linux-ext4 - [RFC PATCH 2/6] ext4: make ext4_es_lookup_extent() return the next extent if not found

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Date: Tue, 21 Nov 2023 17:34:25 +0800
From: Zhang Yi <yi.zhang@...weicloud.com>
To: linux-ext4@...r.kernel.org
Cc: tytso@....edu,
	adilger.kernel@...ger.ca,
	jack@...e.cz,
	ritesh.list@...il.com,
	yi.zhang@...wei.com,
	yi.zhang@...weicloud.com,
	chengzhihao1@...wei.com,
	yukuai3@...wei.com
Subject: [RFC PATCH 2/6] ext4: make ext4_es_lookup_extent() return the next extent if not found

From: Zhang Yi <yi.zhang@...wei.com>

Make ext4_es_lookup_extent() return the next extent entry if we can't
find the extent that lblk belongs to, it's useful to estimate and limit
the length of a potential hole in ext4_map_blocks().

Signed-off-by: Zhang Yi <yi.zhang@...wei.com>
---
 fs/ext4/extents_status.c | 21 ++++++++-------------
 1 file changed, 8 insertions(+), 13 deletions(-)

diff --git a/fs/ext4/extents_status.c b/fs/ext4/extents_status.c
index 1b1b1a8848a8..19a0cc904cd8 100644
--- a/fs/ext4/extents_status.c
+++ b/fs/ext4/extents_status.c
@@ -1012,19 +1012,9 @@ int ext4_es_lookup_extent(struct inode *inode, ext4_lblk_t lblk,
 		goto out;
 	}
 
-	node = tree->root.rb_node;
-	while (node) {
-		es1 = rb_entry(node, struct extent_status, rb_node);
-		if (lblk < es1->es_lblk)
-			node = node->rb_left;
-		else if (lblk > ext4_es_end(es1))
-			node = node->rb_right;
-		else {
-			found = 1;
-			break;
-		}
-	}
-
+	es1 = __es_tree_search(&tree->root, lblk);
+	if (es1 && in_range(lblk, es1->es_lblk, es1->es_len))
+		found = 1;
 out:
 	stats = &EXT4_SB(inode->i_sb)->s_es_stats;
 	if (found) {
@@ -1045,6 +1035,11 @@ int ext4_es_lookup_extent(struct inode *inode, ext4_lblk_t lblk,
 				*next_lblk = 0;
 		}
 	} else {
+		if (es1) {
+			es->es_lblk = es1->es_lblk;
+			es->es_len = es1->es_len;
+			es->es_pblk = es1->es_pblk;
+		}
 		percpu_counter_inc(&stats->es_stats_cache_misses);
 	}
 
-- 
2.39.2