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Date: Sat, 17 Jan 2009 14:37:39 +0100
From: Frederic Weisbecker <fweisbec@...il.com>
To: Arnaldo Carvalho de Melo <acme@...hat.com>,
Jens Axboe <jens.axboe@...cle.com>,
Ingo Molnar <mingo@...e.hu>,
Steven Rostedt <rostedt@...dmis.org>,
linux-kernel@...r.kernel.org
Subject: Re: [RFC][PATCH] ftrace interface for blktrace
On Fri, Jan 16, 2009 at 04:16:11PM -0200, Arnaldo Carvalho de Melo wrote:
> Hi Jens,
>
> The patch below adds a ftrace interface for blktrace, allowing
> people to use it without any required userspace tools, using sysfs to setup the
> act_mask, pid, start_lba, end_lba.
> Example usage:
>
> [root@...-1 ~]# mount -t debugfs none /sys/kernel/debug/
> [root@...-1 ~]# ls /sys/block/sda/sda1/trace/
> act_mask enable end_lba pid start_lba
That reminds me it would be good to provide a more powerful tracer options
Api, to set numeric or string values for the options, like the kernel
parameters..... So you would avoid to implement your own way to do it.
I should put my hands into it one day.
> [root@...-1 ~]# cat /sys/kernel/debug/tracing/available_tracers
> blk function_graph wakeup function sched_switch nop
> [root@...-1 ~]# echo blk > /sys/kernel/debug/tracing/current_tracer
> [root@...-1 ~]# cat /sys/kernel/debug/tracing/trace
> # tracer: blk
> #
> # DEV CPU TIMESTAMP PID ACT FLG
> # | | | | | |
> [root@...-1 ~]# echo 1 > /sys/block/sda/sda1/trace/enable
> [root@...-1 ~]# tail /sys/kernel/debug/tracing/trace
> 8,1 0 143.070085 1208 P NS [tail]
> 8,1 0 143.070087 1208 I RBS 4154375 + 8 [tail]
> 8,1 0 143.070091 1208 A WBS 4155391 + 16 <- (8,1) 4155328
> 8,1 0 143.070091 1208 Q R 4155391 + 16 [tail]
> 8,1 0 143.070094 1208 G RB 4155391 + 16 [tail]
> 8,1 0 143.070094 1208 I RBS 4155391 + 16 [tail]
> 8,1 0 143.070097 1208 U WS [tail] 2
> 8,1 0 143.070101 1208 D WB 4154375 + 8 [tail]
> 8,1 0 143.070341 1208 D WB 4155391 + 16 [tail]
> 8,1 0 143.070635 0 C RS 4154375 + 8 [0]
nice!
> [root@...-1 ~]#
>
> Filters can be set using:
>
> [root@...-1 ~]# echo write,sync > /sys/block/sda/sda1/trace/act_mask
> [root@...-1 ~]# cat /sys/block/sda/sda1/trace/act_mask
> 0xa
That would be better to see the thing as a string, like you set it.
> One can go on interactively adding more filters, for instance:
>
> [root@...-1 ~]# echo `pidof kjournald` > /sys/block/sda/sda1/trace/pid
> [root@...-1 ~]# cat /sys/block/sda/sda1/trace/pid
> 423
Or why not simply kjournald? :-)
> And use the existing ftrace infrastructure to, for instance,
> replicate the btrace (blktrace -o - | blkparse) functionality by simply
> using cat:
>
> [root@...-1 ~]# cat /sys/kernel/debug/tracing/trace_pipe
> 8,1 0 457.253356 423 A WBS 6335 + 8 <- (8,1) 6272
> 8,1 0 457.253360 423 Q R 6335 + 8 [kjournald]
> 8,1 0 457.253367 423 G RB 6335 + 8 [kjournald]
> 8,1 0 457.253372 423 I RBS 6335 + 8 [kjournald]
> 8,1 0 457.253376 423 A WBS 6343 + 8 <- (8,1) 6280
> 8,1 0 457.253376 423 Q R 6343 + 8 [kjournald]
> 8,1 0 457.253378 423 M W 6343 + 8 [kjournald]
> 8,1 0 457.253380 423 A WBS 6351 + 8 <- (8,1) 6288
> CONTROL+C
> [root@...-1 ~]#
>
> This patch was done on Linus tree, I'll now work with it on
> linux-tip so that I can experiment with binary tracing, i.e to ask for
> the output of /sys/kernel/debug/tracing/trace_pipe to be raw, exactly
> the one provide by relayfs based variant, so that we will be able to
> continue using blkparse to validate the trace entries, as a debugging
> aid.
