Linux 5.9 compat: NR_SLAB_RECLAIMABLE

Commit dcdc12e added compatibility code to treat NR_SLAB_RECLAIMABLE_B
as if it were the same as NR_SLAB_RECLAIMABLE.  However, the new value
is in bytes while the old value was in pages which means they are not
interchangeable.

The only place the reclaimable slab size is used is as a component of
the calculation done by arc_free_memory().  This function returns the
amount of memory the ARC considers to be free or reclaimable at little
cost.  Rather than switch to a new interface to get this value it has
been removed it from the calculation.  It is normally a minor component
compared to the number of inactive or free pages, and removing it
aligns the behavior with the FreeBSD version of arc_free_memory().

Reviewed-by: Matthew Ahrens <[email protected]>
Reviewed-by: Coleman Kane <[email protected]>
Signed-off-by: Brian Behlendorf <[email protected]>
Closes #10834 

4 files changed, 1 insertions, 47 deletions

diff --git a/config/kernel-global_page_state.m4 b/config/kernel-global_page_state.m4
index 75043f40b..badb5e5d2 100644
--- a/config/kernel-global_page_state.m4
+++ b/config/kernel-global_page_state.m4
@@ -94,9 +94,6 @@ AC_DEFUN([ZFS_AC_KERNEL_GLOBAL_ZONE_PAGE_STATE_SANITY], [
 	ZFS_AC_KERNEL_GLOBAL_PAGE_STATE_ENUM_CHECK([NR_FILE_PAGES])
 	ZFS_AC_KERNEL_GLOBAL_PAGE_STATE_ENUM_CHECK([NR_INACTIVE_ANON])
 	ZFS_AC_KERNEL_GLOBAL_PAGE_STATE_ENUM_CHECK([NR_INACTIVE_FILE])
-    AS_IF([test -z "$ZFS_ENUM_NODE_STAT_ITEM_NR_SLAB_RECLAIMABLE_B"],[
-	    ZFS_AC_KERNEL_GLOBAL_PAGE_STATE_ENUM_CHECK([NR_SLAB_RECLAIMABLE])
-    ])
 
 	AC_MSG_RESULT(yes)
 ])
@@ -119,10 +116,6 @@ AC_DEFUN([ZFS_AC_KERNEL_GLOBAL_PAGE_STATE], [
 	    [node_stat_item], [$LINUX/include/linux/mmzone.h])
 	ZFS_AC_KERNEL_ENUM_MEMBER([NR_INACTIVE_FILE],
 	    [node_stat_item], [$LINUX/include/linux/mmzone.h])
-	ZFS_AC_KERNEL_ENUM_MEMBER([NR_SLAB_RECLAIMABLE],
-	    [node_stat_item], [$LINUX/include/linux/mmzone.h])
-	ZFS_AC_KERNEL_ENUM_MEMBER([NR_SLAB_RECLAIMABLE_B],
-	    [node_stat_item], [$LINUX/include/linux/mmzone.h])
 
 	ZFS_AC_KERNEL_ENUM_MEMBER([NR_FILE_PAGES],
 	    [zone_stat_item], [$LINUX/include/linux/mmzone.h])
@@ -130,8 +123,6 @@ AC_DEFUN([ZFS_AC_KERNEL_GLOBAL_PAGE_STATE], [
 	    [zone_stat_item], [$LINUX/include/linux/mmzone.h])
 	ZFS_AC_KERNEL_ENUM_MEMBER([NR_INACTIVE_FILE],
 	    [zone_stat_item], [$LINUX/include/linux/mmzone.h])
-	ZFS_AC_KERNEL_ENUM_MEMBER([NR_SLAB_RECLAIMABLE],
-	    [zone_stat_item], [$LINUX/include/linux/mmzone.h])
 
 	ZFS_AC_KERNEL_GLOBAL_ZONE_PAGE_STATE_SANITY
 ])
diff --git a/include/os/linux/kernel/linux/page_compat.h b/include/os/linux/kernel/linux/page_compat.h
index 8ad04f9bb..bd6cb398b 100644
--- a/include/os/linux/kernel/linux/page_compat.h
+++ b/include/os/linux/kernel/linux/page_compat.h
@@ -35,16 +35,6 @@
 #else
 #define	nr_inactive_file_pages() global_zone_page_state(NR_INACTIVE_FILE)
 #endif
-#if	defined(ZFS_ENUM_NODE_STAT_ITEM_NR_SLAB_RECLAIMABLE_B)
-#define	nr_slab_reclaimable_pages() \
-	global_node_page_state(NR_SLAB_RECLAIMABLE_B)
-#else
-#if	defined(ZFS_ENUM_NODE_STAT_ITEM_NR_SLAB_RECLAIMABLE)
-#define	nr_slab_reclaimable_pages() global_node_page_state(NR_SLAB_RECLAIMABLE)
-#else
-#define	nr_slab_reclaimable_pages() global_zone_page_state(NR_SLAB_RECLAIMABLE)
-#endif
-#endif
 
