src/cf/linux-checks.m4

   1 AC_DEFUN([OPENAFS_LINUX_CHECKS],[
   2 case $AFS_SYSNAME in *_linux* | *_umlinux*)
   3
   4                 # Add (sub-) architecture-specific paths needed by conftests
   5                 case $AFS_SYSNAME  in
   6                         *_umlinux26)
   7                                 UMLINUX26_FLAGS="-I$LINUX_KERNEL_PATH/arch/um/include"
   8                                 UMLINUX26_FLAGS="$UMLINUX26_FLAGS -I$LINUX_KERNEL_PATH/arch/um/kernel/tt/include"
   9                                  UMLINUX26_FLAGS="$UMLINUX26_FLAGS -I$LINUX_KERNEL_PATH/arch/um/kernel/skas/include"
  10                                 CPPFLAGS="$CPPFLAGS $UMLINUX26_FLAGS"
  11                 esac
  12
  13                 if test "x$enable_kernel_module" = "xyes"; then
  14                  if test "x$enable_debug_kernel" = "xno"; then
  15                         LINUX_GCC_KOPTS="$LINUX_GCC_KOPTS -fomit-frame-pointer"
  16                  fi
  17                  OPENAFS_GCC_SUPPORTS_MARCH
  18                  AC_SUBST(P5PLUS_KOPTS)
  19                  OPENAFS_GCC_NEEDS_NO_STRENGTH_REDUCE
  20                  OPENAFS_GCC_NEEDS_NO_STRICT_ALIASING
  21                  OPENAFS_GCC_SUPPORTS_NO_COMMON
  22                  OPENAFS_GCC_SUPPORTS_PIPE
  23                  AC_SUBST(LINUX_GCC_KOPTS)
  24
  25                  dnl Setup the kernel build environment
  26                  LINUX_KBUILD_USES_EXTRA_CFLAGS
  27                  LINUX_KERNEL_COMPILE_WORKS
  28
  29                  dnl Operation signature checks
  30                  AC_CHECK_LINUX_OPERATION([inode_operations], [follow_link], [no_nameidata],
  31                                           [#include <linux/fs.h>],
  32                                           [const char *],
  33                                           [struct dentry *dentry, void **link_data])
  34                  AC_CHECK_LINUX_OPERATION([inode_operations], [put_link], [no_nameidata],
  35                                           [#include <linux/fs.h>],
  36                                           [void],
  37                                           [struct inode *inode, void *link_data])
  38                  AC_CHECK_LINUX_OPERATION([inode_operations], [rename], [takes_flags],
  39                                           [#include <linux/fs.h>],
  40                                           [int],
  41                                           [struct inode *oinode, struct dentry *odentry,
  42                                                 struct inode *ninode, struct dentry *ndentry,
  43                                                 unsigned int flags])
  44
  45                  dnl Check for header files
  46                  AC_CHECK_LINUX_HEADER([cred.h])
  47                  AC_CHECK_LINUX_HEADER([config.h])
  48                  AC_CHECK_LINUX_HEADER([exportfs.h])
  49                  AC_CHECK_LINUX_HEADER([freezer.h])
  50                  AC_CHECK_LINUX_HEADER([key-type.h])
  51                  AC_CHECK_LINUX_HEADER([semaphore.h])
  52                  AC_CHECK_LINUX_HEADER([seq_file.h])
  53                  AC_CHECK_LINUX_HEADER([sched/signal.h])
  54                  AC_CHECK_LINUX_HEADER([uaccess.h])
  55
  56                  dnl Type existence checks
  57                  AC_CHECK_LINUX_TYPE([struct vfs_path], [dcache.h])
  58                  AC_CHECK_LINUX_TYPE([kuid_t], [uidgid.h])
  59
  60                  dnl Check for structure elements
  61                  AC_CHECK_LINUX_STRUCT([address_space], [backing_dev_info], [fs.h])
  62                  AC_CHECK_LINUX_STRUCT([address_space_operations],
  63                                        [write_begin], [fs.h])
  64                  AC_CHECK_LINUX_STRUCT([backing_dev_info], [name],
  65                                        [backing-dev.h])
  66                  AC_CHECK_LINUX_STRUCT([cred], [session_keyring], [cred.h])
  67                  AC_CHECK_LINUX_STRUCT([ctl_table], [ctl_name], [sysctl.h])
  68                  AC_CHECK_LINUX_STRUCT([dentry], [d_u.d_alias], [dcache.h])
  69                  AC_CHECK_LINUX_STRUCT([dentry_operations], [d_automount], [dcache.h])
