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From:   Wang Jianchao <jianchao.wan9@gmail.com>
Subject: [PATCH V2 5/7] ext4: get buddy cache after insert successfully
To:     Theodore Ts'o <tytso@mit.edu>,
        Andreas Dilger <adilger.kernel@dilger.ca>
Cc:     linux-ext4@vger.kernel.org, linux-kernel@vger.kernel.org,
        lishujin@kuaishou.com
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Message-ID: <93458049-0d43-617a-a5e7-c7e10325443a@gmail.com>
Date:   Wed, 26 May 2021 16:43:43 +0800
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The getting of bd_bitmap_page and bd_buddy_page should be done
after insert the ext4_free_data successfully. Otherwise, nobody
can put them.

Signed-off-by: Wang Jianchao <wangjianchao@kuaishou.com>
---
 fs/ext4/mballoc.c | 20 ++++++++++----------
 1 file changed, 10 insertions(+), 10 deletions(-)

diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
index b23010c..3e8ad43 100644
--- a/fs/ext4/mballoc.c
+++ b/fs/ext4/mballoc.c
@@ -5116,21 +5116,12 @@ static int ext4_insert_free_data( struct ext4_sb_info *sbi,
 	struct ext4_group_info *db = e4b->bd_info;
 	struct super_block *sb = e4b->bd_sb;
 	struct ext4_sb_info *sbi = EXT4_SB(sb);
+	bool first = RB_EMPTY_ROOT(&db->bb_free_root);
 
 	BUG_ON(!ext4_handle_valid(handle));
 	BUG_ON(e4b->bd_bitmap_page == NULL);
 	BUG_ON(e4b->bd_buddy_page == NULL);
 
-	if (!db->bb_free_root.rb_node) {
-		/* first free block exent. We need to
-		   protect buddy cache from being freed,
-		 * otherwise we'll refresh it from
-		 * on-disk bitmap and lose not-yet-available
-		 * blocks */
-		get_page(e4b->bd_buddy_page);
-		get_page(e4b->bd_bitmap_page);
-	}
-
 	if (ext4_insert_free_data(sbi, &db->bb_free_root, nfd)) {
 		ext4_grp_locked_error(sb, e4b->bd_group, 0,
 				ext4_group_first_block_no(sb, e4b->bd_group) +
@@ -5140,6 +5131,15 @@ static int ext4_insert_free_data( struct ext4_sb_info *sbi,
 		return 0;
 	}
 
+	if (first) {
+		/* first free block exent. We need to protect buddy
+		 * cache from being freed, otherwise we'll refresh it
+		 * from on-disk bitmap and lose not-yet-available blocks
+		 */
+		get_page(e4b->bd_buddy_page);
+		get_page(e4b->bd_bitmap_page);
+	}
+
 	spin_lock(&sbi->s_md_lock);
 	list_add_tail(&nfd->efd_list, &sbi->s_freed_data_list);
 	sbi->s_mb_free_pending += nfd->efd_count;
-- 
1.8.3.1