do_mmap_pgoff's (file == NULL) check was incorrect: it caused shared
MAP_ANONYMOUS objects to be counted twice (again in shmem_file_setup),
and again on fork(); whereas the equivalent shared /dev/zero objects
were correctly counted. Conversely, a private readonly file mapping
was (correctly) not counted, but still not counted when mprotected to
writable: mprotect_fixup had pointless "charged = 0" changes, now it
does vm_enough_memory checking when private is first made writable
(but later we may want to refine behaviour on a noreserve mapping).
Also changed correct (flags & MAP_SHARED) test in do_mmap_pgoff to
equivalent (vm_flags & VM_SHARED) test: because do_mmap_pgoff is
dealing with vm_flags rather than the input flags by that stage.
--- vmacct5/mm/mmap.c Mon Jul 29 19:23:46 2002
+++ vmacct6/mm/mmap.c Mon Jul 29 19:23:46 2002
@@ -527,16 +527,14 @@
> current->rlim[RLIMIT_AS].rlim_cur)
return -ENOMEM;
- if (sysctl_overcommit_memory > 1)
- flags &= ~MAP_NORESERVE;
-
- /* Private writable mapping? Check memory availability.. */
- if ((((vm_flags & (VM_SHARED | VM_WRITE)) == VM_WRITE) ||
- (file == NULL)) && !(flags & MAP_NORESERVE)) {
- charged = len >> PAGE_SHIFT;
- if (!vm_enough_memory(charged))
- return -ENOMEM;
- vm_flags |= VM_ACCOUNT;
+ if (!(flags & MAP_NORESERVE) || sysctl_overcommit_memory > 1) {
+ if ((vm_flags & (VM_SHARED|VM_WRITE)) == VM_WRITE) {
+ /* Private writable mapping: check memory availability */
+ charged = len >> PAGE_SHIFT;
+ if (!vm_enough_memory(charged))
+ return -ENOMEM;
+ vm_flags |= VM_ACCOUNT;
+ }
}
/* Can we just expand an old anonymous mapping? */
@@ -579,7 +577,7 @@
error = file->f_op->mmap(file, vma);
if (error)
goto unmap_and_free_vma;
- } else if (flags & MAP_SHARED) {
+ } else if (vm_flags & VM_SHARED) {
error = shmem_zero_setup(vma);
if (error)
goto free_vma;
--- vmacct5/mm/mprotect.c Mon Jul 29 11:48:04 2002
+++ vmacct6/mm/mprotect.c Mon Jul 29 19:23:46 2002
@@ -257,6 +257,22 @@
*pprev = vma;
return 0;
}
+
+ /*
+ * If we make a private mapping writable we increase our commit;
+ * but (without finer accounting) cannot reduce our commit if we
+ * make it unwritable again.
+ *
+ * FIXME? We haven't defined a VM_NORESERVE flag, so mprotecting
+ * a MAP_NORESERVE private mapping to writable will now reserve.
+ */
+ if ((newflags & VM_WRITE) &&
+ !(vma->vm_flags & (VM_ACCOUNT|VM_WRITE|VM_SHARED))) {
+ charged = (end - start) >> PAGE_SHIFT;
+ if (!vm_enough_memory(charged))
+ return -ENOMEM;
+ newflags |= VM_ACCOUNT;
+ }
newprot = protection_map[newflags & 0xf];
if (start == vma->vm_start) {
if (end == vma->vm_end)
@@ -267,19 +283,10 @@
error = mprotect_fixup_end(vma, pprev, start, newflags, newprot);
else
error = mprotect_fixup_middle(vma, pprev, start, end, newflags, newprot);
-
if (error) {
- if (newflags & PROT_WRITE)
- vm_unacct_memory(charged);
+ vm_unacct_memory(charged);
return error;
}
-
- /*
- * Delayed accounting for reduction of memory use - done last to
- * avoid allocation races
- */
- if (charged && !(newflags & PROT_WRITE))
- vm_unacct_memory(charged);
change_protection(vma, start, end, newprot);
return 0;
}
-
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This archive was generated by hypermail 2b29 : Tue Jul 30 2002 - 14:00:34 EST