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Thu, 10 Apr 2025 23:40:33 -0700 (PDT) Mime-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset=UTF-8 Date: Fri, 11 Apr 2025 16:40:25 +1000 Message-Id: Cc: "Hugh Dickins" , "Guenter Roeck" , "Juergen Gross" , "Jeremy Fitzhardinge" , , , , , , , Subject: Re: [PATCH v1 1/4] kasan: Avoid sleepable page allocation from atomic context From: "Nicholas Piggin" To: "Alexander Gordeev" , "Andrew Morton" , "Andrey Ryabinin" X-Mailer: aerc 0.19.0 References: In-Reply-To: X-Stat-Signature: ouza7nmwc13t8zca3w6b9n4ipe9fqc8s X-Rspam-User: X-Rspamd-Queue-Id: 0CA6F1A0005 X-Rspamd-Server: rspam08 X-HE-Tag: 1744353634-259943 X-HE-Meta: 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 /gxkmCU/ 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Tue Apr 8, 2025 at 1:11 AM AEST, Alexander Gordeev wrote: > apply_to_page_range() enters lazy MMU mode and then invokes > kasan_populate_vmalloc_pte() callback on each page table walk > iteration. The lazy MMU mode may only be entered only under > protection of the page table lock. However, the callback can > go into sleep when trying to allocate a single page. > > Change __get_free_page() allocation mode from GFP_KERNEL to > GFP_ATOMIC to avoid scheduling out while in atomic context. It's a bit unfortunate to make this use atomic allocs for archs that don't need it. Could you make it depend on __HAVE_ARCH_ENTER_LAZY_MMU_MODE or is that overkill? I wanted to remove ppc64's per-CPU page array and replace it with on stack or dynaimc alloc array in the thread... but cost/benefit of working on ppc64 hash MMU code is not high :( Fix itself for ppc64's requirement at least looks right to me so for that, Reviewed-by: Nicholas Piggin > > Signed-off-by: Alexander Gordeev > --- > mm/kasan/shadow.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/mm/kasan/shadow.c b/mm/kasan/shadow.c > index 88d1c9dcb507..edfa77959474 100644 > --- a/mm/kasan/shadow.c > +++ b/mm/kasan/shadow.c > @@ -301,7 +301,7 @@ static int kasan_populate_vmalloc_pte(pte_t *ptep, un= signed long addr, > if (likely(!pte_none(ptep_get(ptep)))) > return 0; > =20 > - page =3D __get_free_page(GFP_KERNEL); > + page =3D __get_free_page(GFP_ATOMIC); > if (!page) > return -ENOMEM; > =20