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Subject[PATCHv10 31/36] thp, mm: split_huge_page(): caller need to lock page
Date
We're going to use migration entries instead of compound_lock() to
stabilize page refcounts. Setup and remove migration entries require
page to be locked.

Some of split_huge_page() callers already have the page locked. Let's
require everybody to lock the page before calling split_huge_page().

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Tested-by: Sasha Levin <sasha.levin@oracle.com>
Tested-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Acked-by: Jerome Marchand <jmarchan@redhat.com>
---
mm/memory-failure.c | 8 +++++++-
mm/migrate.c | 8 ++++++--
2 files changed, 13 insertions(+), 3 deletions(-)

diff --git a/mm/memory-failure.c b/mm/memory-failure.c
index 39591cce45ca..216f1d4768ec 100644
--- a/mm/memory-failure.c
+++ b/mm/memory-failure.c
@@ -1148,7 +1148,9 @@ int memory_failure(unsigned long pfn, int trapno, int flags)
}

if (!PageHuge(p) && PageTransHuge(hpage)) {
+ lock_page(hpage);
if (!PageAnon(hpage) || unlikely(split_huge_page(hpage))) {
+ unlock_page(hpage);
if (!PageAnon(hpage))
pr_err("MCE: %#lx: non anonymous thp\n", pfn);
else
@@ -1158,6 +1160,7 @@ int memory_failure(unsigned long pfn, int trapno, int flags)
put_hwpoison_page(p);
return -EBUSY;
}
+ unlock_page(hpage);
VM_BUG_ON_PAGE(!page_count(p), p);
hpage = compound_head(p);
}
@@ -1735,7 +1738,10 @@ int soft_offline_page(struct page *page, int flags)
return -EBUSY;
}
if (!PageHuge(page) && PageTransHuge(hpage)) {
- if (PageAnon(hpage) && unlikely(split_huge_page(hpage))) {
+ lock_page(page);
+ ret = split_huge_page(hpage);
+ unlock_page(page);
+ if (unlikely(ret)) {
pr_info("soft offline: %#lx: failed to split THP\n",
pfn);
if (flags & MF_COUNT_INCREASED)
diff --git a/mm/migrate.c b/mm/migrate.c
index d63965e2733d..b8e968fab1d2 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -939,9 +939,13 @@ static ICE_noinline int unmap_and_move(new_page_t get_new_page,
goto out;
}

- if (unlikely(PageTransHuge(page)))
- if (unlikely(split_huge_page(page)))
+ if (unlikely(PageTransHuge(page))) {
+ lock_page(page);
+ rc = split_huge_page(page);
+ unlock_page(page);
+ if (rc)
goto out;
+ }

rc = __unmap_and_move(page, newpage, force, mode);

--
2.5.0


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