But I guess there will be some changes to bring on the tracing to make
it support binary flow...
> Also there are other interesting things that one gets from using
> the ftrace infrastructure, such as being able to set see traffic that
> happens in just a cpuset (/sys/kernel/debug/tracing/tracing_cpumask),
> and others that I plan to add such as what Steve did in "[PATCH 2/2]
> ftrace: add stack trace to function tracer", so that we could have
> things like (made up example):
>
> [root@...-1 ~]# cat /sys/kernel/debug/tracing/trace_pipe
> 8,1 0 457.253356 423 A WBS 6335 + 8 <- (8,1) 6272
> 8,1 0 457.253360 423 Q R 6335 + 8 [kjournald]
> 8,1 0 457.253367 423 G RB 6335 + 8 [kjournald]
> 8,1 0 457.253372 423 I RBS 6335 + 8 [kjournald]
> <= sync_buffer
> <= __wait_on_bit
> <= out_of_line_wait_on_bit
> <= __wait_on_buffer
> <= sync_dirty_buffer
> <= journal_commit_transaction
> <= kjournald
> 8,1 0 457.253376 423 A WBS 6343 + 8 <- (8,1) 6280
> 8,1 0 457.253376 423 Q R 6343 + 8 [kjournald]
> 8,1 0 457.253378 423 M W 6343 + 8 [kjournald]
> 8,1 0 457.253380 423 A WBS 6351 + 8 <- (8,1) 6288
Cool, but I guess you will not need this ftrace plugin to do it.
stack traces entries for tracing are already supported for a while.
> More polishing is needed, I wrote the patch this way just to
> show where things are different, with new code, for registering the
> tracer, bits stolen from the userspace blktrace, allowing config via
> sysfs at the bottom.
>
> Ideally we would move this to kernel/trace/block.c, break it
> into smaller self contained patches, etc.
>
> Comments?
>
> - Arnaldo
>
> block/blktrace.c | 578 +++++++++++++++++++++++++++++++++++++++++++++++++-
> fs/partitions/check.c | 7
> 2 files changed, 583 insertions(+), 2 deletions(-)
>
> diff --git a/block/blktrace.c b/block/blktrace.c
> index b0a2cae..10985f9 100644
> --- a/block/blktrace.c
> +++ b/block/blktrace.c
> @@ -25,9 +25,13 @@
> #include <linux/time.h>
> #include <trace/block.h>
> #include <asm/uaccess.h>
> +#include <../kernel/trace/trace.h>
Yeah, it really needs to be moved on kernel/trace :-)
> static unsigned int blktrace_seq __read_mostly = 1;
>
> +static struct trace_array *blk_tr;
> +static int __read_mostly blk_tracer_enabled;
> +
> /* Global reference count of probes */
> static DEFINE_MUTEX(blk_probe_mutex);
> static atomic_t blk_probes_ref = ATOMIC_INIT(0);
> @@ -43,6 +47,9 @@ static void trace_note(struct blk_trace *bt, pid_t pid, int action,
> {
> struct blk_io_trace *t;
>
> + if (!bt->rchan)
> + return;
> +
> t = relay_reserve(bt->rchan, sizeof(*t) + len);
> if (t) {
> const int cpu = smp_processor_id();
> @@ -90,6 +97,9 @@ void __trace_note_message(struct blk_trace *bt, const char *fmt, ...)
