diff options
| author | Mike Kravetz | 2021-09-02 14:58:43 -0700 |
|---|---|---|
| committer | Linus Torvalds | 2021-09-03 09:58:16 -0700 |
| commit | 416d85ed3e08c1164c1405249a94343166837802 (patch) | |
| tree | d9fdd881c4b5ed6fa8b130c91a10a76727740276 /mm | |
| parent | f87060d345232c7d855167a43faf006e24afa999 (diff) | |
hugetlb: simplify prep_compound_gigantic_page ref count racing code
Code in prep_compound_gigantic_page waits for a rcu grace period if it
notices a temporarily inflated ref count on a tail page. This was due to
the identified potential race with speculative page cache references which
could only last for a rcu grace period. This is overly complicated as
this situation is VERY unlikely to ever happen. Instead, just quickly
return an error.
Also, only print a warning in prep_compound_gigantic_page instead of
multiple callers.
Link: https://lkml.kernel.org/r/20210809184832.18342-2-mike.kravetz@oracle.com
Signed-off-by: Mike Kravetz <mike.kravetz@oracle.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mina Almasry <almasrymina@google.com>
Cc: Muchun Song <songmuchun@bytedance.com>
Cc: Naoya Horiguchi <naoya.horiguchi@linux.dev>
Cc: Oscar Salvador <osalvador@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm')
| -rw-r--r-- | mm/hugetlb.c | 17 |
1 files changed, 7 insertions, 10 deletions
diff --git a/mm/hugetlb.c b/mm/hugetlb.c index 8ea35ba6699f..3658398c835d 100644 --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -1657,16 +1657,14 @@ static bool prep_compound_gigantic_page(struct page *page, unsigned int order) * cache adding could take a ref on a 'to be' tail page. * We need to respect any increased ref count, and only set * the ref count to zero if count is currently 1. If count - * is not 1, we call synchronize_rcu in the hope that a rcu - * grace period will cause ref count to drop and then retry. - * If count is still inflated on retry we return an error and - * must discard the pages. + * is not 1, we return an error. An error return indicates + * the set of pages can not be converted to a gigantic page. + * The caller who allocated the pages should then discard the + * pages using the appropriate free interface. */ if (!page_ref_freeze(p, 1)) { - pr_info("HugeTLB unexpected inflated ref count on freshly allocated page\n"); - synchronize_rcu(); - if (!page_ref_freeze(p, 1)) - goto out_error; + pr_warn("HugeTLB page can not be used due to unexpected inflated ref count\n"); + goto out_error; } set_page_count(p, 0); set_compound_head(p, page); @@ -1830,7 +1828,6 @@ retry: retry = true; goto retry; } - pr_warn("HugeTLB page can not be used due to unexpected inflated ref count\n"); return NULL; } } @@ -2828,8 +2825,8 @@ static void __init gather_bootmem_prealloc(void) prep_new_huge_page(h, page, page_to_nid(page)); put_page(page); /* add to the hugepage allocator */ } else { + /* VERY unlikely inflated ref count on a tail page */ free_gigantic_page(page, huge_page_order(h)); - pr_warn("HugeTLB page can not be used due to unexpected inflated ref count\n"); } /* |