linux-kernel - Re: [RFC PATCH v2 2/3] mm: Add PUD level pagetable account

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <YrRqhj3p/KKU73f1@casper.infradead.org>
Date:   Thu, 23 Jun 2022 14:28:38 +0100
From:   Matthew Wilcox <willy@...radead.org>
To:     Mike Rapoport <rppt@...ux.ibm.com>
Cc:     Baolin Wang <baolin.wang@...ux.alibaba.com>,
        akpm@...ux-foundation.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH v2 2/3] mm: Add PUD level pagetable account

On Wed, Jun 22, 2022 at 09:38:30AM -0500, Mike Rapoport wrote:
> On Wed, Jun 22, 2022 at 04:58:53PM +0800, Baolin Wang wrote:
> > +++ b/arch/loongarch/include/asm/pgalloc.h
> > @@ -89,10 +89,15 @@ static inline pmd_t *pmd_alloc_one(struct mm_struct *mm, unsigned long address)
> >  static inline pud_t *pud_alloc_one(struct mm_struct *mm, unsigned long address)
> >  {
> >  	pud_t *pud;
> > +	struct page *pg;
> 
> 	struct page *page;
> 
> looks better IMO.
> 
> > +
> > +	pg = alloc_pages(GFP_KERNEL & ~__GFP_HIGHMEM, PUD_ORDER);

GFP_KERNEL does not include __GFP_HIGHMEM, so you can just use
GFP_KERNEL here.

> > +	if (!pg)
> > +		return NULL;
> >  
> > -	pud = (pud_t *) __get_free_pages(GFP_KERNEL, PUD_ORDER);
> > -	if (pud)
> > -		pud_init((unsigned long)pud, (unsigned long)invalid_pmd_table);
> > +	pgtable_set_and_inc(pg);
> > +	pud = (pud_t *)page_address(pg);
> 
> I don't think __get_free_pages() should be replaced with alloc_pages()
> here, just call pgtable_set_and_inc() with virt_to_page(pud). 

I don't understand why you want that.  Take a look at the implementation
of __get_free_pages().  Converting back to a struct page after calling
that seems like a real waste of time to me.