Port of 0.8.50 acl patch to 2.5

This patch (as well as the following two) implements core ACL support.
This set of convenience functions is used by the ext2/3 filesystem, 
and may be useful to other filesystems that wish to use "struct posix_acl"
as their internal representation of acl's.  User mode tools which
support this interface may be found at http://acl.bestbits.at

fs/Kconfig

@@ -1434,6 +1434,12 @@ config FS_MBCACHE
 	default m if EXT2_FS=m || EXT3_FS=m
 	default y if EXT2_FS=y || EXT3_FS=y
 
+# Posix ACL utility routines (for now, only ext2/ext3)
+config FS_POSIX_ACL
+	bool
+	depends on EXT2_FS_POSIX_ACL || EXT3_FS_POSIX_ACL
+	default y
+
 menu "Partition Types"
 
 source "fs/partitions/Kconfig"

fs/Makefile

@@ -6,7 +6,7 @@
 # 
 
 export-objs :=	open.o dcache.o buffer.o bio.o inode.o dquot.o mpage.o aio.o \
-                fcntl.o read_write.o dcookies.o fcblist.o mbcache.o
+                fcntl.o read_write.o dcookies.o fcblist.o mbcache.o posix_acl.o
 
 obj-y :=	open.o read_write.o devices.o file_table.o buffer.o \
 		bio.o super.o block_dev.o char_dev.o stat.o exec.o pipe.o \
@@ -31,6 +31,7 @@ obj-y				+= binfmt_script.o
 obj-$(CONFIG_BINFMT_ELF)	+= binfmt_elf.o
 
 obj-$(CONFIG_FS_MBCACHE)	+= mbcache.o
+obj-$(CONFIG_FS_POSIX_ACL)	+= posix_acl.o
 
 obj-$(CONFIG_QUOTA)		+= dquot.o
 obj-$(CONFIG_QFMT_V1)		+= quota_v1.o

include/linux/posix_acl.h

+/*
+  File: linux/posix_acl.h
+
+  (C) 2002 Andreas Gruenbacher, <a.gruenbacher@computer.org>
+*/
+
+
+#ifndef __LINUX_POSIX_ACL_H
+#define __LINUX_POSIX_ACL_H
+
+#include <linux/slab.h>
+
+#define ACL_UNDEFINED_ID	(-1)
+
+/* a_type field in acl_user_posix_entry_t */
+#define ACL_TYPE_ACCESS		(0x8000)
+#define ACL_TYPE_DEFAULT	(0x4000)
+
+/* e_tag entry in struct posix_acl_entry */
+#define ACL_USER_OBJ		(0x01)
+#define ACL_USER		(0x02)
+#define ACL_GROUP_OBJ		(0x04)
+#define ACL_GROUP		(0x08)
+#define ACL_MASK		(0x10)
+#define ACL_OTHER		(0x20)
+
+/* permissions in the e_perm field */
+#define ACL_READ		(0x04)
+#define ACL_WRITE		(0x02)
+#define ACL_EXECUTE		(0x01)
+//#define ACL_ADD		(0x08)
+//#define ACL_DELETE		(0x10)
+
+struct posix_acl_entry {
+	short			e_tag;
+	unsigned short		e_perm;
+	unsigned int		e_id;
+};
+
+struct posix_acl {
+	atomic_t		a_refcount;
+	unsigned int		a_count;
+	struct posix_acl_entry	a_entries[0];
+};
+
+#define FOREACH_ACL_ENTRY(pa, acl, pe) \
+	for(pa=(acl)->a_entries, pe=pa+(acl)->a_count; pa<pe; pa++)
+
+
+/*
+ * Duplicate an ACL handle.
+ */
+static inline struct posix_acl *
+posix_acl_dup(struct posix_acl *acl)
+{
+	if (acl)
+		atomic_inc(&acl->a_refcount);
+	return acl;
+}
+
+/*
+ * Free an ACL handle.
+ */
+static inline void
+posix_acl_release(struct posix_acl *acl)
+{
+	if (acl && atomic_dec_and_test(&acl->a_refcount))
+		kfree(acl);
+}
+
+
+/* posix_acl.c */
+
+extern struct posix_acl *posix_acl_alloc(int, int);
+extern struct posix_acl *posix_acl_clone(const struct posix_acl *, int);
+extern int posix_acl_valid(const struct posix_acl *);
+extern int posix_acl_permission(struct inode *, const struct posix_acl *, int);
+extern struct posix_acl *posix_acl_from_mode(mode_t, int);
+extern int posix_acl_equiv_mode(const struct posix_acl *, mode_t *);
+extern int posix_acl_create_masq(struct posix_acl *, mode_t *);
+extern int posix_acl_chmod_masq(struct posix_acl *, mode_t);
+extern int posix_acl_masq_nfs_mode(struct posix_acl *, mode_t *);
+
+extern struct posix_acl *get_posix_acl(struct inode *, int);
+extern int set_posix_acl(struct inode *, int, struct posix_acl *);
+
+#endif  /* __LINUX_POSIX_ACL_H */