Re: Non-GPL export of invalidate_mmap_range

Daniel Phillips
2004-02-20T05:07:25Z

On Thursday 19 February 2004 14:47, Paul E. McKenney wrote:
> OK, I surrender. I got some private email agreeing with this
> viewpoint. Any dissenters, speak soon, or...

An implementation is going to look something like the patch below.
Unfortunately I don't think there is a way around passing an extra parameter
all the way down the unmap call chain. Doubly unfortunately, this doesn't
give any benefit at all to anybody who doesn't use a clustered filesystem
(which is nearly everybody) while there is a marginal cost. Do you know a
better way? Anyway, this is the price of correct MAP_PRIVATE semantics for
clustered filesystems. At least I have quantified it so we can decide if it's
worth it. (My opinion: correctness is always worth it.)

Regards,

Daniel

--- 2.6.3.clean/include/linux/mm.h 2004-02-17 22:57:13.000000000 -0500
+++ 2.6.3/include/linux/mm.h 2004-02-19 23:18:08.000000000 -0500
@@ -434,9 +434,7 @@
unsigned long size);
int unmap_vmas(struct mmu_gather **tlbp, struct mm_struct *mm,
struct vm_area_struct *start_vma, unsigned long start_addr,
- unsigned long end_addr, unsigned long *nr_accounted);
-void unmap_page_range(struct mmu_gather *tlb, struct vm_area_struct *vma,
- unsigned long address, unsigned long size);
+ unsigned long end_addr, unsigned long *nr_accounted, int zap);
void clear_page_tables(struct mmu_gather *tlb, unsigned long first, int nr);
int copy_page_range(struct mm_struct *dst, struct mm_struct *src,
struct vm_area_struct *vma);
@@ -444,8 +442,7 @@
unsigned long size, pgprot_t prot);

extern void invalidate_mmap_range(struct address_space *mapping,
- loff_t const holebegin,
- loff_t const holelen);
+ loff_t const holebegin, loff_t const holelen, int zap);
extern int vmtruncate(struct inode * inode, loff_t offset);
extern pmd_t *FASTCALL(__pmd_alloc(struct mm_struct *mm, pgd_t *pgd, unsigned long address));
extern pte_t *FASTCALL(pte_alloc_kernel(struct mm_struct *mm, pmd_t *pmd, unsigned long address));
--- 2.6.3.clean/mm/memory.c 2004-02-17 22:57:47.000000000 -0500
+++ 2.6.3/mm/memory.c 2004-02-19 23:48:23.000000000 -0500
@@ -386,7 +386,7 @@

static void
zap_pte_range(struct mmu_gather *tlb, pmd_t * pmd,
- unsigned long address, unsigned long size)
+ unsigned long address, unsigned long size, int zap)
{
unsigned long offset;
pte_t *ptep;
@@ -414,7 +414,7 @@
tlb_remove_tlb_entry(tlb, ptep, address+offset);
if (pfn_valid(pfn)) {
struct page *page = pfn_to_page(pfn);
- if (!PageReserved(page)) {
+ if (!PageReserved(page) && (zap || (page->mapping && !PageSwapCache(page)))) {
if (pte_dirty(pte))
set_page_dirty(page);
if (page->mapping && pte_young(pte) &&
@@ -436,7 +436,7 @@

static void
zap_pmd_range(struct mmu_gather *tlb, pgd_t * dir,
- unsigned long address, unsigned long size)
+ unsigned long address, unsigned long size, int zap)
{
pmd_t * pmd;
unsigned long end;
@@ -453,14 +453,14 @@
if (end > ((address + PGDIR_SIZE) & PGDIR_MASK))
end = ((address + PGDIR_SIZE) & PGDIR_MASK);
do {
- zap_pte_range(tlb, pmd, address, end - address);
- address = (address + PMD_SIZE) & PMD_MASK;
+ zap_pte_range(tlb, pmd, address, end - address, zap);
+ address = (address + PMD_SIZE) & PMD_MASK;
pmd++;
} while (address < end);
}

-void unmap_page_range(struct mmu_gather *tlb, struct vm_area_struct *vma,
- unsigned long address, unsigned long end)
+static void unmap_page_range(struct mmu_gather *tlb, struct vm_area_struct *vma,
+ unsigned long address, unsigned long end, int zap)
{
pgd_t * dir;

