From: Hugh Dickins <hugh@veritas.com>
mremap's move_vma VM_LOCKED case was still wrong.
If the do_munmap unmaps a part of new_vma, then its vm_start and vm_end
from before cannot both be the right addresses for the make_pages_present
range, and may BUG() there.
We need [new_addr, new_addr+new_len) to be locked down; but
move_page_tables already transferred the locked pages [new_addr,
new_addr+old_len), and they're either held in a VM_LOCKED vma throughout,
or temporarily in no vma: in neither case can be swapped out, so no need to
run over that range again.
mm/mremap.c | 16 +++++-----------
1 files changed, 5 insertions(+), 11 deletions(-)
diff -puN mm/mremap.c~move_vma-VM_LOCKED-fix mm/mremap.c
--- 25/mm/mremap.c~move_vma-VM_LOCKED-fix 2003-06-26 17:35:21.000000000 -0700
+++ 25-akpm/mm/mremap.c 2003-06-26 17:35:21.000000000 -0700
@@ -244,9 +244,7 @@ static unsigned long move_vma(struct vm_
}
if (!move_page_tables(vma, new_addr, addr, old_len)) {
- unsigned long must_fault_in;
- unsigned long fault_in_start;
- unsigned long fault_in_end;
+ unsigned long vm_locked = vma->vm_flags & VM_LOCKED;
if (allocated_vma) {
*new_vma = *vma;
@@ -272,14 +270,8 @@ static unsigned long move_vma(struct vm_
} else
vma = NULL; /* nothing more to do */
- must_fault_in = new_vma->vm_flags & VM_LOCKED;
- fault_in_start = new_vma->vm_start;
- fault_in_end = new_vma->vm_end;
-
do_munmap(current->mm, addr, old_len);
- /* new_vma could have been invalidated by do_munmap */
-
/* Restore VM_ACCOUNT if one or two pieces of vma left */
if (vma) {
vma->vm_flags |= VM_ACCOUNT;
@@ -288,9 +280,11 @@ static unsigned long move_vma(struct vm_
}
current->mm->total_vm += new_len >> PAGE_SHIFT;
- if (must_fault_in) {
+ if (vm_locked) {
current->mm->locked_vm += new_len >> PAGE_SHIFT;
- make_pages_present(fault_in_start, fault_in_end);
+ if (new_len > old_len)
+ make_pages_present(new_addr + old_len,
+ new_addr + new_len);
}
return new_addr;
}
_