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=-15.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=ham 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 EA748C433DB for ; Thu, 11 Mar 2021 03:46:21 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id B998264FD0 for ; Thu, 11 Mar 2021 03:46:21 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231157AbhCKDpt (ORCPT ); Wed, 10 Mar 2021 22:45:49 -0500 Received: from szxga03-in.huawei.com ([45.249.212.189]:3357 "EHLO szxga03-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230478AbhCKDpn (ORCPT ); Wed, 10 Mar 2021 22:45:43 -0500 Received: from dggeme766-chm.china.huawei.com (unknown [172.30.72.56]) by szxga03-in.huawei.com (SkyGuard) with ESMTP id 4DwvtM5X5tz5VhN; Thu, 11 Mar 2021 11:43:23 +0800 (CST) Received: from [10.110.53.113] (10.110.53.113) by dggeme766-chm.china.huawei.com (10.3.19.112) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256_P256) id 15.1.2106.2; Thu, 11 Mar 2021 11:45:39 +0800 Subject: Re: [PATCH v3] fs/locks: print full locks information To: Jeff Layton , , CC: , , , References: <20210221201024.GB15975@fieldses.org> <685386c2840b76c49b060bf7dcea1fefacf18176.1614322182.git.luolongjun@huawei.com> From: Luo Longjun Message-ID: <649fa593-d534-a23d-4442-2462778662df@huawei.com> Date: Thu, 11 Mar 2021 11:45:38 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.8.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 8bit X-Originating-IP: [10.110.53.113] X-ClientProxiedBy: dggeme711-chm.china.huawei.com (10.1.199.107) To dggeme766-chm.china.huawei.com (10.3.19.112) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 在 2021/3/9 21:37, Jeff Layton 写道: > On Thu, 2021-02-25 at 22:58 -0500, Luo Longjun wrote: >> Commit fd7732e033e3 ("fs/locks: create a tree of dependent requests.") >> has put blocked locks into a tree. >> >> So, with a for loop, we can't check all locks information. >> >> To solve this problem, we should traverse the tree. >> >> Signed-off-by: Luo Longjun >> --- >>  fs/locks.c | 65 ++++++++++++++++++++++++++++++++++++++++++++++-------- >>  1 file changed, 56 insertions(+), 9 deletions(-) >> >> diff --git a/fs/locks.c b/fs/locks.c >> index 99ca97e81b7a..ecaecd1f1b58 100644 >> --- a/fs/locks.c >> +++ b/fs/locks.c >> @@ -2828,7 +2828,7 @@ struct locks_iterator { >>  }; >> >> >> >> >>  static void lock_get_status(struct seq_file *f, struct file_lock *fl, >> - loff_t id, char *pfx) >> + loff_t id, char *pfx, int repeat) >>  { >>   struct inode *inode = NULL; >>   unsigned int fl_pid; >> @@ -2844,7 +2844,11 @@ static void lock_get_status(struct seq_file *f, struct file_lock *fl, >>   if (fl->fl_file != NULL) >>   inode = locks_inode(fl->fl_file); >> >> >> >> >> - seq_printf(f, "%lld:%s ", id, pfx); >> + seq_printf(f, "%lld: ", id); >> + >> + if (repeat) >> + seq_printf(f, "%*s", repeat - 1 + (int)strlen(pfx), pfx); > Shouldn't that be "%.*s" ? > > Also, isn't this likely to end up walking past the end of "pfx" (or even > ending up at an address before the buffer)? You have this below: > > lock_get_status(f, fl, *id, "", 0); > > ...so the "length" value you're passing into the format there is going > to be -1. It also seems like if you get a large "level" value in > locks_show, then you'll end up with a length that is much longer than > the actual string. In my understanding, the difference of "%*s" and "%.*s" is that, "%*s" specifies the minimal filed width while "%.