Re: [PATCHv4 1/8] mm: Add support for unaccepted memory

From: David Hildenbrand <david@redhat.com>
To: "Kirill A. Shutemov" <kirill@shutemov.name>,
	Dave Hansen <dave.hansen@intel.com>
Cc: "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>,
	Mike Rapoport <rppt@kernel.org>,
	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
Date: Mon, 11 Apr 2022 10:47:33 +0200	[thread overview]
Message-ID: <1837b625-c63d-9feb-ec98-3b4c7b0040b4@redhat.com> (raw)
In-Reply-To: <20220409155423.iv2arckmvavvpegt@box.shutemov.name>

>>>  	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))
> 		return false;
> 
> ?
> 

Please don't. Keep the usage of PG_* details inside page-flags.h

-- 
Thanks,

David / dhildenb