[RFC][PATCHv2] ftrace interface for blktrace

From: Arnaldo Carvalho de Melo
Date: Tue Jan 20 2009 - 09:42:53 EST

Em Sat, Jan 17, 2009 at 06:08:04PM -0200, Arnaldo Carvalho de Melo escreveu:
> Em Sat, Jan 17, 2009 at 08:14:30PM +0100, Jens Axboe escreveu:
> > On Sat, Jan 17 2009, Ingo Molnar wrote:
> > > * Arnaldo Carvalho de Melo <acme@xxxxxxxxxx> 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.
> > >
> > > Very nice patch!
> > >
> > > Jens, i'm wondering what's your take on this direction is. I think the
> > > consolidation effect is great and the built-in IO tracing capabilities are
> > > very nice.
> >
> > I like the current patch, from a quick look. I'll look more soonish
> > (monday). I've always liked the concept of being able to mix various
> > traces into the same stream, since it makes it MUCH easier to see what
> > on earth is going wrong. What I didn't like in the patches Acme did was
> > the enable part, I'll need to look into that. Again, from a quick look,
> > what is the BKL doing in there?!
>
> I'm just trying to keep locking expectations in the previous, similar
> path, in block/ioctl.c, blkdev_ioctl, where we setup q->blk_trace:
>
> case BLKTRACESTART:
> case BLKTRACESTOP:
> case BLKTRACESETUP:
> case BLKTRACETEARDOWN:
> lock_kernel();
> ret = blk_trace_ioctl(bdev, cmd, (char __user *) arg);
> unlock_kernel();
> break;
>
> So I took the safest path and grabbed the big K lock.
>
> > > We can still get the raw events too and do user-space post-processing,
> > > when that is desired - so this does not limit anything that blktrace was
> > > able to do before - it only extends on it.
> > >
> > > Is there any particular blktrace feature you can think of that is not
> > > present in the blktrace ftrace plugin?
> >
> > Can't answer that yet, I'll give it a more thorough look next week.
>
> Looking forward to that. And will get it split into multiple patches,
> hopefully by monday.

Ok, still as one patch, but with lots of improvements, lets see them
using examples:

Setup debugfs/tracing environment:

$ mkdir /d
$ mount -t debugfs none /d
$ ln -s /d/tracing /t

Now enable tracing on the desired device, setting up filters if needed:

$ echo 1 > /sys/block/sda/sda1/trace/enable

root@f10-1 ~]# head /t/trace
# tracer: blk
#
bash-955 [000] 565.025000: 8,1 A WBS 3932975 + 8 <- (8,1) 3932912
bash-955 [000] 565.025000: 8,1 Q R 3932975 + 8 [<idle>]
bash-955 [000] 565.025000: 8,1 G RB 3932975 + 8 [<idle>]
bash-955 [000] 565.025000: 8,1 P NS [<idle>]
bash-955 [000] 565.025000: 8,1 I RBS 3932975 + 8 [<idle>]
bash-955 [000] 565.025000: 8,1 U WS [<idle>] 1
bash-955 [000] 565.025000: 8,1 D WB 3932975 + 8 [<idle>]
<idle>-0 [000] 565.044000: 8,1 C RS 3932975 + 8 [0]
[root@f10-1 ~]#

This is the standardized format used in the sched_switch, sched_wakeup and
other tracers.

This is done by adding a tracer option, that starts disabled, named
"blk_classic", using this construct:

/* Select an alternative, minimalistic output than the original one */
#define TRACE_BLK_OPT_CLASSIC 0x1

static struct tracer_opt blk_tracer_opts[] = {
/* Default disable the minimalistic output */
{ TRACER_OPT(blk_classic, TRACE_BLK_OPT_CLASSIC ) },
{ }
};

static struct tracer_flags blk_tracer_flags = {
.val = 0,
.opts = blk_tracer_opts,
};

With this disabled the ->print_line in our struct tracer always returns
TRACE_TYPE_UNHANDLED, leaving to the struct trace_event ->trace routine to
pretty print it if the entry in the ring buffer is of type TRACE_BLK, that
we register now in init_blk_tracer by using register_ftrace_event.

