config/kernel-shrink.m4

   1 dnl #
   2 dnl # 3.1 API change
   3 dnl # The super_block structure now stores a per-filesystem shrinker.
   4 dnl # This interface is preferable because it can be used to specifically
   5 dnl # target only the zfs filesystem for pruning.
   6 dnl #
   7 AC_DEFUN([ZFS_AC_KERNEL_SHRINK], [
   8         AC_MSG_CHECKING([whether super_block has s_shrink])
   9         ZFS_LINUX_TRY_COMPILE([
  10                 #include <linux/fs.h>
  11
  12                 int shrink(struct shrinker *s, struct shrink_control *sc)
  13                     { return 0; }
  14
  15                 static const struct super_block
  16                     sb __attribute__ ((unused)) = {
  17                         .s_shrink.shrink = shrink,
  18                         .s_shrink.seeks = DEFAULT_SEEKS,
  19                         .s_shrink.batch = 0,
  20                 };
  21         ],[
  22         ],[
  23                 AC_MSG_RESULT(yes)
  24                 AC_DEFINE(HAVE_SHRINK, 1, [struct super_block has s_shrink])
  25
  26         ],[
  27                 AC_MSG_RESULT(no)
  28         ])
  29 ])
  30
  31 dnl #
  32 dnl # 3.3 API change
  33 dnl # The super_block structure was changed to use an hlist_node instead
  34 dnl # of a list_head for the .s_instance linkage.
  35 dnl #
  36 dnl # This was done in part to resolve a race in the iterate_supers_type()
  37 dnl # function which was introduced in Linux 3.0 kernel.  The iterator
  38 dnl # was supposed to provide a safe way to call an arbitrary function on
  39 dnl # all super blocks of a specific type.  Unfortunately, because a
  40 dnl # list_head was used it was possible for iterate_supers_type() to
  41 dnl # get stuck spinning a super block which was just deactivated.
  42 dnl #
  43 dnl # This can occur because when the list head is removed from the
  44 dnl # fs_supers list it is reinitialized to point to itself.  If the
  45 dnl # iterate_supers_type() function happened to be processing the
  46 dnl # removed list_head it will get stuck spinning on that list_head.
  47 dnl #
  48 dnl # To resolve the issue for existing 3.0 - 3.2 kernels we detect when
  49 dnl # a list_head is used.  Then to prevent the spinning from occurring
  50 dnl # the .next pointer is set to the fs_supers list_head which ensures
  51 dnl # the iterate_supers_type() function will always terminate.
  52 dnl #
  53 AC_DEFUN([ZFS_AC_KERNEL_S_INSTANCES_LIST_HEAD], [
  54         AC_MSG_CHECKING([whether super_block has s_instances list_head])
  55         ZFS_LINUX_TRY_COMPILE([
  56                 #include <linux/fs.h>
  57         ],[
  58                 struct super_block sb __attribute__ ((unused));
  59
  60                 INIT_LIST_HEAD(&sb.s_instances);
  61         ],[
  62                 AC_MSG_RESULT(yes)
  63                 AC_DEFINE(HAVE_S_INSTANCES_LIST_HEAD, 1,
  64                     [struct super_block has s_instances list_head])
  65         ],[
  66                 AC_MSG_RESULT(no)
  67         ])
  68 ])
  69
  70 AC_DEFUN([ZFS_AC_KERNEL_NR_CACHED_OBJECTS], [
  71         AC_MSG_CHECKING([whether sops->nr_cached_objects() exists])
  72         ZFS_LINUX_TRY_COMPILE([
  73                 #include <linux/fs.h>
  74
  75                 int nr_cached_objects(struct super_block *sb) { return 0; }
  76
  77                 static const struct super_operations
  78                     sops __attribute__ ((unused)) = {
  79                         .nr_cached_objects = nr_cached_objects,
  80                 };
  81         ],[
  82         ],[
  83                 AC_MSG_RESULT(yes)
  84                 AC_DEFINE(HAVE_NR_CACHED_OBJECTS, 1,
  85                         [sops->nr_cached_objects() exists])
  86         ],[
  87                 AC_MSG_RESULT(no)
  88         ])
  89 ])
  90
  91 AC_DEFUN([ZFS_AC_KERNEL_FREE_CACHED_OBJECTS], [
  92         AC_MSG_CHECKING([whether sops->free_cached_objects() exists])
  93         ZFS_LINUX_TRY_COMPILE([
  94                 #include <linux/fs.h>
  95
  96                 void free_cached_objects(struct super_block *sb, int x)
  97                     { return; }
  98
  99                 static const struct super_operations
 100                     sops __attribute__ ((unused)) = {
 101                         .free_cached_objects = free_cached_objects,
 102                 };
 103         ],[
 104         ],[
 105                 AC_MSG_RESULT(yes)
 106                 AC_DEFINE(HAVE_FREE_CACHED_OBJECTS, 1,
 107                         [sops->free_cached_objects() exists])
 108         ],[
 109                 AC_MSG_RESULT(no)
 110         ])
 111 ])
 112
 113 dnl #
 114 dnl # 3.12 API change
 115 dnl # The nid member was added to struct shrink_control to support
 116 dnl # NUMA-aware shrinkers.
 117 dnl #
 118 AC_DEFUN([ZFS_AC_KERNEL_SHRINK_CONTROL_HAS_NID], [
 119         AC_MSG_CHECKING([whether shrink_control has nid])
 120         ZFS_LINUX_TRY_COMPILE([
 121                 #include <linux/fs.h>
 122         ],[
 123                 struct shrink_control sc __attribute__ ((unused));
 124                 unsigned long scnidsize __attribute__ ((unused)) =
 125                     sizeof(sc.nid);
 126         ],[
 127                 AC_MSG_RESULT(yes)
 128                 AC_DEFINE(SHRINK_CONTROL_HAS_NID, 1,
 129                     [struct shrink_control has nid])
 130         ],[
 131                 AC_MSG_RESULT(no)
 132         ])
 133 ])