> unsigned long flags;
> char *buf;
>
> + if (!bt->msg_data)
> + return;
> +
> local_irq_save(flags);
> buf = per_cpu_ptr(bt->msg_data, smp_processor_id());
> va_start(args, fmt);
> @@ -131,13 +141,14 @@ static 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 ring_buffer_event *event = NULL;
> struct blk_io_trace *t;
> unsigned long flags;
> unsigned long *sequence;
> pid_t pid;
> int cpu;
>
> - if (unlikely(bt->trace_state != Blktrace_running))
> + if (unlikely(bt->trace_state != Blktrace_running || !blk_tracer_enabled))
> return;
>
> what |= ddir_act[rw & WRITE];
> @@ -158,6 +169,25 @@ static void __blk_add_trace(struct blk_trace *bt, sector_t sector, int bytes,
> */
> local_irq_save(flags);
Is the local_irq_save still needed here? Note that the ring buffer is safe by itself.
> + if (blk_tr) {
> + struct trace_array_cpu *data;
> +
> + tracing_record_cmdline(current);
> + cpu = raw_smp_processor_id();
I think you can use smp_processor_id(). There is no risk of tracing recursion here.
> + data = blk_tr->data[cpu];
> +
> + if (unlikely(atomic_read(&data->disabled)))
> + goto out_local_irq_restore;
> +
> + event = ring_buffer_lock_reserve(blk_tr->buffer,
> + sizeof(*t) + pdu_len, &flags);
> + if (!event)
> + goto out_local_irq_restore;
> +
> + t = ring_buffer_event_data(event);
> + goto record_it;
> + }
> +
> if (unlikely(tsk->btrace_seq != blktrace_seq))
> trace_note_tsk(bt, tsk);
>
> @@ -169,19 +199,26 @@ static void __blk_add_trace(struct blk_trace *bt, sector_t sector, int bytes,
> t->magic = BLK_IO_TRACE_MAGIC | BLK_IO_TRACE_VERSION;
> t->sequence = ++(*sequence);
> t->time = ktime_to_ns(ktime_get());
You already have a timestamp for each entry on the ring buffer.
> + t->cpu = cpu;
Ditto. But perhaps you can be preempted between the block action and the trace insertion.
I'm not sure of the context here.. So perhaps you must keep it.
> +record_it:
> 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);
> +
> + if (blk_tr) {
> + ring_buffer_unlock_commit(blk_tr->buffer, event, flags);
> + trace_wake_up();
> + }
> }
>
> +out_local_irq_restore:
> local_irq_restore(flags);
> }
>
> @@ -888,3 +925,540 @@ static void blk_unregister_tracepoints(void)
>
> tracepoint_synchronize_unregister();
> }
> +
> +/*
> + * struct blk_io_tracer formatting routines
> + */
> +
> +static void fill_rwbs(char *rwbs, struct blk_io_trace *t)
> +{
> + int i = 0;
> +
> + if (t->action & BLK_TC_DISCARD) rwbs[i++] = 'D';
> + else if (t->action & BLK_TC_WRITE) rwbs[i++] = 'W';
> + else if (t->bytes) rwbs[i++] = 'R';
> + else rwbs[i++] = 'N';
> +
> + if (t->action & BLK_TC_AHEAD) rwbs[i++] = 'A';
> + if (t->action & BLK_TC_BARRIER) rwbs[i++] = 'B';
> + if (t->action & BLK_TC_SYNC) rwbs[i++] = 'S';
> + if (t->action & BLK_TC_META) rwbs[i++] = 'M';
> +
> + rwbs[i] = '\0';
> +}
> +
> +static inline void *pdu_start(struct blk_io_trace *t)
> +{
> + return t + 1;
> +}
> +
> +static inline u32 t_sec(const struct blk_io_trace *t)
> +{
> + return t->bytes >> 9;
> +}
> +
> +static __u64 get_pdu_int(struct blk_io_trace *t)
> +{
> + __u64 *val = pdu_start(t);
