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

[Justin He]

> -----Original Message-----
> From: Al Viro <viro@xxxxxxxxxxxxxxxx> On Behalf Of Al Viro
> Sent: Wednesday, May 19, 2021 8:49 AM
> To: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
> Cc: Justin He <Justin.He@xxxxxxx>; Petr Mladek <pmladek@xxxxxxxx>; Steven
> Rostedt <rostedt@xxxxxxxxxxx>; Sergey Senozhatsky
> <senozhatsky@xxxxxxxxxxxx>; Andy Shevchenko
> <andriy.shevchenko@xxxxxxxxxxxxxxx>; Rasmus Villemoes
> <linux@xxxxxxxxxxxxxxxxxx>; Jonathan Corbet <corbet@xxxxxxx>; Heiko
> Carstens <hca@xxxxxxxxxxxxx>; Vasily Gorbik <gor@xxxxxxxxxxxxx>; Christian
> Borntraeger <borntraeger@xxxxxxxxxx>; Eric W . Biederman
> <ebiederm@xxxxxxxxxxxx>; Darrick J. Wong <darrick.wong@xxxxxxxxxx>; Peter
> Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>; Ira Weiny <ira.weiny@xxxxxxxxx>;
> Eric Biggers <ebiggers@xxxxxxxxxx>; Ahmed S. Darwish
> <a.darwish@xxxxxxxxxxxxx>; open list:DOCUMENTATION <linux-
> doc@xxxxxxxxxxxxxxx>; Linux Kernel Mailing List <linux-
> kernel@xxxxxxxxxxxxxxx>; linux-s390 <linux-s390@xxxxxxxxxxxxxxx>; linux-
> fsdevel <linux-fsdevel@xxxxxxxxxxxxxxx>
> 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@xxxxxxxxxxxxxxxxxx>

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

--
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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