Linux-mm Archive on lore.kernel.org
 help / color / Atom feed
From: nao.horiguchi@gmail.com
To: linux-mm@kvack.org
Cc: mhocko@kernel.org, akpm@linux-foundation.org,
	mike.kravetz@oracle.com, osalvador@suse.de, tony.luck@intel.com,
	david@redhat.com, aneesh.kumar@linux.vnet.ibm.com,
	zeil@yandex-team.ru, cai@lca.pw, naoya.horiguchi@nec.com,
	linux-kernel@vger.kernel.org
Subject: [PATCH v5 03/16] mm,madvise: call soft_offline_page() without MF_COUNT_INCREASED
Date: Fri, 31 Jul 2020 12:20:59 +0000
Message-ID: <20200731122112.11263-4-nao.horiguchi@gmail.com> (raw)
In-Reply-To: <20200731122112.11263-1-nao.horiguchi@gmail.com>

From: Naoya Horiguchi <naoya.horiguchi@nec.com>

The call to get_user_pages_fast is only to get the pointer to a struct
page of a given address, pinning it is memory-poisoning handler's job,
so drop the refcount grabbed by get_user_pages_fast().

Note that the target page is still pinned after this put_page() because
the current process should have refcount from mapping.

Signed-off-by: Naoya Horiguchi <naoya.horiguchi@nec.com>
Signed-off-by: Oscar Salvador <osalvador@suse.de>
Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com>
---
 mm/madvise.c | 24 ++++++++++++------------
 1 file changed, 12 insertions(+), 12 deletions(-)

diff --git v5.8-rc7-mmotm-2020-07-27-18-18/mm/madvise.c v5.8-rc7-mmotm-2020-07-27-18-18_patched/mm/madvise.c
index a16dba21cdf6..1fe89a5b8d33 100644
--- v5.8-rc7-mmotm-2020-07-27-18-18/mm/madvise.c
+++ v5.8-rc7-mmotm-2020-07-27-18-18_patched/mm/madvise.c
@@ -910,16 +910,24 @@ static int madvise_inject_error(int behavior,
 		 */
 		size = page_size(compound_head(page));
 
-		if (PageHWPoison(page)) {
-			put_page(page);
+		/*
+		 * The get_user_pages_fast() is just to get the pfn of the
+		 * given address, and the refcount has nothing to do with
+		 * what we try to test, so it should be released immediately.
+		 * This is racy but it's intended because the real hardware
+		 * errors could happen at any moment and memory error handlers
+		 * must properly handle the race.
+		 */
+		put_page(page);
+
+		if (PageHWPoison(page))
 			continue;
-		}
 
 		if (behavior == MADV_SOFT_OFFLINE) {
 			pr_info("Soft offlining pfn %#lx at process virtual address %#lx\n",
 					pfn, start);
 
-			ret = soft_offline_page(pfn, MF_COUNT_INCREASED);
+			ret = soft_offline_page(pfn, 0);
 			if (ret)
 				return ret;
 			continue;
@@ -927,14 +935,6 @@ static int madvise_inject_error(int behavior,
 
 		pr_info("Injecting memory failure for pfn %#lx at process virtual address %#lx\n",
 				pfn, start);
-
-		/*
-		 * Drop the page reference taken by get_user_pages_fast(). In
-		 * the absence of MF_COUNT_INCREASED the memory_failure()
-		 * routine is responsible for pinning the page to prevent it
-		 * from being released back to the page allocator.
-		 */
-		put_page(page);
 		ret = memory_failure(pfn, 0);
 		if (ret)
 			return ret;
-- 
2.17.1



  parent reply index

Thread overview: 22+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-07-31 12:20 [PATCH v5 00/16] HWPOISON: soft offline rework nao.horiguchi
2020-07-31 12:20 ` [PATCH v5 01/16] mm,hwpoison: cleanup unused PageHuge() check nao.horiguchi
2020-07-31 12:20 ` [PATCH v5 02/16] mm, hwpoison: remove recalculating hpage nao.horiguchi
2020-07-31 12:20 ` nao.horiguchi [this message]
2020-07-31 12:21 ` [PATCH v5 04/16] mm,madvise: Refactor madvise_inject_error nao.horiguchi
2020-07-31 12:21 ` [PATCH v5 05/16] mm,hwpoison-inject: don't pin for hwpoison_filter nao.horiguchi
2020-07-31 12:21 ` [PATCH v5 06/16] mm,hwpoison: Un-export get_hwpoison_page and make it static nao.horiguchi
2020-07-31 12:21 ` [PATCH v5 07/16] mm,hwpoison: Kill put_hwpoison_page nao.horiguchi
2020-07-31 12:21 ` [PATCH v5 08/16] mm,hwpoison: remove MF_COUNT_INCREASED nao.horiguchi
2020-07-31 12:21 ` [PATCH v5 09/16] mm,hwpoison: remove flag argument from soft offline functions nao.horiguchi
2020-07-31 12:21 ` [PATCH v5 10/16] mm,hwpoison: Unify THP handling for hard and soft offline nao.horiguchi
2020-07-31 12:21 ` [PATCH v5 11/16] mm,hwpoison: Rework soft offline for free pages nao.horiguchi
2020-07-31 12:21 ` [PATCH v5 12/16] mm,hwpoison: Rework soft offline for in-use pages nao.horiguchi
2020-07-31 12:21 ` [PATCH v5 13/16] mm,hwpoison: Refactor soft_offline_huge_page and __soft_offline_page nao.horiguchi
2020-07-31 12:21 ` [PATCH v5 14/16] mm,hwpoison: Return 0 if the page is already poisoned in soft-offline nao.horiguchi
2020-07-31 12:21 ` [PATCH v5 15/16] mm,hwpoison: introduce MF_MSG_UNSPLIT_THP nao.horiguchi
     [not found] ` <20200803123954.GA4631@lca.pw>
2020-08-03 13:36   ` [PATCH v5 00/16] HWPOISON: soft offline rework HORIGUCHI NAOYA(堀口 直也)
     [not found]     ` <20200803151907.GA8894@lca.pw>
2020-08-05 20:43       ` HORIGUCHI NAOYA(堀口 直也)
     [not found] ` <20200803190709.GB8894@lca.pw>
2020-08-04  1:16   ` HORIGUCHI NAOYA(堀口 直也)
2020-08-04  1:49     ` Qian Cai
2020-08-04  8:13       ` osalvador
2020-08-05 20:44       ` HORIGUCHI NAOYA(堀口 直也)

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20200731122112.11263-4-nao.horiguchi@gmail.com \
    --to=nao.horiguchi@gmail.com \
    --cc=akpm@linux-foundation.org \
    --cc=aneesh.kumar@linux.vnet.ibm.com \
    --cc=cai@lca.pw \
    --cc=david@redhat.com \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-mm@kvack.org \
    --cc=mhocko@kernel.org \
    --cc=mike.kravetz@oracle.com \
    --cc=naoya.horiguchi@nec.com \
    --cc=osalvador@suse.de \
    --cc=tony.luck@intel.com \
    --cc=zeil@yandex-team.ru \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

Linux-mm Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/linux-mm/0 linux-mm/git/0.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 linux-mm linux-mm/ https://lore.kernel.org/linux-mm \
		linux-mm@kvack.org
	public-inbox-index linux-mm

Example config snippet for mirrors

Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/org.kvack.linux-mm


AGPL code for this site: git clone https://public-inbox.org/public-inbox.git