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Make sure we copy pages inserted with "vm_insert_page()" on fork 

The logic that decides that a fork() might be able to avoid copying a VM
area when it can be re-created by page faults didn't know about the new
vm_insert_page() case.

Also make some things a bit more anal wrt VM_PFNMAP.

Pointed out by Hugh Dickins <hugh@veritas.com>

Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This commit is contained in:
Linus Torvalds 2005-12-16 10:21:23 -08:00
parent 281ab031a8
commit 4d7672b462
4 changed files with 5 additions and 3 deletions
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1
include/linux/mm.h
View File

@ -163,6 +163,7 @@ extern unsigned int kobjsize(const void *objp);
#define VM_HUGETLB 0x00400000 /* Huge TLB Page VM */
#define VM_NONLINEAR 0x00800000 /* Is non-linear (remap_file_pages) */
#define VM_MAPPED_COPY 0x01000000 /* T if mapped copy of data (nommu mmap) */
#define VM_INSERTPAGE 0x02000000 /* The vma has had "vm_insert_page()" done on it */
#ifndef VM_STACK_DEFAULT_FLAGS /* arch can override this */
#define VM_STACK_DEFAULT_FLAGS VM_DATA_DEFAULT_FLAGS

3
mm/memory.c
View File

@ -574,7 +574,7 @@ int copy_page_range(struct mm_struct *dst_mm, struct mm_struct *src_mm,
* readonly mappings. The tradeoff is that copy_page_range is more
* efficient than faulting.
*/
if (!(vma->vm_flags & (VM_HUGETLB|VM_NONLINEAR|VM_PFNMAP))) {
if (!(vma->vm_flags & (VM_HUGETLB|VM_NONLINEAR|VM_PFNMAP|VM_INSERTPAGE))) {
if (!vma->anon_vma)
return 0;
}
@ -1228,6 +1228,7 @@ int vm_insert_page(struct vm_area_struct *vma, unsigned long addr, struct page *
return -EFAULT;
if (!page_count(page))
return -EINVAL;
vma->vm_flags |= VM_INSERTPAGE;
return insert_page(vma->vm_mm, addr, page, vma->vm_page_prot);
}
EXPORT_SYMBOL(vm_insert_page);

2
mm/mmap.c
View File

@ -611,7 +611,7 @@ again: remove_next = 1 + (end > next->vm_end);
* If the vma has a ->close operation then the driver probably needs to release
* per-vma resources, so we don't attempt to merge those.
*/
#define VM_SPECIAL (VM_IO | VM_DONTCOPY | VM_DONTEXPAND | VM_RESERVED)
#define VM_SPECIAL (VM_IO | VM_DONTCOPY | VM_DONTEXPAND | VM_RESERVED | VM_PFNMAP)
static inline int is_mergeable_vma(struct vm_area_struct *vma,
struct file *file, unsigned long vm_flags)

2
mm/mremap.c
View File

@ -323,7 +323,7 @@ unsigned long do_mremap(unsigned long addr,
/* We can't remap across vm area boundaries */
if (old_len > vma->vm_end - addr)
goto out;
if (vma->vm_flags & VM_DONTEXPAND) {
if (vma->vm_flags & (VM_DONTEXPAND | VM_PFNMAP)) {
if (new_len > old_len)
goto out;
}