ACK: [SRU][Bionic][PATCH 1/1] include/uapi/linux/swab.h: fix userspace breakage, use __BITS_PER_LONG for swap

[Andrea Righi]

On Thu, May 07, 2020 at 11:41:22AM +0200, Kleber Sacilotto de Souza wrote:
> From: Christian Borntraeger <borntraeger at de.ibm.com>
> 
> BugLink: https://bugs.launchpad.net/bugs/1877123
> 
> QEMU has a funny new build error message when I use the upstream kernel
> headers:
> 
>       CC      block/file-posix.o
>     In file included from /home/cborntra/REPOS/qemu/include/qemu/timer.h:4,
>                      from /home/cborntra/REPOS/qemu/include/qemu/timed-average.h:29,
>                      from /home/cborntra/REPOS/qemu/include/block/accounting.h:28,
>                      from /home/cborntra/REPOS/qemu/include/block/block_int.h:27,
>                      from /home/cborntra/REPOS/qemu/block/file-posix.c:30:
>     /usr/include/linux/swab.h: In function `__swab':
>     /home/cborntra/REPOS/qemu/include/qemu/bitops.h:20:34: error: "sizeof" is not defined, evaluates to 0 [-Werror=undef]
>        20 | #define BITS_PER_LONG           (sizeof (unsigned long) * BITS_PER_BYTE)
>           |                                  ^~~~~~
>     /home/cborntra/REPOS/qemu/include/qemu/bitops.h:20:41: error: missing binary operator before token "("
>        20 | #define BITS_PER_LONG           (sizeof (unsigned long) * BITS_PER_BYTE)
>           |                                         ^
>     cc1: all warnings being treated as errors
>     make: *** [/home/cborntra/REPOS/qemu/rules.mak:69: block/file-posix.o] Error 1
>     rm tests/qemu-iotests/socket_scm_helper.o
> 
> This was triggered by commit d5767057c9a ("uapi: rename ext2_swab() to
> swab() and share globally in swab.h").  That patch is doing
> 
>   #include <asm/bitsperlong.h>
> 
> but it uses BITS_PER_LONG.
> 
> The kernel file asm/bitsperlong.h provide only __BITS_PER_LONG.
> 
> Let us use the __ variant in swap.h
> 
> Link: http://lkml.kernel.org/r/20200213142147.17604-1-borntraeger@de.ibm.com
> Fixes: d5767057c9a ("uapi: rename ext2_swab() to swab() and share globally in swab.h")
> Signed-off-by: Christian Borntraeger <borntraeger at de.ibm.com>
> Cc: Yury Norov <yury.norov at gmail.com>
> Cc: Allison Randal <allison at lohutok.net>
> Cc: Joe Perches <joe at perches.com>
> Cc: Thomas Gleixner <tglx at linutronix.de>
> Cc: William Breathitt Gray <vilhelm.gray at gmail.com>
> Cc: Torsten Hilbrich <torsten.hilbrich at secunet.com>
> Signed-off-by: Andrew Morton <akpm at linux-foundation.org>
> Signed-off-by: Linus Torvalds <torvalds at linux-foundation.org>
> (cherry picked from commit 467d12f5c7842896d2de3ced74e4147ee29e97c8)
> Signed-off-by: Kleber Sacilotto de Souza <kleber.souza at canonical.com>

Looks good to me. Thanks.

Acked-by: Andrea Righi <andrea.righi at canonical.com>