@@ -474,7 +474,7 @@
dir = pgd_offset(vma->vm_mm, address);
tlb_start_vma(tlb, vma);
do {
- zap_pmd_range(tlb, dir, address, end - address);
+ zap_pmd_range(tlb, dir, address, end - address, zap);
address = (address + PGDIR_SIZE) & PGDIR_MASK;
dir++;
} while (address && (address < end));
@@ -524,7 +524,7 @@
*/
int 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)
+ unsigned long end_addr, unsigned long *nr_accounted, int zap)
{
unsigned long zap_bytes = ZAP_BLOCK_SIZE;
unsigned long tlb_start = 0; /* For tlb_finish_mmu */
@@ -568,7 +568,7 @@
tlb_start_valid = 1;
}

- unmap_page_range(*tlbp, vma, start, start + block);
+ unmap_page_range(*tlbp, vma, start, start + block, zap);
start += block;
zap_bytes -= block;
if ((long)zap_bytes > 0)
@@ -594,8 +594,8 @@
* @address: starting address of pages to zap
* @size: number of bytes to zap
*/
-void zap_page_range(struct vm_area_struct *vma,
- unsigned long address, unsigned long size)
+void invalidate_page_range(struct vm_area_struct *vma,
+ unsigned long address, unsigned long size, int zap)
{
struct mm_struct *mm = vma->vm_mm;
struct mmu_gather *tlb;
@@ -612,11 +612,17 @@
lru_add_drain();
spin_lock(&mm->page_table_lock);
tlb = tlb_gather_mmu(mm, 0);
- unmap_vmas(&tlb, mm, vma, address, end, &nr_accounted);
+ unmap_vmas(&tlb, mm, vma, address, end, &nr_accounted, zap);
tlb_finish_mmu(tlb, address, end);
spin_unlock(&mm->page_table_lock);
}

+void zap_page_range(struct vm_area_struct *vma,
+ unsigned long address, unsigned long size)
+{
+ invalidate_page_range(vma, address, size, 1);
+}
+
/*
* Do a quick page-table lookup for a single page.
* mm->page_table_lock must be held.
@@ -1095,9 +1101,9 @@
continue; /* Mapping disjoint from hole. */
zba = (hba <= vba) ? vba : hba;
zea = (vea <= hea) ? vea : hea;
- zap_page_range(vp,
+ invalidate_page_range(vp,
((zba - vba) << PAGE_SHIFT) + vp->vm_start,
- (zea - zba + 1) << PAGE_SHIFT);
+ (zea - zba + 1) << PAGE_SHIFT, 1);
}
}

@@ -1116,7 +1122,7 @@
* end of the file.
*/
void invalidate_mmap_range(struct address_space *mapping,
- loff_t const holebegin, loff_t const holelen)
+ loff_t const holebegin, loff_t const holelen, int zap)
{
unsigned long hba = holebegin >> PAGE_SHIFT;
unsigned long hlen = (holelen + PAGE_SIZE - 1) >> PAGE_SHIFT;
@@ -1156,7 +1162,7 @@
if (inode->i_size < offset)
goto do_expand;
i_size_write(inode, offset);
- invalidate_mmap_range(mapping, offset + PAGE_SIZE - 1, 0);
+ invalidate_mmap_range(mapping, offset + PAGE_SIZE - 1, 0, 1);
truncate_inode_pages(mapping, offset);
goto out_truncate;

--- 2.6.3.clean/mm/mmap.c 2004-02-17 22:58:32.000000000 -0500
+++ 2.6.3/mm/mmap.c 2004-02-19 22:46:01.000000000 -0500
@@ -1134,7 +1134,7 @@

lru_add_drain();
tlb = tlb_gather_mmu(mm, 0);
- unmap_vmas(&tlb, mm, vma, start, end, &nr_accounted);
+ unmap_vmas(&tlb, mm, vma, start, end, &nr_accounted, 1);
vm_unacct_memory(nr_accounted);

if (is_hugepage_only_range(start, end - start))
@@ -1436,7 +1436,7 @@
flush_cache_mm(mm);
/* Use ~0UL here to ensure all VMAs in the mm are unmapped */
mm->map_count -= unmap_vmas(&tlb, mm, mm->mmap, 0,
- ~0UL, &nr_accounted);
+ ~0UL, &nr_accounted, 1);
vm_unacct_memory(nr_accounted);
BUG_ON(mm->map_count); /* This is just debugging */
clear_page_tables(tlb, FIRST_USER_PGD_NR, USER_PTRS_PER_PGD);