[PATCH] Block queue IO tracing support (blktrace) as of 2006-03-23
Signed-off-by: Jens Axboe <axboe@suse.de>
diff --git a/block/blktrace.c b/block/blktrace.c
new file mode 100644
index 0000000..36f3a17
--- /dev/null
+++ b/block/blktrace.c
@@ -0,0 +1,538 @@
+/*
+ * Copyright (C) 2006 Jens Axboe <axboe@suse.de>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
+ *
+ */
+#include <linux/config.h>
+#include <linux/kernel.h>
+#include <linux/blkdev.h>
+#include <linux/blktrace_api.h>
+#include <linux/percpu.h>
+#include <linux/init.h>
+#include <linux/mutex.h>
+#include <linux/debugfs.h>
+#include <asm/uaccess.h>
+
+static DEFINE_PER_CPU(unsigned long long, blk_trace_cpu_offset) = { 0, };
+static unsigned int blktrace_seq __read_mostly = 1;
+
+/*
+ * Send out a notify for this process, if we haven't done so since a trace
+ * started
+ */
+static void trace_note_tsk(struct blk_trace *bt, struct task_struct *tsk)
+{
+ struct blk_io_trace *t;
+
+ t = relay_reserve(bt->rchan, sizeof(*t) + sizeof(tsk->comm));
+ if (t) {
+ t->magic = BLK_IO_TRACE_MAGIC | BLK_IO_TRACE_VERSION;
+ t->device = bt->dev;
+ t->action = BLK_TC_ACT(BLK_TC_NOTIFY);
+ t->pid = tsk->pid;
+ t->cpu = smp_processor_id();
+ t->pdu_len = sizeof(tsk->comm);
+ memcpy((void *) t + sizeof(*t), tsk->comm, t->pdu_len);
+ tsk->btrace_seq = blktrace_seq;
+ }
+}
+
+static int act_log_check(struct blk_trace *bt, u32 what, sector_t sector,
+ pid_t pid)
+{
+ if (((bt->act_mask << BLK_TC_SHIFT) & what) == 0)
+ return 1;
+ if (sector < bt->start_lba || sector > bt->end_lba)
+ return 1;
+ if (bt->pid && pid != bt->pid)
+ return 1;
+
+ return 0;
+}
+
+/*
+ * Data direction bit lookup
+ */
+static u32 ddir_act[2] __read_mostly = { BLK_TC_ACT(BLK_TC_READ), BLK_TC_ACT(BLK_TC_WRITE) };
+
+/*
+ * Bio action bits of interest
+ */
+static u32 bio_act[3] __read_mostly = { 0, BLK_TC_ACT(BLK_TC_BARRIER), BLK_TC_ACT(BLK_TC_SYNC) };
+
+/*
+ * More could be added as needed, taking care to increment the decrementer
+ * to get correct indexing
+ */
+#define trace_barrier_bit(rw) \
+ (((rw) & (1 << BIO_RW_BARRIER)) >> (BIO_RW_BARRIER - 0))
+#define trace_sync_bit(rw) \
+ (((rw) & (1 << BIO_RW_SYNC)) >> (BIO_RW_SYNC - 1))
+
+/*
+ * The worker for the various blk_add_trace*() types. Fills out a
+ * blk_io_trace structure and places it in a per-cpu subbuffer.
