Re: [PATCH 14/20] scsi: use local buffer for printing CDB

Yoshihiro YUNOMAE
2014-09-05T02:02:42Z

(2014/09/03 19:06), Hannes Reinecke wrote:
> The CDB needs to be printed in one line (ie with one printk
> statement) to avoid the individual bytes to be broken up
> under high load.
> As using individual printk() statements here would lead to
> unnecessary complicated code and needs the stack space to
> hold the format string we should be using a local buffer
> here. If the CDB is longer than the provided buffer
> it will be printed in several lines.
>
> Signed-off-by: Hannes Reinecke <hare@suse.de>
> ---
> drivers/scsi/ch.c | 5 +--
> drivers/scsi/constants.c | 82 ++++++++++++++++++++++++++++++++----------------
> drivers/scsi/sr_ioctl.c | 9 ++++--
> include/scsi/scsi_dbg.h | 2 +-
> 4 files changed, 65 insertions(+), 33 deletions(-)
>
> diff --git a/drivers/scsi/ch.c b/drivers/scsi/ch.c
> index eea94a9..f0df02e 100644
> --- a/drivers/scsi/ch.c
> +++ b/drivers/scsi/ch.c
> @@ -189,6 +189,7 @@ ch_do_scsi(scsi_changer *ch, unsigned char *cmd,
> {
> int errno, retries = 0, timeout, result;
> struct scsi_sense_hdr sshdr;
> + char buf[80];

This patch introduces some magic numbers like here,
but we had better define those.

