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=-16.7 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_RED,USER_AGENT_GIT 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 B65C2C4708E for ; Fri, 28 May 2021 11:40:30 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9B508613D4 for ; Fri, 28 May 2021 11:40:30 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235852AbhE1LmC (ORCPT ); Fri, 28 May 2021 07:42:02 -0400 Received: from foss.arm.com ([217.140.110.172]:39690 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235632AbhE1Ll5 (ORCPT ); Fri, 28 May 2021 07:41:57 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id B9AC8168F; Fri, 28 May 2021 04:40:22 -0700 (PDT) Received: from entos-ampere-02.shanghai.arm.com (entos-ampere-02.shanghai.arm.com [10.169.214.103]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPA id 889003F73B; Fri, 28 May 2021 04:40:16 -0700 (PDT) From: Jia He To: Linus Torvalds , Petr Mladek , Steven Rostedt , Sergey Senozhatsky , Andy Shevchenko , Rasmus Villemoes , Jonathan Corbet , Alexander Viro , Luca Coelho , Kalle Valo , "David S. Miller" , Jakub Kicinski , Heiko Carstens , Vasily Gorbik Cc: Christian Borntraeger , Johannes Berg , linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-wireless@vger.kernel.org, netdev@vger.kernel.org, linux-s390@vger.kernel.org, Jia He Subject: [PATCH RFCv2 2/3] lib/vsprintf.c: make %pD print full path for file Date: Fri, 28 May 2021 19:39:50 +0800 Message-Id: <20210528113951.6225-3-justin.he@arm.com> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20210528113951.6225-1-justin.he@arm.com> References: <20210528113951.6225-1-justin.he@arm.com> Precedence: bulk List-ID: X-Mailing-List: linux-wireless@vger.kernel.org We have '%pD' for printing a filename. It may not be perfect (by default it only prints one component.) As suggested by Linus at [1]: A dentry has a parent, but at the same time, a dentry really does inherently have "one name" (and given just the dentry pointers, you can't show mount-related parenthood, so in many ways the "show just one name" makes sense for "%pd" in ways it doesn't necessarily for "%pD"). But while a dentry arguably has that "one primary component", a _file_ is certainly not exclusively about that last component. Hence "file_dentry_name()" simply shouldn't use "dentry_name()" at all. Despite that shared code origin, and despite that similar letter choice (lower-vs-upper case), a dentry and a file really are very different from a name standpoint. Here stack space is preferred for file_d_path_name() because it is much safer. The stack size 256 is a compromise between stack overflow and too short full path. [1] https://lore.kernel.org/lkml/CAHk-=wimsMqGdzik187YWLb-ru+iktb4MYbMQG1rnZ81dXYFVg@mail.gmail.com/ Suggested-by: Linus Torvalds Signed-off-by: Jia He --- Documentation/core-api/printk-formats.rst | 5 +++-- lib/vsprintf.c | 21 +++++++++++++++++---- 2 files changed, 20 insertions(+), 6 deletions(-) diff --git a/Documentation/core-api/printk-formats.rst b/Documentation/core-api/printk-formats.rst index f063a384c7c8..95ba14dc529b 100644 --- a/Documentation/core-api/printk-formats.rst +++ b/Documentation/core-api/printk-formats.rst @@ -408,12 +408,13 @@ dentry names :: %pd{,2,3,4} - %pD{,2,3,4} + %pD For printing dentry name; if we race with :c:func:`d_move`, the name might be a mix of old and new ones, but it won't oops. %pd dentry is a safer equivalent of %s dentry->d_name.name we used to use, %pd prints ``n`` -last components. %pD does the same thing for struct file. +last components. %pD prints full file path together with mount-related +parenthood. Passed by reference. diff --git a/lib/vsprintf.c b/lib/vsprintf.c index f0c35d9b65bf..2e5387b08d67 100644 --- a/lib/vsprintf.c +++ b/lib/vsprintf.c @@ -27,6 +27,7 @@ #include #include #include +#include #include #include #include @@ -920,13 +921,25 @@ char *dentry_name(char *buf, char *end, const struct dentry *d, struct printf_sp } static noinline_for_stack -char *file_dentry_name(char *buf, char *end, const struct file *f, +char *file_d_path_name(char *buf, char *end, const struct file *f, struct printf_spec spec, const char *fmt) { + const struct path *path; + char *p; + char full_path[256]; + if (check_pointer(&buf, end, f, spec)) return buf; - return dentry_name(buf, end, f->f_path.dentry, spec, fmt); + path = &f->f_path; + if (check_pointer(&buf, end, path, spec)) + return buf; + + p = d_path_fast(path, full_path, sizeof(full_path)); + if (IS_ERR(p)) + return err_ptr(buf, end, p, spec); + + return string_nocheck(buf, end, p, spec); } #ifdef CONFIG_BLOCK static noinline_for_stack @@ -2296,7 +2309,7 @@ early_param("no_hash_pointers", no_hash_pointers_enable); * - 'a[pd]' For address types [p] phys_addr_t, [d] dma_addr_t and derivatives * (default assumed to be phys_addr_t, passed by reference) * - 'd[234]' For a dentry name (optionally 2-4 last components) - * - 'D[234]' Same as 'd' but for a struct file + * - 'D' For full path name of a struct file * - 'g' For block_device name (gendisk + partition number) * - 't[RT][dt][r]' For time and date as represented by: * R struct rtc_time @@ -2395,7 +2408,7 @@ char *pointer(const char *fmt, char *buf, char *end, void *ptr, case 'C': return clock(buf, end, ptr, spec, fmt); case 'D': - return file_dentry_name(buf, end, ptr, spec, fmt); + return file_d_path_name(buf, end, ptr, spec, fmt); #ifdef CONFIG_BLOCK case 'g': return bdev_name(buf, end, ptr, spec, fmt); -- 2.17.1