linux-kernel - [PATCH v1 3/7] mm: rename and move page_is

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Date:   Thu, 29 Apr 2021 14:25:15 +0200
From:   David Hildenbrand <david@...hat.com>
To:     linux-kernel@...r.kernel.org
Cc:     David Hildenbrand <david@...hat.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        "Michael S. Tsirkin" <mst@...hat.com>,
        Jason Wang <jasowang@...hat.com>,
        Alexey Dobriyan <adobriyan@...il.com>,
        Mike Rapoport <rppt@...nel.org>,
        "Matthew Wilcox (Oracle)" <willy@...radead.org>,
        Oscar Salvador <osalvador@...e.de>,
        Michal Hocko <mhocko@...e.com>, Roman Gushchin <guro@...com>,
        Alex Shi <alex.shi@...ux.alibaba.com>,
        Steven Price <steven.price@....com>,
        Mike Kravetz <mike.kravetz@...cle.com>,
        Aili Yao <yaoaili@...gsoft.com>, Jiri Bohac <jbohac@...e.cz>,
        "K. Y. Srinivasan" <kys@...rosoft.com>,
        Haiyang Zhang <haiyangz@...rosoft.com>,
        Stephen Hemminger <sthemmin@...rosoft.com>,
        Wei Liu <wei.liu@...nel.org>,
        Naoya Horiguchi <naoya.horiguchi@....com>,
        linux-hyperv@...r.kernel.org,
        virtualization@...ts.linux-foundation.org,
        linux-fsdevel@...r.kernel.org, linux-mm@...ck.org
Subject: [PATCH v1 3/7] mm: rename and move page_is_poisoned()

Commit d3378e86d182 ("mm/gup: check page posion status for coredump.")
introduced page_is_poisoned(), however, v5 [1] of the patch used
"page_is_hwpoison()" and something went wrong while upstreaming. Rename the
function and move it to page-flags.h, from where it can be used in other
-- kcore -- context.

Move the comment to the place where it belongs and simplify.

[1] https://lkml.kernel.org/r/20210322193318.377c9ce9@alex-virtual-machine

Signed-off-by: David Hildenbrand <david@...hat.com>
---
 include/linux/page-flags.h |  7 +++++++
 mm/gup.c                   |  6 +++++-
 mm/internal.h              | 20 --------------------
 3 files changed, 12 insertions(+), 21 deletions(-)

diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h
index 04a34c08e0a6..b8c56672a588 100644
--- a/include/linux/page-flags.h
+++ b/include/linux/page-flags.h
@@ -694,6 +694,13 @@ PAGEFLAG_FALSE(DoubleMap)
 	TESTSCFLAG_FALSE(DoubleMap)
 #endif
 
+static inline bool is_page_hwpoison(struct page *page)
+{
+	if (PageHWPoison(page))
+		return true;
+	return PageHuge(page) && PageHWPoison(compound_head(page));
+}
+
 /*
  * For pages that are never mapped to userspace (and aren't PageSlab),
  * page_type may be used.  Because it is initialised to -1, we invert the
diff --git a/mm/gup.c b/mm/gup.c
index ef7d2da9f03f..000f3303e7f2 100644
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -1536,7 +1536,11 @@ struct page *get_dump_page(unsigned long addr)
 	if (locked)
 		mmap_read_unlock(mm);
 
-	if (ret == 1 && is_page_poisoned(page))
+	/*
+	 * We might have hwpoisoned pages still mapped into user space. Don't
+	 * read these pages when creating a coredump, access could be fatal.
+	 */
+	if (ret == 1 && is_page_hwpoison(page))
 		return NULL;
 
 	return (ret == 1) ? page : NULL;
diff --git a/mm/internal.h b/mm/internal.h
index cb3c5e0a7799..1432feec62df 100644
--- a/mm/internal.h
+++ b/mm/internal.h
@@ -97,26 +97,6 @@ static inline void set_page_refcounted(struct page *page)
 	set_page_count(page, 1);
 }
 
-/*
- * When kernel touch the user page, the user page may be have been marked
- * poison but still mapped in user space, if without this page, the kernel
- * can guarantee the data integrity and operation success, the kernel is
- * better to check the posion status and avoid touching it, be good not to
- * panic, coredump for process fatal signal is a sample case matching this
- * scenario. Or if kernel can't guarantee the data integrity, it's better
- * not to call this function, let kernel touch the poison page and get to
- * panic.
- */
-static inline bool is_page_poisoned(struct page *page)
-{
-	if (PageHWPoison(page))
-		return true;
-	else if (PageHuge(page) && PageHWPoison(compound_head(page)))
-		return true;
-
-	return false;
-}
-
 extern unsigned long highest_memmap_pfn;
 
 /*
-- 
2.30.2