From: Jia He <justin.he@arm.com>
To: Petr Mladek <pmladek@suse.com>,
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>
Cc: "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, Jia He <justin.he@arm.com>
Subject: [PATCH RFCv3 2/3] lib/vsprintf.c: make %pD print full path for file
Date: Fri, 11 Jun 2021 23:59:52 +0800 [thread overview]
Message-ID: <20210611155953.3010-3-justin.he@arm.com> (raw)
In-Reply-To: <20210611155953.3010-1-justin.he@arm.com>
We have '%pD' for printing a filename. 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.
Things become more complicated when spec.precision and spec.field_width
is added in. string_truncate() is to handle the small space case for
'%pD' precision and field_width.
[1] https://lore.kernel.org/lkml/CAHk-=wimsMqGdzik187YWLb-ru+iktb4MYbMQG1rnZ81dXYFVg@mail.gmail.com/
Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Jia He <justin.he@arm.com>
---
Documentation/core-api/printk-formats.rst | 5 ++-
lib/vsprintf.c | 47 +++++++++++++++++++++--
2 files changed, 46 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<n> 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..317b65280252 100644
--- a/lib/vsprintf.c
+++ b/lib/vsprintf.c
@@ -27,6 +27,7 @@
#include <linux/string.h>
#include <linux/ctype.h>
#include <linux/kernel.h>
+#include <linux/dcache.h>
#include <linux/kallsyms.h>
#include <linux/math64.h>
#include <linux/uaccess.h>
@@ -601,6 +602,20 @@ char *widen_string(char *buf, int n, char *end, struct printf_spec spec)
}
/* Handle string from a well known address. */
+static char *string_truncate(char *buf, char *end, const char *s,
+ u32 full_len, struct printf_spec spec)
+{
+ int lim = 0;
+
+ if (buf < end) {
+ if (spec.precision >= 0)
+ lim = strlen(s) - min_t(int, spec.precision, strlen(s));
+
+ return widen_string(buf + full_len, full_len, end - lim, spec);
+ }
+
+ return buf;
+}
static char *string_nocheck(char *buf, char *end, const char *s,
struct printf_spec spec)
{
@@ -920,13 +935,37 @@ 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);
+
+ /* Minus 1 byte for '\0' */
+ dpath_len = end - buf - prepend_len - 1;
+
+ reserved_size = max_t(int, dpath_len, spec.field_width);
+
+ /* no filling space at all */
+ if (buf >= end || !buf)
+ return buf + reserved_size;
+
+ /* small space for long name */
+ if (buf < end && prepend_len < 0)
+ return string_truncate(buf, end, p, dpath_len, spec);
+
+ /* space is enough */
+ return string_nocheck(buf, end, p, spec);
}
#ifdef CONFIG_BLOCK
static noinline_for_stack
@@ -2296,7 +2335,7 @@ 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 +2434,7 @@ 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
next prev parent reply other threads:[~2021-06-11 16:00 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-06-11 15:59 [PATCH RFCv3 0/3] make '%pD' print full path for file Jia He
2021-06-11 15:59 ` [PATCH RFCv3 1/3] fs: introduce helper d_path_unsafe() Jia He
2021-06-11 15:59 ` Jia He [this message]
2021-06-11 21:28 ` [PATCH RFCv3 2/3] lib/vsprintf.c: make %pD print full path for file Rasmus Villemoes
2021-06-15 6:43 ` Justin He
2021-06-15 7:04 ` Rasmus Villemoes
2021-06-15 8:32 ` Justin He
2021-06-14 15:40 ` Petr Mladek
2021-06-15 6:48 ` Justin He
2021-06-15 7:14 ` Rasmus Villemoes
2021-06-15 7:18 ` Justin He
2021-06-15 14:48 ` Justin He
2021-06-11 15:59 ` [PATCH RFCv3 3/3] lib/test_printf: add test cases for '%pD' Jia He
2021-06-11 21:40 ` Rasmus Villemoes
2021-06-15 7:06 ` Justin He
2021-06-15 7:15 ` Justin He
2021-06-15 7:40 ` Rasmus Villemoes
2021-06-14 15:44 ` Petr Mladek
2021-06-15 7:07 ` Justin He
2021-06-15 7:47 ` Rasmus Villemoes
2021-06-15 7:56 ` Justin He
2021-06-15 8:19 ` Andy Shevchenko
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