On Wed, 15 Sep 2021 10:23:54 -0400
Steven Rostedt <rostedt@xxxxxxxxxxx> wrote:
> On Wed, 15 Sep 2021 22:19:52 +0900
> Masami Hiramatsu <mhiramat@xxxxxxxxxx> wrote:
>
> > @@ -810,6 +811,8 @@ void __init xbc_destroy_all(void)
> > * In error cases, @emsg will be updated with an error message and
> > * @epos will be updated with the error position which is the byte offset
> > * of @buf. If the error is not a parser error, @epos will be -1.
> > + * Note that the @buf ownership is transferred, so it will be freed
> > + * in xbc_destroy_all().
> > */
> > int __init xbc_init(char *buf, const char **emsg, int *epos)
> > {
>
> I hate this "ownership transfer". Looking at the use case here:
>
> init/main.c:
>
> copy = memblock_alloc(size + 1, SMP_CACHE_BYTES);
> if (!copy) {
> pr_err("Failed to allocate memory for bootconfig\n");
> return;
> }
>
> memcpy(copy, data, size);
> copy[size] = '\0';
>
> ret = xbc_init(copy, &msg, &pos);
> if (ret < 0) {
>
> Instead of having xbc_init() return the node count on success, how about
> having it allocate the buffer to use and then return it?
>
> That is, move the:
>
> copy = memblock_alloc(size + 1, SMP_CACHE_BYTES);
> if (!copy) {
> pr_err("Failed to allocate memory for bootconfig\n");
> return;
> }
>
> memcpy(copy, data, size);
> copy[size] = '\0';
>
> into xbc_init(), and have data, and size be passed to it.
>
> Then, have it return the pointer of "copy" or NULL on error?
Thanks for pointing it out, that is also good to me.
Let me update it.
>
> This will keep the semantics of xbc_* owning the buffer that gets
> freed by the destroy.
>
> The xbc_init() could also do the pr_info() that prints the bytes and
> node count. There's no other reason to pass that node count to the
> caller, is there?
Ah, it is my policy that the error or information message is shown
by caller (since caller can also ignore that, e.g. passing the
testing data), not from the library code.
I learned that from perf-probe and ftrace, sometimes the library
code reused in unexpected way. So I decided to decouple the
generating error message and showing it.
Thank you,
>
> -- Steve
--
Masami Hiramatsu <mhiramat@xxxxxxxxxx>
