ext4: refine extent status tree

This commit refines the extent status tree code.

1) A prefix 'es_' is added to to the extent status tree structure
members.

2) Refactored es_remove_extent() so that __es_remove_extent() can be
used by es_insert_extent() to remove the old extent entry(-ies) before
inserting a new one.

3) Rename extent_status_end() to ext4_es_end()

4) ext4_es_can_be_merged() is define to check whether two extents can
be merged or not.

5) Update and clarified comments.
Signed-off-by: Zheng Liu <wenqing.lz@taobao.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Reviewed-by: Jan Kara <jack@suse.cz>

fs/ext4/extents.c

@@ -3528,13 +3528,14 @@ static int ext4_find_delalloc_range(struct inode *inode,
 {
 	struct extent_status es;
 
-	es.start = lblk_start;
-	ext4_es_find_extent(inode, &es);
-	if (es.len == 0)
+	es.es_lblk = lblk_start;
+	(void)ext4_es_find_extent(inode, &es);
+	if (es.es_len == 0)
 		return 0; /* there is no delay extent in this tree */
-	else if (es.start <= lblk_start && lblk_start < es.start + es.len)
+	else if (es.es_lblk <= lblk_start &&
+		 lblk_start < es.es_lblk + es.es_len)
 		return 1;
-	else if (lblk_start <= es.start && es.start <= lblk_end)
+	else if (lblk_start <= es.es_lblk && es.es_lblk <= lblk_end)
 		return 1;
 	else
 		return 0;
@@ -4569,7 +4570,7 @@ static int ext4_find_delayed_extent(struct inode *inode,
 	struct extent_status es;
 	ext4_lblk_t next_del;
 
-	es.start = newex->ec_block;
+	es.es_lblk = newex->ec_block;
 	next_del = ext4_es_find_extent(inode, &es);
 
 	if (newex->ec_start == 0) {
@@ -4577,18 +4578,18 @@ static int ext4_find_delayed_extent(struct inode *inode,
 		 * No extent in extent-tree contains block @newex->ec_start,
 		 * then the block may stay in 1)a hole or 2)delayed-extent.
 		 */
-		if (es.len == 0)
+		if (es.es_len == 0)
 			/* A hole found. */
 			return 0;
 
-		if (es.start > newex->ec_block) {
+		if (es.es_lblk > newex->ec_block) {
 			/* A hole found. */
-			newex->ec_len = min(es.start - newex->ec_block,
+			newex->ec_len = min(es.es_lblk - newex->ec_block,
 					    newex->ec_len);
 			return 0;
 		}
 
-		newex->ec_len = es.start + es.len - newex->ec_block;
+		newex->ec_len = es.es_lblk + es.es_len - newex->ec_block;
 	}
 
 	return next_del;

fs/ext4/extents_status.h

@@ -22,8 +22,8 @@
 
 struct extent_status {
 	struct rb_node rb_node;
-	ext4_lblk_t start;	/* first block extent covers */
-	ext4_lblk_t len;	/* length of extent in block */
+	ext4_lblk_t es_lblk;	/* first logical block extent covers */
+	ext4_lblk_t es_len;	/* length of extent in block */
 };
 
 struct ext4_es_tree {
@@ -35,9 +35,9 @@ extern int __init ext4_init_es(void);
 extern void ext4_exit_es(void);
 extern void ext4_es_init_tree(struct ext4_es_tree *tree);
 
-extern int ext4_es_insert_extent(struct inode *inode, ext4_lblk_t start,
+extern int ext4_es_insert_extent(struct inode *inode, ext4_lblk_t lblk,
 				 ext4_lblk_t len);
-extern int ext4_es_remove_extent(struct inode *inode, ext4_lblk_t start,
+extern int ext4_es_remove_extent(struct inode *inode, ext4_lblk_t lblk,
 				 ext4_lblk_t len);
 extern ext4_lblk_t ext4_es_find_extent(struct inode *inode,
 				struct extent_status *es);

fs/ext4/file.c

@@ -464,10 +464,9 @@ static loff_t ext4_seek_data(struct file *file, loff_t offset, loff_t maxsize)
 		 * If there is a delay extent at this offset,
 		 * it will be as a data.
 		 */
-		es.start = last;
+		es.es_lblk = last;
 		(void)ext4_es_find_extent(inode, &es);
-		if (last >= es.start &&
-		    last < es.start + es.len) {
+		if (es.es_len != 0 && in_range(last, es.es_lblk, es.es_len)) {
 			if (last != start)
 				dataoff = last << blkbits;
 			break;
@@ -549,11 +548,10 @@ static loff_t ext4_seek_hole(struct file *file, loff_t offset, loff_t maxsize)
 		 * If there is a delay extent at this offset,
 		 * we will skip this extent.
 		 */
-		es.start = last;
+		es.es_lblk = last;
 		(void)ext4_es_find_extent(inode, &es);
-		if (last >= es.start &&
-		    last < es.start + es.len) {
-			last = es.start + es.len;
+		if (es.es_len != 0 && in_range(last, es.es_lblk, es.es_len)) {
+			last = es.es_lblk + es.es_len;
 			holeoff = last << blkbits;
 			continue;
 		}

include/trace/events/ext4.h

@@ -2093,75 +2093,75 @@ TRACE_EVENT(ext4_ext_remove_space_done,
 );
 