  70                  AC_CHECK_LINUX_STRUCT([group_info], [gid], [cred.h])
  71                  AC_CHECK_LINUX_STRUCT([inode], [i_alloc_sem], [fs.h])
  72                  AC_CHECK_LINUX_STRUCT([inode], [i_blkbits], [fs.h])
  73                  AC_CHECK_LINUX_STRUCT([inode], [i_blksize], [fs.h])
  74                  AC_CHECK_LINUX_STRUCT([inode], [i_mutex], [fs.h])
  75                  AC_CHECK_LINUX_STRUCT([inode], [i_security], [fs.h])
  76                  AC_CHECK_LINUX_STRUCT([file], [f_path], [fs.h])
  77                  AC_CHECK_LINUX_STRUCT([file_operations], [flock], [fs.h])
  78                  AC_CHECK_LINUX_STRUCT([file_operations], [iterate], [fs.h])
  79                  AC_CHECK_LINUX_STRUCT([file_operations], [read_iter], [fs.h])
  80                  AC_CHECK_LINUX_STRUCT([file_operations], [sendfile], [fs.h])
  81                  AC_CHECK_LINUX_STRUCT([file_system_type], [mount], [fs.h])
  82                  AC_CHECK_LINUX_STRUCT([inode_operations], [truncate], [fs.h])
  83                  AC_CHECK_LINUX_STRUCT([inode_operations], [get_link], [fs.h])
  84                  AC_CHECK_LINUX_STRUCT([key], [payload.value], [key.h])
  85                  AC_CHECK_LINUX_STRUCT([key_type], [instantiate_prep], [key-type.h])
  86                  AC_CHECK_LINUX_STRUCT([key_type], [match_preparse], [key-type.h])
  87                  AC_CHECK_LINUX_STRUCT([key_type], [preparse], [key-type.h])
  88                  AC_CHECK_LINUX_STRUCT([msghdr], [msg_iter], [socket.h])
  89                  AC_CHECK_LINUX_STRUCT([nameidata], [path], [namei.h])
  90                  AC_CHECK_LINUX_STRUCT([proc_dir_entry], [owner], [proc_fs.h])
  91                  AC_CHECK_LINUX_STRUCT([super_block], [s_bdi], [fs.h])
  92                  AC_CHECK_LINUX_STRUCT([super_block], [s_d_op], [fs.h])
  93                  AC_CHECK_LINUX_STRUCT([super_operations], [alloc_inode],
  94                                        [fs.h])
  95                  AC_CHECK_LINUX_STRUCT([super_operations], [evict_inode],
  96                                        [fs.h])
  97                  AC_CHECK_LINUX_STRUCT([task_struct], [cred], [sched.h])
  98                  AC_CHECK_LINUX_STRUCT([task_struct], [exit_state], [sched.h])
  99                  AC_CHECK_LINUX_STRUCT([task_struct], [parent], [sched.h])
 100                  AC_CHECK_LINUX_STRUCT([task_struct], [real_parent], [sched.h])
 101                  AC_CHECK_LINUX_STRUCT([task_struct], [rlim], [sched.h])
 102                  AC_CHECK_LINUX_STRUCT([task_struct], [sig], [sched.h])
 103                  AC_CHECK_LINUX_STRUCT([task_struct], [sighand], [sched.h])
 104                  AC_CHECK_LINUX_STRUCT([task_struct], [sigmask_lock], [sched.h])
 105                  AC_CHECK_LINUX_STRUCT([task_struct], [tgid], [sched.h])
 106                  AC_CHECK_LINUX_STRUCT([task_struct], [thread_info], [sched.h])
 107                  AC_CHECK_LINUX_STRUCT([task_struct], [total_link_count], [sched.h])
 108                  LINUX_SCHED_STRUCT_TASK_STRUCT_HAS_SIGNAL_RLIM
 109
 110                  dnl Check for typed structure elements
 111                  AC_CHECK_LINUX_TYPED_STRUCT([read_descriptor_t],
 112                                                   [buf], [fs.h])
 113
 114                  dnl Function existence checks
 115
 116                  AC_CHECK_LINUX_FUNC([__vfs_write],
 117                                      [#include <linux/fs.h>],
 118                                      [__vfs_write(NULL, NULL, 0, NULL);])
 119                  AC_CHECK_LINUX_FUNC([kernel_write],
 120                                      [#include <linux/fs.h>],
 121                                      [kernel_write(NULL, NULL, 0, NULL);])
 122                  AC_CHECK_LINUX_FUNC([bdi_init],
 123                                      [#include <linux/backing-dev.h>],
 124                                      [bdi_init(NULL);])
 125                  AC_CHECK_LINUX_FUNC([super_setup_bdi],
 126                                      [#include <linux/backing-dev.h>],
 127                                      [struct super_block *sb;
