From: Al Viro <viro@zeniv.linux.org.uk>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Jia He <justin.he@arm.com>, 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>,
Heiko Carstens <hca@linux.ibm.com>,
Vasily Gorbik <gor@linux.ibm.com>,
Christian Borntraeger <borntraeger@de.ibm.com>,
"Eric W . Biederman" <ebiederm@xmission.com>,
"Darrick J. Wong" <darrick.wong@oracle.com>,
"Peter Zijlstra (Intel)" <peterz@infradead.org>,
Ira Weiny <ira.weiny@intel.com>,
Eric Biggers <ebiggers@google.com>,
"Ahmed S. Darwish" <a.darwish@linutronix.de>,
"open list:DOCUMENTATION" <linux-doc@vger.kernel.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
linux-s390 <linux-s390@vger.kernel.org>,
linux-fsdevel <linux-fsdevel@vger.kernel.org>
Subject: [PATCH 03/14] d_path: regularize handling of root dentry in __dentry_path()
Date: Wed, 19 May 2021 00:48:50 +0000 [thread overview]
Message-ID: <20210519004901.3829541-3-viro@zeniv.linux.org.uk> (raw)
In-Reply-To: <20210519004901.3829541-1-viro@zeniv.linux.org.uk>
All path-forming primitives boil down to sequence of prepend_name()
on dentries encountered along the way toward root. Each time we prepend
/ + dentry name to the buffer. Normally that does exactly what we want,
but there's a corner case when we don't call prepend_name() at all (in case
of __dentry_path() that happens if we are given root dentry). We obviously
want to end up with "/", rather than "", so this corner case needs to be
handled.
__dentry_path() used to manually put '/' in the end of buffer before
doing anything else, to be overwritten by the first call of prepend_name()
if one happens and to be left in place if we don't call prepend_name() at
all. That required manually checking that we had space in the buffer
(prepend_name() and prepend() take care of such checks themselves) and lead
to clumsy keeping track of return value.
A better approach is to check if the main loop has added anything
into the buffer and prepend "/" if it hasn't. A side benefit of using prepend()
is that it does the right thing if we'd already run out of buffer, making
the overflow-handling logics simpler.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
---
fs/d_path.c | 21 +++++----------------
1 file changed, 5 insertions(+), 16 deletions(-)
diff --git a/fs/d_path.c b/fs/d_path.c
index 1a1cf05e7780..b3324ae7cfe2 100644
--- a/fs/d_path.c
+++ b/fs/d_path.c
@@ -329,31 +329,22 @@ char *simple_dname(struct dentry *dentry, char *buffer, int buflen)
static char *__dentry_path(const struct dentry *d, char *p, int buflen)
{
const struct dentry *dentry;
- char *end, *retval;
+ char *end;
int len, seq = 0;
- int error = 0;
-
- if (buflen < 1)
- goto Elong;
rcu_read_lock();
restart:
dentry = d;
end = p;
len = buflen;
- /* Get '/' right */
- retval = end-1;
- *retval = '/';
read_seqbegin_or_lock(&rename_lock, &seq);
while (!IS_ROOT(dentry)) {
const struct dentry *parent = dentry->d_parent;
prefetch(parent);
- error = prepend_name(&end, &len, &dentry->d_name);
- if (error)
+ if (unlikely(prepend_name(&end, &len, &dentry->d_name) < 0))
break;
- retval = end;
dentry = parent;
}
if (!(seq & 1))
@@ -363,11 +354,9 @@ static char *__dentry_path(const struct dentry *d, char *p, int buflen)
goto restart;
}
done_seqretry(&rename_lock, seq);
- if (error)
- goto Elong;
- return retval;
-Elong:
- return ERR_PTR(-ENAMETOOLONG);
+ if (len == buflen)
+ prepend(&end, &len, "/", 1);
+ return len >= 0 ? end : ERR_PTR(-ENAMETOOLONG);
}
char *dentry_path_raw(const struct dentry *dentry, char *buf, int buflen)
--
2.11.0
next prev parent reply other threads:[~2021-05-19 0:51 UTC|newest]
