[PATCH 0/3] writeback: tracing support

[PATCH 0/3] writeback: tracing support

[Dave Chinner]

Hi Jens,

These are the writeback tracing patches that have not made it to
mainline yet.  Can you pull these into your writeback tree for
2.6.36?

Cheers,

Dave.

[PATCH 1/3] writeback: initial tracing support

[Dave Chinner]

From: From: Jens Axboe <jens.axboe@oracle.com>

Trace queue/sched/exec parts of the writeback loop. This provides
insight into when and why flusher threads are scheduled to run. e.g
a sync invocation leaves a trace like:

sync-2798  [006] 611323.335713: writeback_queue: 253:16: pages=87879, sb=0, kupdate=0, range_cyclic=0 for_background=0
sync-2798  [006] 611323.335718: writeback_sched: work=37c0, task=task
sync-2798  [006] 611323.335817: writeback_queue: 8:0: pages=92680, sb=1, kupdate=0, range_cyclic=-1 for_background=0
sync-2798  [006] 611323.335819: writeback_sched: work=35c0, task=task
sync-2798  [006] 611323.335855: writeback_queue: 253:16: pages=92680, sb=1, kupdate=0, range_cyclic=-1 for_background=0
sync-2798  [006] 611323.335857: writeback_sched: work=36c0, task=task
sync-2798  [006] 611323.335890: writeback_queue: 8:0: pages=9223372036854775807, sb=1, kupdate=0, range_cyclic=0 for_background=0
sync-2798  [006] 611323.335891: writeback_sched: work=fe58, task=task
sync-2798  [006] 611323.377341: writeback_queue: 253:16: pages=9223372036854775807, sb=1, kupdate=0, range_cyclic=0 for_background=0
sync-2798  [006] 611323.377346: writeback_sched: work=fe58, task=task

This also lays the foundation for adding more writeback tracing to
provide deeper insight into the whole writeback path.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
---
 fs/fs-writeback.c                |   45 ++++++++--
 include/trace/events/writeback.h |  171 ++++++++++++++++++++++++++++++++++++++
 mm/backing-dev.c                 |    3 +
 3 files changed, 209 insertions(+), 10 deletions(-)
 create mode 100644 include/trace/events/writeback.h

diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
index 1d1088f..0949dfd 100644
--- a/fs/fs-writeback.c
+++ b/fs/fs-writeback.c
@@ -26,15 +26,9 @@
 #include <linux/blkdev.h>
 #include <linux/backing-dev.h>
 #include <linux/buffer_head.h>
+#include <linux/ftrace.h>
 #include "internal.h"
 
-#define inode_to_bdi(inode)	((inode)->i_mapping->backing_dev_info)
-
-/*
- * We don't actually have pdflush, but this one is exported though /proc...
- */
-int nr_pdflush_threads;
-
 /*
  * Passed into wb_writeback(), essentially a subset of writeback_control
  */
@@ -62,6 +56,21 @@ struct bdi_work {
 	unsigned long state;		/* flag bits, see WS_* */
 };
 
+/*
+ * Include the creation of the trace points after defining the bdi_work and
+ * wb_writeback_args structures so that the definitions remain local to this
+ * file.
+ */
+#define CREATE_TRACE_POINTS
+#include <trace/events/writeback.h>
+
+#define inode_to_bdi(inode)	((inode)->i_mapping->backing_dev_info)
+
+/*
+ * We don't actually have pdflush, but this one is exported though /proc...
+ */
+int nr_pdflush_threads;
+
 enum {
 	WS_USED_B = 0,
 	WS_ONSTACK_B,
@@ -136,6 +145,8 @@ static void wb_work_complete(struct bdi_work *work)
 
 static void wb_clear_pending(struct bdi_writeback *wb, struct bdi_work *work)
 {
+	trace_writeback_clear(work);
+
 	/*
 	 * The caller has retrieved the work arguments from this work,
 	 * drop our reference. If this is the last ref, delete and free it
@@ -171,12 +182,16 @@ static void bdi_queue_work(struct backing_dev_info *bdi, struct bdi_work *work)
 	 * If the default thread isn't there, make sure we add it. When
 	 * it gets created and wakes up, we'll run this work.
 	 */
-	if (unlikely(list_empty_careful(&bdi->wb_list)))
+	if (unlikely(list_empty_careful(&bdi->wb_list))) {
+		trace_writeback_sched(bdi, work, "default");
 		wake_up_process(default_backing_dev_info.wb.task);
-	else {
+	} else {
 		struct bdi_writeback *wb = &bdi->wb;
+		struct task_struct *task = wb->task;
 
