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From:   Zehao Zhang <zhangzehao@vivo.com>
To:     linkinjeon@kernel.org, sj1557.seo@samsung.com, rostedt@goodmis.org,
        mhiramat@kernel.org
Cc:     linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org,
        linux-trace-kernel@vger.kernel.org,
        Zehao Zhang <zhangzehao@vivo.com>
Subject: [PATCH v2] exfat: Add ftrace support for exfat and add some tracepoints
Date:   Tue, 11 Jul 2023 20:22:08 +0800
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Add ftrace support for exFAT file system,
and add some tracepoints:
exfat_read_folio(), exfat_writepages(), exfat_write_begin(),
exfat_write_end(), exfat_lookup_start(), exfat_lookup_end()

exfat_read_folio():
shows the dev number, inode and the folio index.

exfat_writepages():
shows the inode and fields in struct writeback_control.

exfat_write_begin():
shows the inode, file position offset and length.

exfat_write_end():
shows the inode, file position offset, bytes write to page
and bytes copied from user.

exfat_lookup_start():
shows the target inode, dentry and flags.

exfat_lookup_end():
shows the target inode, dentry and err code.

Signed-off-by: Zehao Zhang <zhangzehao@vivo.com>
---
v2:
- Keep the dereferencing logic out of the code path,
  only happens in the trace event functions.

Thanks for Steve's advice.

 MAINTAINERS                  |   1 +
 fs/exfat/inode.c             |   9 ++
 fs/exfat/namei.c             |  10 +-
 include/trace/events/exfat.h | 190 +++++++++++++++++++++++++++++++++++
 4 files changed, 209 insertions(+), 1 deletion(-)
 create mode 100644 include/trace/events/exfat.h

diff --git a/MAINTAINERS b/MAINTAINERS
index 4f115c355a41..fbe1caa61a38 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -7752,6 +7752,7 @@ L:	linux-fsdevel@vger.kernel.org
 S:	Maintained
 T:	git git://git.kernel.org/pub/scm/linux/kernel/git/linkinjeon/exfat.git
 F:	fs/exfat/
+F:	include/trace/events/exfat.h
 
 EXT2 FILE SYSTEM
 M:	Jan Kara <jack@suse.com>
diff --git a/fs/exfat/inode.c b/fs/exfat/inode.c
index 481dd338f2b8..81fe715baab0 100644
--- a/fs/exfat/inode.c
+++ b/fs/exfat/inode.c
@@ -17,6 +17,9 @@
 #include "exfat_raw.h"
 #include "exfat_fs.h"
 
+#define CREATE_TRACE_POINTS
+#include <trace/events/exfat.h>
+
 int __exfat_write_inode(struct inode *inode, int sync)
 {
 	unsigned long long on_disk_size;
@@ -335,6 +338,7 @@ static int exfat_get_block(struct inode *inode, sector_t iblock,
 
 static int exfat_read_folio(struct file *file, struct folio *folio)
 {
+	trace_exfat_read_folio(folio);
 	return mpage_read_folio(folio, exfat_get_block);
 }
 
@@ -346,6 +350,7 @@ static void exfat_readahead(struct readahead_control *rac)
 static int exfat_writepages(struct address_space *mapping,
 		struct writeback_control *wbc)
 {
+	trace_exfat_writepages(mapping, wbc);
 	return mpage_writepages(mapping, wbc, exfat_get_block);
 }
 
@@ -371,6 +376,8 @@ static int exfat_write_begin(struct file *file, struct address_space *mapping,
 			       exfat_get_block,
 			       &EXFAT_I(mapping->host)->i_size_ondisk);
 
+	trace_exfat_write_begin(mapping, pos, len);
+
 	if (ret < 0)
 		exfat_write_failed(mapping, pos+len);
 
@@ -394,6 +401,8 @@ static int exfat_write_end(struct file *file, struct address_space *mapping,
 		return -EIO;
 	}
 
+	trace_exfat_write_end(inode, pos, len, copied);
+
 	if (err < len)
 		exfat_write_failed(mapping, pos+len);
 
diff --git a/fs/exfat/namei.c b/fs/exfat/namei.c
index e0ff9d156f6f..f4f36de4ca0d 100644
--- a/fs/exfat/namei.c
+++ b/fs/exfat/namei.c
@@ -12,6 +12,8 @@
 #include "exfat_raw.h"
 #include "exfat_fs.h"
 
