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[109.81.31.43]) by smtp.gmail.com with UTF8SMTPSA id a640c23a62f3a-b07b3347b6fsm990538866b.111.2025.09.15.10.16.51 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 15 Sep 2025 10:16:51 -0700 (PDT) Date: Mon, 15 Sep 2025 19:16:50 +0200 From: Michal Hocko To: "Uladzislau Rezki (Sony)" Cc: linux-mm@kvack.org, Andrew Morton , Baoquan He , LKML Subject: Re: [PATCH v2 09/10] mm: Skip might_alloc() warnings when PF_MEMALLOC is set Message-ID: References: <20250915134041.151462-1-urezki@gmail.com> <20250915134041.151462-10-urezki@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250915134041.151462-10-urezki@gmail.com> X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: 6A79C1A0009 X-Stat-Signature: rnheqpfeue4s6yktofe1absut3ahjtj5 X-Rspam-User: X-HE-Tag: 1757956613-585569 X-HE-Meta: U2FsdGVkX1/vKEeC5PGiOvkOf7+4lem9q1KheaktjWpq2kHVznS8NLSzHXBot6dLLgULraZrIP1v0tLVXXeg6IkK4deylbZb/YnWl00Krymbzgg4TV3osSQG7RAUuzQ6M4egFNOq5fk6LV8fCrbEwhXp3RjDvyazuXq1L4uLyiEmKjBlNGckpy3Ws2E4dtDaOxA9N4AOl//KAzUZohqMdN0i8LtRCjw8l8y8+/IIZQqeE+tCPpfcQ59d/JzBPk4P6dfEeL6B5zLrVMJJeI3F+gUZx0vsWYsmKvL3vmOX3hjXECxHtFInTdeP2jnJvUgofnx3ogQ6/kZSdRPj4Ynzfb2eTxuVCCJE5yRngnRIOcFPUPxOJ1K8SdS9BQKJyjzxGJqrl8gzGiP+CQKNox+yCAZPj6UHH8QyYbHdAAbF+v19gWTwsymLk+3Xj5Vu3TivUb02upOD75EYM/a76V75rDFhBuBPuDUz1wTXBRGLnB4Q2RTwhjaz4K4VnfA/kYNyinXQ4nVYOivAdIXkfTyD8yQKfVmWfa/0YghKMMjR/wUt+BuarRMsMFethyJmvxjBjDPlomfKOlugq5BqiKKhK411fI62Z2kTlv7+1pNuFwplgCXkkclSajV6poWK2tvzdVKa4iigcIxqqmIm70UwNfoLLy2SDrzl/kl1cob87l7c413obBX4lSeW5G2t3g3PejF2fhjaXXzUiFpz/DGGLa+MIz+IuaA6VONqsC7UFNSssBkKDfiUlScsIQlOuuqVgwQIi92vpcyJS6rZZCslwXZ9SDbLvOL2eZPpyT8JBOEmeKKi2NEzZQO35d/pDYmj4ZjYEbMH196nubveOlaWrWlWZYP7GT2xNVEDFr+q9ECYezHJPo2gkbeE58JzgItERICkzOgLmxMdxjxhMXgbZCRHpOXCLGDuU3fHxSFs6y+8/Rd4TUZdQABg2fl4JBFMmN7C4Jkg6eqA3UEfxXD BQlZgE+5 ed9LsRPQzuHfqGIT1ewOpAvw12ufAo1h5TWy8KB1CYtR7LqyB1pc3CFgWWCIYTJLCS115lNGjENUtUbslh+uSJ71zW3tqjjOU6zx/Abug2T62xd4ZUA+9pfLYY1tbWh8sSC6EftEDvsfXuxlzYvsj6NgkT2Faix86qM3Mo1IKD4Rsj0irKbqOivZJH/rRPAosWFPBHSBt3ZQSogqK8Lx+pfhLZc29uGs2p1EoKsmBYu2GF/2f5acSia2XXNXn02CZbRDWnf0IoFtNBmUFZz8isEhsdNyffigQ+nELb8DrxDvuVBeKoOM63up5KhTI3wCtMHrIcqFPpc9Qg8Gvqqus/fW/t7j8SKnLfuT+OBgm0vAo7UHQbfme4VbY7HC8hCsyUgBLXv3/BZUj5NCoTEqXRpe2DrkrQT14T5R9WzXXjqPAsfAYN+cjQRlJWiwVIoahoJvX 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 Mon 15-09-25 15:40:39, Uladzislau Rezki wrote: > might_alloc() catches invalid blocking allocations in contexts > where sleeping is not allowed. > > However when PF_MEMALLOC is set, the page allocator already skips > reclaim and other blocking paths. In such cases, a blocking gfp_mask > does not actually lead to blocking, so triggering might_alloc() splats > is misleading. > > Adjust might_alloc() to skip warnings when the current task has > PF_MEMALLOC set, matching the allocator's actual blocking behaviour. > > Signed-off-by: Uladzislau Rezki (Sony) I would probably just bail out early for PF_MEMALLOC to not meddle with might_sleep_if condition as it seems to read better but I do not insist. Acked-by: Michal Hocko Thanks > --- > include/linux/sched/mm.h | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/include/linux/sched/mm.h b/include/linux/sched/mm.h > index 2201da0afecc..dc2d3cab32ef 100644 > --- a/include/linux/sched/mm.h > +++ b/include/linux/sched/mm.h > @@ -318,7 +318,8 @@ static inline void might_alloc(gfp_t gfp_mask) > fs_reclaim_acquire(gfp_mask); > fs_reclaim_release(gfp_mask); > > - might_sleep_if(gfpflags_allow_blocking(gfp_mask)); > + might_sleep_if(gfpflags_allow_blocking(gfp_mask) && > + !(current->flags & PF_MEMALLOC)); > } > > /** > -- > 2.47.3 -- Michal Hocko SUSE Labs