环境

内核版本：linux-4.1.27

打印

sd 1:0:0:0: [sda] sd_setup_read_write_cmnd: block=0, count=32
sd 1:0:0:0: [sda] sd_setup_read_write_cmnd: block=32, count=64

分析

sd_setup_read_write_cmnd
	SCSI_LOG_HLQUEUE(1,
		scmd_printk(KERN_INFO, SCpnt,
			"%s: block=%llu, count=%dn",
			__func__, (unsigned long long)block, this_count));

drivers/scsi/scsi_logging.h 

extern unsigned int scsi_logging_level;

 scsi_logging_level被定义为unsigned int使用32位表示，每3个bit位表示一个打印等级，3个bit位使用偏移表示。

#define SCSI_LOG_HLQUEUE_SHIFT            21
#define SCSI_LOG_HLQUEUE_BITS             3

#define SCSI_LOG_HLQUEUE(LEVEL,CMD)  
        SCSI_CHECK_LOGGING(SCSI_LOG_HLQUEUE_SHIFT, SCSI_LOG_HLQUEUE_BITS, LEVEL,CMD);

#define SCSI_LOG_LEVEL(SHIFT, BITS)				
        ((scsi_logging_level >> (SHIFT)) & ((1 << (BITS)) - 1))
#define SCSI_CHECK_LOGGING(SHIFT, BITS, LEVEL, CMD)		
do {								
        if (unlikely((SCSI_LOG_LEVEL(SHIFT, BITS)) > (LEVEL)))	
		do {						
			CMD;					
		} while (0);					
} while (0)

SCSI_LOG_HLQUEUE 占用bit[23:21]，这3bit值大于LEVEL就会打印，设置 bit[23:21]=2

scsi_logging_level == 0x400000 == 4194304

echo 4194304 > /proc/sys/dev/scsi/logging_level    开打印

echo 0 > /proc/sys/dev/scsi/logging_level    关打印

配置

内核代码依赖配置宏：#define CONFIG_SCSI_LOGGING 1

CONFIG_SCSI_LOGGING=y

打印

写U盘打印：

sd 1:0:0:0: [sda] Send: scmd 0xffffffc033e93080
sd 1:0:0:0: [sda] CCDB: opcode=0x2a 2a 00 01 c0 81 00 00 00 08 00
sd 1:0:0:0: [sda] sd_setup_read_write_cmnd: block=29393424, count=8
sd 1:0:0:0: [sda] block=29393424
sd 1:0:0:0: [sda] writing 8/8 512 byte blocks.
sd 1:0:0:0: [sda] Done: UNKNOWN(0x2002) Result: hostbyte=0x00 driverbyte=0x00
sd 1:0:0:0: [sda] CCDB: opcode=0x2a 2a 00 01 c0 81 00 00 00 08 00
sd 1:0:0:0: [sda] scsi host busy 1 failed 0
sd 1:0:0:0: Notifying upper driver of completion (result 0)
sd 1:0:0:0: [sda] sd_done: completed 4096 of 4096 bytes
sd 1:0:0:0: [sda] CCDB: opcode=0x2a 2a 00 01 c0 81 00 00 00 08 00
sd 1:0:0:0: [sda] 8 sectors total, 4096 bytes done.

读U盘打印：

sd 1:0:0:0: [sda] sd_setup_read_write_cmnd: block=29392960, count=8
sd 1:0:0:0: [sda] block=29392960
sd 1:0:0:0: [sda] reading 8/8 512 byte blocks.
sd 1:0:0:0: [sda] Send: scmd 0xffffffc033e93680
sd 1:0:0:0: [sda] CCDB: opcode=0x28 28 00 01 c0 80 40 00 00 08 00
sd 1:0:0:0: [sda] Done: UNKNOWN(0x2002) Result: hostbyte=0x00 driverbyte=0x00
sd 1:0:0:0: [sda] CCDB: opcode=0x28 28 00 01 c0 80 40 00 00 08 00
sd 1:0:0:0: [sda] scsi host busy 1 failed 0
sd 1:0:0:0: Notifying upper driver of completion (result 0)
sd 1:0:0:0: [sda] sd_done: completed 4096 of 4096 bytes
sd 1:0:0:0: [sda] CCDB: opcode=0x28 28 00 01 c0 80 40 00 00 08 00
sd 1:0:0:0: [sda] 8 sectors total, 4096 bytes done.

最后

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