[PATCH] freepgt: remove MM_VM_SIZE(mm)

There's only one usage of MM_VM_SIZE(mm) left, and it's a troublesome macro
because mm doesn't contain the (32-bit emulation?) info needed. But it too is
only needed because we ignore the end from the vma list.

We could make flush_pgtables return that end, or unmap_vmas. Choose the
latter, since it's a natural fit with unmap_mapping_range_vma needing to know
its restart addr. This does make more than minimal change, but if unmap_vmas
had returned the end before, this is how we'd have done it, rather than
storing the break_addr in zap_details.

unmap_vmas used to return count of vmas scanned, but that's just debug which
hasn't been useful in a while; and if we want the map_count 0 on exit check
back, it can easily come from the final remove_vm_struct loop.

Signed-off-by: Hugh Dickins <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

include/asm-ia64/processor.h

···
 #define TASK_SIZE		(current->thread.task_size)
 
 /*
- * MM_VM_SIZE(mm) gives the maximum address (plus 1) which may contain a mapping for
- * address-space MM.  Note that with 32-bit tasks, this is still DEFAULT_TASK_SIZE,
- * because the kernel may have installed helper-mappings above TASK_SIZE.  For example,
- * for x86 emulation, the LDT and GDT are mapped above TASK_SIZE.
- */
-#define MM_VM_SIZE(mm)		DEFAULT_TASK_SIZE
-
-/*
  * This decides where the kernel will search for a free chunk of vm
  * space during mmap's.
  */

include/asm-ppc64/processor.h

···
 #define TASK_SIZE (test_thread_flag(TIF_32BIT) ? \
 		TASK_SIZE_USER32 : TASK_SIZE_USER64)
 
-/* We can't actually tell the TASK_SIZE given just the mm, but default
- * to the 64-bit case to make sure that enough gets cleaned up. */
-#define MM_VM_SIZE(mm)	TASK_SIZE_USER64
-
 /* This decides where the kernel will search for a free chunk of vm
  * space during mmap's.
  */

include/asm-s390/processor.h

···
 
 #endif /* __s390x__ */
 
-#define MM_VM_SIZE(mm)		DEFAULT_TASK_SIZE
-
 #define HAVE_ARCH_PICK_MMAP_LAYOUT
 
 typedef struct {

include/linux/mm.h

···
 #include <asm/processor.h>
 #include <asm/atomic.h>
 
-#ifndef MM_VM_SIZE
-#define MM_VM_SIZE(mm)	((TASK_SIZE + PGDIR_SIZE - 1) & PGDIR_MASK)
-#endif
-
 #define nth_page(page,n) pfn_to_page(page_to_pfn((page)) + (n))
 
 /*
···
 	pgoff_t	first_index;			/* Lowest page->index to unmap */
 	pgoff_t last_index;			/* Highest page->index to unmap */
 	spinlock_t *i_mmap_lock;		/* For unmap_mapping_range: */
-	unsigned long break_addr;		/* Where unmap_vmas stopped */
 	unsigned long truncate_count;		/* Compare vm_truncate_count */
 };
 
-void zap_page_range(struct vm_area_struct *vma, unsigned long address,
+unsigned long zap_page_range(struct vm_area_struct *vma, unsigned long address,
 		unsigned long size, struct zap_details *);
-int unmap_vmas(struct mmu_gather **tlbp, struct mm_struct *mm,
+unsigned long unmap_vmas(struct mmu_gather **tlb, struct mm_struct *mm,
 		struct vm_area_struct *start_vma, unsigned long start_addr,
 		unsigned long end_addr, unsigned long *nr_accounted,
 		struct zap_details *);

mm/memory.c

···
  * @nr_accounted: Place number of unmapped pages in vm-accountable vma's here
  * @details: details of nonlinear truncation or shared cache invalidation
  *
- * Returns the number of vma's which were covered by the unmapping.
+ * Returns the end address of the unmapping (restart addr if interrupted).
  *
  * Unmap all pages in the vma list.  Called under page_table_lock.
  *
···
  * ensure that any thus-far unmapped pages are flushed before unmap_vmas()
  * drops the lock and schedules.
  */
-int unmap_vmas(struct mmu_gather **tlbp, struct mm_struct *mm,
+unsigned long unmap_vmas(struct mmu_gather **tlbp, struct mm_struct *mm,
 		struct vm_area_struct *vma, unsigned long start_addr,
 		unsigned long end_addr, unsigned long *nr_accounted,
 		struct zap_details *details)
···
 	unsigned long zap_bytes = ZAP_BLOCK_SIZE;
 	unsigned long tlb_start = 0;	/* For tlb_finish_mmu */
 	int tlb_start_valid = 0;
-	int ret = 0;
+	unsigned long start = start_addr;
 	spinlock_t *i_mmap_lock = details? details->i_mmap_lock: NULL;
 	int fullmm = tlb_is_full_mm(*tlbp);
 
 	for ( ; vma && vma->vm_start < end_addr; vma = vma->vm_next) {
-		unsigned long start;
 		unsigned long end;
 
 		start = max(vma->vm_start, start_addr);
···
 		if (vma->vm_flags & VM_ACCOUNT)
 			*nr_accounted += (end - start) >> PAGE_SHIFT;
 