> +
> + return be64_to_cpu(*val);
> +}
> +
> +static void get_pdu_remap(struct blk_io_trace *t, struct blk_io_trace_remap *r)
> +{
> + struct blk_io_trace_remap *__r = pdu_start(t);
> + __u64 sector = __r->sector;
> +
> + r->device = be32_to_cpu(__r->device);
> + r->device_from = be32_to_cpu(__r->device_from);
> + r->sector = be64_to_cpu(sector);
> +}
> +
> +static int blk_log_action(struct trace_iterator *iter, struct blk_io_trace *t,
> + const char *act)
> +{
> + char rwbs[6];
> + unsigned long long ts = ns2usecs(iter->ts);
> + unsigned long usec_rem = do_div(ts, USEC_PER_SEC);
> + unsigned secs = (unsigned long)ts;
> +
> + fill_rwbs(rwbs, t);
> + return trace_seq_printf(&iter->seq,
> + "%3d,%-3d %2d %5d.%06lu %5u %2s %3s ",
> + MAJOR(t->device), MINOR(t->device), iter->cpu,
> + secs, usec_rem, t->pid, act, rwbs);
> +}
> +
> +static int blk_log_generic(struct trace_iterator *iter, struct blk_io_trace *t,
> + const char *act)
> +{
> + int ret = blk_log_action(iter, t, act);
> + if (ret) {
> + const char *cmd = trace_find_cmdline(t->pid);
> +
> + if (t_sec(t))
> + ret = trace_seq_printf(&iter->seq, "%llu + %u [%s]\n",
> + (unsigned long long)t->sector,
> + t_sec(t), cmd);
> + else
> + ret = trace_seq_printf(&iter->seq, "[%s]\n", cmd);
> + }
> + return ret;
> +}
> +
> +static int blk_log_with_err(struct trace_iterator *iter, struct blk_io_trace *t,
> + const char *act)
> +{
> + int ret = blk_log_action(iter, t, act);
> + if (ret) {
> + if (t_sec(t))
> + ret = trace_seq_printf(&iter->seq, "%llu + %u [%d]\n",
> + (unsigned long long)t->sector,
> + t_sec(t), t->error);
> + else
> + ret = trace_seq_printf(&iter->seq, "%llu [%d]\n",
> + (unsigned long long)t->sector,
> + t->error);
> + }
> + return ret;
> +}
> +
> +static int blk_log_remap(struct trace_iterator *iter, struct blk_io_trace *t)
> +{
> + int ret = blk_log_action(iter, t, "A");
> + if (ret) {
> + struct blk_io_trace_remap r = { .device = 0, };
> +
> + get_pdu_remap(t, &r);
> + t->device = r.device_from;
> + ret = trace_seq_printf(&iter->seq, "%llu + %u <- (%d,%d) %llu\n",
> + (unsigned long long)t->sector,
> + t_sec(t), MAJOR(r.device), MINOR(r.device),
> + (unsigned long long)r.sector);
> + }
> + return ret;
> +}
> +
> +static int blk_log_plug(struct trace_iterator *iter, struct blk_io_trace *t)
> +{
> + int ret = blk_log_action(iter, t, "P");
> + if (ret)
> + ret = trace_seq_printf(&iter->seq, "[%s]\n",
> + trace_find_cmdline(t->pid));
> + return ret;
> +}
> +
> +static int blk_log_unplug(struct trace_iterator *iter, struct blk_io_trace *t,
> + const char *act)
> +{
> + int ret = blk_log_action(iter, t, act);
> + if (ret)
> + ret = trace_seq_printf(&iter->seq, "[%s] %u\n",
> + trace_find_cmdline(t->pid),
> + get_pdu_int(t));
> + return ret;
> +}
> +
> +static int blk_log_split(struct trace_iterator *iter, struct blk_io_trace *t,
> + const char *act)
> +{
> + int ret = blk_log_action(iter, t, act);
> + if (ret)
> + ret = trace_seq_printf(&iter->seq, "%llu / %u [%s]\n",
> + (unsigned long long)t->sector,
> + get_pdu_int(t),
> + trace_find_cmdline(t->pid));
