This is a note to let you know that I've just added the patch titled
hugetlb: remove prep_compound_huge_page cleanup
to the 5.13-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
hugetlb-remove-prep_compound_huge_page-cleanup.patch
and it can be found in the queue-5.13 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 8767a52e65600e156f8b4b08a1c33e8997bbe083
Author: Mike Kravetz <mike.kravetz@xxxxxxxxxx>
Date: Wed Jun 30 18:48:31 2021 -0700
hugetlb: remove prep_compound_huge_page cleanup
[ Upstream commit 48b8d744ea841b8adf8d07bfe7a2d55f22e4d179 ]
Patch series "Fix prep_compound_gigantic_page ref count adjustment".
These patches address the possible race between
prep_compound_gigantic_page and __page_cache_add_speculative as described
by Jann Horn in [1].
The first patch simply removes the unnecessary/obsolete helper routine
prep_compound_huge_page to make the actual fix a little simpler.
The second patch is the actual fix and has a detailed explanation in the
commit message.
This potential issue has existed for almost 10 years and I am unaware of
anyone actually hitting the race. I did not cc stable, but would be happy
to squash the patches and send to stable if anyone thinks that is a good
idea.
[1] https://lore.kernel.org/linux-mm/CAG48ez23q0Jy9cuVnwAe7t_fdhMk2S7N5Hdi-GLcCeq5bsfLxw@xxxxxxxxxxxxxx/
This patch (of 2):
I could not think of a reliable way to recreate the issue for testing.
Rather, I 'simulated errors' to exercise all the error paths.
The routine prep_compound_huge_page is a simple wrapper to call either
prep_compound_gigantic_page or prep_compound_page. However, it is only
called from gather_bootmem_prealloc which only processes gigantic pages.
Eliminate the routine and call prep_compound_gigantic_page directly.
Link: https://lkml.kernel.org/r/20210622021423.154662-1-mike.kravetz@xxxxxxxxxx
Link: https://lkml.kernel.org/r/20210622021423.154662-2-mike.kravetz@xxxxxxxxxx
Signed-off-by: Mike Kravetz <mike.kravetz@xxxxxxxxxx>
Cc: Andrea Arcangeli <aarcange@xxxxxxxxxx>
Cc: Jan Kara <jack@xxxxxxx>
Cc: Jann Horn <jannh@xxxxxxxxxx>
Cc: John Hubbard <jhubbard@xxxxxxxxxx>
Cc: "Kirill A . Shutemov" <kirill@xxxxxxxxxxxxx>
Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxxxx>
Cc: Youquan Song <youquan.song@xxxxxxxxx>
Cc: Muchun Song <songmuchun@xxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 5ba5a0da6d57..65e0e8642ded 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -1318,8 +1318,6 @@ static struct page *alloc_gigantic_page(struct hstate *h, gfp_t gfp_mask,
return alloc_contig_pages(nr_pages, gfp_mask, nid, nodemask);
}
-static void prep_new_huge_page(struct hstate *h, struct page *page, int nid);
-static void prep_compound_gigantic_page(struct page *page, unsigned int order);
#else /* !CONFIG_CONTIG_ALLOC */
static struct page *alloc_gigantic_page(struct hstate *h, gfp_t gfp_mask,
int nid, nodemask_t *nodemask)
@@ -2625,16 +2623,10 @@ found:
return 1;
}
-static void __init prep_compound_huge_page(struct page *page,
- unsigned int order)
-{
- if (unlikely(order > (MAX_ORDER - 1)))
- prep_compound_gigantic_page(page, order);
- else
- prep_compound_page(page, order);
-}
-
-/* Put bootmem huge pages into the standard lists after mem_map is up */
+/*
+ * Put bootmem huge pages into the standard lists after mem_map is up.
+ * Note: This only applies to gigantic (order > MAX_ORDER) pages.
+ */
static void __init gather_bootmem_prealloc(void)
{
struct huge_bootmem_page *m;
@@ -2643,20 +2635,19 @@ static void __init gather_bootmem_prealloc(void)
struct page *page = virt_to_page(m);
struct hstate *h = m->hstate;
+ VM_BUG_ON(!hstate_is_gigantic(h));
WARN_ON(page_count(page) != 1);
- prep_compound_huge_page(page, huge_page_order(h));
+ prep_compound_gigantic_page(page, huge_page_order(h));
WARN_ON(PageReserved(page));
prep_new_huge_page(h, page, page_to_nid(page));
put_page(page); /* free it into the hugepage allocator */
/*
- * If we had gigantic hugepages allocated at boot time, we need
- * to restore the 'stolen' pages to totalram_pages in order to
- * fix confusing memory reports from free(1) and another
- * side-effects, like CommitLimit going negative.
+ * We need to restore the 'stolen' pages to totalram_pages
+ * in order to fix confusing memory reports from free(1) and
+ * other side-effects, like CommitLimit going negative.
*/
- if (hstate_is_gigantic(h))
- adjust_managed_page_count(page, pages_per_huge_page(h));
+ adjust_managed_page_count(page, pages_per_huge_page(h));
cond_resched();
}
}