+ */
+void __blk_add_trace(struct blk_trace *bt, sector_t sector, int bytes,
+ int rw, u32 what, int error, int pdu_len, void *pdu_data)
+{
+ struct task_struct *tsk = current;
+ struct blk_io_trace *t;
+ unsigned long flags;
+ unsigned long *sequence;
+ pid_t pid;
+ int cpu;
+
+ if (unlikely(bt->trace_state != Blktrace_running))
+ return;
+
+ what |= ddir_act[rw & WRITE];
+ what |= bio_act[trace_barrier_bit(rw)];
+ what |= bio_act[trace_sync_bit(rw)];
+
+ pid = tsk->pid;
+ if (unlikely(act_log_check(bt, what, sector, pid)))
+ return;
+
+ /*
+ * A word about the locking here - we disable interrupts to reserve
+ * some space in the relay per-cpu buffer, to prevent an irq
+ * from coming in and stepping on our toes. Once reserved, it's
+ * enough to get preemption disabled to prevent read of this data
+ * before we are through filling it. get_cpu()/put_cpu() does this
+ * for us
+ */
+ local_irq_save(flags);
+
+ if (unlikely(tsk->btrace_seq != blktrace_seq))
+ trace_note_tsk(bt, tsk);
+
+ t = relay_reserve(bt->rchan, sizeof(*t) + pdu_len);
+ if (t) {
+ cpu = smp_processor_id();
+ sequence = per_cpu_ptr(bt->sequence, cpu);
+
+ t->magic = BLK_IO_TRACE_MAGIC | BLK_IO_TRACE_VERSION;
+ t->sequence = ++(*sequence);
+ t->time = sched_clock() - per_cpu(blk_trace_cpu_offset, cpu);
+ t->sector = sector;
+ t->bytes = bytes;
+ t->action = what;
+ t->pid = pid;
+ t->device = bt->dev;
+ t->cpu = cpu;
+ t->error = error;
+ t->pdu_len = pdu_len;
+
+ if (pdu_len)
+ memcpy((void *) t + sizeof(*t), pdu_data, pdu_len);
+ }
+
+ local_irq_restore(flags);
+}
+
+EXPORT_SYMBOL_GPL(__blk_add_trace);
+
+static struct dentry *blk_tree_root;
+static struct mutex blk_tree_mutex;
+static unsigned int root_users;
+
+static inline void blk_remove_root(void)
+{
+ if (blk_tree_root) {
+ debugfs_remove(blk_tree_root);
+ blk_tree_root = NULL;
+ }
+}
+
+static void blk_remove_tree(struct dentry *dir)
+{
+ mutex_lock(&blk_tree_mutex);
+ debugfs_remove(dir);
+ if (--root_users == 0)
+ blk_remove_root();
+ mutex_unlock(&blk_tree_mutex);
+}
+
+static struct dentry *blk_create_tree(const char *blk_name)
+{
+ struct dentry *dir = NULL;
+
+ mutex_lock(&blk_tree_mutex);
+
+ if (!blk_tree_root) {
+ blk_tree_root = debugfs_create_dir("block", NULL);
+ if (!blk_tree_root)
+ goto err;
+ }
+
+ dir = debugfs_create_dir(blk_name, blk_tree_root);
+ if (dir)
+ root_users++;
+ else
+ blk_remove_root();
+
+err:
+ mutex_unlock(&blk_tree_mutex);
+ return dir;
+}
+
+static void blk_trace_cleanup(struct blk_trace *bt)
+{
+ relay_close(bt->rchan);
+ debugfs_remove(bt->dropped_file);
+ blk_remove_tree(bt->dir);
+ free_percpu(bt->sequence);
+ kfree(bt);
+}
+
+static int blk_trace_remove(request_queue_t *q)
+{
+ struct blk_trace *bt;
+
+ bt = xchg(&q->blk_trace, NULL);
+ if (!bt)
+ return -EINVAL;
+
+ if (bt->trace_state == Blktrace_setup ||
+ bt->trace_state == Blktrace_stopped)
+ blk_trace_cleanup(bt);
+
+ return 0;
+}
+
+static int blk_dropped_open(struct inode *inode, struct file *filp)
+{
+ filp->private_data = inode->u.generic_ip;
+
+ return 0;
+}
+
+static ssize_t blk_dropped_read(struct file *filp, char __user *buffer,
+ size_t count, loff_t *ppos)
+{
+ struct blk_trace *bt = filp->private_data;
+ char buf[16];
+
+ snprintf(buf, sizeof(buf), "%u\n", atomic_read(&bt->dropped));
+
+ return simple_read_from_buffer(buffer, count, ppos, buf, strlen(buf));
+}
+
+static struct file_operations blk_dropped_fops = {
+ .owner = THIS_MODULE,
+ .open = blk_dropped_open,
+ .read = blk_dropped_read,
+};
+
+/*
+ * Keep track of how many times we encountered a full subbuffer, to aid
+ * the user space app in telling how many lost events there were.