I did this because I want, at least while this patch is being considered by
Jens and the other blktrace developers, to both to have the classic format,
activated by:

[root@f10-1 ~]# echo blk_classic > /t/trace_options
[root@f10-1 ~]# cat /t/trace_options
print-parent nosym-offset nosym-addr noverbose noraw nohex nobin noblock nostacktrace nosched-tree ftrace_printk noftrace_preempt nobranch annotate nouserstacktrace nosym-userobj noprintk-msg-only blk_classic

So that we use struct trace -> print_line and have full control of what is
formatted:

[root@f10-1 ~]# tail /t/trace
8,1 0 289.469000 1054 D WB 526039 + 8 [ls]
8,1 0 289.470000 0 C RS 526039 + 8 [1751]
8,1 0 289.470000 1054 A WBS 266439 + 8 <- (8,1) 266376
8,1 0 289.470000 1054 Q R 266439 + 8 [ls]
8,1 0 289.470000 1054 G RB 266439 + 8 [ls]
8,1 0 289.470000 1054 P NS [ls]
8,1 0 289.470000 1054 I RBS 266439 + 8 [ls]
8,1 0 289.470000 1054 U WS [ls] 1
8,1 0 289.470000 1054 D WB 266439 + 8 [ls]
8,1 0 289.470000 0 C RS 266439 + 8 [4295]
[root@f10-1 ~]#

Now back to non_classic mode...

# echo noblk_classic > /t/trace_options

... where we can mix trace events by doing...

# echo stacktrace > /t/trace_options

... and get something interesting:

[root@f10-1 ~]# tail /t/trace
ls-1060 [000] 431.697000: 8,1 A WBS 12320847 + 8 <- (8,1) 12320784
ls-1060 [000] 431.697000:
<= submit_bio
<= submit_bh
<= __ext3_get_inode_loc
<= ext3_iget
<= ext3_lookup
<= do_lookup
<= __link_path_walk
ls-1060 [000] 431.697000: 8,1 Q R 12320847 + 8 [ls]
ls-1060 [000] 431.697000:
<= generic_make_request
<= submit_bio
<= submit_bh
<= __ext3_get_inode_loc
<= ext3_iget
<= ext3_lookup
<= do_lookup
ls-1060 [000] 431.697000: 8,1 G RB 12320847 + 8 [ls]
ls-1060 [000] 431.697000:
<= get_request
<= get_request_wait
<= __make_request
<= generic_make_request
<= submit_bio
<= submit_bh
<= __ext3_get_inode_loc
ls-1060 [000] 431.697000: 8,1 P NS [ls]
ls-1060 [000] 431.697000:
<= __make_request
<= generic_make_request
<= submit_bio
<= submit_bh
<= __ext3_get_inode_loc
<= ext3_iget
<= ext3_lookup
ls-1060 [000] 431.697000: 8,1 I RBS 12320847 + 8 [ls]
ls-1060 [000] 431.697000:
<= elv_insert
<= __elv_add_request
<= __make_request
<= generic_make_request
<= submit_bio
<= submit_bh
<= __ext3_get_inode_loc
<SNIP>

Now lets disable stacktraces:

# echo nostacktrace > /t/trace_options

And try doing things a bit more verbosely, using the TRACE_ITER_VERBOSE
that were already part of the existing ftrace infrastructure.

# echo verbose > /t/trace_options
# cat /t/trace_pipe
ls-1065 [000] 694.325000: 8,1 remap WBS 3670207 + 8 <- (8,1) 3670144
ls-1065 [000] 694.325000: 8,1 queue R 3670207 + 8 [ls]
ls-1065 [000] 694.325000: 8,1 getrq RB 3670207 + 8 [ls]
ls-1065 [000] 694.325000: 8,1 plug NS [ls]
ls-1065 [000] 694.325000: 8,1 insert RBS 3670207 + 8 [ls]
ls-1065 [000] 694.325000: 8,1 unplug_io WS [ls] 1
ls-1065 [000] 694.325000: 8,1 issue WB 3670207 + 8 [ls]
<idle>-0 [000] 694.343000: 8,1 complete RS 3670207 + 8 [191]

Hint: look at the action (insert, unplug_io, issue, etc).

We can make it a bit more verbose using this iter flag, the above is
just a suggestion on using the standard flags interface.

Frederic, for now I'm using t->action as the "sub-type" we discussed.

Now that we have noblk_classic mode we can actually look at the struct
trace_event->binary() way of doing things + the
don't-print-anything-just-call-me->binary() flag and then we could
synthesize the old blktrace format and simply do:

cat /t/trace_pipe | blkparse -i -

As a test to check that everything is as the old blktrace(8) codebase
expects.