*s" specifies the precision of the string. Here, I use "%*s", because I want to print locks information in the follwing format: 2: FLOCK  ADVISORY  WRITE 110 00:02:493 0 EOF 2: -> FLOCK  ADVISORY  WRITE 111 00:02:493 0 EOF 2:  -> FLOCK  ADVISORY  WRITE 112 00:02:493 0 EOF 2:   -> FLOCK  ADVISORY  WRITE 113 00:02:493 0 EOF 2:    -> FLOCK  ADVISORY  WRITE 114 00:02:493 0 EOF And also, there is another way to show there information, in the format like: 60: FLOCK  ADVISORY  WRITE 23350 08:02:4456514 0 EOF 60: -> FLOCK  ADVISORY  WRITE 23356 08:02:4456514 0 EOF 60: -> FLOCK  ADVISORY  WRITE 24217 08:02:4456514 0 EOF 60: -> FLOCK  ADVISORY  WRITE 24239 08:02:4456514 0 EOF I think both formats are acceptable, but the first format shows competition relationships between these locks. In the following code: > lock_get_status(f, fl, *id, "", 0); repeat is 0, and in the function: + if (repeat) + seq_printf(f, "%*s", repeat - 1 + (int)strlen(pfx), pfx); The if branch will not take effect, so it could not be -1. >> + >>   if (IS_POSIX(fl)) { >>   if (fl->fl_flags & FL_ACCESS) >>   seq_puts(f, "ACCESS"); >> @@ -2906,21 +2910,64 @@ static void lock_get_status(struct seq_file *f, struct file_lock *fl, >>   } >>  } >> >> >> >> >> +static struct file_lock *get_next_blocked_member(struct file_lock *node) >> +{ >> + struct file_lock *tmp; >> + >> + /* NULL node or root node */ >> + if (node == NULL || node->fl_blocker == NULL) >> + return NULL; >> + >> + /* Next member in the linked list could be itself */ >> + tmp = list_next_entry(node, fl_blocked_member); >> + if (list_entry_is_head(tmp, &node->fl_blocker->fl_blocked_requests, fl_blocked_member) >> + || tmp == node) { >> + return NULL; >> + } >> + >> + return tmp; >> +} >> + >>  static int locks_show(struct seq_file *f, void *v) >>  { >>   struct locks_iterator *iter = f->private; >> - struct file_lock *fl, *bfl; >> + struct file_lock *cur, *tmp; >>   struct pid_namespace *proc_pidns = proc_pid_ns(file_inode(f->file)->i_sb); >> + int level = 0; >> >> >> >> >> - fl = hlist_entry(v, struct file_lock, fl_link); >> + cur = hlist_entry(v, struct file_lock, fl_link); >> >> >> >> >> - if (locks_translate_pid(fl, proc_pidns) == 0) >> + if (locks_translate_pid(cur, proc_pidns) == 0) >>   return 0; >> >> >> >> >> - lock_get_status(f, fl, iter->li_pos, ""); >> + /* View this crossed linked list as a binary tree, the first member of fl_blocked_requests >> + * is the left child of current node, the next silibing in fl_blocked_member is the >> + * right child, we can alse get the parent of current node from fl_blocker, so this >> + * question becomes traversal of a binary tree >> + */ >> + while (cur != NULL) { >> + if (level) >> + lock_get_status(f, cur, iter->li_pos, "-> ", level); >> + else >> + lock_get_status(f, cur, iter->li_pos, "", level); >> >> >> >> >> - list_for_each_entry(bfl, &fl->fl_blocked_requests, fl_blocked_member) >> - lock_get_status(f, bfl, iter->li_pos, " ->"); >> + if (!list_empty(&cur->fl_blocked_requests)) { >> + /* Turn left */ >> + cur = list_first_entry_or_null(&cur->fl_blocked_requests, >> + struct file_lock, fl_blocked_member); >> + level++; >> + } else { >> + /* Turn right */ >> + tmp = get_next_blocked_member(cur); >> + /* Fall back to parent node */ >> + while (tmp == NULL && cur->fl_blocker != NULL) { >> + cur = cur->fl_blocker; >> + level--; >> + tmp = get_next_blocked_member(cur); >> + } >> + cur = tmp; >> + } >> + } >> >> >> >> >>   return 0; >>  } >> @@ -2941,7 +2988,7 @@ static void __show_fd_locks(struct seq_file *f, >> >> >> >> >>   (*id)++; >>   seq_puts(f, "lock:\t"); >> - lock_get_status(f, fl, *id, ""); >> + lock_get_status(f, fl, *id, "", 0); >>   } >>  } >> >> >> >>