[PATCH] trace: Add tracepoints to fs subsystem

[Vaibhav Nagarnaik]

From: Jiaying Zhang <jiayingz@xxxxxxxxxx>

Many fs tracepoints can now be traced via ftrace, however there are a
few other tracepoints needed. This patch adds entry and exit tracepoints
for a few additional functions, viz.:
wait_on_buffer
block_write_full_page
mpage_readpages
file_read

Signed-off-by: Vaibhav Nagarnaik <vnagarnaik@xxxxxxxxxx>
---
 fs/buffer.c               |   10 +++
 fs/mpage.c                |    3 +
 include/trace/events/fs.h |  166 +++++++++++++++++++++++++++++++++++++++++++++
 mm/filemap.c              |    4 +-
 4 files changed, 182 insertions(+), 1 deletions(-)
 create mode 100644 include/trace/events/fs.h

diff --git a/fs/buffer.c b/fs/buffer.c
index a08bb8e..40a0ce3 100644
--- a/fs/buffer.c
+++ b/fs/buffer.c
@@ -42,6 +42,9 @@
 #include <linux/mpage.h>
 #include <linux/bit_spinlock.h>
 
+#define CREATE_TRACE_POINTS
+#include <trace/events/fs.h>
+
 static int fsync_buffers_list(spinlock_t *lock, struct list_head *list);
 
 #define BH_ENTRY(list) list_entry((list), struct buffer_head, b_assoc_buffers)
@@ -82,7 +85,9 @@ EXPORT_SYMBOL(unlock_buffer);
  */
 void __wait_on_buffer(struct buffer_head * bh)
 {
+	trace_fs_buffer_wait_start(bh);
 	wait_on_bit(&bh->b_state, BH_Lock, sleep_on_buffer, TASK_UNINTERRUPTIBLE);
+	trace_fs_buffer_wait_end(bh);
 }
 EXPORT_SYMBOL(__wait_on_buffer);
 
@@ -1647,6 +1652,8 @@ static int __block_write_full_page(struct inode *inode, struct page *page,
 	head = page_buffers(page);
 	bh = head;
 
+	trace_block_write_full_page(inode, block, last_block);
+
 	/*
 	 * Get all the dirty buffers mapped to disk addresses and
 	 * handle any aliases from the underlying blockdev's mapping.
@@ -1736,6 +1743,9 @@ done:
 		 * here on.
 		 */
 	}
+
+	trace_block_write_full_page_done(inode, nr_underway, err);
+
 	return err;
 
 recover:
diff --git a/fs/mpage.c b/fs/mpage.c
index 0afc809..1c3b8e1 100644
--- a/fs/mpage.c
+++ b/fs/mpage.c
@@ -28,6 +28,7 @@
 #include <linux/backing-dev.h>
 #include <linux/pagevec.h>
 
+#include <trace/events/fs.h>
 /*
  * I/O completion handler for multipage BIOs.
  *
@@ -373,6 +374,8 @@ mpage_readpages(struct address_space *mapping, struct list_head *pages,
 	for (page_idx = 0; page_idx < nr_pages; page_idx++) {
 		struct page *page = list_entry(pages->prev, struct page, lru);
 