+#include <trace/events/exfat.h>
+
 static inline unsigned long exfat_d_version(struct dentry *dentry)
 {
 	return (unsigned long) dentry->d_fsdata;
@@ -707,6 +709,8 @@ static struct dentry *exfat_lookup(struct inode *dir, struct dentry *dentry,
 	loff_t i_pos;
 	mode_t i_mode;
 
+	trace_exfat_lookup_start(dir, dentry, flags);
+
 	mutex_lock(&EXFAT_SB(sb)->s_lock);
 	err = exfat_find(dir, &dentry->d_name, &info);
 	if (err) {
@@ -766,7 +770,11 @@ static struct dentry *exfat_lookup(struct inode *dir, struct dentry *dentry,
 	if (!inode)
 		exfat_d_version_set(dentry, inode_query_iversion(dir));
 
-	return d_splice_alias(inode, dentry);
+	alias = d_splice_alias(inode, dentry);
+	trace_exfat_lookup_end(dir, !IS_ERR_OR_NULL(alias) ? alias : dentry,
+			IS_ERR(alias) ? PTR_ERR(alias) : err);
+
+	return alias;
 unlock:
 	mutex_unlock(&EXFAT_SB(sb)->s_lock);
 	return ERR_PTR(err);
diff --git a/include/trace/events/exfat.h b/include/trace/events/exfat.h
new file mode 100644
index 000000000000..782dae6e2e42
--- /dev/null
+++ b/include/trace/events/exfat.h
@@ -0,0 +1,190 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#undef TRACE_SYSTEM
+#define TRACE_SYSTEM exfat
+
+#if !defined(_TRACE_EXFAT_H) || defined(TRACE_HEADER_MULTI_READ)
+#define _TRACE_EXFAT_H
+
+#include <linux/tracepoint.h>
+
+#define EXFAT_I(inode)	(container_of(inode, struct exfat_inode_info, vfs_inode))
+
+
+TRACE_EVENT(exfat_write_begin,
+	TP_PROTO(struct address_space *mapping, loff_t pos, unsigned int len),
+
+	TP_ARGS(mapping, pos, len),
+
+	TP_STRUCT__entry(
+		__field(dev_t,        dev)
+		__field(ino_t,        ino)
+		__field(loff_t,       pos)
+		__field(unsigned int, len)
+	),
+
+	TP_fast_assign(
+		__entry->dev    = mapping->host->i_sb->s_dev;
+		__entry->ino    = mapping->host->i_ino;
+		__entry->pos    = pos;
+		__entry->len    = len;
+	),
+
+	TP_printk("dev (%d,%d) ino %lu pos %lld len %u",
+		MAJOR(__entry->dev), MINOR(__entry->dev),
+		(unsigned long) __entry->ino,
+		__entry->pos, __entry->len)
+
+);
+
+TRACE_EVENT(exfat_write_end,
+	TP_PROTO(struct inode *inode, loff_t pos, unsigned int len,
+			unsigned int copied),
+
+	TP_ARGS(inode, pos, len, copied),
+
+	TP_STRUCT__entry(
+		__field(dev_t,	dev)
+		__field(ino_t,	ino)
+		__field(loff_t,	pos)
+		__field(unsigned int, len)
+		__field(unsigned int, copied)
+	),
+
+	TP_fast_assign(
+		__entry->dev	= inode->i_sb->s_dev;
+		__entry->ino	= inode->i_ino;
+		__entry->pos	= pos;
+		__entry->len	= len;
+		__entry->copied	= copied;
+	),
+
+	TP_printk("dev (%d,%d) ino %lu pos %lld len %u copied %u",
+		MAJOR(__entry->dev), MINOR(__entry->dev),
+		(unsigned long) __entry->ino,
+		__entry->pos, __entry->len, __entry->copied)
+);
+
+TRACE_EVENT(exfat_read_folio,
+	TP_PROTO(struct folio *folio),
+
+	TP_ARGS(folio),
+
+	TP_STRUCT__entry(
+		__field(dev_t,	dev)
+		__field(ino_t,	ino)
+		__field(pgoff_t, index)
+
+	),
+
+	TP_fast_assign(
+		__entry->dev	= folio->mapping->host->i_sb->s_dev;
+		__entry->ino	= folio->mapping->host->i_ino;