-		if (wb->task)
+		trace_writeback_sched(bdi, work, task ? "task" : "notask");
+
+		if (task)
 			wake_up_process(wb->task);
 	}
 }
@@ -203,6 +218,7 @@ static void bdi_alloc_queue_work(struct backing_dev_info *bdi,
 	work = kmalloc(sizeof(*work), GFP_ATOMIC);
 	if (work) {
 		bdi_work_init(work, args);
+		trace_writeback_queue(bdi, args);
 		bdi_queue_work(bdi, work);
 	} else {
 		struct bdi_writeback *wb = &bdi->wb;
@@ -236,6 +252,7 @@ static void bdi_sync_writeback(struct backing_dev_info *bdi,
 	bdi_work_init(&work, &args);
 	work.state |= WS_ONSTACK;
 
+	trace_writeback_queue(bdi, &args);
 	bdi_queue_work(bdi, &work);
 	bdi_wait_on_work_clear(&work);
 }
@@ -907,6 +924,8 @@ long wb_do_writeback(struct bdi_writeback *wb, int force_wait)
 		if (force_wait)
 			work->args.sync_mode = args.sync_mode = WB_SYNC_ALL;
 
+		trace_writeback_exec(work);
+
 		/*
 		 * If this isn't a data integrity operation, just notify
 		 * that we have seen this work and we are now starting it.
@@ -942,9 +961,13 @@ int bdi_writeback_task(struct bdi_writeback *wb)
 	unsigned long wait_jiffies = -1UL;
 	long pages_written;
 
+	trace_writeback_thread_start(1);
+
 	while (!kthread_should_stop()) {
 		pages_written = wb_do_writeback(wb, 0);
 
+		trace_writeback_pages_written(pages_written);
+
 		if (pages_written)
 			last_active = jiffies;
 		else if (wait_jiffies != -1UL) {
@@ -974,6 +997,8 @@ int bdi_writeback_task(struct bdi_writeback *wb)
 		try_to_freeze();
 	}
 
