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=-15.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, 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 DCB84C2B9F4 for ; Thu, 17 Jun 2021 14:09:57 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id CB9056128B for ; Thu, 17 Jun 2021 14:09:57 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231536AbhFQOME (ORCPT ); Thu, 17 Jun 2021 10:12:04 -0400 Received: from smtp-out2.suse.de ([195.135.220.29]:33778 "EHLO smtp-out2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230507AbhFQOME (ORCPT ); Thu, 17 Jun 2021 10:12:04 -0400 Received: from relay2.suse.de (relay2.suse.de [149.44.160.134]) by smtp-out2.suse.de (Postfix) with ESMTP id 0C2331FD68; Thu, 17 Jun 2021 14:09:55 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=susede1; t=1623938995; 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=BkqQiO9KSRkh5HLhqz7NulrNPfY6/VvozJpBVz8MwPo=; b=jNPWz1UpsZsq6nqeGeyraszV0WlKT77iXcScMQ3vsX2YsxoiGIn9ppDE3kHTL+k1rtBgnm HLeZM5ZjeXPyO/r53Uz82M2ewRLp3MKO3+0oiO1Q/9p/ssPNWSejkTA8jLNebwJ/RUEjo6 y6Qe6oFVHOxuwnuht3HjcgKaQRlq84g= 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 8A9EEA3BBA; Thu, 17 Jun 2021 14:09:54 +0000 (UTC) Date: Thu, 17 Jun 2021 16:09:54 +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 Subject: Re: [PATCH RFCv4 2/4] lib/vsprintf.c: make '%pD' print full path for file Message-ID: References: <20210615154952.2744-1-justin.he@arm.com> <20210615154952.2744-3-justin.he@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210615154952.2744-3-justin.he@arm.com> Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org On Tue 2021-06-15 23:49:50, 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 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 > --- a/lib/vsprintf.c > +++ b/lib/vsprintf.c > @@ -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); "reserved_size" is kind of confusing. "dpath_widen_len" or just "widen_len" look much more obvious. The below comments are not bad. But they still made me thing about it more than I wanted ;-) I wonder if it following is better: > + /* case 1: no space at all, forward the buf with reserved size */ > + if (buf >= end) > + return buf + reserved_size; /* Case 1: Already started past the buffer. Just forward @buf. */ if (buf >= end) return buf + widen_len; > + > + /* > + * 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); /* * Case 2: The entire remaining space of the buffer filled by * the truncated path. Still need to get moved right when * the filed width is greather than the full path length. */ 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); /* * Case 3: The full path is printed at the end of the buffer. * Print it at the right location in the same buffer. */ return string_nocheck(buf, end, p, spec); > } > #ifdef CONFIG_BLOCK > static noinline_for_stack In each case, I am happy that it was possible to simplify the logic. I got lost several times in the previous version. Best Regards, Petr