 128                                       super_setup_bdi(sb);])
 129                  AC_CHECK_LINUX_FUNC([PageChecked],
 130                                      [#include <linux/mm.h>
 131 #include <linux/page-flags.h>],
 132                                      [struct page *_page;
 133                                       int bchecked = PageChecked(_page);])
 134                  AC_CHECK_LINUX_FUNC([PageFsMisc],
 135                                      [#include <linux/mm.h>
 136 #include <linux/page-flags.h>],
 137                                      [struct page *_page;
 138                                       int bchecked = PageFsMisc(_page);])
 139                  AC_CHECK_LINUX_FUNC([clear_inode],
 140                                      [#include <linux/fs.h>],
 141                                      [clear_inode(NULL);])
 142                  AC_CHECK_LINUX_FUNC([current_kernel_time],
 143                                      [#include <linux/time.h>],
 144                                      [struct timespec s;
 145                                       s = current_kernel_time();])
 146                  AC_CHECK_LINUX_FUNC([d_alloc_anon],
 147                                      [#include <linux/fs.h>],
 148                                      [d_alloc_anon(NULL);])
 149                  AC_CHECK_LINUX_FUNC([d_count],
 150                                      [#include <linux/dcache.h>],
 151                                      [d_count(NULL);])
 152                  AC_CHECK_LINUX_FUNC([d_make_root],
 153                                      [#include <linux/fs.h>],
 154                                      [d_make_root(NULL);])
 155                  AC_CHECK_LINUX_FUNC([do_sync_read],
 156                                      [#include <linux/fs.h>],
 157                                      [do_sync_read(NULL, NULL, 0, NULL);])
 158                  AC_CHECK_LINUX_FUNC([file_dentry],
 159                                      [#include <linux/fs.h>],
 160                                      [struct file *f; file_dentry(f);])
 161                  AC_CHECK_LINUX_FUNC([find_task_by_pid],
 162                                      [#include <linux/sched.h>],
 163                                      [pid_t p; find_task_by_pid(p);])
 164                  AC_CHECK_LINUX_FUNC([generic_file_aio_read],
 165                                      [#include <linux/fs.h>],
 166                                      [generic_file_aio_read(NULL,NULL,0,0);])
 167                  AC_CHECK_LINUX_FUNC([grab_cache_page_write_begin],
 168                                      [#include <linux/pagemap.h>],
 169                                      [grab_cache_page_write_begin(NULL, 0, 0);])
 170                  AC_CHECK_LINUX_FUNC([hlist_unhashed],
 171                                      [#include <linux/list.h>],
 172                                      [hlist_unhashed(0);])
 173                  AC_CHECK_LINUX_FUNC([ihold],
 174                                      [#include <linux/fs.h>],
 175                                      [ihold(NULL);])
 176                  AC_CHECK_LINUX_FUNC([i_size_read],
 177                                      [#include <linux/fs.h>],
 178                                      [i_size_read(NULL);])
 179                  AC_CHECK_LINUX_FUNC([inode_setattr],
 180                                      [#include <linux/fs.h>],
 181                                      [inode_setattr(NULL, NULL);])
 182                  AC_CHECK_LINUX_FUNC([iter_file_splice_write],
 183                                      [#include <linux/fs.h>],
 184                                      [iter_file_splice_write(NULL,NULL,NULL,0,0);])
 185                  AC_CHECK_LINUX_FUNC([kernel_setsockopt],
 186                                      [#include <linux/net.h>],
 187                                      [kernel_setsockopt(NULL, 0, 0, NULL, 0);])
 188                  AC_CHECK_LINUX_FUNC([locks_lock_file_wait],
 189                                      [#include <linux/fs.h>],
 190                                      [locks_lock_file_wait(NULL, NULL);])
 191                  AC_CHECK_LINUX_FUNC([page_follow_link],
