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Date: Mon, 28 Jan 2013 12:05:37 -0500
From: Naoya Horiguchi <n-horiguchi@...jp.nec.com>
To: Xishi Qiu <qiuxishi@...wei.com>
Cc: Naoya Horiguchi <n-horiguchi@...jp.nec.com>,
Andrew Morton <akpm@...ux-foundation.org>,
Andi Kleen <andi@...stfloor.org>,
Tony Luck <tony.luck@...el.com>,
Wu Fengguang <fengguang.wu@...el.com>,
Jiang Liu <jiang.liu@...wei.com>, linux-mm@...ck.org,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] mm: clean up soft_offline_page()
On Mon, Jan 28, 2013 at 03:25:38PM +0800, Xishi Qiu wrote:
> On 2013/1/26 13:02, Naoya Horiguchi wrote:
>
> > Currently soft_offline_page() is hard to maintain because it has many
> > return points and goto statements. All of this mess come from get_any_page().
> > This function should only get page refcount as the name implies, but it does
> > some page isolating actions like SetPageHWPoison() and dequeuing hugepage.
> > This patch corrects it and introduces some internal subroutines to make
> > soft offlining code more readable and maintainable.
> >
> > ChangeLog v2:
> > - receive returned value from __soft_offline_page and soft_offline_huge_page
> > - place __soft_offline_page after soft_offline_page to reduce the diff
> > - rebased onto mmotm-2013-01-23-17-04
> > - add comment on double checks of PageHWpoison
> >
> > Signed-off-by: Naoya Horiguchi <n-horiguchi@...jp.nec.com>
> > ---
> > mm/memory-failure.c | 154 ++++++++++++++++++++++++++++------------------------
> > 1 file changed, 83 insertions(+), 71 deletions(-)
> >
> > diff --git mmotm-2013-01-23-17-04.orig/mm/memory-failure.c mmotm-2013-01-23-17-04/mm/memory-failure.c
> > index c95e19a..302625b 100644
> > --- mmotm-2013-01-23-17-04.orig/mm/memory-failure.c
> > +++ mmotm-2013-01-23-17-04/mm/memory-failure.c
> > @@ -1368,7 +1368,7 @@ static struct page *new_page(struct page *p, unsigned long private, int **x)
> > * that is not free, and 1 for any other page type.
> > * For 1 the page is returned with increased page count, otherwise not.
> > */
> > -static int get_any_page(struct page *p, unsigned long pfn, int flags)
> > +static int __get_any_page(struct page *p, unsigned long pfn, int flags)
> > {
> > int ret;
> >
> > @@ -1393,11 +1393,9 @@ static int get_any_page(struct page *p, unsigned long pfn, int flags)
> > if (!get_page_unless_zero(compound_head(p))) {
> > if (PageHuge(p)) {
> > pr_info("%s: %#lx free huge page\n", __func__, pfn);
> > - ret = dequeue_hwpoisoned_huge_page(compound_head(p));
> > + ret = 0;
> > } else if (is_free_buddy_page(p)) {
> > pr_info("%s: %#lx free buddy page\n", __func__, pfn);
> > - /* Set hwpoison bit while page is still isolated */
> > - SetPageHWPoison(p);
> > ret = 0;
> > } else {
> > pr_info("%s: %#lx: unknown zero refcount page type %lx\n",
> > @@ -1413,42 +1411,62 @@ static int get_any_page(struct page *p, unsigned long pfn, int flags)
> > return ret;
> > }
> >
> > +static int get_any_page(struct page *page, unsigned long pfn, int flags)
> > +{
> > + int ret = __get_any_page(page, pfn, flags);
> > +
> > + if (ret == 1 && !PageHuge(page) && !PageLRU(page)) {
> > + /*
> > + * Try to free it.
> > + */
> > + put_page(page);
> > + shake_page(page, 1);
> > +
> > + /*
> > + * Did it turn free?
> > + */
> > + ret = __get_any_page(page, pfn, 0);
> > + if (!PageLRU(page)) {
> > + pr_info("soft_offline: %#lx: unknown non LRU page type %lx\n",
> > + pfn, page->flags);
> > + return -EIO;
> > + }
> > + }
> > + return ret;
> > +}
> > +
> > static int soft_offline_huge_page(struct page *page, int flags)
> > {
> > int ret;
> > unsigned long pfn = page_to_pfn(page);
> > struct page *hpage = compound_head(page);
> >
> > + /*
> > + * This double-check of PageHWPoison is to avoid the race with
> > + * memory_failure(). See also comment in __soft_offline_page().
> > + */
> > + lock_page(hpage);
> > if (PageHWPoison(hpage)) {
> > + unlock_page(hpage);
> > + put_page(hpage);
> > pr_info("soft offline: %#lx hugepage already poisoned\n", pfn);
> > - ret = -EBUSY;
> > - goto out;
> > + return -EBUSY;
> > }
> > -
> > - ret = get_any_page(page, pfn, flags);
> > - if (ret < 0)
> > - goto out;
> > - if (ret == 0)
> > - goto done;
> > + unlock_page(hpage);
> >
> > /* Keep page count to indicate a given hugepage is isolated. */
> > ret = migrate_huge_page(hpage, new_page, MPOL_MF_MOVE_ALL, false,
> > MIGRATE_SYNC);
> > put_page(hpage);
> > - if (ret) {
> > + if (ret)
> > pr_info("soft offline: %#lx: migration failed %d, type %lx\n",
> > pfn, ret, page->flags);
> > - goto out;
> > - }
> > -done:
> > /* keep elevated page count for bad page */
> > - atomic_long_add(1 << compound_trans_order(hpage), &num_poisoned_pages);
> > - set_page_hwpoison_huge_page(hpage);
> > - dequeue_hwpoisoned_huge_page(hpage);
>
> Hi Naoya,
>
> Does num_poisoned_pages be added when soft_offline_huge_page? I mean the in-use huge pages.
Hi Xishi,
Yes, we should add it, and also need set_page_hwpoison_huge_page and
dequeue_hwpoisoned_huge_page because that means 'soft offline'.
I'll repost the fixed one soon. Thank you for your awareness.
Naoya
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