Messages in this thread | | | From | Justin He <> | Subject | RE: [PATCH v2 2/4] lib/vsprintf.c: make '%pD' print the full path of file | Date | Fri, 25 Jun 2021 02:29:38 +0000 |
| |
Hi Petr
> -----Original Message----- > From: Petr Mladek <pmladek@suse.com> > Sent: Thursday, June 24, 2021 5:02 PM > To: Justin He <Justin.He@arm.com> > Cc: Steven Rostedt <rostedt@goodmis.org>; Sergey Senozhatsky > <senozhatsky@chromium.org>; Andy Shevchenko > <andriy.shevchenko@linux.intel.com>; Rasmus Villemoes > <linux@rasmusvillemoes.dk>; Jonathan Corbet <corbet@lwn.net>; Alexander > Viro <viro@zeniv.linux.org.uk>; Linus Torvalds <torvalds@linux- > foundation.org>; Peter Zijlstra (Intel) <peterz@infradead.org>; Eric > Biggers <ebiggers@google.com>; Ahmed S. Darwish <a.darwish@linutronix.de>; > linux-doc@vger.kernel.org; linux-kernel@vger.kernel.org; linux- > fsdevel@vger.kernel.org; Matthew Wilcox <willy@infradead.org>; Christoph > Hellwig <hch@infradead.org>; nd <nd@arm.com> > Subject: Re: [PATCH v2 2/4] lib/vsprintf.c: make '%pD' print the full path > of file > > 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. > Tend to remove this paragraph since the comments in do_path_unsafe (patch1/4) was clear enough.
> > 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. > Okay
> > 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/ ? > Ah, sorry, I changed it. I would have thought it as a typo 😊
-- Cheers, Justin (Jia He)
| |