From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-5.6 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,USER_AGENT_MUTT autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id D5498C28CC1 for ; Sat, 1 Jun 2019 16:08:31 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 9A7AE2774F for ; Sat, 1 Jun 2019 16:08:31 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=joelfernandes.org header.i=@joelfernandes.org header.b="WxiKyCmW" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726485AbfFAQI0 (ORCPT ); Sat, 1 Jun 2019 12:08:26 -0400 Received: from mail-pg1-f193.google.com ([209.85.215.193]:37744 "EHLO mail-pg1-f193.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726149AbfFAQI0 (ORCPT ); Sat, 1 Jun 2019 12:08:26 -0400 Received: by mail-pg1-f193.google.com with SMTP id 20so5769909pgr.4 for ; Sat, 01 Jun 2019 09:08:25 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=joelfernandes.org; s=google; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=pexNnjdwXBXMeIxyaoaSmCkUfu6bHwCGflifoKJOFh0=; b=WxiKyCmWdRQmhIM5wm597zw50+YXZSfnILxjSM+htuaoO3TVbi42Ic3cQD2H1eFPms zYeDKktowvvWhpXgNzNl9Vdbd6TuLR9OL1pUp7EyKOkDKG9iy3t6AIKW84swRBDDNq+/ TqjqfMAODdL/2QgUqXCy0m625xS/5DeAmg0lM= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to:user-agent; bh=pexNnjdwXBXMeIxyaoaSmCkUfu6bHwCGflifoKJOFh0=; b=un91++e20pD75YzUlmCx7r4HVa2ePqimf4R6S/WULGR+wsx3ojoFb4y/JDEzgL779p sDQp2O/AbFz2VFoSPvt2PQL6gtlw4Vcl410ZXblNEo7Tn82leMtOw7PFG0ayriU6HvL6 KsMuK1DUH5sNDQ6+oDo5XkZ6lAW0neT4Xvwtgm06T0qaayPNXmKilLU29Yjlafl2EM36 iEOqMsQRWe6upnBnAf0+hhovWhgHrBHpkZd67UC/q56NH3w7FGb3AtTmYKWWpWsPj4bY 8G4OlsrGvYlr+w7uB4ml6SZhcgvBys6eZNqK3q23I7E/vig6rX3UO7cwIjt7n52FRAX6 3DCQ== X-Gm-Message-State: APjAAAXv7vzF/yFP+HzfbpraDDSOhadnZZaCpMSM5LZ8FWGlSuZH1ZYe jhCbXNXydqSh2eaOSAf+qvi8jg== X-Google-Smtp-Source: APXvYqxZXZK4WGk89b4N6G6WMvGKLWjnBUS6OedyKpMkltuoQFWUABkWLtnkfNyZxNLQsgW0T8LOsA== X-Received: by 2002:a17:90a:342:: with SMTP id 2mr15845957pjf.128.1559405305086; Sat, 01 Jun 2019 09:08:25 -0700 (PDT) Received: from localhost ([2620:15c:6:12:9c46:e0da:efbf:69cc]) by smtp.gmail.com with ESMTPSA id 2sm5013896pfo.41.2019.06.01.09.08.23 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Sat, 01 Jun 2019 09:08:24 -0700 (PDT) Date: Sat, 1 Jun 2019 12:08:22 -0400 From: Joel Fernandes To: David Howells Cc: viro@zeniv.linux.org.uk, raven@themaw.net, linux-api@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, mszeredi@redhat.com Subject: Re: [PATCH 09/25] vfs: Allow mount information to be queried by fsinfo() [ver #13] Message-ID: <20190601160822.GA77761@google.com> References: <155905626142.1662.18430571708534506785.stgit@warthog.procyon.org.uk> <155905633578.1662.8087594848892366318.stgit@warthog.procyon.org.uk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <155905633578.1662.8087594848892366318.stgit@warthog.procyon.org.uk> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org On Tue, May 28, 2019 at 04:12:15PM +0100, David Howells wrote: [snip] > + > +/* > + * Store a mount record into the fsinfo buffer. > + */ > +static void store_mount_fsinfo(struct fsinfo_kparams *params, > + struct fsinfo_mount_child *child) > +{ > + unsigned int usage = params->usage; > + unsigned int total = sizeof(*child); > + > + if (params->usage >= INT_MAX) > + return; > + params->usage = usage + total; > + if (params->buffer && params->usage <= params->buf_size) > + memcpy(params->buffer + usage, child, total); > +} > + > +/* > + * Return information about the submounts relative to path. > + */ > +int fsinfo_generic_mount_children(struct path *path, struct fsinfo_kparams *params) > +{ > + struct fsinfo_mount_child record; > + struct mount *m, *child; > + > + if (!path->mnt) > + return -ENODATA; > + > + rcu_read_lock(); > + > + m = real_mount(path->mnt); > + list_for_each_entry_rcu(child, &m->mnt_mounts, mnt_child) { > + if (child->mnt_parent != m) > + continue; > + record.mnt_id = child->mnt_id; > + record.notify_counter = atomic_read(&child->mnt_notify_counter); > + store_mount_fsinfo(params, &record); > + } > + > + record.mnt_id = m->mnt_id; > + record.notify_counter = atomic_read(&m->mnt_notify_counter); > + store_mount_fsinfo(params, &record); > + > + rcu_read_unlock(); Not super familiar with this code, but wanted to check with you: Here, if the rcu_read_lock is supposed to protect the RCU list, can rcu_read_lock() scope be reduced to just wrapping around the list_for_each_entry_rcu? rcu_read_lock(); list_for_each_entry_rcu(..) { ... } rcu_read_unlock(); (and similarly to other similar parts of this patch). thanks, - Joel > + return params->usage; > +} > + > +/* > + * Return the path of the Nth submount relative to path. This is derived from > + * d_path(), but the root determination is more complicated. > + */ > +int fsinfo_generic_mount_submount(struct path *path, struct fsinfo_kparams *params) > +{ > + struct mountpoint *mp; > + struct mount *m, *child; > + struct path mountpoint, root; > + unsigned int n = params->Nth; > + size_t len; > + void *p; > + > + if (!path->mnt) > + return -ENODATA; > + > + rcu_read_lock(); > + > + m = real_mount(path->mnt); > + list_for_each_entry_rcu(child, &m->mnt_mounts, mnt_child) { > + mp = READ_ONCE(child->mnt_mp); > + if (child->mnt_parent != m || !mp) > + continue; > + if (n-- == 0) > + goto found; > + } > + rcu_read_unlock(); > + return -ENODATA; > + > +found: > + mountpoint.mnt = path->mnt; > + mountpoint.dentry = READ_ONCE(mp->m_dentry); > + > + get_fs_root_rcu(current->fs, &root); > + if (root.mnt != path->mnt) { > + root.mnt = path->mnt; > + root.dentry = path->mnt->mnt_root; > + } > + > + p = __d_path(&mountpoint, &root, params->buffer, params->buf_size); > + rcu_read_unlock(); > + > + if (IS_ERR(p)) > + return PTR_ERR(p); > + if (!p) > + return -EPERM; > + > + len = (params->buffer + params->buf_size) - p; > + memmove(params->buffer, p, len); > + return len; > +} > +#endif /* CONFIG_FSINFO */ > diff --git a/include/uapi/linux/fsinfo.h b/include/uapi/linux/fsinfo.h > index dae2e8dd757e..7f7a75e9758a 100644 > --- a/include/uapi/linux/fsinfo.h > +++ b/include/uapi/linux/fsinfo.h > @@ -32,6 +32,10 @@ enum fsinfo_attribute { > FSINFO_ATTR_PARAM_ENUM = 14, /* Nth enum-to-val */ > FSINFO_ATTR_PARAMETERS = 15, /* Mount parameters (large string) */ > FSINFO_ATTR_LSM_PARAMETERS = 16, /* LSM Mount parameters (large string) */ > + FSINFO_ATTR_MOUNT_INFO = 17, /* Mount object information */ > + FSINFO_ATTR_MOUNT_DEVNAME = 18, /* Mount object device name (string) */ > + FSINFO_ATTR_MOUNT_CHILDREN = 19, /* Submount list (array) */ > + FSINFO_ATTR_MOUNT_SUBMOUNT = 20, /* Relative path of Nth submount (string) */ > FSINFO_ATTR__NR > }; > > @@ -268,4 +272,28 @@ struct fsinfo_param_enum { > char name[252]; /* Name of the enum value */ > }; > > +/* > + * Information struct for fsinfo(FSINFO_ATTR_MOUNT_INFO). > + */ > +struct fsinfo_mount_info { > + __u64 f_sb_id; /* Superblock ID */ > + __u32 mnt_id; /* Mount identifier (use with AT_FSINFO_MOUNTID_PATH) */ > + __u32 parent_id; /* Parent mount identifier */ > + __u32 group_id; /* Mount group ID */ > + __u32 master_id; /* Slave master group ID */ > + __u32 from_id; /* Slave propogated from ID */ > + __u32 attr; /* MOUNT_ATTR_* flags */ > + __u32 notify_counter; /* Number of notifications generated. */ > + __u32 __reserved[1]; > +}; > + > +/* > + * Information struct element for fsinfo(FSINFO_ATTR_MOUNT_CHILDREN). > + * - An extra element is placed on the end representing the parent mount. > + */ > +struct