From: Joonsoo Kim <iamjoonsoo.kim@lge.com>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: Mel Gorman <mgorman@suse.de>, Hugh Dickins <hughd@google.com>,
Rik van Riel <riel@redhat.com>, Ingo Molnar <mingo@kernel.org>,
Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>,
Hillf Danton <dhillf@gmail.com>,
linux-kernel@vger.kernel.org, linux-mm@kvack.org
Subject: Re: [PATCH 1/9] mm/rmap: recompute pgoff for huge page
Date: Tue, 3 Dec 2013 11:01:41 +0900 [thread overview]
Message-ID: <20131203020141.GA31168@lge.com> (raw)
In-Reply-To: <20131202144434.2afc2b5bb69f2b4b45608e4e@linux-foundation.org>
On Mon, Dec 02, 2013 at 02:44:34PM -0800, Andrew Morton wrote:
> On Thu, 28 Nov 2013 16:48:38 +0900 Joonsoo Kim <iamjoonsoo.kim@lge.com> wrote:
>
> > We have to recompute pgoff if the given page is huge, since result based
> > on HPAGE_SIZE is not approapriate for scanning the vma interval tree, as
> > shown by commit 36e4f20af833 ("hugetlb: do not use vma_hugecache_offset()
> > for vma_prio_tree_foreach") and commit 369a713e ("rmap: recompute pgoff
> > for unmapping huge page").
> >
> > ...
> >
> > --- a/mm/rmap.c
> > +++ b/mm/rmap.c
> > @@ -1714,6 +1714,10 @@ static int rmap_walk_file(struct page *page, int (*rmap_one)(struct page *,
> >
> > if (!mapping)
> > return ret;
> > +
> > + if (PageHuge(page))
> > + pgoff = page->index << compound_order(page);
> > +
> > mutex_lock(&mapping->i_mmap_mutex);
> > vma_interval_tree_foreach(vma, &mapping->i_mmap, pgoff, pgoff) {
> > unsigned long address = vma_address(page, vma);
>
> a) Can't we just do this?
>
> --- a/mm/rmap.c~mm-rmap-recompute-pgoff-for-huge-page-fix
> +++ a/mm/rmap.c
> @@ -1708,16 +1708,13 @@ static int rmap_walk_file(struct page *p
> struct vm_area_struct *, unsigned long, void *), void *arg)
> {
> struct address_space *mapping = page->mapping;
> - pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
> + pgoff_t pgoff = page->index << compound_order(page);
> struct vm_area_struct *vma;
> int ret = SWAP_AGAIN;
>
> if (!mapping)
> return ret;
>
> - if (PageHuge(page))
> - pgoff = page->index << compound_order(page);
> -
> mutex_lock(&mapping->i_mmap_mutex);
> vma_interval_tree_foreach(vma, &mapping->i_mmap, pgoff, pgoff) {
> unsigned long address = vma_address(page, vma);
>
> compound_order() does the right thing for all styles of page, yes?
Yes. I will change.
>
> b) If that PageHuge() test you added the correct thing to use?
>
> /*
> * PageHuge() only returns true for hugetlbfs pages, but not for normal or
> * transparent huge pages. See the PageTransHuge() documentation for more
> * details.
> */
>
> Obviously we won't be encountering transparent huge pages here,
> but what's the best future-safe approach?
compound_order() also works for transparent huge pages, so it may be safe way.
> I hate that PageHuge() oddity with a passion! Maybe it would be better
> if it was called PageHugetlbfs.
I also think that PageHuge() is odd name.
It has only 50 call sites. Let's change it :)
Thanks.
> --
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next prev parent reply other threads:[~2013-12-03 1:59 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-11-28 7:48 [PATCH 0/9] mm/rmap: unify rmap traversing functions through rmap_walk Joonsoo Kim
2013-11-28 7:48 ` [PATCH 1/9] mm/rmap: recompute pgoff for huge page Joonsoo Kim
2013-12-02 20:09 ` Naoya Horiguchi
2013-12-02 22:44 ` Andrew Morton
2013-12-03 2:01 ` Joonsoo Kim [this message]
2013-11-28 7:48 ` [PATCH 2/9] mm/rmap: factor nonlinear handling out of try_to_unmap_file() Joonsoo Kim
2013-12-02 20:09 ` Naoya Horiguchi
2013-11-28 7:48 ` [PATCH 3/9] mm/rmap: factor lock function out of rmap_walk_anon() Joonsoo Kim
2013-12-02 20:09 ` Naoya Horiguchi
2013-11-28 7:48 ` [PATCH 4/9] mm/rmap: make rmap_walk to get the rmap_walk_control argument Joonsoo Kim
2013-12-02 20:09 ` Naoya Horiguchi
2013-12-02 22:51 ` Andrew Morton
2013-12-03 2:03 ` Joonsoo Kim
2013-12-02 22:52 ` Andrew Morton
2013-11-28 7:48 ` [PATCH 5/9] mm/rmap: extend rmap_walk_xxx() to cope with different cases Joonsoo Kim
2013-12-02 20:09 ` Naoya Horiguchi
2013-12-03 2:05 ` Joonsoo Kim
2013-11-28 7:48 ` [PATCH 6/9] mm/rmap: use rmap_walk() in try_to_unmap() Joonsoo Kim
2013-12-02 20:09 ` Naoya Horiguchi
2013-12-02 23:01 ` Andrew Morton
2013-12-03 2:08 ` Joonsoo Kim
2013-11-28 7:48 ` [PATCH 7/9] mm/rmap: use rmap_walk() in try_to_munlock() Joonsoo Kim
2013-12-02 20:09 ` Naoya Horiguchi
2013-11-28 7:48 ` [PATCH 8/9] mm/rmap: use rmap_walk() in page_referenced() Joonsoo Kim
2013-12-02 20:10 ` Naoya Horiguchi
2013-11-28 7:48 ` [PATCH 9/9] mm/rmap: use rmap_walk() in page_mkclean() Joonsoo Kim
2013-12-02 20:10 ` Naoya Horiguchi
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