+	trace_writeback_thread_start(0);
+
 	return 0;
 }
 
diff --git a/include/trace/events/writeback.h b/include/trace/events/writeback.h
new file mode 100644
index 0000000..6f510fa
--- /dev/null
+++ b/include/trace/events/writeback.h
@@ -0,0 +1,171 @@
+#undef TRACE_SYSTEM
+#define TRACE_SYSTEM writeback
+
+#if !defined(_TRACE_WRITEBACK_H) || defined(TRACE_HEADER_MULTI_READ)
+#define _TRACE_WRITEBACK_H
+
+#include <linux/backing-dev.h>
+#include <linux/writeback.h>
+
+TRACE_EVENT(writeback_queue,
+
+	TP_PROTO(struct backing_dev_info *bdi, struct wb_writeback_args *args),
+
+	TP_ARGS(bdi, args),
+
+	TP_STRUCT__entry(
+		__array(char,		name,		16)
+		__field(long,		nr_pages)
+		__field(int,		sb)
+		__field(int,		sync_mode)
+		__field(int,		for_kupdate)
+		__field(int,		range_cyclic)
+		__field(int,		for_background)
+	),
+
+	TP_fast_assign(
+		strlcpy(__entry->name, dev_name(bdi->dev), 16);
+		__entry->nr_pages	= args->nr_pages;
+		__entry->sb		= !!args->sb;
+		__entry->for_kupdate	= args->for_kupdate;
+		__entry->range_cyclic	= args->range_cyclic;
+		__entry->for_background	= args->for_background;
+	),
+
+	TP_printk("%s: pages=%ld, sb=%d, kupdate=%d, range_cyclic=%d "
+		  "for_background=%d", __entry->name, __entry->nr_pages,
+			__entry->sb, __entry->for_kupdate,
+			__entry->range_cyclic, __entry->for_background)
+);
+
+TRACE_EVENT(writeback_sched,
+
+	TP_PROTO(struct backing_dev_info *bdi, struct bdi_work *work,
+		 const char *msg),
+
+	TP_ARGS(bdi, work, msg),
+
+	TP_STRUCT__entry(
+		__array(char,			name,		16)
+		__field(unsigned int,		work)
+		__array(char,			task,		8)
+	),
+
+	TP_fast_assign(
+		strlcpy(__entry->name, dev_name(bdi->dev), 16);
+		__entry->work = (unsigned long) work & 0xffff;
+		snprintf(__entry->task, 8, "%s", msg);
+	),
+
+	TP_printk("work=%x, task=%s", __entry->work, __entry->task)
+);
+
+TRACE_EVENT(writeback_exec,
+
+	TP_PROTO(struct bdi_work *work),
+
+	TP_ARGS(work),
+
+	TP_STRUCT__entry(
+		__field(unsigned int,	work)
+		__field(long,		nr_pages)
+		__field(int,		sb)
+		__field(int,		sync_mode)
+		__field(int,		for_kupdate)
+		__field(int,		range_cyclic)
+		__field(int,		for_background)
+	),
+
+	TP_fast_assign(
+		__entry->work		= (unsigned long) work & 0xffff;
+		__entry->nr_pages	= work->args.nr_pages;
+		__entry->sb		= !!work->args.sb;
+		__entry->for_kupdate	= work->args.for_kupdate;
+		__entry->range_cyclic	= work->args.range_cyclic;
+		__entry->for_background	= work->args.for_background;
+
+	),
+
+	TP_printk("work=%x pages=%ld, sb=%d, kupdate=%d, range_cyclic=%d"
+		  " for_background=%d", __entry->work,
+			__entry->nr_pages, __entry->sb, __entry->for_kupdate,
+			__entry->range_cyclic, __entry->for_background)
+);
+
+TRACE_EVENT(writeback_clear,
+
+	TP_PROTO(struct bdi_work *work),
+
+	TP_ARGS(work),
+
+	TP_STRUCT__entry(
+		__field(struct bdi_work *,	work)
+		__field(int,			refs)
+	),
+
+	TP_fast_assign(
+		__entry->work		= work;
+		__entry->refs		= atomic_read(&work->pending);
+	),
+
+	TP_printk("work=%p, refs=%d", __entry->work, __entry->refs)
+);
+
+TRACE_EVENT(writeback_pages_written,
+
+	TP_PROTO(long pages_written),
+
+	TP_ARGS(pages_written),
+
+	TP_STRUCT__entry(
+		__field(long,		pages)
+	),
+
+	TP_fast_assign(
+		__entry->pages		= pages_written;
+	),
+
+	TP_printk("%ld", __entry->pages)
+);
+
+
+TRACE_EVENT(writeback_thread_start,
+
+	TP_PROTO(int start),
+
+	TP_ARGS(start),
+
+	TP_STRUCT__entry(
+		__field(int,	start)
+	),
+
+	TP_fast_assign(
+		__entry->start = start;
+	),
+
+	TP_printk("%s", __entry->start ? "started" : "exited")
+);
+
+TRACE_EVENT(writeback_bdi_register,
+
+	TP_PROTO(const char *name, int start),
+
+	TP_ARGS(name, start),
+
+	TP_STRUCT__entry(
+		__array(char,	name,		16)
+		__field(int,	start)
+	),
+
+	TP_fast_assign(
+		strlcpy(__entry->name, name, 16);
+		__entry->start = start;
+	),
+
+	TP_printk("%s: %s", __entry->name,
+			__entry->start ? "registered" : "unregistered")
+);
+#endif /* _TRACE_WRITEBACK_H */
+
+/* This part must be outside protection */
+#include <trace/define_trace.h>
diff --git a/mm/backing-dev.c b/mm/backing-dev.c
index 660a87a..1f7723b 100644
--- a/mm/backing-dev.c
+++ b/mm/backing-dev.c
@@ -10,6 +10,7 @@
 #include <linux/module.h>
 #include <linux/writeback.h>
 #include <linux/device.h>
+#include <trace/events/writeback.h>
 
 static atomic_long_t bdi_seq = ATOMIC_LONG_INIT(0);
 
@@ -585,6 +586,7 @@ int bdi_register(struct backing_dev_info *bdi, struct device *parent,
 
 	bdi_debug_register(bdi, dev_name(dev));
 	set_bit(BDI_registered, &bdi->state);
+	trace_writeback_bdi_register(dev_name(dev), 1);
 exit:
 	return ret;
 }
@@ -647,6 +649,7 @@ static void bdi_prune_sb(struct backing_dev_info *bdi)
 void bdi_unregister(struct backing_dev_info *bdi)
 {
 	if (bdi->dev) {
+		trace_writeback_bdi_register(dev_name(bdi->dev), 0);
 		bdi_prune_sb(bdi);
 
 		if (!bdi_cap_flush_forker(bdi))
-- 
1.7.1

[PATCH 2/3] writeback: Add tracing to balance_dirty_pages

[Dave Chinner]

