ANDROID: fs: FS tracepoints to track IO.

Adds tracepoints in ext4/f2fs/mpage to track readpages/buffered
write()s. This allows us to track files that are being read/written
to PIDs. (Merged from android4.4-common).

Signed-off-by: Mohan Srinivasan <srmohan@google.com>
diff --git a/fs/mpage.c b/fs/mpage.c
index d2413af..2bb117d 100644
--- a/fs/mpage.c
+++ b/fs/mpage.c
@@ -31,6 +31,14 @@
 #include <linux/cleancache.h>
 #include "internal.h"
 
+#define CREATE_TRACE_POINTS
+#include <trace/events/android_fs.h>
+
+EXPORT_TRACEPOINT_SYMBOL(android_fs_datawrite_start);
+EXPORT_TRACEPOINT_SYMBOL(android_fs_datawrite_end);
+EXPORT_TRACEPOINT_SYMBOL(android_fs_dataread_start);
+EXPORT_TRACEPOINT_SYMBOL(android_fs_dataread_end);
+
 /*
  * I/O completion handler for multipage BIOs.
  *
@@ -48,6 +56,16 @@
 	struct bio_vec *bv;
 	int i;
 
+	if (trace_android_fs_dataread_end_enabled() &&
+	    (bio_data_dir(bio) == READ)) {
+		struct page *first_page = bio->bi_io_vec[0].bv_page;
+
+		if (first_page != NULL)
+			trace_android_fs_dataread_end(first_page->mapping->host,
+						      page_offset(first_page),
+						      bio->bi_iter.bi_size);
+	}
+
 	bio_for_each_segment_all(bv, bio, i) {
 		struct page *page = bv->bv_page;
 		page_endio(page, op_is_write(bio_op(bio)), bio->bi_error);
@@ -58,6 +76,18 @@
 
 static struct bio *mpage_bio_submit(int op, int op_flags, struct bio *bio)
 {
+	if (trace_android_fs_dataread_start_enabled() && (op == REQ_OP_READ)) {
+		struct page *first_page = bio->bi_io_vec[0].bv_page;
+
+		if (first_page != NULL) {
+			trace_android_fs_dataread_start(
+				first_page->mapping->host,
+				page_offset(first_page),
+				bio->bi_iter.bi_size,
+				current->pid,
+				current->comm);
+		}
+	}
 	bio->bi_end_io = mpage_end_io;
 	bio_set_op_attrs(bio, op, op_flags);
 	guard_bio_eod(op, bio);