From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-185.mta0.migadu.com (out-185.mta0.migadu.com [91.218.175.185]) (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 4BEBB187F for ; Thu, 23 May 2024 18:34:38 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=91.218.175.185 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1716489282; cv=none; b=RSJQOHWYkpqP1r9CEU/YTteNdkrT1JrOvqrj9fA+/KqJ8ZYePA+CCS7hfUMm7aagpVyXe8qHY4j7TmO67VeyD7UWxZk+ELgtjU8yjK80L5Mi44Rr1N+mHbY8KNL0ufnKfXkQ50MOSrZrmdO/9fi+PMDFaX6kLBGAUvhGldfZ+4A= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1716489282; c=relaxed/simple; bh=9JEPqtwzGJPdoN549kW6zVHj7oHo3E7htBSRvBJcOyQ=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=VaX7eEntnJqqeFu4Eh5hk88w8tgqzI2kYzs8s489JbsbiNCoyfnckCRqhoJdfK6553Yzxa17QWkncquM42FuAopOTGcegCYBiYboIdZg8T8n/VQtvi/XhvbMSdGn9N3Qjao6cwn6sZ73A89KFH0W28uZ/6PcLIt0EbMv5w2cXds= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=YYYJXeVY; arc=none smtp.client-ip=91.218.175.185 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="YYYJXeVY" X-Envelope-To: sinquersw@gmail.com DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1716489277; 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=TFGz3NC4BLUUZvi/mrdIrIUNJCdNGxG+b3MeyH3azgU=; b=YYYJXeVYeJxYM2ikjq7VX62HI23AKQpYKZOe5DkOVcIhNviR4ptGHBzUfsBphU+rR51XH8 9rorpowOpxEoivN63Svt91janyqKVYk4ndmLDLVg75+faOyqpwCCwG0YKHIQtDfBNkkNYV 25Qed9fEBkwu4LAdaVsroHpBedyS0Ow= X-Envelope-To: thinker.li@gmail.com X-Envelope-To: bpf@vger.kernel.org X-Envelope-To: ast@kernel.org X-Envelope-To: song@kernel.org X-Envelope-To: kernel-team@meta.com X-Envelope-To: andrii@kernel.org X-Envelope-To: kuifeng@meta.com Message-ID: Date: Thu, 23 May 2024 11:34:32 -0700 Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Subject: Re: [PATCH bpf-next v4 3/7] bpf: support epoll from bpf struct_ops links. To: Kui-Feng Lee , Kui-Feng Lee Cc: bpf@vger.kernel.org, ast@kernel.org, song@kernel.org, kernel-team@meta.com, andrii@kernel.org, kuifeng@meta.com References: <20240521225121.770930-1-thinker.li@gmail.com> <20240521225121.770930-4-thinker.li@gmail.com> <787e0274-5592-4b74-8a7f-3d1962d41d35@gmail.com> Content-Language: en-US X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Martin KaFai Lau In-Reply-To: <787e0274-5592-4b74-8a7f-3d1962d41d35@gmail.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT On 5/23/24 11:24 AM, Kui-Feng Lee wrote: > > > On 5/23/24 10:23, Martin KaFai Lau wrote: >> On 5/21/24 3:51 PM, Kui-Feng Lee wrote: >>> +static __poll_t bpf_link_poll(struct file *file, struct poll_table_struct *pts) >>> +{ >>> +    struct bpf_link *link = file->private_data; >>> + >>> +    if (link->ops->poll) >>> +        return link->ops->poll(file, pts); >>> + >>> +    return 0; >> >> The current bpf_link_fops.poll is NULL before this patch. From vfs_poll, it >> seems to be DEFAULT_POLLMASK for this case. Please double check. > > > Yes, it returns DEFAULT_POLLMASK if file->f_op->epoll is NULL. But, > before this patch, link can not be added to an epoll. See the > explanation below. How about select() and poll() that do not need epoll_ctl() setup? > >> >>> +} >>> + >>>   static const struct file_operations bpf_link_fops = { >>>   #ifdef CONFIG_PROC_FS >>>       .show_fdinfo    = bpf_link_show_fdinfo, >>> @@ -3157,6 +3167,7 @@ static const struct file_operations bpf_link_fops = { >>>       .release    = bpf_link_release, >>>       .read        = bpf_dummy_read, >>>       .write        = bpf_dummy_write, >>> +    .poll        = bpf_link_poll, >> >> Same here. What does the epoll_ctl(EPOLL_CTL_ADD) currently expect for link >> (e.g. cgroup) that does not support poll? >> > > epoll_ctl() always returns -EPERM for files not supporting poll. > Should I add another instance of struct file_operations to keep the > consistency for other types of links? imo, it makes sense to have another instance for link that supports poll such that epoll_ctl(EPOLL_CTL_ADD) can fail early for the unsupported links. > >>>   }; >>