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author | Peter Collingbourne <pcc@google.com> | 2023-03-10 07:29:13 +0300 |
---|---|---|
committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2023-03-30 13:49:26 +0300 |
commit | 450317033f04e6dff5cf9b675a9797ee602e25e3 (patch) | |
tree | 4f8f2a70cf13c99d4761496bff238304cb56aa42 /mm | |
parent | 7b100a45dc19ffd708f364ba66601efaca1ccf56 (diff) | |
download | linux-450317033f04e6dff5cf9b675a9797ee602e25e3.tar.xz |
Revert "kasan: drop skip_kasan_poison variable in free_pages_prepare"
commit f446883d12b8bfa486f7c98d403054d61d38c989 upstream.
This reverts commit 487a32ec24be819e747af8c2ab0d5c515508086a.
should_skip_kasan_poison() reads the PG_skip_kasan_poison flag from
page->flags. However, this line of code in free_pages_prepare():
page->flags &= ~PAGE_FLAGS_CHECK_AT_PREP;
clears most of page->flags, including PG_skip_kasan_poison, before calling
should_skip_kasan_poison(), which meant that it would never return true as
a result of the page flag being set. Therefore, fix the code to call
should_skip_kasan_poison() before clearing the flags, as we were doing
before the reverted patch.
This fixes a measurable performance regression introduced in the reverted
commit, where munmap() takes longer than intended if HW tags KASAN is
supported and enabled at runtime. Without this patch, we see a
single-digit percentage performance regression in a particular
mmap()-heavy benchmark when enabling HW tags KASAN, and with the patch,
there is no statistically significant performance impact when enabling HW
tags KASAN.
Link: https://lkml.kernel.org/r/20230310042914.3805818-2-pcc@google.com
Fixes: 487a32ec24be ("kasan: drop skip_kasan_poison variable in free_pages_prepare")
Link: https://linux-review.googlesource.com/id/Ic4f13affeebd20548758438bb9ed9ca40e312b79
Signed-off-by: Peter Collingbourne <pcc@google.com>
Reviewed-by: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com>
Cc: Catalin Marinas <catalin.marinas@arm.com> [arm64]
Cc: Evgenii Stepanov <eugenis@google.com>
Cc: Vincenzo Frascino <vincenzo.frascino@arm.com>
Cc: Will Deacon <will@kernel.org>
Cc: <stable@vger.kernel.org> [6.1]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'mm')
-rw-r--r-- | mm/page_alloc.c | 3 |
1 files changed, 2 insertions, 1 deletions
diff --git a/mm/page_alloc.c b/mm/page_alloc.c index b2877a84ed19..5cae08963984 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -1402,6 +1402,7 @@ static __always_inline bool free_pages_prepare(struct page *page, unsigned int order, bool check_free, fpi_t fpi_flags) { int bad = 0; + bool skip_kasan_poison = should_skip_kasan_poison(page, fpi_flags); bool init = want_init_on_free(); VM_BUG_ON_PAGE(PageTail(page), page); @@ -1476,7 +1477,7 @@ static __always_inline bool free_pages_prepare(struct page *page, * With hardware tag-based KASAN, memory tags must be set before the * page becomes unavailable via debug_pagealloc or arch_free_page. */ - if (!should_skip_kasan_poison(page, fpi_flags)) { + if (!skip_kasan_poison) { kasan_poison_pages(page, order, init); /* Memory is already initialized if KASAN did it internally. */ |