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=-16.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,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 9E34EC48BDF for ; Tue, 15 Jun 2021 15:53:16 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 7511960FEE for ; Tue, 15 Jun 2021 15:53:16 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232602AbhFOPzT (ORCPT ); Tue, 15 Jun 2021 11:55:19 -0400 Received: from foss.arm.com ([217.140.110.172]:39072 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232343AbhFOPwT (ORCPT ); Tue, 15 Jun 2021 11:52:19 -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 1D8BC1424; Tue, 15 Jun 2021 08:50:14 -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 6F5003F694; Tue, 15 Jun 2021 08:50:09 -0700 (PDT) From: Jia He To: Petr Mladek , Steven Rostedt , Sergey Senozhatsky , Andy Shevchenko , Rasmus Villemoes , Jonathan Corbet , Alexander Viro , Linus Torvalds Cc: "Peter Zijlstra (Intel)" , Eric Biggers , "Ahmed S. Darwish" , linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, Matthew Wilcox , Jia He Subject: [PATCH RFCv4 2/4] lib/vsprintf.c: make '%pD' print full path for file Date: Tue, 15 Jun 2021 23:49:50 +0800 Message-Id: <20210615154952.2744-3-justin.he@arm.com> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20210615154952.2744-1-justin.he@arm.com> References: <20210615154952.2744-1-justin.he@arm.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Previously, the specifier '%pD' is for printing dentry name of struct file. 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 change the behavior of '%pD' to print full path of that file. Precision is never going to be used with %p (or any of its kernel extensions) if -Wformat is turned on. . [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 | 37 ++++++++++++++++++++--- 2 files changed, 36 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..9d3166332726 100644 --- a/lib/vsprintf.c +++ b/lib/vsprintf.c @@ -27,6 +27,7 @@ #include #include #include +#include #include #include #include @@ -920,13 +921,41 @@ 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; + int prepend_len, reserved_size, dpath_len; + 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_unsafe(path, buf, end - buf, &prepend_len); + + /* Calculate the full d_path length, ignoring the tail '\0' */ + dpath_len = end - buf - prepend_len - 1; + + reserved_size = max_t(int, dpath_len, spec.field_width); + + /* case 1: no space at all, forward the buf with reserved size */ + if (buf >= end) + return buf + reserved_size; + + /* + * case 2: small scratch space for long d_path name. The space + * [buf,end] has been filled with truncated string. Hence use the + * full dpath_len for further string widening. + */ + if (prepend_len < 0) + return widen_string(buf + dpath_len, dpath_len, end, spec); + + /* case3: space is big enough */ + return string_nocheck(buf, end, p, spec); } #ifdef CONFIG_BLOCK static noinline_for_stack @@ -2296,7 +2325,7 @@ 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 +2424,7 @@ 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