Jens, there are several fields in struct blk_io_trace that could go,
like pid, cpu, timestamp, because they are already in struct
trace_entry, and sequence, if my understanding of what was discussed
here is not flawed:

http://kerneltrap.org/mailarchive/linux-kernel/2008/9/23/3375544

Patch against yesterday's linux-tip,

Comments?

- Arnaldo

diff --git a/block/blktrace.c b/block/blktrace.c
index b0a2cae..21116c4 100644
--- a/block/blktrace.c
+++ b/block/blktrace.c
@@ -25,9 +25,27 @@
#include <linux/time.h>
#include <trace/block.h>
#include <asm/uaccess.h>
+#include <../kernel/trace/trace_output.h>

static unsigned int blktrace_seq __read_mostly = 1;

+static struct trace_array *blk_tr;
+static int __read_mostly blk_tracer_enabled;
+
+/* Select an alternative, minimalistic output than the original one */
+#define TRACE_BLK_OPT_CLASSIC 0x1
+
+static struct tracer_opt blk_tracer_opts[] = {
+ /* Default disable the minimalistic output */
+ { TRACER_OPT(blk_classic, TRACE_BLK_OPT_CLASSIC ) },
+ { }
+};
+
+static struct tracer_flags blk_tracer_flags = {
+ .val = 0,
+ .opts = blk_tracer_opts,
+};
+
/* Global reference count of probes */
static DEFINE_MUTEX(blk_probe_mutex);
static atomic_t blk_probes_ref = ATOMIC_INIT(0);
@@ -43,6 +61,9 @@ 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 +111,9 @@ 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 +155,14 @@ 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;
+ int cpu, pc = 0;

- if (unlikely(bt->trace_state != Blktrace_running))
+ if (unlikely(bt->trace_state != Blktrace_running || !blk_tracer_enabled))
return;

what |= ddir_act[rw & WRITE];
@@ -150,6 +175,24 @@ static void __blk_add_trace(struct blk_trace *bt, sector_t sector, int bytes,
pid = tsk->pid;
if (unlikely(act_log_check(bt, what, sector, pid)))
return;
+ cpu = raw_smp_processor_id();
+
+ if (blk_tr) {
+ struct trace_entry *ent;
+ tracing_record_cmdline(current);
+
+ event = ring_buffer_lock_reserve(blk_tr->buffer,
+ sizeof(*t) + pdu_len, &flags);
+ if (!event)
+ return;
+
+ ent = ring_buffer_event_data(event);
+ t = (struct blk_io_trace *)ent;
+ pc = preempt_count();
+ tracing_generic_entry_update(ent, 0, pc);
+ ent->type = TRACE_BLK;
+ goto record_it;
+ }

/*
* A word about the locking here - we disable interrupts to reserve
@@ -163,23 +206,33 @@ static void __blk_add_trace(struct blk_trace *bt, sector_t sector, int bytes,

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 = ktime_to_ns(ktime_get());
+ t->cpu = cpu;
+ t->pid = pid;
+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);
+ if (pid != 0 &&
+ (blk_tracer_flags.val & TRACE_BLK_OPT_CLASSIC) == 0 &&
+ (trace_flags & TRACE_ITER_STACKTRACE) != 0)
+ __trace_stack(blk_tr, NULL, flags, 5, pc);
+ trace_wake_up();
+ return;
+ }
}

local_irq_restore(flags);
@@ -888,3 +941,584 @@ static void blk_unregister_tracepoints(void)

