md/bitmap: add blktrace event for writes to the bitmap
We trace wheneven bitmap_unplug() finds that it needs to write
to the bitmap, or when bitmap_daemon_work() find there is work
to do.
This makes it easier to correlate bitmap updates with data writes.
Signed-off-by: NeilBrown <neilb@suse.com>
Signed-off-by: Shaohua Li <shli@fb.com>
diff --git a/drivers/md/bitmap.c b/drivers/md/bitmap.c
index 1a7f402..cf77cbf 100644
--- a/drivers/md/bitmap.c
+++ b/drivers/md/bitmap.c
@@ -27,6 +27,7 @@
#include <linux/mount.h>
#include <linux/buffer_head.h>
#include <linux/seq_file.h>
+#include <trace/events/block.h>
#include "md.h"
#include "bitmap.h"
@@ -1008,8 +1009,12 @@ void bitmap_unplug(struct bitmap *bitmap)
need_write = test_and_clear_page_attr(bitmap, i,
BITMAP_PAGE_NEEDWRITE);
if (dirty || need_write) {
- if (!writing)
+ if (!writing) {
bitmap_wait_writes(bitmap);
+ if (bitmap->mddev->queue)
+ blk_add_trace_msg(bitmap->mddev->queue,
+ "md bitmap_unplug");
+ }
clear_page_attr(bitmap, i, BITMAP_PAGE_PENDING);
write_page(bitmap, bitmap->storage.filemap[i], 0);
writing = 1;
@@ -1234,6 +1239,10 @@ void bitmap_daemon_work(struct mddev *mddev)
}
bitmap->allclean = 1;
+ if (bitmap->mddev->queue)
+ blk_add_trace_msg(bitmap->mddev->queue,
+ "md bitmap_daemon_work");
+
/* Any file-page which is PENDING now needs to be written.
* So set NEEDWRITE now, then after we make any last-minute changes
* we will write it.
