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authorMike Kravetz <mike.kravetz@oracle.com>2021-06-30 18:48:31 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2021-06-30 20:47:26 -0700
commit48b8d744ea841b8adf8d07bfe7a2d55f22e4d179 (patch)
treef4d37570255cefc5e52da2ae3dc0269b4d2df7ae /mm/hugetlb.c
parente6d41f12df0efcaa6e30b575d40f2529024cfce9 (diff)
downloadlinux-48b8d744ea841b8adf8d07bfe7a2d55f22e4d179.tar.bz2
hugetlb: remove prep_compound_huge_page cleanup
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@mail.gmail.com/ 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@oracle.com Link: https://lkml.kernel.org/r/20210622021423.154662-2-mike.kravetz@oracle.com Signed-off-by: Mike Kravetz <mike.kravetz@oracle.com> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: Jan Kara <jack@suse.cz> Cc: Jann Horn <jannh@google.com> Cc: John Hubbard <jhubbard@nvidia.com> Cc: "Kirill A . Shutemov" <kirill@shutemov.name> Cc: Matthew Wilcox <willy@infradead.org> Cc: Michal Hocko <mhocko@kernel.org> Cc: Youquan Song <youquan.song@intel.com> Cc: Muchun Song <songmuchun@bytedance.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/hugetlb.c')
-rw-r--r--mm/hugetlb.c29
1 files changed, 10 insertions, 19 deletions
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index b14f4d1749b2..8048763e98a7 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -1320,8 +1320,6 @@ 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)
@@ -2759,16 +2757,10 @@ 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;
@@ -2777,20 +2769,19 @@ 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();
}
}