+ */
+static int blk_subbuf_start_callback(struct rchan_buf *buf, void *subbuf,
+ void *prev_subbuf, size_t prev_padding)
+{
+ struct blk_trace *bt;
+
+ if (!relay_buf_full(buf))
+ return 1;
+
+ bt = buf->chan->private_data;
+ atomic_inc(&bt->dropped);
+ return 0;
+}
+
+static int blk_remove_buf_file_callback(struct dentry *dentry)
+{
+ debugfs_remove(dentry);
+ return 0;
+}
+
+static struct dentry *blk_create_buf_file_callback(const char *filename,
+ struct dentry *parent,
+ int mode,
+ struct rchan_buf *buf,
+ int *is_global)
+{
+ return debugfs_create_file(filename, mode, parent, buf,
+ &relay_file_operations);
+}
+
+static struct rchan_callbacks blk_relay_callbacks = {
+ .subbuf_start = blk_subbuf_start_callback,
+ .create_buf_file = blk_create_buf_file_callback,
+ .remove_buf_file = blk_remove_buf_file_callback,
+};
+
+/*
+ * Setup everything required to start tracing
+ */
+static int blk_trace_setup(request_queue_t *q, struct block_device *bdev,
+ char __user *arg)
+{
+ struct blk_user_trace_setup buts;
+ struct blk_trace *old_bt, *bt = NULL;
+ struct dentry *dir = NULL;
+ char b[BDEVNAME_SIZE];
+ int ret, i;
+
+ if (copy_from_user(&buts, arg, sizeof(buts)))
+ return -EFAULT;
+
+ if (!buts.buf_size || !buts.buf_nr)
+ return -EINVAL;
+
+ strcpy(buts.name, bdevname(bdev, b));
+
+ /*
+ * some device names have larger paths - convert the slashes
+ * to underscores for this to work as expected
+ */
+ for (i = 0; i < strlen(buts.name); i++)
+ if (buts.name[i] == '/')
+ buts.name[i] = '_';
+
+ if (copy_to_user(arg, &buts, sizeof(buts)))
+ return -EFAULT;
+
+ ret = -ENOMEM;
+ bt = kzalloc(sizeof(*bt), GFP_KERNEL);
+ if (!bt)
+ goto err;
+
+ bt->sequence = alloc_percpu(unsigned long);
+ if (!bt->sequence)
+ goto err;
+
+ ret = -ENOENT;
+ dir = blk_create_tree(buts.name);
+ if (!dir)
+ goto err;
+
+ bt->dir = dir;
+ bt->dev = bdev->bd_dev;
+ atomic_set(&bt->dropped, 0);
+
+ ret = -EIO;
+ bt->dropped_file = debugfs_create_file("dropped", 0444, dir, bt, &blk_dropped_fops);
+ if (!bt->dropped_file)
+ goto err;
+
+ bt->rchan = relay_open("trace", dir, buts.buf_size, buts.buf_nr, &blk_relay_callbacks);
+ if (!bt->rchan)
+ goto err;
+ bt->rchan->private_data = bt;
+
+ bt->act_mask = buts.act_mask;
+ if (!bt->act_mask)
+ bt->act_mask = (u16) -1;
+
+ bt->start_lba = buts.start_lba;
+ bt->end_lba = buts.end_lba;
+ if (!bt->end_lba)
+ bt->end_lba = -1ULL;
+
+ bt->pid = buts.pid;
+ bt->trace_state = Blktrace_setup;
+
+ ret = -EBUSY;
+ old_bt = xchg(&q->blk_trace, bt);
+ if (old_bt) {
+ (void) xchg(&q->blk_trace, old_bt);
+ goto err;
+ }
+
+ return 0;
+err:
+ if (dir)
+ blk_remove_tree(dir);
+ if (bt) {
+ if (bt->dropped_file)
+ debugfs_remove(bt->dropped_file);
+ if (bt->sequence)
+ free_percpu(bt->sequence);
+ if (bt->rchan)
+ relay_close(bt->rchan);
+ kfree(bt);
+ }
+ return ret;
+}
+
+static int blk_trace_startstop(request_queue_t *q, int start)
+{
+ struct blk_trace *bt;
+ int ret;
+
+ if ((bt = q->blk_trace) == NULL)
+ return -EINVAL;
+
+ /*
+ * For starting a trace, we can transition from a setup or stopped
