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Commit ded85c19 authored by Hannes Reinecke's avatar Hannes Reinecke Committed by Christoph Hellwig
Browse files

scsi: Implement per-cpu logging buffer 



Implement a per-cpu buffer for formatting messages to avoid line breaks
up under high load.  This patch implements scmd_printk() and
sdev_prefix_printk() using the per-cpu buffer and makes sdev_printk() a
wrapper for sdev_prefix_printk().

Tested-by: default avatarRobert Elliott <elliott@hp.com>
Reviewed-by: default avatarRobert Elliott <elliott@hp.com>
Signed-off-by: default avatarHannes Reinecke <hare@suse.de>
Signed-off-by: default avatarChristoph Hellwig <hch@lst.de>
parent b0a93d96

drivers/scsi/Makefile

+1 −1
Original line number Diff line number Diff line
@@ -167,7 +167,7 @@ scsi_mod-y += scsi_scan.o scsi_sysfs.o scsi_devinfo.o 
scsi_mod-$(CONFIG_SCSI_NETLINK)	+= scsi_netlink.o

scsi_mod-$(CONFIG_SYSCTL)	+= scsi_sysctl.o

scsi_mod-$(CONFIG_SCSI_PROC_FS)	+= scsi_proc.o

scsi_mod-y			+= scsi_trace.o

scsi_mod-y			+= scsi_trace.o scsi_logging.o

scsi_mod-$(CONFIG_PM)		+= scsi_pm.o



hv_storvsc-y			:= storvsc_drv.o

drivers/scsi/scsi_logging.c

0 → 100644
+124 −0
Original line number Diff line number Diff line 
/*

 * scsi_logging.c

 *

 * Copyright (C) 2014 SUSE Linux Products GmbH

 * Copyright (C) 2014 Hannes Reinecke <hare@suse.de>

 *

 * This file is released under the GPLv2

 */



#include <linux/kernel.h>

#include <linux/atomic.h>



#include <scsi/scsi.h>

#include <scsi/scsi_cmnd.h>

#include <scsi/scsi_device.h>

#include <scsi/scsi_dbg.h>



#define SCSI_LOG_SPOOLSIZE 4096

#define SCSI_LOG_BUFSIZE 128



#if (SCSI_LOG_SPOOLSIZE / SCSI_LOG_BUFSIZE) > BITS_PER_LONG

#warning SCSI logging bitmask too large

#endif



struct scsi_log_buf {

	char buffer[SCSI_LOG_SPOOLSIZE];

	unsigned long map;

};



static DEFINE_PER_CPU(struct scsi_log_buf, scsi_format_log);



static char *scsi_log_reserve_buffer(size_t *len)

{

	struct scsi_log_buf *buf;

	unsigned long map_bits = sizeof(buf->buffer) / SCSI_LOG_BUFSIZE;

	unsigned long idx = 0;



	preempt_disable();

	buf = this_cpu_ptr(&scsi_format_log);

	idx = find_first_zero_bit(&buf->map, map_bits);

	if (likely(idx < map_bits)) {

		while (test_and_set_bit(idx, &buf->map)) {

			idx = find_next_zero_bit(&buf->map, map_bits, idx);

			if (idx >= map_bits)

				break;

		}

	}

	if (WARN_ON(idx >= map_bits)) {

		preempt_enable();

		return NULL;

	}

	*len = SCSI_LOG_BUFSIZE;

	return buf->buffer + idx * SCSI_LOG_BUFSIZE;

}



static void scsi_log_release_buffer(char *bufptr)

{

	struct scsi_log_buf *buf;

	unsigned long idx;

	int ret;



	buf = this_cpu_ptr(&scsi_format_log);

	if (bufptr >= buf->buffer &&

	    bufptr < buf->buffer + SCSI_LOG_SPOOLSIZE) {

		idx = (bufptr - buf->buffer) / SCSI_LOG_BUFSIZE;

		ret = test_and_clear_bit(idx, &buf->map);

		WARN_ON(!ret);

	}

	preempt_enable();

}



int sdev_prefix_printk(const char *level, const struct scsi_device *sdev,

		       const char *name, const char *fmt, ...)

{

	va_list args;

	char *logbuf;

	size_t off = 0, logbuf_len;

	int ret;



	if (!sdev)

		return 0;



	logbuf = scsi_log_reserve_buffer(&logbuf_len);

	if (!logbuf)

		return 0;



	if (name)

		off += scnprintf(logbuf + off, logbuf_len - off,

				 "[%s] ", name);

	va_start(args, fmt);

	off += vscnprintf(logbuf + off, logbuf_len - off, fmt, args);

	va_end(args);

	ret = dev_printk(level, &sdev->sdev_gendev, "%s", logbuf);

	scsi_log_release_buffer(logbuf);

	return ret;

}

EXPORT_SYMBOL(sdev_prefix_printk);



int scmd_printk(const char *level, const struct scsi_cmnd *scmd,

		const char *fmt, ...)

{

	struct gendisk *disk = scmd->request->rq_disk;

	va_list args;

	char *logbuf;

	size_t off = 0, logbuf_len;

	int ret;



	if (!scmd || !scmd->cmnd)

		return 0;



	logbuf = scsi_log_reserve_buffer(&logbuf_len);

	if (!logbuf)

		return 0;

	if (disk)

		off += scnprintf(logbuf + off, logbuf_len - off,

				 "[%s] ", disk->disk_name);

	va_start(args, fmt);

	off += vscnprintf(logbuf + off, logbuf_len - off, fmt, args);

	va_end(args);

	ret = dev_printk(level, &scmd->device->sdev_gendev, "%s", logbuf);

	scsi_log_release_buffer(logbuf);

	return ret;

}

EXPORT_SYMBOL(scmd_printk);

include/scsi/scsi_device.h

+8 −13
Original line number Diff line number Diff line
@@ -230,9 +230,6 @@ struct scsi_dh_data { 
#define transport_class_to_sdev(class_dev) \

	to_scsi_device(class_dev->parent)



#define sdev_printk(prefix, sdev, fmt, a...)	\

	dev_printk(prefix, &(sdev)->sdev_gendev, fmt, ##a)



#define sdev_dbg(sdev, fmt, a...) \

	dev_dbg(&(sdev)->sdev_gendev, fmt, ##a)
@@ -240,16 +237,14 @@ struct scsi_dh_data { 
 * like scmd_printk, but the device name is passed in

 * as a string pointer

 */

#define sdev_prefix_printk(l, sdev, p, fmt, a...)			\

	(p) ?								\

	sdev_printk(l, sdev, "[%s] " fmt, p, ##a) :			\

	sdev_printk(l, sdev, fmt, ##a)



#define scmd_printk(prefix, scmd, fmt, a...)				\

        (scmd)->request->rq_disk ?					\

	sdev_printk(prefix, (scmd)->device, "[%s] " fmt,		\

		    (scmd)->request->rq_disk->disk_name, ##a) :		\

	sdev_printk(prefix, (scmd)->device, fmt, ##a)

extern int sdev_prefix_printk(const char *, const struct scsi_device *,

			      const char *, const char *, ...);



#define sdev_printk(l, sdev, fmt, a...)				\

	sdev_prefix_printk(l, sdev, NULL, fmt, ##a)



extern int scmd_printk(const char *, const struct scsi_cmnd *,

		       const char *, ...);



#define scmd_dbg(scmd, fmt, a...)					   \

	do {								   \