 TRACE_EVENT(ext4_es_insert_extent,
-	TP_PROTO(struct inode *inode, ext4_lblk_t start, ext4_lblk_t len),
+	TP_PROTO(struct inode *inode, ext4_lblk_t lblk, ext4_lblk_t len),
 
-	TP_ARGS(inode, start, len),
+	TP_ARGS(inode, lblk, len),
 
 	TP_STRUCT__entry(
 		__field(	dev_t,	dev			)
 		__field(	ino_t,	ino			)
-		__field(	loff_t,	start			)
+		__field(	loff_t,	lblk			)
 		__field(	loff_t, len			)
 	),
 
 	TP_fast_assign(
 		__entry->dev	= inode->i_sb->s_dev;
 		__entry->ino	= inode->i_ino;
-		__entry->start	= start;
+		__entry->lblk	= lblk;
 		__entry->len	= len;
 	),
 
 	TP_printk("dev %d,%d ino %lu es [%lld/%lld)",
 		  MAJOR(__entry->dev), MINOR(__entry->dev),
 		  (unsigned long) __entry->ino,
-		  __entry->start, __entry->len)
+		  __entry->lblk, __entry->len)
 );
 
 TRACE_EVENT(ext4_es_remove_extent,
-	TP_PROTO(struct inode *inode, ext4_lblk_t start, ext4_lblk_t len),
+	TP_PROTO(struct inode *inode, ext4_lblk_t lblk, ext4_lblk_t len),
 
-	TP_ARGS(inode, start, len),
+	TP_ARGS(inode, lblk, len),
 
 	TP_STRUCT__entry(
 		__field(	dev_t,	dev			)
 		__field(	ino_t,	ino			)
-		__field(	loff_t,	start			)
+		__field(	loff_t,	lblk			)
 		__field(	loff_t,	len			)
 	),
 
 	TP_fast_assign(
 		__entry->dev	= inode->i_sb->s_dev;
 		__entry->ino	= inode->i_ino;
-		__entry->start	= start;
+		__entry->lblk	= lblk;
 		__entry->len	= len;
 	),
 
 	TP_printk("dev %d,%d ino %lu es [%lld/%lld)",
 		  MAJOR(__entry->dev), MINOR(__entry->dev),
 		  (unsigned long) __entry->ino,
-		  __entry->start, __entry->len)
+		  __entry->lblk, __entry->len)
 );
 
 TRACE_EVENT(ext4_es_find_extent_enter,
-	TP_PROTO(struct inode *inode, ext4_lblk_t start),
+	TP_PROTO(struct inode *inode, ext4_lblk_t lblk),
 
-	TP_ARGS(inode, start),
+	TP_ARGS(inode, lblk),
 
 	TP_STRUCT__entry(
 		__field(	dev_t,		dev		)
 		__field(	ino_t,		ino		)
-		__field(	ext4_lblk_t,	start		)
+		__field(	ext4_lblk_t,	lblk		)
 	),
 
 	TP_fast_assign(
 		__entry->dev	= inode->i_sb->s_dev;
 		__entry->ino	= inode->i_ino;
-		__entry->start	= start;
+		__entry->lblk	= lblk;
 	),
 
-	TP_printk("dev %d,%d ino %lu start %u",
+	TP_printk("dev %d,%d ino %lu lblk %u",
 		  MAJOR(__entry->dev), MINOR(__entry->dev),
-		  (unsigned long) __entry->ino, __entry->start)
+		  (unsigned long) __entry->ino, __entry->lblk)
 );
 
 TRACE_EVENT(ext4_es_find_extent_exit,
@@ -2173,7 +2173,7 @@ TRACE_EVENT(ext4_es_find_extent_exit,
 	TP_STRUCT__entry(
 		__field(	dev_t,		dev		)
 		__field(	ino_t,		ino		)
-		__field(	ext4_lblk_t,	start		)
+		__field(	ext4_lblk_t,	lblk		)
 		__field(	ext4_lblk_t,	len		)
 		__field(	ext4_lblk_t,	ret		)
 	),
@@ -2181,15 +2181,15 @@ TRACE_EVENT(ext4_es_find_extent_exit,
 	TP_fast_assign(
 		__entry->dev	= inode->i_sb->s_dev;
 		__entry->ino	= inode->i_ino;
-		__entry->start	= es->start;
-		__entry->len	= es->len;
+		__entry->lblk	= es->es_lblk;
+		__entry->len	= es->es_len;
 		__entry->ret	= ret;
 	),
 
 	TP_printk("dev %d,%d ino %lu es [%u/%u) ret %u",
 		  MAJOR(__entry->dev), MINOR(__entry->dev),
 		  (unsigned long) __entry->ino,
-		  __entry->start, __entry->len, __entry->ret)
+		  __entry->lblk, __entry->len, __entry->ret)
 );
 
 #endif /* _TRACE_EXT4_H */