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DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1766459361; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=/ZcZnllijaalGMrElgL86g18d/eiz3nxCYnvfBLSc0k=; b=hhoQX0TEXgJB7rWiNxT4i3slue/uWm/NO9pe5bG3CNmAc0ky5okhCeylMjNbsQsyrHoOKr RL1mtMMGm+s9eMaPcA5K3dip3fHNMrQBh2A/DzL36Vq+yPsR01qj3It9eLJKUWV16nIGyN cWsokGNXndUoPM7ovLn8DOZv5bGjaZA= From: Roman Gushchin To: Alexei Starovoitov Cc: bpf , linux-mm , LKML , JP Kobryn , Alexei Starovoitov , Daniel Borkmann , Shakeel Butt , Michal Hocko , Johannes Weiner Subject: Re: [PATCH bpf-next v3 4/6] mm: introduce BPF kfuncs to access memcg statistics and events In-Reply-To: (Alexei Starovoitov's message of "Mon, 22 Dec 2025 16:11:19 -1000") References: <20251222221754.186191-1-roman.gushchin@linux.dev> <20251222221754.186191-5-roman.gushchin@linux.dev> Date: Mon, 22 Dec 2025 19:09:14 -0800 Message-ID: <87ms39c2sl.fsf@linux.dev> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable X-Migadu-Flow: FLOW_OUT X-Rspam-User: X-Rspamd-Queue-Id: 413EF100007 X-Rspamd-Server: rspam04 X-Stat-Signature: khr1jaqguzm9dw66cao3a9uruedkdeyx X-HE-Tag: 1766459365-669031 X-HE-Meta: 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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: Alexei Starovoitov writes: > On Mon, Dec 22, 2025 at 12:18=E2=80=AFPM Roman Gushchin > wrote: >> >> + if (idx < 0 || idx >=3D MEMCG_NR_STAT || !memcg_stat_item_valid(= idx)) >> + return (unsigned long)-1; > > memcg_stat_item_valid() and memcg_stat_item_valid() > helpers introduced specifically to be used in these kfuncs, > so I feel it's cleaner to do all idx checking within them > instead of splitting the checks like this. > Then it will be easier to see that > memcg_stat_item_valid(idx) access is in bounds when idx < MEMCG_NR_STAT > > Also I'd do one check like (u32)idx >=3D MEMCG_NR_STAT > and drop idx < 0 part. Compiler is probably smart enough to > optimize this way itself, but I'd still do one check. Sure, good point. Thanks for reviews!