[#LU-10785] ll_acl_{access,default}_xattr_handler confuse name and prefix

In the definition of ll_acl_access_xattr_handler we use the xattr name ("system.posix_acl_access") to initialize the prefix member:

static const struct xattr_handler ll_acl_access_xattr_handler = {
	.prefix = XATTR_NAME_POSIX_ACL_ACCESS,
	.flags = XATTR_ACL_ACCESS_T,
#if defined(HAVE_XATTR_HANDLER_SIMPLIFIED)
	.get = ll_xattr_get_common_4_3,
	.set = ll_xattr_set_common_4_3,
#elif !defined(HAVE_XATTR_HANDLER_INODE_PARAM)
	.get = ll_xattr_get_common_3_11,
	.set = ll_xattr_set_common_3_11,
#else
     	.get = ll_xattr_get_common,
	.set = ll_xattr_set_common,
#endif
};

We should leave prefix unassigned and use the name member instead. This causes getfacl() (which uses getxattr()) to fail for some kernel versions. Similarly for ll_acl_default_xattr_handler.

There also may be conflicts between Lustre and upstream regarding the use of the flags member of struct xattr_handler. Lustre uses

#define XATTR_ACL_ACCESS_T      4
#define XATTR_ACL_DEFAULT_T     5

Upstream uses:

/* a_type field in acl_user_posix_entry_t */
#define ACL_TYPE_ACCESS		(0x8000)
#define ACL_TYPE_DEFAULT	(0x4000)

I did not try to determine how the kernel uses the flags member.

Other filesystems use kernel defined handers for ACLs:

static const struct xattr_handler *ext4_xattr_handler_map[] = {
	[EXT4_XATTR_INDEX_USER]		     = &ext4_xattr_user_handler,
#ifdef CONFIG_EXT4_FS_POSIX_ACL
	[EXT4_XATTR_INDEX_POSIX_ACL_ACCESS]  = &posix_acl_access_xattr_handler,
	[EXT4_XATTR_INDEX_POSIX_ACL_DEFAULT] = &posix_acl_default_xattr_handler,
#endif
	[EXT4_XATTR_INDEX_TRUSTED]	     = &ext4_xattr_trusted_handler,
#ifdef CONFIG_EXT4_FS_SECURITY
	[EXT4_XATTR_INDEX_SECURITY]	     = &ext4_xattr_security_handler,
#endif
};

We should see if these can be used by Lustre as well.

Some auditing is needed.

[LU-10785] ll_acl_{access,default}_xattr_handler confuse name and prefix Created: 07/Mar/18 Updated: 09/Apr/18 Resolved: 09/Apr/18
Status:	Resolved
Project:	Lustre
Component/s:	None
Affects Version/s:	Lustre 2.11.0, Lustre 2.10.3
Fix Version/s:	Lustre 2.12.0

[LU-10785] ll_acl_{access,default}_xattr_handler confuse name and prefix Created: 07/Mar/18 Updated: 09/Apr/18 Resolved: 09/Apr/18