Remove global memory variables

Platforms such as Illumos and FreeBSD have historically provided
global variables which summerize the memory state of a system.
Linux on the otherhand doesn't expose any of this information
to kernel modules and uses entirely different mechanisms for
memory management.

In order to simplify the original ZFS port to Linux these global
variables were emulated by the SPL for the benefit of ZFS.  As ZoL
has matured over the years it has moved steadily away from these
interfaces and now no longer depends on them at all.

Therefore, this patch completely removes the global variables
availrmem, minfree, desfree, lotsfree, needfree, swapfs_minfree,
and swapfs_reserve.  This greatly simplifies the memory management
code and eliminates a common area of confusion.

Signed-off-by: Brian Behlendorf <[email protected]>

2 files changed, 5 insertions, 84 deletions

diff --git a/include/linux/mm_compat.h b/include/linux/mm_compat.h
index 37c9b0875..97e5af012 100644
--- a/include/linux/mm_compat.h
+++ b/include/linux/mm_compat.h
@@ -28,22 +28,6 @@
 #include <linux/mm.h>
 #include <linux/fs.h>
 
-/*
- * Linux 2.6.31 API Change.
- * Individual pages_{min,low,high} moved in to watermark array.
- */
-#ifndef min_wmark_pages
-#define min_wmark_pages(z)	(z->pages_min)
-#endif
-
-#ifndef low_wmark_pages
-#define low_wmark_pages(z)	(z->pages_low)
-#endif
-
-#ifndef high_wmark_pages
-#define high_wmark_pages(z)	(z->pages_high)
-#endif
-
 #if !defined(HAVE_SHRINK_CONTROL_STRUCT)
 struct shrink_control {
 	gfp_t gfp_mask;
diff --git a/include/sys/vmsystm.h b/include/sys/vmsystm.h
index ee3ed6d72..c6b86866b 100644
--- a/include/sys/vmsystm.h
+++ b/include/sys/vmsystm.h
@@ -33,31 +33,14 @@
 #include <sys/types.h>
 #include <asm/uaccess.h>
 
-/* These values are loosely coupled with the VM page reclaim.
- * Linux uses its own heuristics to trigger page reclamation, and
- * because those interface are difficult to interface with.  These
- * values should only be considered as a rough guide to the system
- * memory state and not as direct evidence that page reclamation.
- * is or is not currently in progress.
- */
-#define membar_producer()		smp_wmb()
-
-#define physmem				totalram_pages
-#define freemem				nr_free_pages()
-#define availrmem			spl_kmem_availrmem()
-
-extern pgcnt_t minfree;			/* Sum of zone->pages_min */
-extern pgcnt_t desfree;			/* Sum of zone->pages_low */
-extern pgcnt_t lotsfree;		/* Sum of zone->pages_high */
-extern pgcnt_t needfree;		/* Always 0 unused in new Solaris */
-extern pgcnt_t swapfs_minfree;		/* Solaris default value */
-extern pgcnt_t swapfs_reserve;		/* Solaris default value */
+#define	membar_producer()		smp_wmb()
+#define	physmem				totalram_pages
+#define	freemem				nr_free_pages()
 
 extern vmem_t *heap_arena;		/* primary kernel heap arena */
 extern vmem_t *zio_alloc_arena;		/* arena for zio caches */
 extern vmem_t *zio_arena;		/* arena for allocating zio memory */
 
-extern pgcnt_t spl_kmem_availrmem(void);
 extern size_t vmem_size(vmem_t *vmp, int typemask);
 
 #define	VMEM_ALLOC	0x01
@@ -67,54 +50,8 @@ extern size_t vmem_size(vmem_t *vmp, int typemask);
 #define	VMALLOC_TOTAL	(VMALLOC_END - VMALLOC_START)
 #endif
 
-#ifdef HAVE_PGDAT_HELPERS
-/* Source linux/mm/mmzone.c */
-# ifndef HAVE_FIRST_ONLINE_PGDAT
-typedef struct pglist_data *(*first_online_pgdat_t)(void);
-extern first_online_pgdat_t first_online_pgdat_fn;
-# define first_online_pgdat()	first_online_pgdat_fn()
-# endif /* HAVE_FIRST_ONLINE_PGDAT */
-
-# ifndef HAVE_NEXT_ONLINE_PGDAT
-typedef struct pglist_data *(*next_online_pgdat_t)(struct pglist_data *);
-extern next_online_pgdat_t next_online_pgdat_fn;
-# define next_online_pgdat(pgd)	next_online_pgdat_fn(pgd)
-# endif /* HAVE_NEXT_ONLINE_PGDAT */
-
-# ifndef HAVE_NEXT_ZONE
-typedef struct zone *(*next_zone_t)(struct zone *);
-extern next_zone_t next_zone_fn;
-# define next_zone(zone)	next_zone_fn(zone)
-# endif /* HAVE_NEXT_ZONE */
-
-#else /* HAVE_PGDAT_HELPERS */
-
-# ifndef HAVE_PGDAT_LIST
-extern struct pglist_data *pgdat_list_addr;
-# define pgdat_list		pgdat_list_addr
-# endif /* HAVE_PGDAT_LIST */
-
-#endif /* HAVE_PGDAT_HELPERS */
-
-/* Source linux/mm/vmstat.c */
-#if defined(NEED_GET_ZONE_COUNTS) && !defined(HAVE_GET_ZONE_COUNTS)
-typedef void (*get_zone_counts_t)(unsigned long *, unsigned long *,
-				  unsigned long *);
-extern get_zone_counts_t get_zone_counts_fn;
-# define get_zone_counts(a,i,f)	get_zone_counts_fn(a,i,f)
-#endif /* NEED_GET_ZONE_COUNTS && !HAVE_GET_ZONE_COUNTS */
-
-typedef enum spl_zone_stat_item {
-	SPL_NR_FREE_PAGES,
-	SPL_NR_INACTIVE,
-	SPL_NR_ACTIVE,
-	SPL_NR_ZONE_STAT_ITEMS
-} spl_zone_stat_item_t;
-
-extern unsigned long spl_global_page_state(spl_zone_stat_item_t);
-
-#define xcopyin(from, to, size)		copy_from_user(to, from, size)
-#define xcopyout(from, to, size)	copy_to_user(to, from, size)
+#define	xcopyin(from, to, size)		copy_from_user(to, from, size)
+#define	xcopyout(from, to, size)	copy_to_user(to, from, size)
 
 static __inline__ int
 copyin(const void *from, void *to, size_t len)