Thanks,
Yoshihiro YUNOMAE

> timeout = (cmd[0] == INITIALIZE_ELEMENT_STATUS)
> ? timeout_init : timeout_move;
> @@ -196,8 +197,8 @@ ch_do_scsi(scsi_changer *ch, unsigned char *cmd,
> retry:
> errno = 0;
> if (debug) {
> - DPRINTK("command: ");
> - __scsi_print_command(cmd);
> + __scsi_print_command(cmd, buf, 80);
> + DPRINTK("command: %s", buf);
> }
>
> result = scsi_execute_req(ch->device, cmd, direction, buffer,
> diff --git a/drivers/scsi/constants.c b/drivers/scsi/constants.c
> index 6076969..5486816 100644
> --- a/drivers/scsi/constants.c
> +++ b/drivers/scsi/constants.c
> @@ -322,19 +322,20 @@ static bool scsi_opcode_sa_name(int cmd, int service_action,
> return true;
> }
>
> -/* attempt to guess cdb length if cdb_len==0 . No trailing linefeed. */
> -static void print_opcode_name(unsigned char * cdbp, int cdb_len)
> +/* attempt to guess cdb length if cdb_len==0 */
> +static int print_opcode_name(unsigned char * cdbp, int cdb_len,
> + char *buf, int buf_len)
> {
> - int sa, len, cdb0;
> + int sa, len, cdb0, off = 0;
> const char *cdb_name = NULL, *sa_name = NULL;
>
> cdb0 = cdbp[0];
> if (cdb0 == VARIABLE_LENGTH_CMD) {
> len = scsi_varlen_cdb_length(cdbp);
> if (len < 10) {
> - printk("short variable length command, "
> - "len=%d ext_len=%d", len, cdb_len);
> - return;
> + return scnprintf(buf, buf_len,
> + "short variable length command, "
> + "len=%d ext_len=%d", len, cdb_len);
> }
> sa = (cdbp[8] << 8) + cdbp[9];
> } else {
> @@ -344,54 +345,81 @@ static void print_opcode_name(unsigned char * cdbp, int cdb_len)
>
> if (!scsi_opcode_sa_name(cdb0, sa, &cdb_name, &sa_name)) {
> if (cdb_name)
> - printk("%s", cdb_name);
> + off = scnprintf(buf, buf_len, "%s", cdb_name);
> else if (cdb0 > 0xc0)
> - printk("cdb[0]=0x%x (vendor)", cdb0);
> + off = scnprintf(buf, buf_len,
> + "cdb[0]=0x%x (vendor)", cdb0);
> else if (cdb0 > 0x60 && cdb0 < 0x7e)
> - printk("cdb[0]=0x%x (reserved)", cdb0);
> + off = scnprintf(buf, buf_len,
> + "cdb[0]=0x%x (reserved)", cdb0);
> else
> - printk("cdb[0]=0x%x", cdb0);
> + off = scnprintf(buf, buf_len, "cdb[0]=0x%x", cdb0);
> } else {
> if (sa_name)
> - printk("%s", sa_name);
> + off = scnprintf(buf, buf_len, "%s", sa_name);
> else if (cdb_name)
> - printk("%s, sa=0x%x", cdb_name, sa);
> + off = scnprintf(buf, buf_len,
> + "%s, sa=0x%x", cdb_name, sa);
> else
> - printk("cdb[0]=0x%x, sa=0x%x", cdb0, sa);
> + off = scnprintf(buf, buf_len,
> + "cdb[0]=0x%x, sa=0x%x", cdb0, sa);
>
> if (cdb_len > 0 && len != cdb_len)
> - printk(", in_cdb_len=%d, ext_len=%d", len, cdb_len);
> + off += scnprintf(buf + off, buf_len - off,
> + ", in_cdb_len=%d, ext_len=%d",
> + len, cdb_len);
> }
> + return off;
> }
>
> -void __scsi_print_command(unsigned char *cdb)
> +void __scsi_print_command(unsigned char *cdb, char *buf, int buf_len)
> {
> - int k, len;
> + int len, off;
>
> - print_opcode_name(cdb, 0);
> + off = print_opcode_name(cdb, 0, buf, buf_len);
> len = scsi_command_size(cdb);
> + /* Variable length CDBs are not supported */
> + if (len > 16)
> + return;
> /* print out all bytes in cdb */
> - for (k = 0; k < len; ++k)
> - printk(" %02x", cdb[k]);
> - printk("\n");
> + hex_dump_to_buffer(cdb, len, 16, 1,
> + buf, buf_len - off, false);
> }
> EXPORT_SYMBOL(__scsi_print_command);
>
> void scsi_print_command(struct scsi_cmnd *cmd)
> {
> - int k;
> + int k, off = 0;
> + /* 16 bytes + space take up 48 bytes */
> + char buf[48];
> + int buf_len = 48, linelen;
>
> if (cmd->cmnd == NULL)
> return;
>
> - scmd_printk(KERN_INFO, cmd, "CDB: ");
> - print_opcode_name(cmd->cmnd, cmd->cmd_len);
> + off = print_opcode_name(cmd->cmnd, cmd->cmd_len, buf, buf_len);
>
> /* print out all bytes in cdb */
> - printk(":");
> - for (k = 0; k < cmd->cmd_len; ++k)
> - printk(" %02x", cmd->cmnd[k]);
> - printk("\n");
> + if (buf_len - off > cmd->cmd_len * 3 + 2) {
> + /* If we have enough space print CDB in one line */
> + off += scnprintf(buf + off, buf_len - off, ": ");
> + hex_dump_to_buffer(cmd->cmnd, cmd->cmd_len, 16, 1,
> + buf, buf_len - off, false);
> + scmd_printk(KERN_INFO, cmd, "CDB: %s\n", buf);
> + } else {
> + /*
> + * Otherwise print opcode in one line and use
> + * separate lines for the CDB
> + */
> + scmd_printk(KERN_INFO, cmd, "CDB: %s\n", buf);
> + for (k = 0; k < cmd->cmd_len; k += 16) {
> + linelen = min(cmd->cmd_len - k, 16);
> + hex_dump_to_buffer(cmd->cmnd, linelen, 16, 1,
> + buf, sizeof(buf), false);
> + scmd_printk(KERN_INFO, cmd, "CDB[%0x2]: %s\n",
> + k / 16, buf);
> + }
> + }
> }
> EXPORT_SYMBOL(scsi_print_command);
>
> diff --git a/drivers/scsi/sr_ioctl.c b/drivers/scsi/sr_ioctl.c
> index 17e0c2b..8090571 100644
> --- a/drivers/scsi/sr_ioctl.c
> +++ b/drivers/scsi/sr_ioctl.c
> @@ -188,6 +188,7 @@ int sr_do_ioctl(Scsi_CD *cd, struct packet_command *cgc)
> struct scsi_sense_hdr sshdr;
> int result, err = 0, retries = 0;
> struct request_sense *sense = cgc->sense;
> + char buf[80];
>
> SDev = cd->device;
>
> @@ -257,14 +258,16 @@ int sr_do_ioctl(Scsi_CD *cd, struct packet_command *cgc)
> /* sense: Invalid command operation code */
> err = -EDRIVE_CANT_DO_THIS;
> #ifdef DEBUG
> - __scsi_print_command(cgc->cmd);
> + __scsi_print_command(cgc->cmd, buf, 80);
> + sr_printk(KERN_ERR, cd,
> + "CDROM (ioctl) invalid command %s\n", buf);
> scsi_print_sense_hdr(cd->device, cd->cdi.name, &sshdr);
> #endif
> break;
> default:
> + __scsi_print_command(cgc->cmd, buf, 80);
> sr_printk(KERN_ERR, cd,
> - "CDROM (ioctl) error, command: ");
> - __scsi_print_command(cgc->cmd);
> + "CDROM (ioctl) error, command: %s\n", buf);
> scsi_print_sense_hdr(cd->device, cd->cdi.name, &sshdr);
> err = -EIO;
> }
> diff --git a/include/scsi/scsi_dbg.h b/include/scsi/scsi_dbg.h
> index 44bea15..5020e5e 100644
> --- a/include/scsi/scsi_dbg.h
> +++ b/include/scsi/scsi_dbg.h
> @@ -6,7 +6,7 @@ struct scsi_device;
> struct scsi_sense_hdr;
>
> extern void scsi_print_command(struct scsi_cmnd *);
> -extern void __scsi_print_command(unsigned char *);
> +extern void __scsi_print_command(unsigned char *, char *, int);
> extern void scsi_show_extd_sense(struct scsi_device *, const char *,
> unsigned char, unsigned char);
> extern void scsi_show_sense_hdr(struct scsi_device *, const char *,
>

--
Yoshihiro YUNOMAE
Software Platform Research Dept. Linux Technology Center
Hitachi, Ltd., Yokohama Research Laboratory
E-mail: yoshihiro.yunomae.ez@hitachi.com