> + return ret;
> +}
> +
> +/*
> + * struct tracer operations
> + */
> +
> +static void blk_tracer_print_header(struct seq_file *m)
> +{
> + seq_puts(m, "# DEV CPU TIMESTAMP PID ACT FLG\n"
> + "# | | | | | |\n");
> +}
> +
> +static enum print_line_t blk_tracer_print_line(struct trace_iterator *iter)
> +{
> + struct trace_seq *s = &iter->seq;
> + struct blk_io_trace *t = (struct blk_io_trace *)iter->ent;
> + const u16 what = t->action & ((1 << BLK_TC_SHIFT) - 1);
> + int ret;
> +
> + switch (what) {
> + case __BLK_TA_ISSUE: ret = blk_log_generic(iter, t, "D"); break;
> + case __BLK_TA_INSERT: ret = blk_log_generic(iter, t, "I"); break;
> + case __BLK_TA_QUEUE: ret = blk_log_generic(iter, t, "Q"); break;
> + case __BLK_TA_BOUNCE: ret = blk_log_generic(iter, t, "B"); break;
> + case __BLK_TA_BACKMERGE: ret = blk_log_generic(iter, t, "M"); break;
> + case __BLK_TA_FRONTMERGE: ret = blk_log_generic(iter, t, "F"); break;
> + case __BLK_TA_GETRQ: ret = blk_log_generic(iter, t, "G"); break;
> + case __BLK_TA_SLEEPRQ: ret = blk_log_generic(iter, t, "S"); break;
> + case __BLK_TA_REQUEUE: ret = blk_log_with_err(iter, t, "R"); break;
> + case __BLK_TA_COMPLETE: ret = blk_log_with_err(iter, t, "C"); break;
> + case __BLK_TA_PLUG: ret = blk_log_plug(iter, t); break;
> + case __BLK_TA_UNPLUG_IO: ret = blk_log_unplug(iter, t, "U"); break;
> + case __BLK_TA_UNPLUG_TIMER: ret = blk_log_unplug(iter, t, "UT"); break;
> + case __BLK_TA_REMAP: ret = blk_log_remap(iter, t); break;
> + case __BLK_TA_SPLIT: ret = blk_log_split(iter, t, "X"); break;
> + default:
> + ret = trace_seq_printf(s, "Bad pc action %x\n", what);
> + break;
> + }
> +
> + if (ret == 0)
> + return TRACE_TYPE_PARTIAL_LINE;
> +
> + return TRACE_TYPE_HANDLED;
> +}
> +
> +static void blk_tracer_start(struct trace_array *tr)
> +{
> + int cpu;
> +
> + tr->time_start = ftrace_now(tr->cpu);
> +
> + for_each_online_cpu(cpu)
> + tracing_reset(tr, cpu);
> +
> + mutex_lock(&blk_probe_mutex);
> + if (atomic_add_return(1, &blk_probes_ref) == 1)
> + if (blk_register_tracepoints())
> + atomic_dec(&blk_probes_ref);
> + mutex_unlock(&blk_probe_mutex);
Is this mutex really needed? You already use an atomic test that make
your wall.
> +}
> +
> +static int blk_tracer_init(struct trace_array *tr)
> +{
> + blk_tr = tr;
> + blk_tracer_start(tr);
> + mutex_lock(&blk_probe_mutex);
> + blk_tracer_enabled++;
I think you will not have more than one blk_tracer_init() call
while your tracer is enabled.
So, unless there are other callsites that use your tracer, I guess this counter
is useless.
> + mutex_unlock(&blk_probe_mutex);
> + return 0;
> +}
> +
> +static void blk_tracer_stop(struct trace_array *tr)
> +{
> + mutex_lock(&blk_probe_mutex);
> + if (atomic_dec_and_test(&blk_probes_ref))
> + blk_unregister_tracepoints();
> + mutex_unlock(&blk_probe_mutex);
> +}
> +
> +static void blk_tracer_reset(struct trace_array *tr)
> +{
> + if (!atomic_read(&blk_probes_ref))
> + return;
> +
> + mutex_lock(&blk_probe_mutex);
> + blk_tracer_enabled--;
> + WARN_ON(blk_tracer_enabled < 0);
Ditto, I don't think that can happen.
