RE: [PATCH 06/14] d_path: don't bother with return value of prepend()

Justin He
2021-06-24T06:13:53Z

> -----Original Message-----
> From: Al Viro <viro@ftp.linux.org.uk> On Behalf Of Al Viro
> Sent: Wednesday, May 19, 2021 8:49 AM
> To: Linus Torvalds <torvalds@linux-foundation.org>
> Cc: Justin 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 06/14] d_path: don't bother with return value of prepend()
>
> Only simple_dname() checks it, and there we can simply do those
> calls and check for overflow (by looking of negative buflen)
> in the end.
>
> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

Reviewed-by: Jia He <justin.he@arm.com>

--
Cheers,
Justin (Jia He)
> ---
> fs/d_path.c | 20 +++++++++-----------
> 1 file changed, 9 insertions(+), 11 deletions(-)
>
> diff --git a/fs/d_path.c b/fs/d_path.c
> index 311d43287572..72b8087aaf9c 100644
> --- a/fs/d_path.c
> +++ b/fs/d_path.c
> @@ -8,14 +8,13 @@
> #include <linux/prefetch.h>
> #include "mount.h"
>
> -static int prepend(char **buffer, int *buflen, const char *str, int
> namelen)
> +static void prepend(char **buffer, int *buflen, const char *str, int
> namelen)
> {
> *buflen -= namelen;
> - if (*buflen < 0)
> - return -ENAMETOOLONG;
> - *buffer -= namelen;
> - memcpy(*buffer, str, namelen);
> - return 0;
> + if (likely(*buflen >= 0)) {
> + *buffer -= namelen;
> + memcpy(*buffer, str, namelen);
> + }
> }
>
> /**
> @@ -298,11 +297,10 @@ char *simple_dname(struct dentry *dentry, char
> *buffer, int buflen)
> {
> char *end = buffer + buflen;
> /* these dentries are never renamed, so d_lock is not needed */
> - if (prepend(&end, &buflen, " (deleted)", 11) ||
> - prepend(&end, &buflen, dentry->d_name.name, dentry->d_name.len)
> ||
> - prepend(&end, &buflen, "/", 1))
> - end = ERR_PTR(-ENAMETOOLONG);
> - return end;
> + prepend(&end, &buflen, " (deleted)", 11);
> + prepend(&end, &buflen, dentry->d_name.name, dentry->d_name.len);
> + prepend(&end, &buflen, "/", 1);
> + return buflen >= 0 ? end : ERR_PTR(-ENAMETOOLONG);
> }
>
> /*
> --
> 2.11.0

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