bcache: Use DEFINE_MUTEX() for mutex lock

Mutex lock can be initialized automatically with DEFINE_MUTEX() rather
than explicitly calling mutex_init().

This patch will reduce the size of bcache.ko about 16 bytes, the
reason as follows:

Though this patch will increase the size of .data segment about 32
bytes, it will also reduce the size of .init.text and
.rodata.str1.1(at x86_64), .rodata_str1.8(at arm64) total about 48
bytes which reduce the size more than .data segment;

Here is the statistics:
Sections: (arm64 platform)
Idx name                size
-.init.text             00000240
+.init.text             00000228

-.rodata.str1.8	000012cd
+.rodata.str1.8	000012b5

-.data                  00000c60
+.data                  00000c80

Sections: (x86 platform)
Idx name                size
-.init.text             000001d9
+.init.text             000001bf

-.rodata.str1.1	00000c80
+.rodata.str1.1	00000c6d

-.data                  00000cc0
+.data                  00000ce0

Reported-by: Hulk Robot <redacted>
Signed-off-by: Zheng Yongjun <redacted>
---

v4:
- change commit log, delete bss information at commit description.

8 more lines

diff --git a/drivers/md/bcache/super.c b/drivers/md/bcache/super.c
index 03e1fe4de53d..3635f454309e 100644
--- a/drivers/md/bcache/super.c
+++ b/drivers/md/bcache/super.c

@@ -40,7 +40,7 @@ static const char invalid_uuid[] = {
 };
 
 static struct kobject *bcache_kobj;
-struct mutex bch_register_lock;
+DEFINE_MUTEX(bch_register_lock);
 bool bcache_is_reboot;
 LIST_HEAD(bch_cache_sets);
 static LIST_HEAD(uncached_devices);

@@ -2869,7 +2869,6 @@ static int __init bcache_init(void)
 
 	check_module_parameters();
 
-	mutex_init(&bch_register_lock);
 	init_waitqueue_head(&unregister_wait);
 	register_reboot_notifier(&reboot);
 

-- 
2.25.1

On 5/5/21 7:06 PM, Zheng Yongjun wrote:

Mutex lock can be initialized automatically with DEFINE_MUTEX() rather
than explicitly calling mutex_init().

This patch will reduce the size of bcache.ko about 16 bytes, the
reason as follows:

Though this patch will increase the size of .data segment about 32
bytes, it will also reduce the size of .init.text and
.rodata.str1.1(at x86_64), .rodata_str1.8(at arm64) total about 48
bytes which reduce the size more than .data segment;

Here is the statistics:
Sections: (arm64 platform)
Idx name                size
-.init.text             00000240
+.init.text             00000228

-.rodata.str1.8	000012cd
+.rodata.str1.8	000012b5

-.data                  00000c60
+.data                  00000c80

Sections: (x86 platform)
Idx name                size
-.init.text             000001d9
+.init.text             000001bf

-.rodata.str1.1	00000c80
+.rodata.str1.1	00000c6d

-.data                  00000cc0
+.data                  00000ce0

Reported-by: Hulk Robot <redacted>
Signed-off-by: Zheng Yongjun <redacted>

Added in my for-test queue.

Thanks.

Coly Li

[snipped]

I've been on a business trip some time ago and didn't do upstream work. Thanks for your patience:)

-----邮件原件-----
发件人: Coly Li [mailto:colyli@suse.de] 
发送时间: 2021年5月6日 11:27
收件人: zhengyongjun [off-list ref]
抄送: pmail_hulkci [off-list ref]; kent.overstreet@gmail.com; linux-bcache@vger.kernel.org; linux-kernel@vger.kernel.org
主题: Re: [PATCH -next v4] bcache: Use DEFINE_MUTEX() for mutex lock

On 5/5/21 7:06 PM, Zheng Yongjun wrote:

Mutex lock can be initialized automatically with DEFINE_MUTEX() rather 
than explicitly calling mutex_init().

This patch will reduce the size of bcache.ko about 16 bytes, the 
reason as follows:

Though this patch will increase the size of .data segment about 32 
bytes, it will also reduce the size of .init.text and 
.rodata.str1.1(at x86_64), .rodata_str1.8(at arm64) total about 48 
bytes which reduce the size more than .data segment;

Here is the statistics:
Sections: (arm64 platform)
Idx name                size
-.init.text             00000240
+.init.text             00000228

-.rodata.str1.8	000012cd
+.rodata.str1.8	000012b5

-.data                  00000c60
+.data                  00000c80

Sections: (x86 platform)
Idx name                size
-.init.text             000001d9
+.init.text             000001bf

-.rodata.str1.1	00000c80
+.rodata.str1.1	00000c6d

-.data                  00000cc0
+.data                  00000ce0

Reported-by: Hulk Robot <redacted>
Signed-off-by: Zheng Yongjun <redacted>

Added in my for-test queue.

Thanks.

Coly Li

[snipped]