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: Robert Elliott <elliott@hp.com>
Reviewed-by: Robert Elliott <elliott@hp.com>
Signed-off-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: Christoph Hellwig <hch@lst.de>

diff --git a/drivers/scsi/Makefile b/drivers/scsi/Makefile
index 58158f1..447c2d2 100644 (file)
--- a/drivers/scsi/Makefile
+++ b/drivers/scsi/Makefile
@@ -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

diff --git a/drivers/scsi/scsi_logging.c b/drivers/scsi/scsi_logging.c
new file mode 100644 (file)
index 0000000..09d65de
--- /dev/null
+++ b/drivers/scsi/scsi_logging.c
@@ -0,0 +1,124 @@
+/*
+ * 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);

diff --git a/include/scsi/scsi_device.h b/include/scsi/scsi_device.h
index 3a4edd1..d1aad4d 100644 (file)
--- a/include/scsi/scsi_device.h
+++ b/include/scsi/scsi_device.h
@@ -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 {                                                               \