tracepoint_synchronize_unregister();
}
+
+/*
+ * struct blk_io_tracer formatting routines
+ */
+
+static void fill_rwbs(char *rwbs, const 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
+const struct blk_io_trace *te_blk_io_trace(const struct trace_entry *ent)
+{
+ return (const struct blk_io_trace *)ent;
+}
+
+static inline const void *pdu_start(const struct trace_entry *ent)
+{
+ return te_blk_io_trace(ent) + 1;
+}
+
+static inline u32 t_sec(const struct trace_entry *ent)
+{
+ return te_blk_io_trace(ent)->bytes >> 9;
+}
+
+static inline unsigned long long t_sector(const struct trace_entry *ent)
+{
+ return te_blk_io_trace(ent)->sector;
+}
+
+static inline __u16 t_error(const struct trace_entry *ent)
+{
+ return te_blk_io_trace(ent)->sector;
+}
+
+static __u64 get_pdu_int(const struct trace_entry *ent)
+{
+ const __u64 *val = pdu_start(ent);
+ return be64_to_cpu(*val);
+}
+
+static void get_pdu_remap(const struct trace_entry *ent,
+ struct blk_io_trace_remap *r)
+{
+ const struct blk_io_trace_remap *__r = pdu_start(ent);
+ __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_iter(struct trace_iterator *iter, 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;
+ const struct trace_entry *ent = iter->ent;
+ const struct blk_io_trace *t = (const struct blk_io_trace *)ent;
+
+ 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, ent->pid, act, rwbs);
+}
+
+static int blk_log_action_seq(struct trace_seq *s, const struct blk_io_trace *t,
+ const char *act)
+{
+ char rwbs[6];
+ fill_rwbs(rwbs, t);
+ return trace_seq_printf(s, "%3d,%-3d %2s %3s ",
+ MAJOR(t->device), MINOR(t->device), act, rwbs);
+}
+
+static int blk_log_generic(struct trace_seq *s, const struct trace_entry *ent)
+{
+ const char *cmd = trace_find_cmdline(ent->pid);
+
+ if (t_sec(ent))
+ return trace_seq_printf(s, "%llu + %u [%s]\n",
+ t_sector(ent), t_sec(ent), cmd);
+ return trace_seq_printf(s, "[%s]\n", cmd);
+}
+
+static int blk_log_with_error(struct trace_seq *s, const struct trace_entry *ent)
+{
+ if (t_sec(ent))
+ return trace_seq_printf(s, "%llu + %u [%d]\n", t_sector(ent),
+ t_sec(ent), t_error(ent));
+ return trace_seq_printf(s, "%llu [%d]\n", t_sector(ent), t_error(ent));
+}
+
+static int blk_log_remap(struct trace_seq *s, const struct trace_entry *ent)
+{
+ struct blk_io_trace_remap r = { .device = 0, };
+
+ get_pdu_remap(ent, &r);
+ return trace_seq_printf(s, "%llu + %u <- (%d,%d) %llu\n",
+ t_sector(ent),
+ t_sec(ent), MAJOR(r.device), MINOR(r.device),
+ (unsigned long long)r.sector);
+}
+
+static int blk_log_plug(struct trace_seq *s, const struct trace_entry *ent)
+{
+ return trace_seq_printf(s, "[%s]\n", trace_find_cmdline(ent->pid));
+}
+
+static int blk_log_unplug(struct trace_seq *s, const struct trace_entry *ent)
+{
+ return trace_seq_printf(s, "[%s] %llu\n", trace_find_cmdline(ent->pid),
+ get_pdu_int(ent));
+}
+
+static int blk_log_split(struct trace_seq *s, const struct trace_entry *ent)
+{
+ return trace_seq_printf(s, "%llu / %llu [%s]\n", t_sector(ent),
+ get_pdu_int(ent), trace_find_cmdline(ent->pid));
+}
+
+/*
+ * struct tracer operations
+ */
+
+static void blk_tracer_print_header(struct seq_file *m)
+{
+ if (!(blk_tracer_flags.val & TRACE_BLK_OPT_CLASSIC))
+ return;
+ seq_puts(m, "# DEV CPU TIMESTAMP PID ACT FLG\n"
+ "# | | | | | |\n");
+}
+
+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);
+}
+
+static int blk_tracer_init(struct trace_array *tr)
+{
+ blk_tr = tr;
+ blk_tracer_start(tr);
+ mutex_lock(&blk_probe_mutex);
+ blk_tracer_enabled++;
+ 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);
+ mutex_unlock(&blk_probe_mutex);
+
+ blk_tracer_stop(tr);
