From: Masami Hiramatsu <mhiramat@kernel.org>
To: Steven Rostedt <rostedt@goodmis.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
Mike Rapoport <rppt@kernel.org>,
Andrew Morton <akpm@linux-foundation.org>,
LKML <linux-kernel@vger.kernel.org>,
Ingo Molnar <mingo@kernel.org>, Linux-MM <linux-mm@kvack.org>,
Vlastimil Babka <vbabka@suse.cz>
Subject: Re: [PATCH v3 3/3] bootconfig: Free xbc_data in xbc_destroy_all()
Date: Thu, 16 Sep 2021 09:05:03 +0900 [thread overview]
Message-ID: <20210916090503.c9d8209e8c88e9c4c7d3072c@kernel.org> (raw)
In-Reply-To: <20210915102354.2841798d@oasis.local.home>
On Wed, 15 Sep 2021 10:23:54 -0400
Steven Rostedt <rostedt@goodmis.org> wrote:
> On Wed, 15 Sep 2021 22:19:52 +0900
> Masami Hiramatsu <mhiramat@kernel.org> 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@kernel.org>
next prev parent reply other threads:[~2021-09-16 0:05 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-09-15 13:19 [PATCH v3 0/3] bootconfig: Fixes to bootconfig memory management Masami Hiramatsu
2021-09-15 13:19 ` [PATCH v3 1/3] bootconfig: init: Fix memblock leak in xbc_make_cmdline() Masami Hiramatsu
2021-09-15 13:19 ` [PATCH v3 2/3] bootconfig: init: Fix memblock leak in setup_boot_config() Masami Hiramatsu
2021-09-15 13:19 ` [PATCH v3 3/3] bootconfig: Free xbc_data in xbc_destroy_all() Masami Hiramatsu
2021-09-15 14:23 ` Steven Rostedt
2021-09-16 0:05 ` Masami Hiramatsu [this message]
2021-09-16 0:17 ` Steven Rostedt
2021-09-15 16:47 ` [PATCH v3 0/3] bootconfig: Fixes to bootconfig memory management Linus Torvalds
2021-09-15 16:51 ` Linus Torvalds
2021-09-16 0:07 ` Masami Hiramatsu
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