RESULT(yes)
AC_DEFINE(HAVE_HANDLER_XATTR_SET, 1,
[xattr_handler->set() wants xattr_handler])
AC_DEFINE(HAVE_XATTR_SET_DENTRY, 1,
[xattr_handler->set() wants dentry])
],[
dnl #
dnl # 2.6.32 API
dnl #
AC_MSG_RESULT(no)
AC_MSG_CHECKING(
[whether xattr_handler->set() wants inode])
ZFS_LINUX_TRY_COMPILE([
#include <linux/xattr.h>
int set(struct inode *ip, const char *name,
const void *buffer, size_t size, int flags)
{ return 0; }
static const struct xattr_handler
xops __attribute__ ((unused)) = {
.set = set,
};
],[
],[
AC_MSG_RESULT(yes)
AC_DEFINE(HAVE_XATTR_SET_INODE, 1,
[xattr_handler->set() wants inode])
],[
AC_MSG_ERROR([no; please file a bug report])
])
])
])
])

dnl #
dnl # 2.6.33 API change,
dnl # The xattr_hander->list() callback was changed to take a dentry
dnl # instead of an inode, and a handler_flags argument was added.
dnl #
dnl # 4.4 API change,
dnl # The xattr_hander->list() callback was changed to take a xattr_handler,
dnl # and handler_flags argument was removed and should be accessed by
dnl # handler->flags.
dnl # Supported xattr handler list() interfaces checked newest to oldest.
dnl #
AC_DEFUN([ZFS_AC_KERNEL_XATTR_HANDLER_LIST], [
AC_MSG_CHECKING([whether xattr_handler->list() wants dentry])
dnl # 4.5 API change,
dnl # The xattr_handler->list() callback was changed to take only a
dnl # dentry and it only needs to return if it's accessable.
AC_MSG_CHECKING([whether xattr_handler->list() wants simple])
ZFS_LINUX_TRY_COMPILE([
#include <linux/xattr.h>
size_t list(struct dentry *dentry, char *list, size_t list_size,
const char *name, size_t name_len, int handler_flags)
{ return 0; }
bool list(struct dentry *dentry) { return 0; }
static const struct xattr_handler
xops __attribute__ ((unused)) = {
.list = list,
};
],[
],[
AC_MSG_RESULT(yes)
AC_DEFINE(HAVE_DENTRY_XATTR_LIST, 1,
[xattr_handler->list() wants dentry])
AC_DEFINE(HAVE_XATTR_LIST_SIMPLE, 1,
[xattr_handler->list() wants simple])
],[
dnl #
dnl # 4.4 API change,
dnl # The xattr_handler->list() callback was changed to take a
dnl # xattr_handler, and handler_flags argument was removed
dnl # and should be accessed by handler->flags.
dnl #
AC_MSG_RESULT(no)
AC_MSG_CHECKING([whether xattr_handler->list() wants xattr_handler])
AC_MSG_CHECKING(
[whether xattr_handler->list() wants xattr_handler])
ZFS_LINUX_TRY_COMPILE([
#include <linux/xattr.h>
size_t list(const struct xattr_handler *handler, struct dentry *dentry,
char *list, size_t list_size, const char *name, size_t name_len) { return 0; }
size_t list(const struct xattr_handler *handler,
struct dentry *dentry, char *list, size_t list_size,
const char *name, size_t name_len) { return 0; }
static const struct xattr_handler
xops __attribute__ ((unused)) = {
.list = list,
};
],[
],[
AC_MSG_RESULT(yes)
AC_DEFINE(HAVE_HANDLER_XATTR_LIST, 1,
AC_DEFINE(HAVE_XATTR_LIST_HANDLER, 1,
[xattr_handler->list() wants xattr_handler])
],[
dnl #
dnl # 2.6.33 API change,
dnl # The xattr_handler->list() callback was changed
dnl # to take a dentry instead of an inode, and a
dnl # handler_flags argument was added.
dnl #
AC_MSG_RESULT(no)
AC_MSG_CHECKING(
[whether xattr_handler->list() wants dentry])
ZFS_LINUX_TRY_COMPILE([
#include <linux/xattr.h>
size_t list(struct dentry *dentry,
char *list, size_t list_size,
const char *name, size_t name_len,
int handler_flags) { return 0; }
static const struct xattr_handler
xops __attribute__ ((unused)) = {
.list = list,
};
],[
],[
AC_MSG_RESULT(yes)
AC_DEFINE(HAVE_XATTR_LIST_DENTRY, 1,
[xattr_handler->list() wants dentry])
],[
dnl #
dnl # 2.6.32 API
dnl #
AC_MSG_RESULT(no)
AC_MSG_CHECKING(
[whether xattr_handler->list() wants inode])
ZFS_LINUX_TRY_COMPILE([
#include <linux/xattr.h>
size_t list(struct inode *ip, char *lst,
size_t list_size, const char *name,
size_t name_len) { return 0; }
static const struct xattr_handler
xops __attribute__ ((unused)) = {
.list = list,
};
],[
],[
AC_MSG_RESULT(yes)
AC_DEFINE(HAVE_XATTR_LIST_INODE, 1,
[xattr_handler->list() wants inode])
],[
AC_MSG_ERROR(
[no; please file a bug report])
])
])
])
])
])
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