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From: Miquel Raynal <miquel.raynal@bootlin.com>
To: David Laight <david.laight.linux@gmail.com>
Cc: Karl Mehltretter <kmehltretter@gmail.com>,
	 Richard Weinberger <richard@nod.at>,
	 Vignesh Raghavendra <vigneshr@ti.com>,
	 Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
	 Lukas Wunner <lukas@wunner.de>,
	linux-mtd@lists.infradead.org,  linux-kernel@vger.kernel.org
Subject: Re: [PATCH] mtd: cfi_cmdset_0001: shrink do_write_buffer() stack frame
Date: Tue, 25 Aug 2026 14:35:33 +0200	[thread overview]
Message-ID: <87o6eqgyy2.fsf@bootlin.com> (raw)
In-Reply-To: <20260824085632.2dd08ba9@pumpkin> (David Laight's message of "Mon, 24 Aug 2026 08:56:32 +0100")

Hi David & Vignesh,

On 24/08/2026 at 08:56:32 +01, David Laight <david.laight.linux@gmail.com> wrote:

> On Mon, 24 Aug 2026 03:47:03 +0200
> Karl Mehltretter <kmehltretter@gmail.com> wrote:
>
>> arm32 allmodconfig fails to build with gcc:
>> 
>>   drivers/mtd/chips/cfi_cmdset_0001.c:1883:1: error: the frame size of 1296
>>   bytes is larger than 1280 bytes [-Werror=frame-larger-than=]
>> 
>> With MTD_MAP_BANK_WIDTH_32 a map_word is 32 bytes, and with KASAN_STACK
>> every temporary gets its own redzoned slot.  do_write_buffer() builds a
>> map_word for each of the twelve commands it issues, and those temporaries
>> dominate its frame.
>
> Looks to me like pretty much all of mtd/map.h should be real functions
> and not #defines or inlines.
>
> The bloat from all those expansions is going to be significant.
> They only time they get optimised to anything small is when only
> CONFIG_MTD_MAP_BANK_WIDTH_1 is set.
>
> The execution time of all those that do real io (especially reads)
> will be dominated by the io access itself.

David, may I ask if you acknowledge the fix?

Vignesh, same question, maybe you also test that there is no apparent
regression?

Thanks,
Miquèl

______________________________________________________
Linux MTD discussion mailing list
http://lists.infradead.org/mailman/listinfo/linux-mtd/

WARNING: multiple messages have this Message-ID (diff)
From: Miquel Raynal <miquel.raynal@bootlin.com>
To: David Laight <david.laight.linux@gmail.com>
Cc: Karl Mehltretter <kmehltretter@gmail.com>,
	 Richard Weinberger <richard@nod.at>,
	 Vignesh Raghavendra <vigneshr@ti.com>,
	 Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
	 Lukas Wunner <lukas@wunner.de>,
	linux-mtd@lists.infradead.org,  linux-kernel@vger.kernel.org
Subject: Re: [PATCH] mtd: cfi_cmdset_0001: shrink do_write_buffer() stack frame
Date: Tue, 25 Aug 2026 14:35:33 +0200	[thread overview]
Message-ID: <87o6eqgyy2.fsf@bootlin.com> (raw)
In-Reply-To: <20260824085632.2dd08ba9@pumpkin> (David Laight's message of "Mon, 24 Aug 2026 08:56:32 +0100")

Hi David & Vignesh,

On 24/08/2026 at 08:56:32 +01, David Laight <david.laight.linux@gmail.com> wrote:

> On Mon, 24 Aug 2026 03:47:03 +0200
> Karl Mehltretter <kmehltretter@gmail.com> wrote:
>
>> arm32 allmodconfig fails to build with gcc:
>> 
>>   drivers/mtd/chips/cfi_cmdset_0001.c:1883:1: error: the frame size of 1296
>>   bytes is larger than 1280 bytes [-Werror=frame-larger-than=]
>> 
>> With MTD_MAP_BANK_WIDTH_32 a map_word is 32 bytes, and with KASAN_STACK
>> every temporary gets its own redzoned slot.  do_write_buffer() builds a
>> map_word for each of the twelve commands it issues, and those temporaries
>> dominate its frame.
>
> Looks to me like pretty much all of mtd/map.h should be real functions
> and not #defines or inlines.
>
> The bloat from all those expansions is going to be significant.
> They only time they get optimised to anything small is when only
> CONFIG_MTD_MAP_BANK_WIDTH_1 is set.
>
> The execution time of all those that do real io (especially reads)
> will be dominated by the io access itself.

David, may I ask if you acknowledge the fix?

Vignesh, same question, maybe you also test that there is no apparent
regression?

Thanks,
Miquèl

  reply	other threads:[~2026-08-25 12:35 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2026-08-24  1:47 [PATCH] mtd: cfi_cmdset_0001: shrink do_write_buffer() stack frame Karl Mehltretter
2026-08-24  1:47 ` Karl Mehltretter
2026-08-24  7:56 ` David Laight
2026-08-24  7:56   ` David Laight
2026-08-25 12:35   ` Miquel Raynal [this message]
2026-08-25 12:35     ` Miquel Raynal
2026-09-04 17:38 ` Miquel Raynal

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