From: Dave Chinner <dchinner@redhat.com>

Tracing high level background writeback events is good, but it doesn't
give the entire picture. Add IO dispatched by foreground throttling to the
writeback events.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
---
 fs/fs-writeback.c                |    5 ++
 include/trace/events/writeback.h |   80 ++++++++++++++++++++++++++++++++++++++
 mm/page-writeback.c              |    4 ++
 3 files changed, 89 insertions(+), 0 deletions(-)

diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
index 0949dfd..6f777d6 100644
--- a/fs/fs-writeback.c
+++ b/fs/fs-writeback.c
@@ -807,7 +807,11 @@ static long wb_writeback(struct bdi_writeback *wb,
 		wbc.more_io = 0;
 		wbc.nr_to_write = MAX_WRITEBACK_PAGES;
 		wbc.pages_skipped = 0;
+
+		trace_wbc_writeback_start(&wbc);
 		writeback_inodes_wb(wb, &wbc);
+		trace_wbc_writeback_written(&wbc);
+
 		args->nr_pages -= MAX_WRITEBACK_PAGES - wbc.nr_to_write;
 		wrote += MAX_WRITEBACK_PAGES - wbc.nr_to_write;
 
@@ -835,6 +839,7 @@ static long wb_writeback(struct bdi_writeback *wb,
 		if (!list_empty(&wb->b_more_io))  {
 			inode = list_entry(wb->b_more_io.prev,
 						struct inode, i_list);
+			trace_wbc_writeback_wait(&wbc);
 			inode_wait_for_writeback(inode);
 		}
 		spin_unlock(&inode_lock);
diff --git a/include/trace/events/writeback.h b/include/trace/events/writeback.h
index 6f510fa..7867c16 100644
--- a/include/trace/events/writeback.h
+++ b/include/trace/events/writeback.h
@@ -7,6 +7,9 @@
 #include <linux/backing-dev.h>
 #include <linux/writeback.h>
 
+struct wb_writeback_args;
+struct bdi_work;
+
 TRACE_EVENT(writeback_queue,
 
 	TP_PROTO(struct backing_dev_info *bdi, struct wb_writeback_args *args),
@@ -165,6 +168,83 @@ TRACE_EVENT(writeback_bdi_register,
 	TP_printk("%s: %s", __entry->name,
 			__entry->start ? "registered" : "unregistered")
 );
+
+/* pass flags explicitly */
+DECLARE_EVENT_CLASS(wbc_class,
+	TP_PROTO(struct writeback_control *wbc),
+	TP_ARGS(wbc),
+	TP_STRUCT__entry(
+		__field(unsigned int, wbc)
+		__array(char, name, 16)
+		__field(long, nr_to_write)
+		__field(long, pages_skipped)
+		__field(int, sb)
+		__field(int, sync_mode)
+		__field(int, nonblocking)
+		__field(int, encountered_congestion)
+		__field(int, for_kupdate)
+		__field(int, for_background)
+		__field(int, for_reclaim)
+		__field(int, range_cyclic)
+		__field(int, more_io)
+		__field(unsigned long, older_than_this)
+		__field(long, range_start)
+		__field(long, range_end)
+	),
+
+	TP_fast_assign(
+		char *__name = "(none)";
+
+		__entry->wbc		= (unsigned long)wbc & 0xffff;
+		if (wbc->bdi)
+			strncpy(__entry->name, dev_name(wbc->bdi->dev), 16);
+		else
+			strncpy(__entry->name, __name, 16);
+		__entry->nr_to_write	= wbc->nr_to_write;
+		__entry->pages_skipped	= wbc->pages_skipped;
+		__entry->sb		= !!wbc->sb;
+		__entry->sync_mode	= wbc->sync_mode;
+		__entry->for_kupdate	= wbc->for_kupdate;
+		__entry->for_background	= wbc->for_background;
+		__entry->for_reclaim	= wbc->for_reclaim;
+		__entry->range_cyclic	= wbc->range_cyclic;
+		__entry->more_io	= wbc->more_io;
+		__entry->older_than_this = wbc->older_than_this ?
+						*wbc->older_than_this : 0;
+		__entry->range_start	= (long)wbc->range_start;
+		__entry->range_end	= (long)wbc->range_end;
+	),
+
+	TP_printk("dev %s wbc=%x towrt=%ld skip=%ld sb=%d mode=%d kupd=%d "
+		"bgrd=%d reclm=%d cyclic=%d more=%d older=0x%lx "
+		"start=0x%lx end=0x%lx",
+		__entry->name,
+		__entry->wbc,
+		__entry->nr_to_write,
+		__entry->pages_skipped,
+		__entry->sb,
+		__entry->sync_mode,
+		__entry->for_kupdate,
+		__entry->for_background,
+		__entry->for_reclaim,
+		__entry->range_cyclic,
+		__entry->more_io,
+		__entry->older_than_this,
+		__entry->range_start,
+		__entry->range_end)
+)
+
+#define DEFINE_WBC_EVENT(name) \
+DEFINE_EVENT(wbc_class, name, \
+	TP_PROTO(struct writeback_control *wbc), \
+	TP_ARGS(wbc))
+DEFINE_WBC_EVENT(wbc_writeback_start);
+DEFINE_WBC_EVENT(wbc_writeback_written);
+DEFINE_WBC_EVENT(wbc_writeback_wait);
+DEFINE_WBC_EVENT(wbc_balance_dirty_start);
+DEFINE_WBC_EVENT(wbc_balance_dirty_written);
+DEFINE_WBC_EVENT(wbc_balance_dirty_wait);
+
 #endif /* _TRACE_WRITEBACK_H */
 
