From: Lukas Wunner <lukas@wunner.de>
To: David Laight <david.laight.linux@gmail.com>
Cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
linux-mtd@lists.infradead.org, linux-kernel@vger.kernel.org,
Miquel Raynal <miquel.raynal@bootlin.com>,
Richard Weinberger <richard@nod.at>,
Vignesh Raghavendra <vigneshr@ti.com>,
Andrew Morton <akpm@linux-foundation.org>
Subject: Re: [PATCH v3 1/1] mtd: cfi_cmdset_0001: Factor out do_write_buffer_locked() to reduce stack frame
Date: Thu, 9 Apr 2026 09:58:28 +0200 [thread overview]
Message-ID: <addcJP2erqYh8pD2@wunner.de> (raw)
In-Reply-To: <20260409082611.73fac9ab@pumpkin>
On Thu, Apr 09, 2026 at 08:26:11AM +0100, David Laight wrote:
> On Wed, 8 Apr 2026 23:11:48 +0200 Andy Shevchenko <andriy.shevchenko@linux.intel.com> wrote:
> > Compiler is not happy about used stack frame:
> >
> > drivers/mtd/chips/cfi_cmdset_0001.c: In function 'do_write_buffer':
> > drivers/mtd/chips/cfi_cmdset_0001.c:1887:1: error: the frame size of 1296 bytes is larger than 1280 bytes [-Werror=frame-larger-than=]
> >
> > Fix this by factoring out do_write_buffer_locked().
>
> Does this just split the large stack frame between two nested functions?
> I'd also expect the compiler to inline do_write_buffer_locked() so it
> makes little difference.
> OTOH I can't immediately see where the large stack frame comes from.
The error occurs for an allmodconfig build on arm, which implies
CONFIG_KASAN_STACK=y and thus increases stack usage vis-à-vis a
"regular" build.
Stack usage is high here because of the three "map_word" types,
which can each be up to 256 unsigned longs (32 * 8), see the
definitions of MAX_MAP_LONGS, MAX_MAP_BANKWIDTH, map_word in
include/linux/mtd/map.h.
Possible solutions:
- Disable KASAN entirely for this file:
https://lore.kernel.org/all/adX3SHYgazijahbG@wunner.de/
Not always a good option, particularly for stuff like lib/maple_tree.c
where the same issue exists in mas_wr_spanning_store() and KASAN would
certainly be good to have for that one.
- Use heap instead of stack.
- Split function in smaller chunks and mark them "noinline".
Thanks,
Lukas
______________________________________________________
Linux MTD discussion mailing list
http://lists.infradead.org/mailman/listinfo/linux-mtd/
next prev parent reply other threads:[~2026-04-09 7:58 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-04-08 21:11 [PATCH v3 1/1] mtd: cfi_cmdset_0001: Factor out do_write_buffer_locked() to reduce stack frame Andy Shevchenko
2026-04-09 7:26 ` David Laight
2026-04-09 7:58 ` Lukas Wunner [this message]
2026-04-09 11:28 ` David Laight
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=addcJP2erqYh8pD2@wunner.de \
--to=lukas@wunner.de \
--cc=akpm@linux-foundation.org \
--cc=andriy.shevchenko@linux.intel.com \
--cc=david.laight.linux@gmail.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mtd@lists.infradead.org \
--cc=miquel.raynal@bootlin.com \
--cc=richard@nod.at \
--cc=vigneshr@ti.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox