From: Petr Mladek <pmladek@suse.com>
To: Jia 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@arm.com
Subject: Re: [PATCH v2 2/4] lib/vsprintf.c: make '%pD' print the full path of file
Date: Thu, 24 Jun 2021 11:01:31 +0200 [thread overview]
Message-ID: <YNRJ61m6duXjpGrp@alley> (raw)
In-Reply-To: <20210623055011.22916-3-justin.he@arm.com>
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
next prev parent reply other threads:[~2021-06-24 9:01 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-06-23 5:50 [PATCH v2 0/4] make '%pD' print the full path of file Jia He
2021-06-23 5:50 ` [PATCH v2 1/4] fs: introduce helper d_path_unsafe() Jia He
2021-06-23 9:10 ` Andy Shevchenko
2021-06-24 5:48 ` Justin He
2021-07-14 8:33 ` Justin He
2021-07-14 9:17 ` Andy Shevchenko
2021-06-28 5:13 ` Justin He
2021-06-28 9:06 ` Petr Mladek
2021-07-02 6:36 ` Justin He
2021-06-23 5:50 ` [PATCH v2 2/4] lib/vsprintf.c: make '%pD' print the full path of file Jia He
2021-06-23 9:14 ` Andy Shevchenko
2021-06-24 9:01 ` Petr Mladek [this message]
2021-06-24 10:49 ` Andy Shevchenko
2021-06-25 2:29 ` Justin He
2021-06-25 2:32 ` Justin He
2021-06-23 5:50 ` [PATCH v2 3/4] lib/test_printf.c: split write-beyond-buffer check in two Jia He
2021-06-23 9:16 ` Andy Shevchenko
2021-06-23 5:50 ` [PATCH v2 4/4] lib/test_printf.c: add test cases for '%pD' Jia He
2021-06-23 9:17 ` [PATCH v2 0/4] make '%pD' print the full path of file Andy Shevchenko
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=YNRJ61m6duXjpGrp@alley \
--to=pmladek@suse.com \
--cc=a.darwish@linutronix.de \
--cc=andriy.shevchenko@linux.intel.com \
--cc=corbet@lwn.net \
--cc=ebiggers@google.com \
--cc=hch@infradead.org \
--cc=justin.he@arm.com \
--cc=linux-doc@vger.kernel.org \
--cc=linux-fsdevel@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux@rasmusvillemoes.dk \
--cc=nd@arm.com \
--cc=peterz@infradead.org \
--cc=rostedt@goodmis.org \
--cc=senozhatsky@chromium.org \
--cc=torvalds@linux-foundation.org \
--cc=viro@zeniv.linux.org.uk \
--cc=willy@infradead.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).