for-next/sysfs-fix/0003-bcache-add-sysfs_strtoul_bool-for-setting-bit-field-.patch

From 29b3582aba1e717b612825cb97bb7e9d3725748d Mon Sep 17 00:00:00 2001
From: Coly Li <colyli@suse.de>
Date: Thu, 20 Dec 2018 16:54:50 +0800
Subject: [PATCH 03/11] bcache: add sysfs_strtoul_bool() for setting bit-field
 variables

When setting bool values via sysfs interface, e.g. writeback_metadata,
if writing 1 into writeback_metadata file, dc->writeback_metadata is
set to 1, but if writing 2 into the file, dc->writeback_metadata is
0. This is misleading, a better result should be 1 for all non-zero
input value.

It is because dc->writeback_metadata is a bit-field variable, and
current code simply use d_strtoul() to convert a string into integer
and takes the lowest bit value. To fix such error, we need a routine
to convert the input string into unsigned integer, and set target
variable to 1 if the converted integer is non-zero.

This patch introduces a new macro called sysfs_strtoul_bool(), it can
be used to convert input string into bool value, we can use it to set
bool value for bit-field vairables.

Signed-off-by: Coly Li <colyli@suse.de>
---
 drivers/md/bcache/sysfs.h | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/drivers/md/bcache/sysfs.h b/drivers/md/bcache/sysfs.h
index 3fe82425859c..c89bf6d78c03 100644
--- a/drivers/md/bcache/sysfs.h
+++ b/drivers/md/bcache/sysfs.h
@@ -79,6 +79,16 @@ do {									\
 		return strtoul_safe(buf, var) ?: (ssize_t) size;	\
 } while (0)
 
+#define sysfs_strtoul_bool(file, var)					\
+do {									\
+	if (attr == &sysfs_## file) {					\
+		unsigned long v = strtoul_or_return(buf);		\
+									\
+		var = v ? 1 : 0;					\
+		return size;						\
+	}								\
+} while (0)
+
 #define sysfs_strtoul_clamp(file, var, min, max)			\
 do {									\
 	if (attr == &sysfs_ ## file)					\
-- 
2.16.4