From: Jia He <justin.he@arm.com>
To: Linus Torvalds <torvalds@linux-foundation.org>,
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>,
Luca Coelho <luciano.coelho@intel.com>,
Kalle Valo <kvalo@codeaurora.org>,
"David S. Miller" <davem@davemloft.net>,
Jakub Kicinski <kuba@kernel.org>,
Heiko Carstens <hca@linux.ibm.com>,
Vasily Gorbik <gor@linux.ibm.com>
Cc: Christian Borntraeger <borntraeger@de.ibm.com>,
Johannes Berg <johannes.berg@intel.com>,
linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org,
linux-wireless@vger.kernel.org, netdev@vger.kernel.org,
linux-s390@vger.kernel.org, Jia He <justin.he@arm.com>
Subject: [PATCH RFCv2 2/3] lib/vsprintf.c: make %pD print full path for file
Date: Fri, 28 May 2021 19:39:50 +0800 [thread overview]
Message-ID: <20210528113951.6225-3-justin.he@arm.com> (raw)
In-Reply-To: <20210528113951.6225-1-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 "file_dentry_name()" simply shouldn't use "dentry_name()" at all.
Despite that shared code origin, and despite that similar letter
choice (lower-vs-upper case), a dentry and a file really are very
different from a name standpoint.
Here stack space is preferred for file_d_path_name() because it is
much safer. The stack size 256 is a compromise between stack overflow
and too short full path.
[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 | 21 +++++++++++++++++----
2 files changed, 20 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..2e5387b08d67 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>
@@ -920,13 +921,25 @@ 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;
+ char full_path[256];
+
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_fast(path, full_path, sizeof(full_path));
+ if (IS_ERR(p))
+ return err_ptr(buf, end, p, spec);
+
+ return string_nocheck(buf, end, p, spec);
}
#ifdef CONFIG_BLOCK
static noinline_for_stack
@@ -2296,7 +2309,7 @@ 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 +2408,7 @@ 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:[~2021-05-28 11:40 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-05-28 11:39 [PATCH RFCv2 0/3] make '%pD' print full path for file Jia He
2021-05-28 11:39 ` [PATCH RFCv2 1/3] fs: introduce helper d_path_fast() Jia He
2021-05-28 12:44 ` Al Viro
2021-05-28 12:51 ` Matthew Wilcox
2021-05-28 14:23 ` Justin He
2021-05-28 11:39 ` Jia He [this message]
2021-05-28 12:59 ` [PATCH RFCv2 2/3] lib/vsprintf.c: make %pD print full path for file Matthew Wilcox
2021-05-28 14:22 ` Justin He
2021-05-28 14:52 ` Matthew Wilcox
2021-05-28 15:09 ` Justin He
2021-05-28 15:22 ` Matthew Wilcox
2021-05-31 0:39 ` Justin He
2021-06-01 14:42 ` Justin He
2021-06-01 15:30 ` Matthew Wilcox
2021-06-01 15:36 ` Andy Shevchenko
2021-06-01 15:44 ` Matthew Wilcox
2021-06-01 15:53 ` Andy Shevchenko
2021-06-01 16:10 ` Andy Shevchenko
2021-06-01 17:05 ` Matthew Wilcox
2021-06-01 19:01 ` Rasmus Villemoes
2021-06-02 5:47 ` Justin He
2021-05-28 20:06 ` Rasmus Villemoes
2021-05-30 15:18 ` Matthew Wilcox
2021-05-31 9:40 ` Petr Mladek
2021-05-28 11:39 ` [PATCH RFCv2 3/3] s390/hmcdrv: remove the redundant directory path in debug message Jia He
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