The patch titled
Subject: mm: move call to compound_head() in release_pages()
has been added to the -mm tree. Its filename is
mm-move-call-to-compound_head-in-release_pages.patch
This patch should soon appear at
https://ozlabs.org/~akpm/mmots/broken-out/mm-move-call-to-compound_head-in-release_pages.patch
and later at
https://ozlabs.org/~akpm/mmotm/broken-out/mm-move-call-to-compound_head-in-release_pages.patch
Before you just go and hit "reply", please:
a) Consider who else should be cc'ed
b) Prefer to cc a suitable mailing list as well
c) Ideally: find the original patch on the mailing list and do a
reply-to-all to that, adding suitable additional cc's
*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***
The -mm tree is included into linux-next and is updated
there every 3-4 working days
------------------------------------------------------
From: Ralph Campbell <rcampbell@xxxxxxxxxx>
Subject: mm: move call to compound_head() in release_pages()
The function is_huge_zero_page() doesn't call compound_head() to make sure
the page pointer is a head page. The call to is_huge_zero_page() in
release_pages() is made before compound_head() is called so the test would
fail if release_pages() was called with a tail page of the huge_zero_page
and put_page_testzero() would be called releasing the page.
This is unlikely to be happening in normal use or we would be seeing all
sorts of process data corruption when accessing a THP zero page.
Looking at other places where is_huge_zero_page() is called, all seem to
only pass a head page so I think the right solution is to move the call
to compound_head() in release_pages() to a point before calling
is_huge_zero_page().
Link: https://lkml.kernel.org/r/20200917173938.16420-1-rcampbell@xxxxxxxxxx
Signed-off-by: Ralph Campbell <rcampbell@xxxxxxxxxx>
Reviewed-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Yu Zhao <yuzhao@xxxxxxxxxx>
Cc: Dan Williams <dan.j.williams@xxxxxxxxx>
Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx>
Cc: Christoph Hellwig <hch@xxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/swap.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
--- a/mm/swap.c~mm-move-call-to-compound_head-in-release_pages
+++ a/mm/swap.c
@@ -848,6 +848,7 @@ void release_pages(struct page **pages,
locked_pgdat = NULL;
}
+ page = compound_head(page);
if (is_huge_zero_page(page))
continue;
@@ -869,7 +870,6 @@ void release_pages(struct page **pages,
}
}
- page = compound_head(page);
if (!put_page_testzero(page))
continue;
_
Patches currently in -mm which might be from rcampbell@xxxxxxxxxx are
mm-thp-fix-__split_huge_pmd_locked-for-migration-pmd.patch
mm-test-use-the-new-skip-macro.patch
hmm-test-remove-unused-dmirror_zero_page.patch
mm-move-call-to-compound_head-in-release_pages.patch
mm-migrate-remove-cpages-in-migrate_vma_finalize.patch
mm-migrate-remove-obsolete-comment-about-device-public.patch
