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([2600:1700:6cf8:1240:70f9:8463:f3b1:c282]) by smtp.gmail.com with ESMTPSA id nd25-20020a056871441900b0022f7268ec29sm2030133oab.54.2024.04.22.10.30.47 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 22 Apr 2024 10:30:47 -0700 (PDT) Message-ID: <70bf97a6-19d8-4a26-8879-17db7c44a2cc@gmail.com> Date: Mon, 22 Apr 2024 10:30:45 -0700 Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH bpf-next 1/2] bpf: enable the "open" operator on a pinned path of a struct_osp link. From: Kui-Feng Lee To: Martin KaFai Lau , Kui-Feng Lee , andrii@kernel.org Cc: kuifeng@meta.com, bpf@vger.kernel.org, ast@kernel.org, song@kernel.org, kernel-team@meta.com References: <20240417002513.1534535-1-thinker.li@gmail.com> <20240417002513.1534535-2-thinker.li@gmail.com> <8dadfcc9-1f6a-4b93-951b-548e4560ce5a@linux.dev> <0326d150-6b43-465c-ba43-7e7033b13408@gmail.com> Content-Language: en-US In-Reply-To: <0326d150-6b43-465c-ba43-7e7033b13408@gmail.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit On 4/22/24 10:12, Kui-Feng Lee wrote: > > > On 4/19/24 17:05, Martin KaFai Lau wrote: >> On 4/16/24 5:25 PM, Kui-Feng Lee wrote: >>> +int bpffs_struct_ops_link_open(struct inode *inode, struct file *filp) >>> +{ >>> +    struct bpf_struct_ops_link *link = inode->i_private; >>> + >>> +    /* Paired with bpf_link_put_direct() in bpf_link_release(). */ >>> +    bpf_link_inc(&link->link); >>> +    filp->private_data = link; >>> +    return 0; >>> +} >>> diff --git a/kernel/bpf/inode.c b/kernel/bpf/inode.c >>> index af5d2ffadd70..b020d761ab0a 100644 >>> --- a/kernel/bpf/inode.c >>> +++ b/kernel/bpf/inode.c >>> @@ -360,11 +360,16 @@ static int bpf_mkmap(struct dentry *dentry, >>> umode_t mode, void *arg) >>>   static int bpf_mklink(struct dentry *dentry, umode_t mode, void *arg) >>>   { >>> +    const struct file_operations *fops; >>>       struct bpf_link *link = arg; >>> -    return bpf_mkobj_ops(dentry, mode, arg, &bpf_link_iops, >>> -                 bpf_link_is_iter(link) ? >>> -                 &bpf_iter_fops : &bpffs_obj_fops); >>> +    if (bpf_link_is_iter(link)) >>> +        fops = &bpf_iter_fops; >>> +    else if (link->type == BPF_LINK_TYPE_STRUCT_OPS) >> >> Open a pinned link and then update should not be specific to >> struct_ops link. e.g. should be useful to the cgroup link also? > > It could be. Here, I played safe in case it creates any unwanted side > effect for links of unknown types. By the way, may I put it in a follow up patch if we want cgroup links? > >> >> Andrii, wdyt about supporting other link types also? >> >>> +        fops = &bpf_link_fops; >>> +    else >>> +        fops = &bpffs_obj_fops; >>> +    return bpf_mkobj_ops(dentry, mode, arg, &bpf_link_iops, fops); >>>   } >>>   static struct dentry * >>> diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c >>> index 7d392ec83655..f66bc6215faa 100644 >>> --- a/kernel/bpf/syscall.c >>> +++ b/kernel/bpf/syscall.c >>> @@ -3108,7 +3108,19 @@ static void bpf_link_show_fdinfo(struct >>> seq_file *m, struct file *filp) >>>   } >>>   #endif >>> -static const struct file_operations bpf_link_fops = { >>> +/* Support opening pinned links */ >>> +static int bpf_link_open(struct inode *inode, struct file *filp) >>> +{ >>> +    struct bpf_link *link = inode->i_private; >>> + >>> +    if (link->type == BPF_LINK_TYPE_STRUCT_OPS) >>> +        return bpffs_struct_ops_link_open(inode, filp); >>> + >>> +    return -EOPNOTSUPP; >>> +} >>> + >>> +const struct file_operations bpf_link_fops = { >>> +    .open = bpf_link_open, >>>   #ifdef CONFIG_PROC_FS >>>       .show_fdinfo    = bpf_link_show_fdinfo, >>>   #endif >>