+ mmhwpoison-return-0-if-the-page-is-already-poisoned-in-soft-offline.patch added to -mm tree

[akpm@linux-foundation.org]

The patch titled
     Subject: mm,hwpoison: return 0 if the page is already poisoned in soft-offline
has been added to the -mm tree.  Its filename is
     mmhwpoison-return-0-if-the-page-is-already-poisoned-in-soft-offline.patch

This patch should soon appear at
    https://ozlabs.org/~akpm/mmots/broken-out/mmhwpoison-return-0-if-the-page-is-already-poisoned-in-soft-offline.patch
and later at
    https://ozlabs.org/~akpm/mmotm/broken-out/mmhwpoison-return-0-if-the-page-is-already-poisoned-in-soft-offline.patch

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------------------------------------------------------
From: Oscar Salvador <osalvador@suse.de>
Subject: mm,hwpoison: return 0 if the page is already poisoned in soft-offline

Currently, there is an inconsistency when calling soft-offline from
different paths on a page that is already poisoned.

1) madvise:

        madvise_inject_error skips any poisoned page and continues
        the loop.
        If that was the only page to madvise, it returns 0.

2) /sys/devices/system/memory/:

        When calling soft_offline_page_store()->soft_offline_page(),
        we return -EBUSY in case the page is already poisoned.
        This is inconsistent with a) the above example and b)
        memory_failure, where we return 0 if the page was poisoned.

Fix this by dropping the PageHWPoison() check in madvise_inject_error, and
let soft_offline_page return 0 if it finds the page already poisoned.

Please, note that this represents a user-api change, since now the return
error when calling soft_offline_page_store()->soft_offline_page() will be
different.

Link: https://lkml.kernel.org/r/20200922135650.1634-12-osalvador@suse.de
Signed-off-by: Oscar Salvador <osalvador@suse.de>
Cc: "Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com>
Cc: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Cc: Aristeu Rozanski <aris@ruivo.org>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Dmitry Yakunin <zeil@yandex-team.ru>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Naoya Horiguchi <naoya.horiguchi@nec.com>
Cc: Oscar Salvador <osalvador@suse.com>
Cc: Qian Cai <cai@lca.pw>
Cc: Tony Luck <tony.luck@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/madvise.c        |    5 -----
 mm/memory-failure.c |    4 ++--
 2 files changed, 2 insertions(+), 7 deletions(-)

--- a/mm/madvise.c~mmhwpoison-return-0-if-the-page-is-already-poisoned-in-soft-offline
+++ a/mm/madvise.c
@@ -896,11 +896,6 @@ static int madvise_inject_error(int beha
 		 */
 		size = page_size(compound_head(page));
 
-		if (PageHWPoison(page)) {
-			put_page(page);
-			continue;
-		}
-
 		if (behavior == MADV_SOFT_OFFLINE) {
 			pr_info("Soft offlining pfn %#lx at process virtual address %#lx\n",
 				 pfn, start);
--- a/mm/memory-failure.c~mmhwpoison-return-0-if-the-page-is-already-poisoned-in-soft-offline
+++ a/mm/memory-failure.c
@@ -1802,7 +1802,7 @@ static int __soft_offline_page(struct pa
 		unlock_page(page);
 		put_page(page);
 		pr_info("soft offline: %#lx page already poisoned\n", pfn);
-		return -EBUSY;
+		return 0;
 	}
 
 	if (!PageHuge(page))
@@ -1906,7 +1906,7 @@ int soft_offline_page(unsigned long pfn,
 		pr_info("soft offline: %#lx page already poisoned\n", pfn);
 		if (flags & MF_COUNT_INCREASED)
 			put_page(page);
-		return -EBUSY;
+		return 0;
 	}
 
 	get_online_mems();
_

Patches currently in -mm which might be from osalvador@suse.de are

mmhwpoison-unexport-get_hwpoison_page-and-make-it-static.patch
mmhwpoison-refactor-madvise_inject_error.patch
mmhwpoison-kill-put_hwpoison_page.patch
mmhwpoison-unify-thp-handling-for-hard-and-soft-offline.patch
mmhwpoison-rework-soft-offline-for-free-pages.patch
mmhwpoison-rework-soft-offline-for-in-use-pages.patch
mmhwpoison-refactor-soft_offline_huge_page-and-__soft_offline_page.patch
mmhwpoison-return-0-if-the-page-is-already-poisoned-in-soft-offline.patch
mmhwpoison-try-to-narrow-window-race-for-free-pages.patch
mmhwpoison-take-free-pages-off-the-buddy-freelists.patch
mmhwpoison-drain-pcplists-before-bailing-out-for-non-buddy-zero-refcount-page.patch
mmhwpoison-drop-unneeded-pcplist-draining.patch
mmhwpoison-remove-stale-code.patch