+}
+
+static struct {
+ const char *act[2];
+ int (*print)(struct trace_seq *s, const struct trace_entry *ent);
+} what2act[] __read_mostly = {
+ [__BLK_TA_QUEUE] = {{ "Q", "queue" }, blk_log_generic },
+ [__BLK_TA_BACKMERGE] = {{ "M", "backmerge" }, blk_log_generic },
+ [__BLK_TA_FRONTMERGE] = {{ "F", "frontmerge" }, blk_log_generic },
+ [__BLK_TA_GETRQ] = {{ "G", "getrq" }, blk_log_generic },
+ [__BLK_TA_SLEEPRQ] = {{ "S", "sleeprq" }, blk_log_generic },
+ [__BLK_TA_REQUEUE] = {{ "R", "requeue" }, blk_log_with_error },
+ [__BLK_TA_ISSUE] = {{ "D", "issue" }, blk_log_generic },
+ [__BLK_TA_COMPLETE] = {{ "C", "complete" }, blk_log_with_error },
+ [__BLK_TA_PLUG] = {{ "P", "plug" }, blk_log_plug },
+ [__BLK_TA_UNPLUG_IO] = {{ "U", "unplug_io" }, blk_log_unplug },
+ [__BLK_TA_UNPLUG_TIMER] = {{ "UT", "unplug_timer" }, blk_log_unplug },
+ [__BLK_TA_INSERT] = {{ "I", "insert" }, blk_log_generic },
+ [__BLK_TA_SPLIT] = {{ "X", "split" }, blk_log_split },
+ [__BLK_TA_BOUNCE] = {{ "B", "bounce" }, blk_log_generic },
+ [__BLK_TA_REMAP] = {{ "A", "remap" }, blk_log_remap },
+};
+
+static int blk_trace_event_print(struct trace_seq *s, struct trace_entry *ent,
+ int flags)
+{
+ const struct blk_io_trace *t = (struct blk_io_trace *)ent;
+ const u16 what = t->action & ((1 << BLK_TC_SHIFT) - 1);
+ int ret;
+
+ if (unlikely(what == 0 || what > ARRAY_SIZE(what2act)))
+ ret = trace_seq_printf(s, "Bad pc action %x\n", what);
+ else {
+ const bool long_act = !!(trace_flags & TRACE_ITER_VERBOSE);
+ ret = blk_log_action_seq(s, t, what2act[what].act[long_act]);
+ if (ret)
+ ret = what2act[what].print(s, ent);
+ }
+
+ return ret ? TRACE_TYPE_HANDLED : TRACE_TYPE_PARTIAL_LINE;
+}
+
+static enum print_line_t blk_tracer_print_line(struct trace_iterator *iter)
+{
+ const struct blk_io_trace *t;
+ u16 what;
+ int ret;
+
+ if (!(blk_tracer_flags.val & TRACE_BLK_OPT_CLASSIC))
+ return TRACE_TYPE_UNHANDLED;
+
+ t = (const struct blk_io_trace *)iter->ent;
+ what = t->action & ((1 << BLK_TC_SHIFT) - 1);
+
+ if (unlikely(what == 0 || what > ARRAY_SIZE(what2act)))
+ ret = trace_seq_printf(&iter->seq, "Bad pc action %x\n", what);
+ else {
+ const bool long_act = !!(trace_flags & TRACE_ITER_VERBOSE);
+ ret = blk_log_action_iter(iter, what2act[what].act[long_act]);
+ if (ret)
+ ret = what2act[what].print(&iter->seq, iter->ent);
+ }
+
+ return ret ? TRACE_TYPE_HANDLED : TRACE_TYPE_PARTIAL_LINE;
+}
+
+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,
+ .flags = &blk_tracer_flags,
+};
+
+static struct trace_event trace_blk_event = {
+ .type = TRACE_BLK,
+ .trace = blk_trace_event_print,
+ .latency_trace = blk_trace_event_print,
+ .raw = trace_nop_print,
+ .hex = trace_nop_print,
+ .binary = trace_nop_print,
+};
+
+static int __init init_blk_tracer(void)
+{
+ if (!register_ftrace_event(&trace_blk_event)) {
+ pr_warning("Warning: could not register block events\n");
+ return 1;
+ }
+
+ if (register_tracer(&blk_tracer) != 0) {
+ pr_warning("Warning: could not register the block tracer\n");
+ unregister_ftrace_event(&trace_blk_event);
+ return 1;
+ }
+
+ return 0;
+}
+
+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;
+ 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();
+ 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);
+ 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
};

diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index 54b7278..0d6e314 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -32,6 +32,7 @@ enum trace_type {
TRACE_KMEM_ALLOC,
TRACE_KMEM_FREE,
TRACE_POWER,
+ TRACE_BLK,

__TRACE_LAST_TYPE,
};
--
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