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Tue, 5 May 2020 20:28:24 +0000 Subject: Re: [PATCH bpf-next v2 06/20] bpf: create anonymous bpf iterator To: Andrii Nakryiko CC: Andrii Nakryiko , bpf , Martin KaFai Lau , Networking , Alexei Starovoitov , Daniel Borkmann , Kernel Team References: <20200504062547.2047304-1-yhs@fb.com> <20200504062553.2047848-1-yhs@fb.com> From: Yonghong Song Message-ID: <8cf5ea90-6805-84fe-faae-3c894cd1b203@fb.com> Date: Tue, 5 May 2020 13:28:18 -0700 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.14; rv:68.0) Gecko/20100101 Thunderbird/68.7.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-ClientProxiedBy: BYAPR07CA0031.namprd07.prod.outlook.com (2603:10b6:a02:bc::44) To BYAPR15MB4088.namprd15.prod.outlook.com (2603:10b6:a02:c3::18) MIME-Version: 1.0 X-MS-Exchange-MessageSentRepresentingType: 1 Received: from macbook-pro-52.local.dhcp.thefacebook.com (2620:10d:c090:400::5:99aa) by BYAPR07CA0031.namprd07.prod.outlook.com (2603:10b6:a02:bc::44) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.2958.27 via Frontend Transport; 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X-MS-Exchange-AntiSpam-MessageData: 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 X-MS-Exchange-CrossTenant-Network-Message-Id: efbf3211-5080-441d-ad45-08d7f132dc1a X-MS-Exchange-CrossTenant-OriginalArrivalTime: 05 May 2020 20:28:24.1168 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: 8ae927fe-1255-47a7-a2af-5f3a069daaa2 X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: CeIi2xrNyN56D8GDfCAJsHNVQDSTj4MGzmYvSWYLr7TxXj2P1h0zL2PMRyX77ags X-MS-Exchange-Transport-CrossTenantHeadersStamped: BYAPR15MB3461 X-OriginatorOrg: fb.com X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.138,18.0.676 definitions=2020-05-05_10:2020-05-04,2020-05-05 signatures=0 X-Proofpoint-Spam-Details: rule=fb_default_notspam policy=fb_default score=0 mlxlogscore=999 priorityscore=1501 impostorscore=0 lowpriorityscore=0 phishscore=0 adultscore=0 bulkscore=0 spamscore=0 malwarescore=0 suspectscore=0 mlxscore=0 clxscore=1015 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2003020000 definitions=main-2005050157 X-FB-Internal: deliver Sender: bpf-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org On 5/5/20 1:11 PM, Andrii Nakryiko wrote: > On Sun, May 3, 2020 at 11:29 PM Yonghong Song wrote: >> >> A new bpf command BPF_ITER_CREATE is added. >> >> The anonymous bpf iterator is seq_file based. >> The seq_file private data are referenced by targets. >> The bpf_iter infrastructure allocated additional space >> at seq_file->private before the space used by targets >> to store some meta data, e.g., >> prog: prog to run >> session_id: an unique id for each opened seq_file >> seq_num: how many times bpf programs are queried in this session >> do_stop: an internal state to decide whether bpf program >> should be called in seq_ops->stop() or not >> >> Signed-off-by: Yonghong Song >> --- >> include/linux/bpf.h | 1 + >> include/uapi/linux/bpf.h | 6 ++ >> kernel/bpf/bpf_iter.c | 128 +++++++++++++++++++++++++++++++++ >> kernel/bpf/syscall.c | 26 +++++++ >> tools/include/uapi/linux/bpf.h | 6 ++ >> 5 files changed, 167 insertions(+) >> > > [...] > >> /* The description below is an attempt at providing documentation to eBPF >> diff --git a/kernel/bpf/bpf_iter.c b/kernel/bpf/bpf_iter.c >> index 2674c9cbc3dc..2a9f939be6e6 100644 >> --- a/kernel/bpf/bpf_iter.c >> +++ b/kernel/bpf/bpf_iter.c >> @@ -2,6 +2,7 @@ >> /* Copyright (c) 2020 Facebook */ >> >> #include >> +#include >> #include >> #include >> >> @@ -20,12 +21,26 @@ struct bpf_iter_link { >> struct bpf_iter_target_info *tinfo; >> }; >> >> +struct bpf_iter_priv_data { >> + struct { > > nit: anon struct seems unnecessary here? is it just for visual grouping? Yes, this is just for virtual grouping. Not 100% sure whether this is needed or not. > >> + struct bpf_iter_target_info *tinfo; >> + struct bpf_prog *prog; >> + u64 session_id; >> + u64 seq_num; >> + u64 do_stop; >> + }; >> + u8 target_private[] __aligned(8); >> +}; >> + >> static struct list_head targets = LIST_HEAD_INIT(targets); >> static DEFINE_MUTEX(targets_mutex); >> >> /* protect bpf_iter_link changes */ >> static DEFINE_MUTEX(link_mutex); >> >> +/* incremented on every opened seq_file */ >> +static atomic64_t session_id; >> + >> /* bpf_seq_read, a customized and simpler version for bpf iterator. >> * no_llseek is assumed for this file. >> * The following are differences from seq_read(): >> @@ -154,6 +169,31 @@ static ssize_t bpf_seq_read(struct file *file, char __user *buf, size_t size, >> goto Done; >> } >> >> +static int iter_release(struct inode *inode, struct file *file) >> +{ >> + struct bpf_iter_priv_data *iter_priv; >> + void *file_priv = file->private_data; >> + struct seq_file *seq; >> + >> + seq = file_priv; > > > seq might be NULL, if anon_inode_getfile succeeded, but then > prepare_seq_file failed, so you need to handle that. Thanks for catching this. Missed this case. > > Also, file_priv is redundant, assign to seq directly from file->private_data? Ack. > >> + iter_priv = container_of(seq->private, struct bpf_iter_priv_data, >> + target_private); >> + >> + if (iter_priv->tinfo->fini_seq_private) >> + iter_priv->tinfo->fini_seq_private(seq->private); >> + >> + bpf_prog_put(iter_priv->prog); >> + seq->private = iter_priv; >> + >> + return seq_release_private(inode, file); >> +} >> + >> +static const struct file_operations bpf_iter_fops = { >> + .llseek = no_llseek, >> + .read = bpf_seq_read, >> + .release = iter_release, >> +}; >> + >> int bpf_iter_reg_target(struct bpf_iter_reg *reg_info) >> { >> struct bpf_iter_target_info *tinfo; >> @@ -289,3 +329,91 @@ int bpf_iter_link_attach(const union bpf_attr *attr, struct bpf_prog *prog) >> >> return bpf_link_settle(&link_primer); >> } >> + >> +static void init_seq_meta(struct bpf_iter_priv_data *priv_data, >> + struct bpf_iter_target_info *tinfo, >> + struct bpf_prog *prog) >> +{ >> + priv_data->tinfo = tinfo; >> + priv_data->prog = prog; >> + priv_data->session_id = atomic64_add_return(1, &session_id); > > nit: atomic64_inc_return? Ack. > >> + priv_data->seq_num = 0; >> + priv_data->do_stop = 0; >> +} >> + > > [...] >