[PATCH 1/2] f2fs: check the largest extent at look-up time

[Jaegeuk Kim <jaegeuk@kernel.org>]

Because of the extent shrinker or other -ENOMEM scenarios, it cannot guarantee
that the largest extent would be cached in the tree all the time.

Instead of relying on extent_tree, we can simply check the cached one in extent
tree accordingly.

Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
---
 fs/f2fs/data.c              | 16 ++++++++++++++--
 include/trace/events/f2fs.h | 12 ++++++------
 2 files changed, 20 insertions(+), 8 deletions(-)

diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
index b6c28bb..8f059e0 100644
--- a/fs/f2fs/data.c
+++ b/fs/f2fs/data.c
@@ -511,12 +511,22 @@ static bool f2fs_lookup_extent_tree(struct inode *inode, pgoff_t pgofs,
 	struct f2fs_sb_info *sbi = F2FS_I_SB(inode);
 	struct extent_tree *et = F2FS_I(inode)->extent_tree;
 	struct extent_node *en;
+	bool ret = false;
 
 	f2fs_bug_on(sbi, !et);
 
 	trace_f2fs_lookup_extent_tree_start(inode, pgofs);
 
 	read_lock(&et->lock);
+
+	if (et->largest.fofs <= pgofs &&
+			et->largest.fofs + et->largest.len > pgofs) {
+		*ei = et->largest;
+		ret = true;
+		stat_inc_read_hit(sbi->sb);
+		goto out;
+	}
+
 	en = __lookup_extent_tree(et, pgofs);
 	if (en) {
 		*ei = en->ei;
@@ -525,13 +535,15 @@ static bool f2fs_lookup_extent_tree(struct inode *inode, pgoff_t pgofs,
 			list_move_tail(&en->list, &sbi->extent_list);
 		et->cached_en = en;
 		spin_unlock(&sbi->extent_lock);
+		ret = true;
 		stat_inc_read_hit(sbi->sb);
 	}
+out:
 	stat_inc_total_hit(sbi->sb);
 	read_unlock(&et->lock);
 
-	trace_f2fs_lookup_extent_tree_end(inode, pgofs, en);
-	return en ? true : false;
+	trace_f2fs_lookup_extent_tree_end(inode, pgofs, ei);
+	return ret;
 }
 
 /* return true, if on-disk extent should be updated */
diff --git a/include/trace/events/f2fs.h b/include/trace/events/f2fs.h
index 04856a2..a019465 100644
--- a/include/trace/events/f2fs.h
+++ b/include/trace/events/f2fs.h
@@ -1099,11 +1099,11 @@ TRACE_EVENT(f2fs_lookup_extent_tree_start,
 TRACE_EVENT_CONDITION(f2fs_lookup_extent_tree_end,
 
 	TP_PROTO(struct inode *inode, unsigned int pgofs,
-						struct extent_node *en),
+						struct extent_info *ei),
 
-	TP_ARGS(inode, pgofs, en),
+	TP_ARGS(inode, pgofs, ei),
 
-	TP_CONDITION(en),
+	TP_CONDITION(ei),
 
 	TP_STRUCT__entry(
 		__field(dev_t,	dev)
@@ -1118,9 +1118,9 @@ TRACE_EVENT_CONDITION(f2fs_lookup_extent_tree_end,
 		__entry->dev = inode->i_sb->s_dev;
 		__entry->ino = inode->i_ino;
 		__entry->pgofs = pgofs;
-		__entry->fofs = en->ei.fofs;
-		__entry->blk = en->ei.blk;
-		__entry->len = en->ei.len;
+		__entry->fofs = ei->fofs;
+		__entry->blk = ei->blk;
+		__entry->len = ei->len;
 	),
 
 	TP_printk("dev = (%d,%d), ino = %lu, pgofs = %u, "
-- 
2.1.1