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Date: Mon, 11 Apr 2022 13:07:29 +0300
From: Mike Rapoport <rppt@kernel.org>
To: Dave Hansen <dave.hansen@intel.com>
Cc: "Kirill A. Shutemov" <kirill@shutemov.name>,
	"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
	Borislav Petkov <bp@alien8.de>, Andy Lutomirski <luto@kernel.org>,
	Sean Christopherson <seanjc@google.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Joerg Roedel <jroedel@suse.de>, Ard Biesheuvel <ardb@kernel.org>,
	Andi Kleen <ak@linux.intel.com>,
	Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>,
	David Rientjes <rientjes@google.com>,
	Vlastimil Babka <vbabka@suse.cz>,
	Tom Lendacky <thomas.lendacky@amd.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Peter Zijlstra <peterz@infradead.org>,
	Paolo Bonzini <pbonzini@redhat.com>, Ingo Molnar <mingo@redhat.com>,
	Varad Gautam <varad.gautam@suse.com>,
	Dario Faggioli <dfaggioli@suse.com>,
	Brijesh Singh <brijesh.singh@amd.com>,
	David Hildenbrand <david@redhat.com>, x86@kernel.org,
	linux-mm@kvack.org, linux-coco@lists.linux.dev,
	linux-efi@vger.kernel.org, linux-kernel@vger.kernel.org,
	Mike Rapoport <rppt@linux.ibm.com>
Subject: Re: [PATCHv4 1/8] mm: Add support for unaccepted memory
Message-ID: <YlP94T1ACwxKTgep@kernel.org>
References: <20220405234343.74045-1-kirill.shutemov@linux.intel.com>
 <20220405234343.74045-2-kirill.shutemov@linux.intel.com>
 <767c2100-c171-1fd3-6a92-0af2e4bf3067@intel.com>
 <20220409155423.iv2arckmvavvpegt@box.shutemov.name>
 <6c976344-fdd6-95cd-2cb0-b0e817bf0392@intel.com>
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In-Reply-To: <6c976344-fdd6-95cd-2cb0-b0e817bf0392@intel.com>

On Sun, Apr 10, 2022 at 11:38:08PM -0700, Dave Hansen wrote:
> On 4/9/22 08:54, Kirill A. Shutemov wrote:
> > On Fri, Apr 08, 2022 at 11:55:43AM -0700, Dave Hansen wrote:
> 
> >>>  	if (fpi_flags & FPI_TO_TAIL)
> >>>  		to_tail = true;
> >>>  	else if (is_shuffle_order(order))
> >>> @@ -1149,7 +1192,8 @@ static inline void __free_one_page(struct page *page,
> >>>  static inline bool page_expected_state(struct page *page,
> >>>  					unsigned long check_flags)
> >>>  {
> >>> -	if (unlikely(atomic_read(&page->_mapcount) != -1))
> >>> +	if (unlikely(atomic_read(&page->_mapcount) != -1) &&
> >>> +	    !PageUnaccepted(page))
> >>>  		return false;
> >>
> >> That probably deserves a comment, and maybe its own if() statement.
> > 
> > Own if does not work. PageUnaccepted() is encoded in _mapcount.
> > 
> > What about this:
> > 
> > 	/*
> > 	 * page->_mapcount is expected to be -1.
> > 	 *
> > 	 * There is an exception for PageUnaccepted(). The page type can be set
> > 	 * for pages on free list. Page types are encoded in _mapcount.
> > 	 *
> > 	 * PageUnaccepted() will get cleared in post_alloc_hook().
> > 	 */
> > 	if (unlikely((atomic_read(&page->_mapcount) | PG_unaccepted) != -1))

Maybe I'm missing something, but isn't this true for any PageType?

> > 		return false;
> > 
> > ?
> 
> That's better.  But, aren't the PG_* names usually reserved for real
> page->flags bits?  That naming might be part of my confusion.

We use them for PageType as well like PG_buddy, PG_offline, PG_Table.

-- 
Sincerely yours,
Mike.