> + mutex_unlock(&blk_probe_mutex);
> +
> + blk_tracer_stop(tr);
> +}
> +
> +static struct tracer blk_tracer __read_mostly = {
> + .name = "blk",
> + .init = blk_tracer_init,
> + .reset = blk_tracer_reset,
> + .start = blk_tracer_start,
> + .stop = blk_tracer_stop,
> + .print_header = blk_tracer_print_header,
> + .print_line = blk_tracer_print_line,
> +};
> +
> +static int __init init_blk_tracer(void)
> +{
> + return register_tracer(&blk_tracer);
> +}
> +
> +device_initcall(init_blk_tracer);
> +
> +static int blk_trace_remove_queue(struct request_queue *q)
> +{
> + struct blk_trace *bt;
> +
> + bt = xchg(&q->blk_trace, NULL);
> + if (bt == NULL)
> + return -EINVAL;
> +
> + kfree(bt);
> + return 0;
> +}
> +
> +/*
> + * Setup everything required to start tracing
> + */
> +static int blk_trace_setup_queue(struct request_queue *q, dev_t dev)
> +{
> + struct blk_trace *old_bt, *bt = NULL;
> + int ret;
> +
> + ret = -ENOMEM;
> + bt = kzalloc(sizeof(*bt), GFP_KERNEL);
> + if (!bt)
> + goto err;
> +
> + bt->dev = dev;
> + bt->act_mask = (u16)-1;
That looks strange on a first view.
Why not ~0 ? But that doesn't really matter...
> + bt->end_lba = -1ULL;
> + bt->trace_state = Blktrace_running;
> +
> + old_bt = xchg(&q->blk_trace, bt);
> + if (old_bt != NULL) {
> + (void)xchg(&q->blk_trace, old_bt);
> + kfree(bt);
> + ret = -EBUSY;
> + }
> + return 0;
> +err:
> + return ret;
> +}
> +
> +/*
> + * sysfs interface to enable and configure tracing
> + */
> +
> +static ssize_t sysfs_blk_trace_enable_show(struct device *dev,
> + struct device_attribute *attr,
> + char *buf)
> +{
> + struct hd_struct *p = dev_to_part(dev);
> + struct block_device *bdev;
> + ssize_t ret = -ENXIO;
> +
> + lock_kernel();
Ouch, I hope you will add a comment to explain why you are using the bkl
here, I guess this is block related but I'm not sure of anything :-)
> + bdev = bdget(part_devt(p));
> + if (bdev != NULL) {
> + struct request_queue *q = bdev_get_queue(bdev);
> +
> + if (q != NULL) {
> + mutex_lock(&bdev->bd_mutex);
> + ret = sprintf(buf, "%u\n", !!q->blk_trace);
I guess you can be a bit racy here and drop the mutex. That wouldn't matter.
