[PATCH] mm acct accounting fix

[PATCH] mm acct accounting fix

[Kirill Korotaev]

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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@sw.ru>

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--- ./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 */

Re: [PATCH] mm acct accounting fix

[Hugh Dickins]

On Wed, 11 May 2005, Kirill Korotaev wrote:

> 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@sw.ru>
> 
> --- ./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.

Hugh

Re: [PATCH] mm acct accounting fix

[Kirill Korotaev]

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>>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@sw.ru>
>>
>>--- ./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


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--- ./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;

Re: [PATCH] mm acct accounting fix

[Hugh Dickins]

On Thu, 12 May 2005, Kirill Korotaev wrote:
> 
> It would be nice to accept this small patch with a comment.

Adding such a comment is okay, but moving the total_vm += line
away from the __vm_stat_account and locked_vm += seems odd to me
- I'd rather you added your comment after the do_munmap(),
but no big deal (mmap_sem is held for writing throughout).

Hugh

--- ./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;