 /* This part must be outside protection */
diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index bbd396a..6c0ad0a 100644
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -34,6 +34,7 @@
 #include <linux/syscalls.h>
 #include <linux/buffer_head.h>
 #include <linux/pagevec.h>
+#include <trace/events/writeback.h>
 
 /*
  * After a CPU has dirtied this many pages, balance_dirty_pages_ratelimited
@@ -536,11 +537,13 @@ static void balance_dirty_pages(struct address_space *mapping,
 		 * threshold otherwise wait until the disk writes catch
 		 * up.
 		 */
+		trace_wbc_balance_dirty_start(&wbc);
 		if (bdi_nr_reclaimable > bdi_thresh) {
 			writeback_inodes_wbc(&wbc);
 			pages_written += write_chunk - wbc.nr_to_write;
 			get_dirty_limits(&background_thresh, &dirty_thresh,
 				       &bdi_thresh, bdi);
+			trace_wbc_balance_dirty_written(&wbc);
 		}
 
 		/*
@@ -566,6 +569,7 @@ static void balance_dirty_pages(struct address_space *mapping,
 		if (pages_written >= write_chunk)
 			break;		/* We've done our duty */
 
+		trace_wbc_balance_dirty_wait(&wbc);
 		__set_current_state(TASK_INTERRUPTIBLE);
 		io_schedule_timeout(pause);
 
-- 
1.7.1

[PATCH 3/3] writeback: Add tracing to write_cache_pages

[Dave Chinner]

From: Dave Chinner <dchinner@redhat.com>

Add a trace event to the ->writepage loop in write_cache_pages to give
visibility into how the ->writepage call is changing variables within the
writeback control structure. Of most interest is how wbc->nr_to_write changes
from call to call, especially with filesystems that write multiple pages
in ->writepage.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
---
 include/trace/events/writeback.h |    1 +
 mm/page-writeback.c              |    1 +
 2 files changed, 2 insertions(+), 0 deletions(-)

diff --git a/include/trace/events/writeback.h b/include/trace/events/writeback.h
index 7867c16..6797c46 100644
--- a/include/trace/events/writeback.h
+++ b/include/trace/events/writeback.h
@@ -244,6 +244,7 @@ DEFINE_WBC_EVENT(wbc_writeback_wait);
 DEFINE_WBC_EVENT(wbc_balance_dirty_start);
 DEFINE_WBC_EVENT(wbc_balance_dirty_written);
 DEFINE_WBC_EVENT(wbc_balance_dirty_wait);
+DEFINE_WBC_EVENT(wbc_writepage);
 
 #endif /* _TRACE_WRITEBACK_H */
 
diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index 6c0ad0a..1a361f0 100644
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -935,6 +935,7 @@ continue_unlock:
 			if (!clear_page_dirty_for_io(page))
 				goto continue_unlock;
 
+			trace_wbc_writepage(wbc);
 			ret = (*writepage)(page, wbc, data);
 			if (unlikely(ret)) {
 				if (ret == AOP_WRITEPAGE_ACTIVATE) {
-- 
1.7.1

Re: [PATCH 1/3] writeback: initial tracing support

[Christoph Hellwig]

On Mon, Jun 21, 2010 at 11:25:24AM +1000, Dave Chinner wrote:
> +#include <linux/ftrace.h>

I think this should be <linux/tracepoint.h>.


