The patch titled
Subject: mm: fix the handling Non-LRU pages returned by follow_page
has been added to the -mm mm-unstable branch. Its filename is
mm-fix-the-handling-non-lru-pages-returned-by-follow_page.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-fix-the-handling-non-lru-pages-returned-by-follow_page.patch
This patch will later appear in the mm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: Haiyue Wang <haiyue.wang@xxxxxxxxx>
Subject: mm: fix the handling Non-LRU pages returned by follow_page
Date: Tue, 23 Aug 2022 21:58:41 +0800
The handling Non-LRU pages returned by follow_page() jumps directly, it
doesn't call put_page() to handle the reference count, since 'FOLL_GET'
flag for follow_page() has get_page() called. Fix the zone device page
check by handling the page reference count correctly before returning.
And as David reviewed, "device pages are never PageKsm pages". Drop this
zone device page check for break_ksm().
Since the zone device page can't be a transparent huge page, so drop the
redundant zone device page check for split_huge_pages_pid(). (by Miaohe)
Link: https://lkml.kernel.org/r/20220823135841.934465-3-haiyue.wang@xxxxxxxxx
Fixes: 3218f8712d6b ("mm: handling Non-LRU pages returned by vm_normal_pages")
Signed-off-by: Haiyue Wang <haiyue.wang@xxxxxxxxx>
Reviewed-by: "Huang, Ying" <ying.huang@xxxxxxxxx>
Reviewed-by: Felix Kuehling <Felix.Kuehling@xxxxxxx>
Reviewed-by: Alistair Popple <apopple@xxxxxxxxxx>
Reviewed-by: Miaohe Lin <linmiaohe@xxxxxxxxxx>
Acked-by: David Hildenbrand <david@xxxxxxxxxx>
Cc: Alex Sierra <alex.sierra@xxxxxxx>
Cc: Gerald Schaefer <gerald.schaefer@xxxxxxxxxxxxx>
Cc: Mike Kravetz <mike.kravetz@xxxxxxxxxx>
Cc: Muchun Song <songmuchun@xxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/huge_memory.c | 2 +-
mm/ksm.c | 12 +++++++++---
mm/migrate.c | 19 ++++++++++++-------
3 files changed, 22 insertions(+), 11 deletions(-)
--- a/mm/huge_memory.c~mm-fix-the-handling-non-lru-pages-returned-by-follow_page
+++ a/mm/huge_memory.c
@@ -2979,7 +2979,7 @@ static int split_huge_pages_pid(int pid,
/* FOLL_DUMP to ignore special (like zero) pages */
page = follow_page(vma, addr, FOLL_GET | FOLL_DUMP);
- if (IS_ERR_OR_NULL(page) || is_zone_device_page(page))
+ if (IS_ERR_OR_NULL(page))
continue;
if (!is_transparent_hugepage(page))
--- a/mm/ksm.c~mm-fix-the-handling-non-lru-pages-returned-by-follow_page
+++ a/mm/ksm.c
@@ -475,7 +475,7 @@ static int break_ksm(struct vm_area_stru
cond_resched();
page = follow_page(vma, addr,
FOLL_GET | FOLL_MIGRATION | FOLL_REMOTE);
- if (IS_ERR_OR_NULL(page) || is_zone_device_page(page))
+ if (IS_ERR_OR_NULL(page))
break;
if (PageKsm(page))
ret = handle_mm_fault(vma, addr,
@@ -560,12 +560,15 @@ static struct page *get_mergeable_page(s
goto out;
page = follow_page(vma, addr, FOLL_GET);
- if (IS_ERR_OR_NULL(page) || is_zone_device_page(page))
+ if (IS_ERR_OR_NULL(page))
goto out;
+ if (is_zone_device_page(page))
+ goto out_putpage;
if (PageAnon(page)) {
flush_anon_page(vma, page, addr);
flush_dcache_page(page);
} else {
+out_putpage:
put_page(page);
out:
page = NULL;
@@ -2321,11 +2324,13 @@ next_mm:
if (ksm_test_exit(mm))
break;
*page = follow_page(vma, ksm_scan.address, FOLL_GET);
- if (IS_ERR_OR_NULL(*page) || is_zone_device_page(*page)) {
+ if (IS_ERR_OR_NULL(*page)) {
ksm_scan.address += PAGE_SIZE;
cond_resched();
continue;
}
+ if (is_zone_device_page(*page))
+ goto next_page;
if (PageAnon(*page)) {
flush_anon_page(vma, *page, ksm_scan.address);
flush_dcache_page(*page);
@@ -2340,6 +2345,7 @@ next_mm:
mmap_read_unlock(mm);
return rmap_item;
}
+next_page:
put_page(*page);
ksm_scan.address += PAGE_SIZE;
cond_resched();
--- a/mm/migrate.c~mm-fix-the-handling-non-lru-pages-returned-by-follow_page
+++ a/mm/migrate.c
@@ -1691,9 +1691,12 @@ static int add_page_for_migration(struct
goto out;
err = -ENOENT;
- if (!page || is_zone_device_page(page))
+ if (!page)
goto out;
+ if (is_zone_device_page(page))
+ goto out_putpage;
+
err = 0;
if (page_to_nid(page) == node)
goto out_putpage;
@@ -1891,13 +1894,15 @@ static void do_pages_stat_array(struct m
if (IS_ERR(page))
goto set_status;
- if (page && !is_zone_device_page(page)) {
+ err = -ENOENT;
+ if (!page)
+ goto set_status;
+
+ if (!is_zone_device_page(page))
err = page_to_nid(page);
- if (foll_flags & FOLL_GET)
- put_page(page);
- } else {
- err = -ENOENT;
- }
+
+ if (foll_flags & FOLL_GET)
+ put_page(page);
set_status:
*status = err;
_
Patches currently in -mm which might be from haiyue.wang@xxxxxxxxx are
mm-migration-fix-the-foll_get-failure-on-following-huge-page.patch
mm-fix-the-handling-non-lru-pages-returned-by-follow_page.patch
