linux-kernel - [PATCH V3] block: uapi: Use unsigned int type for IOPRIO_PRIO

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Message-ID: <1722409287-12183-1-git-send-email-zhiguo.niu@unisoc.com>
Date: Wed, 31 Jul 2024 15:01:27 +0800
From: Zhiguo Niu <zhiguo.niu@...soc.com>
To: <axboe@...nel.dk>, <dlemoal@...nel.org>, <hch@....de>
CC: <bvanassche@....org>, <linux-block@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <niuzhiguo84@...il.com>,
        <zhiguo.niu@...soc.com>, <ke.wang@...soc.com>,
        <Hao_hao.Wang@...soc.com>
Subject: [PATCH V3] block: uapi: Use unsigned int type for IOPRIO_PRIO_MASK

Generally, the input of IOPRIO_PRIO_DATA has 16 bits, but the output of
IOPRIO_PRIO_DATA will be expanded to "UL" from IOPRIO_PRIO_MASK.
 #define IOPRIO_PRIO_MASK	((1UL << IOPRIO_CLASS_SHIFT) - 1)
This is not reasonable and meaningless, unsigned int is more suitable for it.

So if use format "%d" to print IOPRIO_PRIO_DATA directly, there will be a
build warning or error showned as the following, which is from the
local test when I modify f2fs codes.

fs/f2fs/sysfs.c:348:31: warning: format ‘%d’ expects argument of type ‘int’,
but argument 4 has type ‘long unsigned int’ [-Wformat=]
   return sysfs_emit(buf, "%s,%d\n",
                              ~^
                              %ld

When modules use IOPRIO_PRIO_CLASS & IOPRIO_PRIO_LEVEL get ioprio's class and
level, their outputs are both unsigned int.
 IOPRIO_CLASS_MASK is:
 #define IOPRIO_CLASS_SHIFT	13
 #define IOPRIO_NR_CLASSES	8
 #define IOPRIO_CLASS_MASK	(IOPRIO_NR_CLASSES - 1)
 IOPRIO_LEVEL_MASK is:
 #define IOPRIO_LEVEL_NR_BITS	3
 #define IOPRIO_NR_LEVELS	(1 << IOPRIO_LEVEL_NR_BITS)
 #define IOPRIO_LEVEL_MASK	(IOPRIO_NR_LEVELS - 1)

Ioprio is passed along as an int internally, so we should not be using an
unsigned long for IOPRIO_PRIO_MASK to not end up with IOPRIO_PRIO_DATA
returning an unsigned long as well.

Fixes: 06447ae5e33b ("ioprio: move user space relevant ioprio bits to UAPI includes")
Cc: stable@...r.kernel.org
Cc: Oliver Hartkopp <socketcan@...tkopp.net>
Signed-off-by: Zhiguo Niu <zhiguo.niu@...soc.com>
Reviewed-by: Bart Van Assche <bvanassche@....org>
Link: https://lore.kernel.org/all/1717155071-20409-1-git-send-email-zhiguo.niu@unisoc.com
---
v3: modify commit message according to Damien Le Moal'ssuggestion
v2: add Fixes tag and Cc tag
---
---
 include/uapi/linux/ioprio.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/uapi/linux/ioprio.h b/include/uapi/linux/ioprio.h
index bee2bdb0..9ead07f 100644
--- a/include/uapi/linux/ioprio.h
+++ b/include/uapi/linux/ioprio.h
@@ -11,7 +11,7 @@
 #define IOPRIO_CLASS_SHIFT	13
 #define IOPRIO_NR_CLASSES	8
 #define IOPRIO_CLASS_MASK	(IOPRIO_NR_CLASSES - 1)
-#define IOPRIO_PRIO_MASK	((1UL << IOPRIO_CLASS_SHIFT) - 1)
+#define IOPRIO_PRIO_MASK	((1U << IOPRIO_CLASS_SHIFT) - 1)

 #define IOPRIO_PRIO_CLASS(ioprio)	\
 	(((ioprio) >> IOPRIO_CLASS_SHIFT) & IOPRIO_CLASS_MASK)
-- 
1.9.1