fsinfo_mount_child { > + __u32 mnt_id; /* Mount identifier (use with AT_FSINFO_MOUNTID_PATH) */ > + __u32 notify_counter; /* Number of notifications generated on mount. */ > +}; > + > #endif /* _UAPI_LINUX_FSINFO_H */ > diff --git a/samples/vfs/test-fsinfo.c b/samples/vfs/test-fsinfo.c > index 90926024e1c5..a838adcdca9e 100644 > --- a/samples/vfs/test-fsinfo.c > +++ b/samples/vfs/test-fsinfo.c > @@ -21,10 +21,10 @@ > #include > #include > #include > -#include > #include > #include > #include > +#include > #include > #include > > @@ -83,6 +83,10 @@ static const struct fsinfo_attr_info fsinfo_buffer_info[FSINFO_ATTR__NR] = { > FSINFO_STRUCT_N (PARAM_ENUM, param_enum), > FSINFO_OVERLARGE (PARAMETERS, -), > FSINFO_OVERLARGE (LSM_PARAMETERS, -), > + FSINFO_STRUCT (MOUNT_INFO, mount_info), > + FSINFO_STRING (MOUNT_DEVNAME, mount_devname), > + FSINFO_STRUCT_ARRAY (MOUNT_CHILDREN, mount_child), > + FSINFO_STRING_N (MOUNT_SUBMOUNT, mount_submount), > }; > > #define FSINFO_NAME(X,Y) [FSINFO_ATTR_##X] = #Y > @@ -104,6 +108,10 @@ static const char *fsinfo_attr_names[FSINFO_ATTR__NR] = { > FSINFO_NAME (PARAM_ENUM, param_enum), > FSINFO_NAME (PARAMETERS, parameters), > FSINFO_NAME (LSM_PARAMETERS, lsm_parameters), > + FSINFO_NAME (MOUNT_INFO, mount_info), > + FSINFO_NAME (MOUNT_DEVNAME, mount_devname), > + FSINFO_NAME (MOUNT_CHILDREN, mount_children), > + FSINFO_NAME (MOUNT_SUBMOUNT, mount_submount), > }; > > union reply { > @@ -116,6 +124,8 @@ union reply { > struct fsinfo_capabilities caps; > struct fsinfo_timestamp_info timestamps; > struct fsinfo_volume_uuid uuid; > + struct fsinfo_mount_info mount_info; > + struct fsinfo_mount_child mount_children[1]; > }; > > static void dump_hex(unsigned int *data, int from, int to) > @@ -312,6 +322,29 @@ static void dump_attr_VOLUME_UUID(union reply *r, int size) > f->uuid[14], f->uuid[15]); > } > > +static void dump_attr_MOUNT_INFO(union reply *r, int size) > +{ > + struct fsinfo_mount_info *f = &r->mount_info; > + > + printf("\n"); > + printf("\tsb_id : %llx\n", (unsigned long long)f->f_sb_id); > + printf("\tmnt_id : %x\n", f->mnt_id); > + printf("\tparent : %x\n", f->parent_id); > + printf("\tgroup : %x\n", f->group_id); > + printf("\tattr : %x\n", f->attr); > + printf("\tnotifs : %x\n", f->notify_counter); > +} > + > +static void dump_attr_MOUNT_CHILDREN(union reply *r, int size) > +{ > + struct fsinfo_mount_child *f = r->mount_children; > + int i = 0; > + > + printf("\n"); > + for (; size >= sizeof(*f); size -= sizeof(*f), f++) > + printf("\t[%u] %8x %8x\n", i++, f->mnt_id, f->notify_counter); > +} > + > /* > * > */ > @@ -327,6 +360,8 @@ static const dumper_t fsinfo_attr_dumper[FSINFO_ATTR__NR] = { > FSINFO_DUMPER(CAPABILITIES), > FSINFO_DUMPER(TIMESTAMP_INFO), > FSINFO_DUMPER(VOLUME_UUID), > + FSINFO_DUMPER(MOUNT_INFO), > + FSINFO_DUMPER(MOUNT_CHILDREN), > }; > > static void dump_fsinfo(enum fsinfo_attribute attr, > @@ -529,16 +564,21 @@ int main(int argc, char **argv) > unsigned int attr; > int raw = 0, opt, Nth, Mth; > > - while ((opt = getopt(argc, argv, "adlr"))) { > + while ((opt = getopt(argc, argv, "Madlr"))) { > switch (opt) { > + case 'M': > + params.at_flags = AT_FSINFO_MOUNTID_PATH; > + continue; > case 'a': > params.at_flags |= AT_NO_AUTOMOUNT; > + params.at_flags &= ~AT_FSINFO_MOUNTID_PATH; > continue; > case 'd': > debug = true; > continue; > case 'l': > params.at_flags &= ~AT_SYMLINK_NOFOLLOW; > + params.at_flags &= ~AT_FSINFO_MOUNTID_PATH; > continue; > case 'r': > raw = 1; > @@ -551,7 +591,8 @@ int main(int argc, char **argv) > argv += optind; > > if (argc != 1) { > - printf("Format: test-fsinfo [-alr] \n"); > + printf("Format: test-fsinfo [-adlr] \n"); > + printf("Format: test-fsinfo [-dr] -M \n"); > exit(2); > } > >