> + mutex_unlock(&bdev->bd_mutex);
> + }
> +
> + bdput(bdev);
> + }
> +
> + unlock_kernel();
> + return ret;
> +}
> +
> +static ssize_t sysfs_blk_trace_enable_store(struct device *dev,
> + struct device_attribute *attr,
> + const char *buf, size_t count)
> +{
> + struct block_device *bdev;
> + struct request_queue *q;
> + struct hd_struct *p;
> + int value;
> + ssize_t ret = -ENXIO;
> +
> + if (count == 0 || sscanf(buf, "%d", &value) != 1)
> + goto out;
> +
> + lock_kernel();
> + p = dev_to_part(dev);
> + bdev = bdget(part_devt(p));
> + if (bdev == NULL)
> + goto out_unlock_kernel;
> +
> + q = bdev_get_queue(bdev);
> + if (q == NULL)
> + goto out_bdput;
> +
> + mutex_lock(&bdev->bd_mutex);
> + if (value)
> + ret = blk_trace_setup_queue(q, bdev->bd_dev);
> + else
> + ret = blk_trace_remove_queue(q);
> + mutex_unlock(&bdev->bd_mutex);
> +
> + if (ret == 0)
> + ret = count;
> +out_bdput:
> + bdput(bdev);
> +out_unlock_kernel:
> + unlock_kernel();
> +out:
> + return ret;
> +}
> +
> +static ssize_t sysfs_blk_trace_attr_show(struct device *dev,
> + struct device_attribute *attr,
> + char *buf);
> +static ssize_t sysfs_blk_trace_attr_store(struct device *dev,
> + struct device_attribute *attr,
> + const char *buf, size_t count);
> +#define BLK_TRACE_DEVICE_ATTR(_name) \
> + DEVICE_ATTR(_name, S_IRUGO | S_IWUSR, \
> + sysfs_blk_trace_attr_show, \
> + sysfs_blk_trace_attr_store)
> +
> +static DEVICE_ATTR(enable, S_IRUGO | S_IWUSR,
> + sysfs_blk_trace_enable_show, sysfs_blk_trace_enable_store);
> +static BLK_TRACE_DEVICE_ATTR(act_mask);
> +static BLK_TRACE_DEVICE_ATTR(pid);
> +static BLK_TRACE_DEVICE_ATTR(start_lba);
> +static BLK_TRACE_DEVICE_ATTR(end_lba);
> +
> +static struct attribute *blk_trace_attrs[] = {
> + &dev_attr_enable.attr,
> + &dev_attr_act_mask.attr,
> + &dev_attr_pid.attr,
> + &dev_attr_start_lba.attr,
> + &dev_attr_end_lba.attr,
> + NULL
> +};
> +
> +struct attribute_group blk_trace_attr_group = {
> + .name = "trace",
> + .attrs = blk_trace_attrs,
> +};
> +
> +static int blk_str2act_mask(const char *str)
> +{
> + int mask = 0;
> + char *copy = kstrdup(str, GFP_KERNEL), *s;
> +
> + if (copy == NULL)
> + return -ENOMEM;
> +
> + s = strstrip(copy);
> +
> + while (1) {
> + char *sep = strchr(s, ',');
> +
> + if (sep != NULL)
> + *sep = '\0';
> +
> + if (strcasecmp(s, "barrier") == 0)
> + mask |= BLK_TC_BARRIER;
> + else if (strcasecmp(s, "complete") == 0)
> + mask |= BLK_TC_COMPLETE;
> + else if (strcasecmp(s, "fs") == 0)
> + mask |= BLK_TC_FS;
> + else if (strcasecmp(s, "issue") == 0)
> + mask |= BLK_TC_ISSUE;
> + else if (strcasecmp(s, "pc") == 0)
> + mask |= BLK_TC_PC;
> + else if (strcasecmp(s, "queue") == 0)
> + mask |= BLK_TC_QUEUE;
> + else if (strcasecmp(s, "read") == 0)
> + mask |= BLK_TC_READ;
> + else if (strcasecmp(s, "requeue") == 0)
> + mask |= BLK_TC_REQUEUE;
> + else if (strcasecmp(s, "sync") == 0)
> + mask |= BLK_TC_SYNC;
> + else if (strcasecmp(s, "write") == 0)
> + mask |= BLK_TC_WRITE;
> +
> + if (sep == NULL)
> + break;
> +
> + s = sep + 1;
> + }
> + kfree(copy);
> +
> + return mask;
> +}
> +
> +static ssize_t sysfs_blk_trace_attr_show(struct device *dev,
> + struct device_attribute *attr,