+		if (page_idx == 0)
+			trace_mpage_readpages(page, mapping, nr_pages);
 		prefetchw(&page->flags);
 		list_del(&page->lru);
 		if (!add_to_page_cache_lru(page, mapping,
diff --git a/include/trace/events/fs.h b/include/trace/events/fs.h
new file mode 100644
index 0000000..40b71db
--- /dev/null
+++ b/include/trace/events/fs.h
@@ -0,0 +1,166 @@
+#undef TRACE_SYSTEM
+#define TRACE_SYSTEM fs
+
+#if !defined(_TRACE_FS_H) || defined(TRACE_HEADER_MULTI_READ)
+#define _TRACE_FS_H
+
+#include <linux/tracepoint.h>
+
+TRACE_EVENT(fs_buffer_wait_start,
+
+	TP_PROTO(struct buffer_head *bh),
+
+	TP_ARGS(bh),
+
+	TP_STRUCT__entry(
+		__field(	void *,	bh	)
+	),
+
+	TP_fast_assign(
+		__entry->bh = bh;
+	),
+
+	TP_printk("bh %p", __entry->bh)
+);
+
+TRACE_EVENT(fs_buffer_wait_end,
+
+	TP_PROTO(struct buffer_head *bh),
+
+	TP_ARGS(bh),
+
+	TP_STRUCT__entry(
+		__field(void *, bh)
+	),
+
+	TP_fast_assign(
+		__entry->bh = bh;
+	),
+
+	TP_printk("bh %p", __entry->bh)
+);
+
+TRACE_EVENT(block_write_full_page,
+
+	TP_PROTO(struct inode *inode, sector_t block, sector_t last_block),
+
+	TP_ARGS(inode, block, last_block),
+
+	TP_STRUCT__entry(
+		__field(	dev_t,		dev		)
+		__field(	unsigned long,	ino		)
+		__field(	sector_t,	block		)
+		__field(	sector_t,	last_block	)
+	),
+
+	TP_fast_assign(
+		__entry->dev		= inode->i_sb->s_dev;
+		__entry->ino		= inode->i_ino;
+		__entry->block		= block;
+		__entry->last_block	= last_block;
+	),
+
+	TP_printk("dev %d,%d ino %lu block %lu last block %lu",
+		  MAJOR(__entry->dev), MINOR(__entry->dev),
+		  __entry->ino,
+		  (unsigned long)__entry->block,
+		  (unsigned long)__entry->last_block)
+);
+
+TRACE_EVENT(block_write_full_page_done,
+
+	TP_PROTO(struct inode *inode, int nr_underway, int err),
+
+	TP_ARGS(inode, nr_underway, err),
+
+	TP_STRUCT__entry(
+		__field(	dev_t,		dev		)
+		__field(	unsigned long,	ino		)
+		__field(	int,		nr_underway	)
+		__field(	int,		err		)
+	),
+
+	TP_fast_assign(
+		__entry->dev		= inode->i_sb->s_dev;
+		__entry->ino		= inode->i_ino;
+		__entry->nr_underway	= nr_underway;
+		__entry->err		= err;
+	),
+
+	TP_printk("dev %d,%d ino %lu nr_underway %d err %d",
+		  MAJOR(__entry->dev), MINOR(__entry->dev),
+		  __entry->ino, __entry->nr_underway, __entry->err)
+);
+
+DECLARE_EVENT_CLASS(file_read,
+	TP_PROTO(struct inode *inode, loff_t pos, size_t len),
+
+	TP_ARGS(inode, pos, len),
+
+	TP_STRUCT__entry(
+		__field(	ino_t,	ino			)
+		__field(	dev_t,	dev			)
+		__field(	loff_t,	pos			)
+		__field(	size_t,	len			)
+	),
+
+	TP_fast_assign(
+		__entry->ino	= inode->i_ino;
+		__entry->dev	= inode->i_sb->s_dev;
+		__entry->pos	= pos;
+		__entry->len	= len;
+	),
+
+	TP_printk("dev %d,%d ino %lu pos %llu len %lu",
+		  MAJOR(__entry->dev), MINOR(__entry->dev),
+		  (unsigned long) __entry->ino,
+		  (unsigned long long) __entry->pos,
+		  (unsigned long) __entry->len)
+);
+
+DEFINE_EVENT(file_read, file_read_enter,
+
+	TP_PROTO(struct inode *inode, loff_t pos, size_t len),
+
+	TP_ARGS(inode, pos, len)
+);
+
+DEFINE_EVENT(file_read, file_read_exit,
+
+	TP_PROTO(struct inode *inode, loff_t pos, size_t len),
+
+	TP_ARGS(inode, pos, len)
+);
+
+TRACE_EVENT(mpage_readpages,
+	TP_PROTO(struct page *page, struct address_space *mapping,
+		 unsigned nr_pages),
+
+	TP_ARGS(page, mapping, nr_pages),
+
+	TP_STRUCT__entry(
+		__field(	pgoff_t, index			)
+		__field(	ino_t,	ino			)
+		__field(	dev_t,	dev			)
+		__field(	unsigned,	nr_pages	)
+
+	),
+
+	TP_fast_assign(
+		__entry->index	= page->index;
+		__entry->ino	= mapping->host->i_ino;
+		__entry->dev	= mapping->host->i_sb->s_dev;
+		__entry->nr_pages	= nr_pages;
+	),
+
+	TP_printk("dev %d,%d ino %lu page_index %lu nr_pages %u",
+		  MAJOR(__entry->dev), MINOR(__entry->dev),
+		  (unsigned long) __entry->ino,
+		  __entry->index, __entry->nr_pages)
+);
+
+#endif /* _TRACE_FS_H */
+
+/* This part must be outside protection */
+#include <trace/define_trace.h>
+
diff --git a/mm/filemap.c b/mm/filemap.c
index c641edf..94e549c 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -42,7 +42,7 @@
 #include <linux/buffer_head.h> /* for try_to_free_buffers */
 
 #include <asm/mman.h>
-
+#include <trace/events/fs.h>
 /*
  * Shared mappings implemented 30.11.1994. It's not fully working yet,
  * though.
@@ -1054,6 +1054,7 @@ static void do_generic_file_read(struct file *filp, loff_t *ppos,
 	unsigned int prev_offset;
 	int error;
 
+	trace_file_read_enter(inode, *ppos, desc->count);
 	index = *ppos >> PAGE_CACHE_SHIFT;
 	prev_index = ra->prev_pos >> PAGE_CACHE_SHIFT;
 	prev_offset = ra->prev_pos & (PAGE_CACHE_SIZE-1);
@@ -1254,6 +1255,7 @@ out:
 	ra->prev_pos <<= PAGE_CACHE_SHIFT;
 	ra->prev_pos |= prev_offset;
 
+	trace_file_read_exit(inode, *ppos, desc->written);
 	*ppos = ((loff_t)index << PAGE_CACHE_SHIFT) + offset;
 	file_accessed(filp);
 }
-- 
1.7.3.1

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