[PATCH] mm: mremap correct rmap accounting
Nick Piggin points out that page accounting on MIPS multiple ZERO_PAGEs
is not maintained by its move_pte, and could lead to freeing a ZERO_PAGE.
Instead of complicating that move_pte, just forget the minor optimization
when mremapping, and change the one thing which needed it for correctness
- filemap_xip use ZERO_PAGE(0) throughout instead of according to address.
[ "There is no block device driver one could use for XIP on mips
platforms" - Carsten Otte ]
Signed-off-by: Hugh Dickins <hugh@veritas.com>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Cc: Andrew Morton <akpm@osdl.org>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Carsten Otte <cotte@de.ibm.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/include/asm-mips/pgtable.h b/include/asm-mips/pgtable.h
index f2e1325..3fcfd79 100644
--- a/include/asm-mips/pgtable.h
+++ b/include/asm-mips/pgtable.h
@@ -69,16 +69,6 @@
#define ZERO_PAGE(vaddr) \
(virt_to_page((void *)(empty_zero_page + (((unsigned long)(vaddr)) & zero_page_mask))))
-#define __HAVE_ARCH_MOVE_PTE
-#define move_pte(pte, prot, old_addr, new_addr) \
-({ \
- pte_t newpte = (pte); \
- if (pte_present(pte) && pfn_valid(pte_pfn(pte)) && \
- pte_page(pte) == ZERO_PAGE(old_addr)) \
- newpte = mk_pte(ZERO_PAGE(new_addr), (prot)); \
- newpte; \
-})
-
extern void paging_init(void);
/*
diff --git a/mm/filemap_xip.c b/mm/filemap_xip.c
index 45b3553..9dd9fbb 100644
--- a/mm/filemap_xip.c
+++ b/mm/filemap_xip.c
@@ -183,7 +183,7 @@
address = vma->vm_start +
((pgoff - vma->vm_pgoff) << PAGE_SHIFT);
BUG_ON(address < vma->vm_start || address >= vma->vm_end);
- page = ZERO_PAGE(address);
+ page = ZERO_PAGE(0);
pte = page_check_address(page, mm, address, &ptl);
if (pte) {
/* Nuke the page table entry. */
@@ -246,7 +246,7 @@
__xip_unmap(mapping, pgoff);
} else {
/* not shared and writable, use ZERO_PAGE() */
- page = ZERO_PAGE(address);
+ page = ZERO_PAGE(0);
}
out:
diff --git a/mm/mremap.c b/mm/mremap.c
index 9c769fa..5d4bd4f 100644
--- a/mm/mremap.c
+++ b/mm/mremap.c
@@ -105,7 +105,6 @@
if (pte_none(*old_pte))
continue;
pte = ptep_clear_flush(vma, old_addr, old_pte);
- /* ZERO_PAGE can be dependant on virtual addr */
pte = move_pte(pte, new_vma->vm_page_prot, old_addr, new_addr);
set_pte_at(mm, new_addr, new_pte, pte);
}