From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 8C87D10E9; Mon, 26 Aug 2024 17:30:54 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1724693454; cv=none; b=TNqpukuZzbyPtg9+1BFhIr0SDtQIdrvET/CutLpxNIT8MnospdMvmk14gQcR7XAgceFoXQ3dt7GzDHNOOtEM0jQfz9PnNWKVsfthfq21VU8pA/AuLh/mLOL9rabXvi+0BetmG9L1SOzKI39gZ3QjOg6izPRindKuH4qRCxt7Gqw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1724693454; c=relaxed/simple; bh=hvjbSglVG52utS/TNtvwDZVFsSLINCOLzNEh+HdAtW8=; h=Date:From:To:Cc:Subject:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=R2EhiC23zNoHzMMT3Q2jUShCSBIvpB4jlroJfl/UtqJ1KS9S7Xm+3alid/KHo2H5qsmWQVToPmw0WhkPj/N4zCT0KuZ8TTfysFCxNrn/syROjVdyZyNZqsHqDOTeo/zBNaZTHdF2YdMFwfVM727M50JAfh0pcZ9DHU9WfXIzX6s= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 Received: by smtp.kernel.org (Postfix) with ESMTPSA id 8217DC8B7BF; Mon, 26 Aug 2024 17:30:53 +0000 (UTC) Date: Mon, 26 Aug 2024 13:31:33 -0400 From: Steven Rostedt To: Viktor Malik Cc: linux-trace-kernel@vger.kernel.org, Masami Hiramatsu , Matt Wu , bpf@vger.kernel.org, Andrii Nakryiko Subject: Re: [PATCH v2] objpool: fix choosing allocation for percpu slots Message-ID: <20240826133133.5affc7e6@gandalf.local.home> In-Reply-To: <20240826060718.267261-1-vmalik@redhat.com> References: <20240826060718.267261-1-vmalik@redhat.com> X-Mailer: Claws Mail 3.20.0git84 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Precedence: bulk X-Mailing-List: linux-trace-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit On Mon, 26 Aug 2024 08:07:18 +0200 Viktor Malik wrote: > objpool intends to use vmalloc for default (non-atomic) allocations of > percpu slots and objects. However, the condition checking if GFP flags > are equal to GFP_ATOMIC is wrong b/c GFP_ATOMIC is a combination of bits > (__GFP_HIGH|__GFP_KSWAPD_RECLAIM) and so `pool->gfp & GFP_ATOMIC` will > be true if either bit is set. Since GFP_ATOMIC and GFP_KERNEL share the > ___GFP_KSWAPD_RECLAIM bit, kmalloc will be used in cases when GFP_KERNEL > is specified, i.e. in all current usages of objpool. > > This may lead to unexpected OOM errors since kmalloc cannot allocate > large amounts of memory. > > For instance, objpool is used by fprobe rethook which in turn is used by > BPF kretprobe.multi and kprobe.session probe types. Trying to attach > these to all kernel functions with libbpf using > > SEC("kprobe.session/*") > int kprobe(struct pt_regs *ctx) > { > [...] > } > > fails on objpool slot allocation with ENOMEM. > > Fix the condition to truly use vmalloc by default. > > Fixes: b4edb8d2d464 ("lib: objpool added: ring-array based lockless MPMC") > Signed-off-by: Viktor Malik > Acked-by: Andrii Nakryiko > Reviewed-by: Matt Wu Reviewed-by: Steven Rostedt (Google) -- Steve > --- > lib/objpool.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/lib/objpool.c b/lib/objpool.c > index 234f9d0bd081..fd108fe0d095 100644 > --- a/lib/objpool.c > +++ b/lib/objpool.c > @@ -76,7 +76,7 @@ objpool_init_percpu_slots(struct objpool_head *pool, int nr_objs, > * mimimal size of vmalloc is one page since vmalloc would > * always align the requested size to page size > */ > - if (pool->gfp & GFP_ATOMIC) > + if ((pool->gfp & GFP_ATOMIC) == GFP_ATOMIC) > slot = kmalloc_node(size, pool->gfp, cpu_to_node(i)); > else > slot = __vmalloc_node(size, sizeof(void *), pool->gfp,