+ * trace. For stopping a trace, the state must be running
+ */
+ ret = -EINVAL;
+ if (start) {
+ if (bt->trace_state == Blktrace_setup ||
+ bt->trace_state == Blktrace_stopped) {
+ blktrace_seq++;
+ smp_mb();
+ bt->trace_state = Blktrace_running;
+ ret = 0;
+ }
+ } else {
+ if (bt->trace_state == Blktrace_running) {
+ bt->trace_state = Blktrace_stopped;
+ relay_flush(bt->rchan);
+ ret = 0;
+ }
+ }
+
+ return ret;
+}
+
+/**
+ * blk_trace_ioctl: - handle the ioctls associated with tracing
+ * @bdev: the block device
+ * @cmd: the ioctl cmd
+ * @arg: the argument data, if any
+ *
+ **/
+int blk_trace_ioctl(struct block_device *bdev, unsigned cmd, char __user *arg)
+{
+ request_queue_t *q;
+ int ret, start = 0;
+
+ q = bdev_get_queue(bdev);
+ if (!q)
+ return -ENXIO;
+
+ mutex_lock(&bdev->bd_mutex);
+
+ switch (cmd) {
+ case BLKTRACESETUP:
+ ret = blk_trace_setup(q, bdev, arg);
+ break;
+ case BLKTRACESTART:
+ start = 1;
+ case BLKTRACESTOP:
+ ret = blk_trace_startstop(q, start);
+ break;
+ case BLKTRACETEARDOWN:
+ ret = blk_trace_remove(q);
+ break;
+ default:
+ ret = -ENOTTY;
+ break;
+ }
+
+ mutex_unlock(&bdev->bd_mutex);
+ return ret;
+}
+
+/**
+ * blk_trace_shutdown: - stop and cleanup trace structures
+ * @q: the request queue associated with the device
+ *
+ **/
+void blk_trace_shutdown(request_queue_t *q)
+{
+ blk_trace_startstop(q, 0);
+ blk_trace_remove(q);
+}
+
+/*
+ * Average offset over two calls to sched_clock() with a gettimeofday()
+ * in the middle
+ */
+static void blk_check_time(unsigned long long *t)
+{
+ unsigned long long a, b;
+ struct timeval tv;
+
+ a = sched_clock();
+ do_gettimeofday(&tv);
+ b = sched_clock();
+
+ *t = tv.tv_sec * 1000000000 + tv.tv_usec * 1000;
+ *t -= (a + b) / 2;
+}
+
+static void blk_trace_check_cpu_time(void *data)
+{
+ unsigned long long *t;
+ int cpu = get_cpu();
+
+ t = &per_cpu(blk_trace_cpu_offset, cpu);
+
+ /*
+ * Just call it twice, hopefully the second call will be cache hot
+ * and a little more precise
+ */
+ blk_check_time(t);
+ blk_check_time(t);
+
+ put_cpu();
+}
+
+/*
+ * Call blk_trace_check_cpu_time() on each CPU to calibrate our inter-CPU
+ * timings
+ */
+static void blk_trace_calibrate_offsets(void)
+{
+ unsigned long flags;
+
+ smp_call_function(blk_trace_check_cpu_time, NULL, 1, 1);
+ local_irq_save(flags);
+ blk_trace_check_cpu_time(NULL);
+ local_irq_restore(flags);
+}
+
+static void blk_trace_set_ht_offsets(void)
+{
+#if defined(CONFIG_SCHED_SMT)
+ int cpu, i;
+
+ /*
+ * now make sure HT siblings have the same time offset
+ */
+ preempt_disable();
+ for_each_online_cpu(cpu) {
+ unsigned long long *cpu_off, *sibling_off;
+
+ for_each_cpu_mask(i, cpu_sibling_map[cpu]) {
+ if (i == cpu)
+ continue;
+
+ cpu_off = &per_cpu(blk_trace_cpu_offset, cpu);
+ sibling_off = &per_cpu(blk_trace_cpu_offset, i);
+ *sibling_off = *cpu_off;
+ }
+ }
+ preempt_enable();
+#endif
+}
+
+static __init int blk_trace_init(void)
+{
+ mutex_init(&blk_tree_mutex);
+ blk_trace_calibrate_offsets();
+ blk_trace_set_ht_offsets();
+
+ return 0;
+}
+
+module_init(blk_trace_init);
+