 192                                      [#include <linux/fs.h>],
 193                                      [page_follow_link(0,0);])
 194                  AC_CHECK_LINUX_FUNC([page_get_link],
 195                                      [#include <linux/fs.h>],
 196                                      [page_get_link(0,0,0);])
 197                  AC_CHECK_LINUX_FUNC([page_offset],
 198                                      [#include <linux/pagemap.h>],
 199                                      [page_offset(NULL);])
 200                  AC_CHECK_LINUX_FUNC([pagevec_lru_add_file],
 201                                      [#include <linux/pagevec.h>],
 202                                      [__pagevec_lru_add_file(NULL);])
 203                  AC_CHECK_LINUX_FUNC([path_lookup],
 204                                      [#include <linux/fs.h>
 205                                       #include <linux/namei.h>],
 206                                      [path_lookup(NULL, 0, NULL);])
 207                  AC_CHECK_LINUX_FUNC([proc_create],
 208                                      [#include <linux/proc_fs.h>],
 209                                      [proc_create(NULL, 0, NULL, NULL);])
 210                  AC_CHECK_LINUX_FUNC([rcu_read_lock],
 211                                      [#include <linux/rcupdate.h>],
 212                                      [rcu_read_lock();])
 213                  AC_CHECK_LINUX_FUNC([set_nlink],
 214                                      [#include <linux/fs.h>],
 215                                      [set_nlink(NULL, 1);])
 216                  AC_CHECK_LINUX_FUNC([setattr_prepare],
 217                                      [#include <linux/fs.h>],
 218                                      [setattr_prepare(NULL, NULL);])
 219                  AC_CHECK_LINUX_FUNC([sock_create_kern],
 220                                      [#include <linux/net.h>],
 221                                      [sock_create_kern(0, 0, 0, NULL);])
 222                  AC_CHECK_LINUX_FUNC([sock_create_kern_ns],
 223                                      [#include <linux/net.h>],
 224                                      [sock_create_kern(NULL, 0, 0, 0, NULL);])
 225                  AC_CHECK_LINUX_FUNC([splice_direct_to_actor],
 226                                      [#include <linux/splice.h>],
 227                                      [splice_direct_to_actor(NULL,NULL,NULL);])
 228                  AC_CHECK_LINUX_FUNC([default_file_splice_read],
 229                                      [#include <linux/fs.h>],
 230                                      [default_file_splice_read(NULL,NULL,NULL, 0, 0);])
 231                  AC_CHECK_LINUX_FUNC([svc_addr_in],
 232                                      [#include <linux/sunrpc/svc.h>],
 233                                      [svc_addr_in(NULL);])
 234                  AC_CHECK_LINUX_FUNC([zero_user_segments],
 235                                      [#include <linux/highmem.h>],
 236                                      [zero_user_segments(NULL, 0, 0, 0, 0);])
 237                  AC_CHECK_LINUX_FUNC([noop_fsync],
 238                                      [#include <linux/fs.h>],
 239                                      [void *address = &noop_fsync; printk("%p\n", address)];)
 240                  AC_CHECK_LINUX_FUNC([kthread_run],
 241                                      [#include <linux/kernel.h>
 242                                       #include <linux/kthread.h>],
 243                                      [kthread_run(NULL, NULL, "test");])
 244                  AC_CHECK_LINUX_FUNC([inode_nohighmem],
 245                                      [#include <linux/fs.h>],
 246                                      [inode_nohighmem(NULL);])
 247                  AC_CHECK_LINUX_FUNC([inode_lock],
 248                                      [#include <linux/fs.h>],
 249                                      [inode_lock(NULL);])
 250
 251                  dnl Consequences - things which get set as a result of the
 252                  dnl                above tests
 253                  AS_IF([test "x$ac_cv_linux_func_d_alloc_anon" = "xno"],
