Re: [PATCH] mm acct accounting fix

[Kirill Korotaev]

> > Sorry, forgot to write that all these patches are against 2.6.12-rc4...
> >
> > This patch fixes mm->total_vm and mm->locked_vm acctounting in case
> > when move_page_tables() fails inside move_vma().
> >
> > Signed-Off-By: Kirill Korotaev <dev@xxxxx>
> >
> > --- ./mm/mremap.c.mmacct	2005-05-10 16:10:40.000000000 +0400
> > +++ ./mm/mremap.c	2005-05-10 18:12:13.000000000 +0400
> > @@ -213,6 +213,7 @@ static unsigned long move_vma(struct vm_
> > 		old_len = new_len;
> > 		old_addr = new_addr;
> > 		new_addr = -ENOMEM;
> > +		new_len = 0;
> > 	}
> >
> > 	/* Conceal VM_ACCOUNT so old reservation is not undone */
>
>
> Are you sure?
>
> The way it's supposed to work is that the do_munmap(,,old_len) which
> follows, which normally unmaps the area moved from, when unsuccessful
> unmaps the area moved to: which will "mistakenly" decrement total_vm etc.
> by old_len, which needs to be bumped back up by that amount before leaving.

Yup, I was wrong. Sorry for taking your time.
It would be nice to accept this small patch with a comment.

Kirill

--- ./mm/mremap.c.mmacct	2005-05-10 16:10:40.000000000 +0400
+++ ./mm/mremap.c	2005-05-12 11:56:17.000000000 +0400
@@ -224,6 +224,12 @@ static unsigned long move_vma(struct vm_
 			split = 1;
 	}
 
+	/*
+	 * if we failed to move page tables we still do total_vm increment
+	 * since do_munmap() will decrement it by old_len == new_len
+	 */
+	mm->total_vm += new_len >> PAGE_SHIFT;
+
 	if (do_munmap(mm, old_addr, old_len) < 0) {
 		/* OOM: unable to split vma, just get accounts right */
 		vm_unacct_memory(excess >> PAGE_SHIFT);
@@ -237,7 +243,6 @@ static unsigned long move_vma(struct vm_
 			vma->vm_next->vm_flags |= VM_ACCOUNT;
 	}
 
-	mm->total_vm += new_len >> PAGE_SHIFT;
 	__vm_stat_account(mm, vma->vm_flags, vma->vm_file, new_len>>PAGE_SHIFT);
 	if (vm_flags & VM_LOCKED) {
 		mm->locked_vm += new_len >> PAGE_SHIFT;