-		ret++;
 		while (start != end) {
 			unsigned long block;
 
···
 				if (i_mmap_lock) {
 					/* must reset count of rss freed */
 					*tlbp = tlb_gather_mmu(mm, fullmm);
-					details->break_addr = start;
 					goto out;
 				}
 				spin_unlock(&mm->page_table_lock);
···
 		}
 	}
 out:
-	return ret;
+	return start;	/* which is now the end (or restart) address */
 }
 
 /**
···
  * @size: number of bytes to zap
  * @details: details of nonlinear truncation or shared cache invalidation
  */
-void zap_page_range(struct vm_area_struct *vma, unsigned long address,
+unsigned long zap_page_range(struct vm_area_struct *vma, unsigned long address,
 		unsigned long size, struct zap_details *details)
 {
 	struct mm_struct *mm = vma->vm_mm;
···
 
 	if (is_vm_hugetlb_page(vma)) {
 		zap_hugepage_range(vma, address, size);
-		return;
+		return end;
 	}
 
 	lru_add_drain();
 	spin_lock(&mm->page_table_lock);
 	tlb = tlb_gather_mmu(mm, 0);
-	unmap_vmas(&tlb, mm, vma, address, end, &nr_accounted, details);
+	end = unmap_vmas(&tlb, mm, vma, address, end, &nr_accounted, details);
 	tlb_finish_mmu(tlb, address, end);
 	spin_unlock(&mm->page_table_lock);
+	return end;
 }
 
 /*
···
  * i_mmap_lock.
  *
  * In order to make forward progress despite repeatedly restarting some
- * large vma, note the break_addr set by unmap_vmas when it breaks out:
+ * large vma, note the restart_addr from unmap_vmas when it breaks out:
  * and restart from that address when we reach that vma again.  It might
  * have been split or merged, shrunk or extended, but never shifted: so
  * restart_addr remains valid so long as it remains in the vma's range.
···
 		}
 	}
 
-	details->break_addr = end_addr;
-	zap_page_range(vma, start_addr, end_addr - start_addr, details);
+	restart_addr = zap_page_range(vma, start_addr,
+					end_addr - start_addr, details);
 
 	/*
 	 * We cannot rely on the break test in unmap_vmas:
···
 	need_break = need_resched() ||
 			need_lockbreak(details->i_mmap_lock);
 
-	if (details->break_addr >= end_addr) {
+	if (restart_addr >= end_addr) {
 		/* We have now completed this vma: mark it so */
 		vma->vm_truncate_count = details->truncate_count;
 		if (!need_break)
 			return 0;
 	} else {
 		/* Note restart_addr in vma's truncate_count field */
-		vma->vm_truncate_count = details->break_addr;
+		vma->vm_truncate_count = restart_addr;
 		if (!need_break)
 			goto again;
 	}

mm/mmap.c

···
 	struct mmu_gather *tlb;
 	struct vm_area_struct *vma = mm->mmap;
 	unsigned long nr_accounted = 0;
+	unsigned long end;
 
 	lru_add_drain();
 
···
 	flush_cache_mm(mm);
 	tlb = tlb_gather_mmu(mm, 1);
 	/* Use -1 here to ensure all VMAs in the mm are unmapped */
-	mm->map_count -= unmap_vmas(&tlb, mm, vma, 0, -1, &nr_accounted, NULL);
+	end = unmap_vmas(&tlb, mm, vma, 0, -1, &nr_accounted, NULL);
 	vm_unacct_memory(nr_accounted);
 	free_pgtables(&tlb, vma, 0, 0);
-	tlb_finish_mmu(tlb, 0, MM_VM_SIZE(mm));
+	tlb_finish_mmu(tlb, 0, end);
 
 	mm->mmap = mm->mmap_cache = NULL;
 	mm->mm_rb = RB_ROOT;
···
 		vma = next;
 	}
 
-	BUG_ON(mm->map_count);	/* This is just debugging */
 	BUG_ON(mm->nr_ptes);	/* This is just debugging */
 }