 254                        [AC_DEFINE([AFS_NONFSTRANS], 1,
 255                                   [define to disable the nfs translator])])
 256
 257                  dnl Assorted more complex tests
 258                  LINUX_AIO_NONVECTOR
 259                  LINUX_EXPORTS_PROC_ROOT_FS
 260                  LINUX_KMEM_CACHE_INIT
 261                  LINUX_HAVE_KMEM_CACHE_T
 262                  LINUX_KMEM_CACHE_CREATE_TAKES_DTOR
 263                  LINUX_KMEM_CACHE_CREATE_CTOR_TAKES_VOID
 264                  LINUX_D_PATH_TAKES_STRUCT_PATH
 265                  LINUX_NEW_EXPORT_OPS
 266                  LINUX_INODE_SETATTR_RETURN_TYPE
 267                  LINUX_IOP_I_CREATE_TAKES_NAMEIDATA
 268                  LINUX_IOP_I_LOOKUP_TAKES_NAMEIDATA
 269                  LINUX_IOP_I_PERMISSION_TAKES_FLAGS
 270                    LINUX_IOP_I_PERMISSION_TAKES_NAMEIDATA
 271                    LINUX_IOP_I_PUT_LINK_TAKES_COOKIE
 272                  LINUX_DOP_D_DELETE_TAKES_CONST
 273                    LINUX_DOP_D_REVALIDATE_TAKES_NAMEIDATA
 274                    LINUX_FOP_F_FLUSH_TAKES_FL_OWNER_T
 275                    LINUX_FOP_F_FSYNC_TAKES_DENTRY
 276                  LINUX_FOP_F_FSYNC_TAKES_RANGE
 277                    LINUX_AOP_WRITEBACK_CONTROL
 278                  LINUX_FS_STRUCT_FOP_HAS_SPLICE
 279                  LINUX_KERNEL_POSIX_LOCK_FILE_WAIT_ARG
 280                  LINUX_KERNEL_PAGEVEC_INIT_COLD_ARG
 281                  LINUX_POSIX_TEST_LOCK_RETURNS_CONFLICT
 282                  LINUX_POSIX_TEST_LOCK_CONFLICT_ARG
 283                  LINUX_KERNEL_SOCK_CREATE
 284                  LINUX_EXPORTS_KEY_TYPE_KEYRING
 285                  LINUX_NEED_RHCONFIG
 286                  LINUX_RECALC_SIGPENDING_ARG_TYPE
 287                  LINUX_EXPORTS_TASKLIST_LOCK
 288                  LINUX_GET_SB_HAS_STRUCT_VFSMOUNT
 289                  LINUX_STATFS_TAKES_DENTRY
 290                  LINUX_REFRIGERATOR
 291                  LINUX_HAVE_TRY_TO_FREEZE
 292                  LINUX_LINUX_KEYRING_SUPPORT
 293                  LINUX_KEY_ALLOC_NEEDS_STRUCT_TASK
 294                  LINUX_KEY_ALLOC_NEEDS_CRED
 295                  LINUX_INIT_WORK_HAS_DATA
 296                  LINUX_REGISTER_SYSCTL_TABLE_NOFLAG
 297                  LINUX_HAVE_DCACHE_LOCK
 298                  LINUX_D_COUNT_IS_INT
 299                  LINUX_IOP_GETATTR_TAKES_PATH_STRUCT
 300                  LINUX_IOP_MKDIR_TAKES_UMODE_T
 301                  LINUX_IOP_CREATE_TAKES_UMODE_T
 302                  LINUX_EXPORT_OP_ENCODE_FH_TAKES_INODES
 303                  LINUX_KMAP_ATOMIC_TAKES_NO_KM_TYPE
 304                  LINUX_DENTRY_OPEN_TAKES_PATH
 305                  LINUX_D_ALIAS_IS_HLIST
 306                  LINUX_HLIST_ITERATOR_NO_NODE
 307                  LINUX_IOP_I_CREATE_TAKES_BOOL
 308                  LINUX_DOP_D_REVALIDATE_TAKES_UNSIGNED
 309                  LINUX_IOP_LOOKUP_TAKES_UNSIGNED
 310                  LINUX_D_INVALIDATE_IS_VOID
 311                  LINUX_KERNEL_READ_OFFSET_IS_LAST
 312
 313                  dnl If we are guaranteed that keyrings will work - that is
 314                  dnl  a) The kernel has keyrings enabled
 315                  dnl  b) The code is new enough to give us a key_type_keyring
 316                  dnl then we just disable syscall probing unless we've been
 317                  dnl told otherwise
 318
 319                  AS_IF([test "$enable_linux_syscall_probing" = "maybe"],
 320                    [AS_IF([test "$ac_cv_linux_keyring_support" = "yes" -a "$ac_cv_linux_exports_key_type_keyring" = "yes"],
 321                           [enable_linux_syscall_probing="no"],
 322                           [enable_linux_syscall_probing="yes"])
 323                  ])
 324
 325                  dnl Syscall probing needs a few tests of its own, and just
 326                  dnl won't work if the kernel doesn't export init_mm
 327                  AS_IF([test "$enable_linux_syscall_probing" = "yes"], [
 328                    LINUX_EXPORTS_INIT_MM
 329                    AS_IF([test "$ac_cv_linux_exports_init_mm" = "no"], [