+		__entry->index	= folio->index;
+	),
+
+	TP_printk("dev (%d,%d) ino %lu folio_index %lu",
+		MAJOR(__entry->dev), MINOR(__entry->dev),
+		(unsigned long) __entry->ino,
+		(unsigned long) __entry->index)
+);
+
+TRACE_EVENT(exfat_writepages,
+	TP_PROTO(struct address_space *mapping, struct writeback_control *wbc),
+
+	TP_ARGS(mapping, wbc),
+
+	TP_STRUCT__entry(
+		__field(dev_t,	dev)
+		__field(ino_t,	ino)
+		__field(long,	nr_to_write)
+		__field(long,	pages_skipped)
+		__field(loff_t,		range_start)
+		__field(loff_t,		range_end)
+		__field(pgoff_t,	writeback_index)
+		__field(int,	sync_mode)
+		__field(char,	for_kupdate)
+		__field(char,	range_cyclic)
+	),
+
+	TP_fast_assign(
+		__entry->dev		= mapping->host->i_sb->s_dev;
+		__entry->ino		= mapping->host->i_ino;
+		__entry->nr_to_write	= wbc->nr_to_write;
+		__entry->pages_skipped	= wbc->pages_skipped;
+		__entry->range_start	= wbc->range_start;
+		__entry->range_end	= wbc->range_end;
+		__entry->writeback_index = mapping->host->i_mapping->writeback_index;
+		__entry->sync_mode	= wbc->sync_mode;
+		__entry->for_kupdate	= wbc->for_kupdate;
+		__entry->range_cyclic	= wbc->range_cyclic;
+	),
+
+	TP_printk("dev (%d,%d) ino %lu nr_to_write %ld pages_skipped %ld "
+		"range_start %lld range_end %lld sync_mode %d "
+		"for_kupdate %d range_cyclic %d writeback_index %lu",
+		MAJOR(__entry->dev), MINOR(__entry->dev),
+		(unsigned long) __entry->ino, __entry->nr_to_write,
+		__entry->pages_skipped, __entry->range_start,
+		__entry->range_end, __entry->sync_mode,
+		__entry->for_kupdate, __entry->range_cyclic,
+		(unsigned long) __entry->writeback_index)
+);
+
+TRACE_EVENT(exfat_lookup_start,
+
+	TP_PROTO(struct inode *dir, struct dentry *dentry, unsigned int flags),
+
+	TP_ARGS(dir, dentry, flags),
+
+	TP_STRUCT__entry(
+		__field(dev_t,	dev)
+		__field(ino_t,	ino)
+		__string(name,	dentry->d_name.name)
+		__field(unsigned int, flags)
+	),
+
+	TP_fast_assign(
+		__entry->dev	= dir->i_sb->s_dev;
+		__entry->ino	= dir->i_ino;
+		__assign_str(name, dentry->d_name.name);
+		__entry->flags	= flags;
+	),
+
+	TP_printk("dev = (%d,%d), pino = %lu, name:%s, flags:%u",
+		MAJOR(__entry->dev), MINOR(__entry->dev),
+		(unsigned long)__entry->ino,
+		__get_str(name),
+		__entry->flags)
+);
+
+TRACE_EVENT(exfat_lookup_end,
+
+	TP_PROTO(struct inode *dir, struct dentry *dentry, int err),
+
+	TP_ARGS(dir, dentry, err),
+
+	TP_STRUCT__entry(
+		__field(dev_t,	dev)
+		__field(ino_t,	ino)
+		__string(name,	dentry->d_name.name)
+		__field(int,	err)
+	),
+
+	TP_fast_assign(
+		__entry->dev	= dir->i_sb->s_dev;
+		__entry->ino	= dir->i_ino;
+		__assign_str(name, dentry->d_name.name);
+		__entry->err	= err;
+	),
+
+	TP_printk("dev = (%d,%d), pino = %lu, name:%s, err:%d",
+		MAJOR(__entry->dev), MINOR(__entry->dev),
+		(unsigned long)__entry->ino,
+		__get_str(name),
+		__entry->err)
+);
+
+#endif /* _TRACE_EXFAT_H */
+
+/* This part must be outside protection */
+#include <trace/define_trace.h>
-- 
2.35.3