> + char *buf)
> +{
> + struct hd_struct *p = dev_to_part(dev);
> + struct request_queue *q;
> + struct block_device *bdev;
> + ssize_t ret = -ENXIO;
> +
> + lock_kernel();
> + bdev = bdget(part_devt(p));
> + if (bdev == NULL)
> + goto out_unlock_kernel;
> +
> + q = bdev_get_queue(bdev);
> + if (q == NULL)
> + goto out_bdput;
> + mutex_lock(&bdev->bd_mutex);
> + if (q->blk_trace == NULL)
> + ret = sprintf(buf, "disabled\n");
> + else if (attr == &dev_attr_act_mask)
> + ret = sprintf(buf, "%#x\n", q->blk_trace->act_mask);
> + else if (attr == &dev_attr_pid)
> + ret = sprintf(buf, "%u\n", q->blk_trace->pid);
> + else if (attr == &dev_attr_start_lba)
> + ret = sprintf(buf, "%llu\n", q->blk_trace->start_lba);
> + else if (attr == &dev_attr_end_lba)
> + ret = sprintf(buf, "%llu\n", q->blk_trace->end_lba);
> + mutex_unlock(&bdev->bd_mutex);
> +out_bdput:
> + bdput(bdev);
> +out_unlock_kernel:
> + unlock_kernel();
> + return ret;
> +}
> +
> +static ssize_t sysfs_blk_trace_attr_store(struct device *dev,
> + struct device_attribute *attr,
> + const char *buf, size_t count)
> +{
> + struct block_device *bdev;
> + struct request_queue *q;
> + struct hd_struct *p;
> + u64 value;
> + ssize_t ret = -ENXIO;
> +
> + if (count == 0)
> + goto out;
> +
> + if (attr == &dev_attr_act_mask) {
> + if (sscanf(buf, "%llx", &value) != 1) {
> + /* Assume it is a list of trace category names */
> + value = blk_str2act_mask(buf);
> + if (value < 0)
> + goto out;
> + }
> + } else if (sscanf(buf, "%llu", &value) != 1)
> + goto out;
> +
> + lock_kernel();
> + p = dev_to_part(dev);
> + bdev = bdget(part_devt(p));
> + if (bdev == NULL)
> + goto out_unlock_kernel;
> +
> + q = bdev_get_queue(bdev);
> + if (q == NULL)
> + goto out_bdput;
> +
> + mutex_lock(&bdev->bd_mutex);
> + ret = 0;
> + if (q->blk_trace == NULL)
> + ret = blk_trace_setup_queue(q, bdev->bd_dev);
> +
> + if (ret == 0) {
> + if (attr == &dev_attr_act_mask)
> + q->blk_trace->act_mask = value;
> + else if (attr == &dev_attr_pid)
> + q->blk_trace->pid = value;
> + else if (attr == &dev_attr_start_lba)
> + q->blk_trace->start_lba = value;
> + else if (attr == &dev_attr_end_lba)
> + q->blk_trace->end_lba = value;
> + ret = count;
> + }
> + mutex_unlock(&bdev->bd_mutex);
> +out_bdput:
> + bdput(bdev);
> +out_unlock_kernel:
> + unlock_kernel();
> +out:
> + return ret;
> +}
> diff --git a/fs/partitions/check.c b/fs/partitions/check.c
> index 6d72024..01714ef 100644
> --- a/fs/partitions/check.c
> +++ b/fs/partitions/check.c
> @@ -268,6 +268,10 @@ ssize_t part_fail_store(struct device *dev,
> }
> #endif
>
> +#ifdef CONFIG_BLK_DEV_IO_TRACE
> +extern struct attribute_group blk_trace_attr_group;
> +#endif
> +
> static DEVICE_ATTR(partition, S_IRUGO, part_partition_show, NULL);
> static DEVICE_ATTR(start, S_IRUGO, part_start_show, NULL);
> static DEVICE_ATTR(size, S_IRUGO, part_size_show, NULL);
> @@ -294,6 +298,9 @@ static struct attribute_group part_attr_group = {
>
> static struct attribute_group *part_attr_groups[] = {
> &part_attr_group,
> +#ifdef CONFIG_BLK_DEV_IO_TRACE
> + &blk_trace_attr_group,
> +#endif
> NULL
> };
This tracer looks good :-)
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