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=-10.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 5CDA5C48BDF for ; Thu, 24 Jun 2021 09:01:41 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 44237613E3 for ; Thu, 24 Jun 2021 09:01:41 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230147AbhFXJD6 (ORCPT ); Thu, 24 Jun 2021 05:03:58 -0400 Received: from smtp-out2.suse.de ([195.135.220.29]:56832 "EHLO smtp-out2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229918AbhFXJDw (ORCPT ); Thu, 24 Jun 2021 05:03:52 -0400 Received: from relay2.suse.de (relay2.suse.de [149.44.160.134]) by smtp-out2.suse.de (Postfix) with ESMTP id 04E8C1FD67; Thu, 24 Jun 2021 09:01:33 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=susede1; t=1624525293; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=gOxneZwjI52NGf5YtOkngslNEIWH7cmjZeAOERs/N1o=; b=qVGFmIBZsXtc/KT5jd285fvitzFu/HscGDU/99JWXqmysYTcbcTp9+7CHCAIoQ7Zd/SQN4 +Pmf2DguX4xoL3fBRQ/m7U6Z6ksPr+Ksf1Khn7T7GuSn2N7GVrujAgMmsVGNcme+KhAQIX OmFu0wLVuZuu+Neo77oDGjco/guIs3A= Received: from suse.cz (unknown [10.100.224.162]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by relay2.suse.de (Postfix) with ESMTPS id 9C85AA3B91; Thu, 24 Jun 2021 09:01:32 +0000 (UTC) Date: Thu, 24 Jun 2021 11:01:31 +0200 From: Petr Mladek To: Jia He Cc: Steven Rostedt , Sergey Senozhatsky , Andy Shevchenko , Rasmus Villemoes , Jonathan Corbet , Alexander Viro , Linus Torvalds , "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 , Christoph Hellwig , nd@arm.com Subject: Re: [PATCH v2 2/4] lib/vsprintf.c: make '%pD' print the full path of file Message-ID: References: <20210623055011.22916-1-justin.he@arm.com> <20210623055011.22916-3-justin.he@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210623055011.22916-3-justin.he@arm.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed 2021-06-23 13:50:09, Jia He wrote: > 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 [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 the full path of that file. > > If someone invokes snprintf() with small but positive space, > prepend_name_with_len() moves or truncates the string partially. Does this comment belong to the 1st patch? prepend_name_with_len() is not called in this patch. > More > than that, kasprintf() will pass NULL @buf and @end as the parameters, > and @end - @buf can be negative in some case. Hence make it return at > the very beginning with false in these cases. Same here. file_d_path_name() does not return bool. Well, please mention in the commit message that %pD uses the entire given buffer as a scratch space. It might write something behind the trailing '\0'. It would make sense to warn about this also in Documentation/core-api/printk-formats.rst. It is a bit non-standard behavior. > diff --git a/lib/vsprintf.c b/lib/vsprintf.c > index f0c35d9b65bf..f4494129081f 100644 > --- a/lib/vsprintf.c > +++ b/lib/vsprintf.c > @@ -920,13 +921,44 @@ 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) > { > + char *p; > + const struct path *path; > + int prepend_len, widen_len, 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; > + > + widen_len = max_t(int, dpath_len, spec.field_width); > + > + /* Case 1: Already started past the buffer. Just forward @buf. */ > + if (buf >= end) > + return buf + widen_len; > + > + /* > + * Case 2: The entire remaining space of the buffer filled by > + * the truncated path. Still need to get moved right when > + * the filled width is greather than the full path length. s/filled/field/ ? > + */ > + if (prepend_len < 0) > + return widen_string(buf + dpath_len, dpath_len, end, spec); Otherwise, it looks good to me. Best Regards, Petr