 330                      AC_MSG_ERROR(
 331                        [Can't do syscall probing without exported init_mm])
 332                    ])
 333                    LINUX_EXPORTS_SYS_CHDIR
 334                    LINUX_EXPORTS_SYS_OPEN
 335                    AC_DEFINE(ENABLE_LINUX_SYSCALL_PROBING, 1,
 336                              [define to enable syscall table probes])
 337                  ])
 338
 339                  dnl Packaging and SMP build
 340                  if test "x$with_linux_kernel_packaging" != "xyes" ; then
 341                    LINUX_WHICH_MODULES
 342                  else
 343                    AC_SUBST(MPS,'SP')
 344                  fi
 345
 346                  dnl Syscall probing
 347                  if test "x$ac_cv_linux_config_modversions" = "xno" -o $AFS_SYSKVERS -ge 26; then
 348                    AS_IF([test "$enable_linux_syscall_probing" = "yes"], [
 349                      AC_MSG_WARN([Cannot determine sys_call_table status. assuming it isn't exported])
 350                    ])
 351                    ac_cv_linux_exports_sys_call_table=no
 352                    if test -f "$LINUX_KERNEL_PATH/include/asm/ia32_unistd.h"; then
 353                      ac_cv_linux_exports_ia32_sys_call_table=yes
 354                    fi
 355                  else
 356                    LINUX_EXPORTS_KALLSYMS_ADDRESS
 357                    LINUX_EXPORTS_KALLSYMS_SYMBOL
 358                    LINUX_EXPORTS_SYS_CALL_TABLE
 359                    LINUX_EXPORTS_IA32_SYS_CALL_TABLE
 360                    if test "x$ac_cv_linux_exports_sys_call_table" = "xno"; then
 361                          linux_syscall_method=none
 362                          if test "x$ac_cv_linux_exports_init_mm" = "xyes"; then
 363                             linux_syscall_method=scan
 364                             if test "x$ac_cv_linux_exports_kallsyms_address" = "xyes"; then
 365                                linux_syscall_method=scan_with_kallsyms_address
 366                             fi
 367                          fi
 368                          if test "x$ac_cv_linux_exports_kallsyms_symbol" = "xyes"; then
 369                             linux_syscall_method=kallsyms_symbol
 370                          fi
 371                          if test "x$linux_syscall_method" = "xnone"; then
 372                             AC_MSG_WARN([no available sys_call_table access method -- guessing scan])
 373                             linux_syscall_method=scan
 374                          fi
 375                    fi
 376                  fi
 377                  if test -f "$LINUX_KERNEL_PATH/include/linux/in_systm.h"; then
 378                   AC_DEFINE(HAVE_IN_SYSTM_H, 1, [define if you have in_systm.h header file])
 379                  fi
 380                  if test -f "$LINUX_KERNEL_PATH/include/linux/mm_inline.h"; then
 381                   AC_DEFINE(HAVE_MM_INLINE_H, 1, [define if you have mm_inline.h header file])
 382                  fi
 383                  if test "x$ac_cv_linux_func_page_get_link" = "xyes" -o "x$ac_cv_linux_func_i_put_link_takes_cookie" = "xyes"; then
 384                   AC_DEFINE(USABLE_KERNEL_PAGE_SYMLINK_CACHE, 1, [define if your kernel has a usable symlink cache API])
 385                  else
 386                   AC_MSG_WARN([your kernel does not have a usable symlink cache API])
 387                  fi
 388                  if test "x$ac_cv_linux_func_page_get_link" != "xyes" -a "x$ac_cv_linux_struct_inode_operations_has_get_link" = "xyes"; then
 389                         AC_MSG_ERROR([Your kernel does not use follow_link - not supported without symlink cache API])
 390                         exit 1
 391                  fi
 392                 :
 393                 fi
 394                 if test "x$enable_linux_d_splice_alias_extra_iput" = xyes; then
 395                     AC_DEFINE(D_SPLICE_ALIAS_LEAK_ON_ERROR, 1, [for internal use])
 396                 fi
 397 dnl Linux-only, but just enable always.
 398                 AC_DEFINE(AFS_CACHE_BYPASS, 1, [define to activate cache bypassing Unix client])
 399 esac
 400 ])