 #elif	defined(ZFS_GLOBAL_NODE_PAGE_STATE)
 
@@ -64,16 +54,6 @@
 #else
 #define	nr_inactive_file_pages() global_page_state(NR_INACTIVE_FILE)
 #endif
-#if	defined(ZFS_ENUM_NODE_STAT_ITEM_NR_SLAB_RECLAIMABLE_B)
-#define	nr_slab_reclaimable_pages() \
-	global_node_page_state(NR_SLAB_RECLAIMABLE_B)
-#else
-#if	defined(ZFS_ENUM_NODE_STAT_ITEM_NR_SLAB_RECLAIMABLE)
-#define	nr_slab_reclaimable_pages() global_node_page_state(NR_SLAB_RECLAIMABLE)
-#else
-#define	nr_slab_reclaimable_pages() global_page_state(NR_SLAB_RECLAIMABLE)
-#endif
-#endif
 
 #else
 
@@ -81,11 +61,6 @@
 #define	nr_file_pages()			global_page_state(NR_FILE_PAGES)
 #define	nr_inactive_anon_pages()	global_page_state(NR_INACTIVE_ANON)
 #define	nr_inactive_file_pages()	global_page_state(NR_INACTIVE_FILE)
-#ifdef ZFS_ENUM_NODE_STAT_ITEM_NR_SLAB_RECLAIMABLE_B
-#define	nr_slab_reclaimable_pages()	global_page_state(NR_SLAB_RECLAIMABLE_B)
-#else
-#define	nr_slab_reclaimable_pages()	global_page_state(NR_SLAB_RECLAIMABLE)
-#endif /* ZFS_ENUM_NODE_STAT_ITEM_NR_SLAB_RECLAIMABLE_B */
 
 #endif /* ZFS_GLOBAL_ZONE_PAGE_STATE */
 
diff --git a/include/os/linux/spl/sys/vmsystm.h b/include/os/linux/spl/sys/vmsystm.h
index 705339486..8783231dc 100644
--- a/include/os/linux/spl/sys/vmsystm.h
+++ b/include/os/linux/spl/sys/vmsystm.h
@@ -47,17 +47,6 @@
 
 #define	membar_producer()		smp_wmb()
 #define	physmem				zfs_totalram_pages
-#ifdef ZFS_ENUM_NODE_STAT_ITEM_NR_SLAB_RECLAIMABLE_B
-#define	freemem			(nr_free_pages() + \
-				global_page_state(NR_INACTIVE_FILE) + \
-				global_page_state(NR_INACTIVE_ANON) + \
-				global_page_state(NR_SLAB_RECLAIMABLE_B))
-#else
-#define	freemem			(nr_free_pages() + \
-				global_page_state(NR_INACTIVE_FILE) + \
-				global_page_state(NR_INACTIVE_ANON) + \
-				global_page_state(NR_SLAB_RECLAIMABLE))
-#endif /* ZFS_ENUM_NODE_STAT_ITEM_NR_SLAB_RECLAIMABLE_B */
 
 #define	xcopyin(from, to, size)		copy_from_user(to, from, size)
 #define	xcopyout(from, to, size)	copy_to_user(to, from, size)
diff --git a/module/os/linux/zfs/arc_os.c b/module/os/linux/zfs/arc_os.c
index 92f9bae8c..792c75d46 100644
--- a/module/os/linux/zfs/arc_os.c
+++ b/module/os/linux/zfs/arc_os.c
@@ -113,8 +113,7 @@ arc_free_memory(void)
 	return (ptob(si.freeram - si.freehigh));
 #else
 	return (ptob(nr_free_pages() +
-	    nr_inactive_file_pages() +
-	    nr_slab_reclaimable_pages()));
+	    nr_inactive_file_pages()));
 #endif /* CONFIG_HIGHMEM */
 }