Fix free memory calculation on v3.14+

Provide infrastructure to auto-configure to enum and API changes in the
global page stats used for our free memory calculations.

arc_free_memory has been broken since an API change in Linux v3.14:

2016-07-28 v4.8 599d0c95 mm, vmscan: move LRU lists to node
2016-07-28 v4.8 75ef7184 mm, vmstat: add infrastructure for per-node
  vmstats

These commits moved some of global_page_state() into
global_node_page_state(). The API change was particularly egregious as,
instead of breaking the old code, it silently did the wrong thing and we
continued using global_page_state() where we should have been using
global_node_page_state(), thus indexing into the wrong array via
NR_SLAB_RECLAIMABLE et al.

There have been further API changes along the way:

2017-07-06 v4.13 385386cf mm: vmstat: move slab statistics from zone to
  node counters
2017-09-06 v4.14 c41f012a mm: rename global_page_state to
  global_zone_page_state

...and various (incomplete, as it turns out) attempts to accomodate
these changes in ZoL:

2017-08-24 2209e409 Linux 4.8+ compatibility fix for vm stats
2017-09-16 787acae0 Linux 3.14 compat: IO acct, global_page_state, etc
2017-09-19 661907e6 Linux 4.14 compat: IO acct, global_page_state, etc

The config infrastructure provided here resolves these issues going back
to the original API change in v3.14 and is robust against further Linux
changes in this area.

Reviewed-by: Giuseppe Di Natale <[email protected]>
Reviewed-by: Brian Behlendorf <[email protected]>
Reviewed-by: George Melikov <[email protected]>
Signed-off-by: Chris Dunlop <[email protected]>
Closes #7170 

1 files changed, 0 insertions, 22 deletions

diff --git a/config/kernel-vm_node_stat.m4 b/config/kernel-vm_node_stat.m4
deleted file mode 100644
index 5dcd9d827..000000000
--- a/config/kernel-vm_node_stat.m4
+++ /dev/null
@@ -1,22 +0,0 @@
-dnl #
-dnl # 4.8 API change
-dnl # kernel vm counters change
-dnl #
-AC_DEFUN([ZFS_AC_KERNEL_VM_NODE_STAT], [
-	AC_MSG_CHECKING([whether to use vm_node_stat based fn's])
-	ZFS_LINUX_TRY_COMPILE([
-		#include <linux/mm.h>
-		#include <linux/vmstat.h>
-	],[
-			int a __attribute__ ((unused)) = NR_VM_NODE_STAT_ITEMS;
-			long x __attribute__ ((unused)) =
-				atomic_long_read(&vm_node_stat[0]);
-			(void) global_node_page_state(0);
-	],[
-		AC_MSG_RESULT(yes)
-		AC_DEFINE(ZFS_GLOBAL_NODE_PAGE_STATE, 1,
-			[using global_node_page_state()])
-	],[
-		AC_MSG_RESULT(no)
-	])
-])