Thread overview: 75+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-05-08 12:25 [PATCH RFC 0/3] make '%pD' print full path for file Jia He
2021-05-08 12:25 ` [PATCH RFC 1/3] fs: introduce helper d_path_fast() Jia He
2021-05-08 15:30 ` Linus Torvalds
2021-05-08 19:13 ` Al Viro
2021-05-08 20:39 ` Linus Torvalds
2021-05-08 21:05 ` Al Viro
2021-05-08 22:17 ` Linus Torvalds
2021-05-08 22:46 ` Al Viro
2021-05-08 22:48 ` Linus Torvalds
2021-05-08 23:15 ` Al Viro
2021-05-08 23:18 ` Al Viro
2021-05-09 22:58 ` Eric W. Biederman
2021-05-10 12:51 ` Christian Brauner
2021-05-10 7:20 ` Christian Brauner
2021-05-08 22:42 ` Linus Torvalds
2021-05-08 22:47 ` Linus Torvalds
2021-05-09 2:28 ` Al Viro
2021-05-09 2:53 ` Linus Torvalds
2021-05-19 0:43 ` [PATCHSET] d_path cleanups Al Viro
2021-05-19 0:48 ` [PATCH 01/14] d_path: "\0" is {0,0}, not {0} Al Viro
2021-05-19 0:48 ` [PATCH 02/14] d_path: saner calling conventions for __dentry_path() Al Viro
2021-06-25 9:32 ` Justin He
2021-07-07 4:52 ` Justin He
2021-05-19 0:48 ` Al Viro [this message]
2021-07-07 4:50 ` [PATCH 03/14] d_path: regularize handling of root dentry in __dentry_path() Justin He
2021-05-19 0:48 ` [PATCH 04/14] d_path: get rid of path_with_deleted() Al Viro
2021-05-19 0:48 ` [PATCH 05/14] getcwd(2): saner logics around prepend_path() call Al Viro
2021-07-07 7:41 ` Justin He
2021-05-19 0:48 ` [PATCH 06/14] d_path: don't bother with return value of prepend() Al Viro
2021-06-24 6:13 ` Justin He
2021-05-19 0:48 ` [PATCH 07/14] d_path: lift -ENAMETOOLONG handling into callers of prepend_path() Al Viro
2021-06-25 9:18 ` Justin He
2021-06-28 5:20 ` Justin He
2021-05-19 0:48 ` [PATCH 08/14] d_path: make prepend_name() boolean Al Viro
2021-05-20 9:12 ` Justin He
2021-05-20 9:19 ` Andy Shevchenko
2021-05-20 14:53 ` Petr Mladek
2021-05-20 19:35 ` Al Viro
2021-07-07 7:43 ` Justin He
2021-05-19 0:48 ` [PATCH 09/14] d_path: introduce struct prepend_buffer Al Viro
2021-06-23 13:28 ` Justin He
2021-06-24 9:29 ` Enrico Weigelt, metux IT consult
2021-06-25 0:43 ` Justin He
2021-06-28 16:42 ` Enrico Weigelt, metux IT consult
2021-06-28 17:10 ` Andy Shevchenko
2021-05-19 0:48 ` [PATCH 10/14] d_path: prepend_path(): get rid of vfsmnt Al Viro
2021-05-19 0:48 ` [PATCH 11/14] d_path: prepend_path(): lift resetting b in case when we'd return 3 out of loop Al Viro
2021-05-19 0:48 ` [PATCH 12/14] d_path: prepend_path(): lift the inner loop into a new helper Al Viro
2021-05-19 8:07 ` Andy Shevchenko
2021-05-19 15:55 ` Al Viro
2021-07-07 7:52 ` Justin He
2021-05-19 0:49 ` [PATCH 13/14] d_path: prepend_path() is unlikely to return non-zero Al Viro
2021-06-25 8:00 ` Justin He
2021-06-25 17:58 ` Al Viro
2021-06-28 3:28 ` Justin He
2021-06-28 4:14 ` Al Viro
2021-06-28 4:36 ` Justin He
2021-06-28 4:37 ` Justin He
2021-05-19 0:49 ` [PATCH 14/14] getcwd(2): clean up error handling Al Viro
2021-07-07 8:03 ` Justin He
2021-06-24 6:05 ` [PATCH 01/14] d_path: "\0" is {0,0}, not {0} Justin He
2021-05-19 2:39 ` [PATCHSET] d_path cleanups Linus Torvalds
2021-06-22 14:00 ` Justin He
2021-05-09 2:20 ` [PATCH RFC 1/3] fs: introduce helper d_path_fast() Al Viro
2021-05-09 4:58 ` Al Viro
2021-05-10 16:16 ` Eric W. Biederman
2021-05-10 15:07 ` Justin He
2021-05-10 17:03 ` Linus Torvalds
2021-05-08 12:25 ` [PATCH RFC 2/3] lib/vsprintf.c: make %pD print full path for file Jia He
2021-05-10 3:46 ` Sergey Senozhatsky
2021-05-10 13:04 ` Petr Mladek
2021-05-10 14:25 ` Justin He
2021-05-27 7:20 ` Justin He
2021-05-27 9:14 ` Petr Mladek
2021-05-08 12:25 ` [PATCH RFC 3/3] s390/hmcdrv: remove the redundant directory path in debug message Jia He
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