Re: [dm-devel] [PATCH 15/21] libmultipath: update_bindings_file: use a single write()

[Benjamin Marzinski]

On Fri, Sep 01, 2023 at 08:02:28PM +0200, mwi...@suse.com wrote:
> From: Martin Wilck <mwi...@suse.com>
> 
> Save code and syscalls by assembling the content in memory first.
> write() may return less bytes written than expected. Deal with it.
> 
Reviewed-by: Benjamin Marzinski <bmarz...@redhat.com>
> Signed-off-by: Martin Wilck <mwi...@suse.com>
> ---
>  libmultipath/alias.c | 26 +++++++++++++++++---------
>  1 file changed, 17 insertions(+), 9 deletions(-)
> 
> diff --git a/libmultipath/alias.c b/libmultipath/alias.c
> index 76d852f..c26f37c 100644
> --- a/libmultipath/alias.c
> +++ b/libmultipath/alias.c
> @@ -118,22 +118,30 @@ static int add_binding(Bindings *bindings, const char 
> *alias, const char *wwid)
>  static int write_bindings_file(const Bindings *bindings, int fd)
>  {
>       struct binding *bnd;
> -     STRBUF_ON_STACK(line);
> +     STRBUF_ON_STACK(content);
>       int i;
> +     size_t len;
>  
> -     if (write(fd, BINDINGS_FILE_HEADER, sizeof(BINDINGS_FILE_HEADER) - 1)
> -         != sizeof(BINDINGS_FILE_HEADER) - 1)
> +     if (__append_strbuf_str(&content, BINDINGS_FILE_HEADER,
> +                             sizeof(BINDINGS_FILE_HEADER) - 1) == -1)
>               return -1;
>  
>       vector_foreach_slot(bindings, bnd, i) {
> -             int len;
> +             if (print_strbuf(&content, "%s %s\n",
> +                                     bnd->alias, bnd->wwid) < 0)
> +                     return -1;
> +     }
> +     len = get_strbuf_len(&content);
> +     while (len > 0) {
> +             ssize_t n = write(fd, get_strbuf_str(&content), len);
>  
> -             if ((len = print_strbuf(&line, "%s %s\n",
> -                                     bnd->alias, bnd->wwid)) < 0)
> +             if (n < 0)
> +                     return n;
> +             else if (n == 0) {
> +                     condlog(2, "%s: short write", __func__);
>                       return -1;
> -             if (write(fd, get_strbuf_str(&line), len) != len)
> -                     return -1;
> -             truncate_strbuf(&line, 0);
> +             }
> +             len -= n;
>       }
>       return 0;
>  }
> -- 
> 2.41.0
--
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