I fear this might need some more rediffing after my latests writeback
patches.

> +	TP_fast_assign(
> +		strlcpy(__entry->name, dev_name(bdi->dev), 16);

For most other fs/block dev tracepoints we print the dev_t as
major:minor.  It would be good to have some consitency to match on
for the trace points.

> +		__entry->nr_pages	= args->nr_pages;
> +		__entry->sb		= !!args->sb;

It might be worth to store the dev_t of the superblock here?

> +	TP_printk("%s: pages=%ld, sb=%d, kupdate=%d, range_cyclic=%d "
> +		  "for_background=%d", __entry->name, __entry->nr_pages,
> +			__entry->sb, __entry->for_kupdate,
> +			__entry->range_cyclic, __entry->for_background)

> +TRACE_EVENT(writeback_sched,
> +
> +	TP_PROTO(struct backing_dev_info *bdi, struct bdi_work *work,
> +		 const char *msg),
> +
> +	TP_ARGS(bdi, work, msg),
> +
> +	TP_STRUCT__entry(
> +		__array(char,			name,		16)
> +		__field(unsigned int,		work)
> +		__array(char,			task,		8)
> +	),

Instead of the task field I'd make this a calss with three instances
for the different types of wakeups.

> +
> +	TP_fast_assign(
> +		strlcpy(__entry->name, dev_name(bdi->dev), 16);
> +		__entry->work = (unsigned long) work & 0xffff;

The unsigned long allows to store the whole pointer.  Or we could just
store it as a void pointer and print it using %p to make the types
simpler.

> +	TP_PROTO(const char *name, int start),
> +
> +	TP_ARGS(name, start),
> +
> +	TP_STRUCT__entry(
> +		__array(char,	name,		16)
> +		__field(int,	start)
> +	),
> +
> +	TP_fast_assign(
> +		strlcpy(__entry->name, name, 16);
> +		__entry->start = start;
> +	),
> +
> +	TP_printk("%s: %s", __entry->name,
> +			__entry->start ? "registered" : "unregistered")

Again, the clean way would be to have class with two instances instead
of using one tracepoint for two different events and differenciate them
by a string.

Re: [PATCH 2/3] writeback: Add tracing to balance_dirty_pages

[Christoph Hellwig]

> +/* pass flags explicitly */

which flags?

> +	TP_fast_assign(
> +		char *__name = "(none)";
> +
> +		__entry->wbc		= (unsigned long)wbc & 0xffff;

The wbc generally is allocated on stack, does it reall make sense to
keep this?

> +		if (wbc->bdi)
> +			strncpy(__entry->name, dev_name(wbc->bdi->dev), 16);
> +		else
> +			strncpy(__entry->name, __name, 16);

> +		__entry->sb		= !!wbc->sb;

The bdi and sb fields are now gone from the writeback_control.  But
I think passing the bdi explicitly for the device name makes sense
here.

Re: [PATCH 0/3] writeback: tracing support

[Jens Axboe]

On 2010-06-21 03:25, Dave Chinner wrote:
> Hi Jens,
> 
> These are the writeback tracing patches that have not made it to
> mainline yet.  Can you pull these into your writeback tree for
> 2.6.36?

Will you send an updated and rediffed version against the
current patches? Just generate against for-2.6.36 of the block
git tree [1].

[1] git://git.kernel.dk/linux-2.6-block.git

-- 
Jens Axboe

Re: [PATCH 0/3] writeback: tracing support

[Dave Chinner]

On Thu, Jun 24, 2010 at 02:12:27PM +0200, Jens Axboe wrote:
> On 2010-06-21 03:25, Dave Chinner wrote:
> > Hi Jens,
> > 
> > These are the writeback tracing patches that have not made it to
> > mainline yet.  Can you pull these into your writeback tree for
> > 2.6.36?
> 
> Will you send an updated and rediffed version against the
> current patches? Just generate against for-2.6.36 of the block
> git tree [1].
> 
> [1] git://git.kernel.dk/linux-2.6-block.git

Yes, will do.


Cheers,

Dave.
-- 
Dave Chinner
david@fromorbit.com