From: Hugh Dickins <hughd@google.com>
To: Matthew Wilcox <willy@infradead.org>
Cc: Hugh Dickins <hughd@google.com>,
Andrew Morton <akpm@linux-foundation.org>,
"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
Zhang Yi <wetpzy@gmail.com>,
Mel Gorman <mgorman@techsingularity.net>,
Mike Kravetz <mike.kravetz@oracle.com>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>,
Peter Zijlstra <peterz@infradead.org>,
Darren Hart <dvhart@infradead.org>,
Davidlohr Bueso <dave@stgolabs.net>,
Neel Natu <neelnatu@google.com>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] mm, futex: Fix shared futex pgoff on shmem huge page
Date: Sat, 12 Jun 2021 20:14:37 -0700 (PDT) [thread overview]
Message-ID: <e3d322e4-57e6-61d0-23e7-11f96f87415d@google.com> (raw)
In-Reply-To: <YMTdtRZG+7q8OtkK@casper.infradead.org>
On Sat, 12 Jun 2021, Matthew Wilcox wrote:
> On Fri, Jun 11, 2021 at 09:31:16PM -0700, Hugh Dickins wrote:
> > +++ linux/include/linux/pagemap.h 2021-06-11 17:30:28.726720252 -0700
> > @@ -516,8 +516,7 @@ static inline struct page *read_mapping_
> > }
> >
> > /*
> > - * Get index of the page with in radix-tree
> > - * (TODO: remove once hugetlb pages will have ->index in PAGE_SIZE)
> > + * Get index of the page within radix-tree (but not for hugetlb pages).
> > */
>
> I think the TODO should be retained. It's still something that I
> intend to do.
Okay. I did not mean to imply, by removing those TODOs, that they
should not be done: just that they were a developer's notes to self,
that I found distracting there.
I've restored both TODOs (but changed the second to say
"hugetlb pages" explicitly, rather than the ambiguous "hugepage").
> > --- 5.13-rc5/mm/hugetlb.c 2021-06-06 16:57:26.263006733 -0700
> > +++ linux/mm/hugetlb.c 2021-06-11 17:30:28.730720276 -0700
> > @@ -1588,15 +1588,12 @@ struct address_space *hugetlb_page_mappi
> > return NULL;
> > }
> >
> > -pgoff_t __basepage_index(struct page *page)
> > +pgoff_t hugetlb_basepage_index(struct page *page)
> > {
> > struct page *page_head = compound_head(page);
> > pgoff_t index = page_index(page_head);
> > unsigned long compound_idx;
> >
> > - if (!PageHuge(page_head))
> > - return page_index(page);
> > -
> > if (compound_order(page_head) >= MAX_ORDER)
> > compound_idx = page_to_pfn(page) - page_to_pfn(page_head);
> > else
> >
>
> urgh. this trailing bit should be:
>
> #if defined(CONFIG_SPARSEMEM) && !defined(CONFIG_SPARSEMEM_VMEMMAP)
> compound_idx = page_to_pfn(page) - page_to_pfn(page_head);
> #else
> compound_idx = page - page_head;
> #endif
I don't see what's wrong with what's there, myself. Unfamiliar territory
to me, but mem_map_next() appears to have the same MAX_ORDER expectation.
Or perhaps you're just suggesting an optimization.
If it were obvious to me, I'd have gladly folded it in; but no,
please send your own patch for that, running it by Mike Kravetz
and Mike Rapoport and David Hildenbrand, I think.
Thanks, v2 follows,
Hugh
next prev parent reply other threads:[~2021-06-13 3:15 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-06-12 4:31 [PATCH] mm, futex: Fix shared futex pgoff on shmem huge page Hugh Dickins
2021-06-12 16:15 ` Matthew Wilcox
2021-06-13 3:14 ` Hugh Dickins [this message]
2021-06-13 3:16 ` [PATCH v2] " Hugh Dickins
2021-06-13 10:27 ` Matthew Wilcox
2021-06-15 14:53 ` Thomas Gleixner
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