Patch "ext4: regenerate buddy after block freeing failed if under fc replay" has been added to the 6.6-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    ext4: regenerate buddy after block freeing failed if under fc replay

to the 6.6-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     ext4-regenerate-buddy-after-block-freeing-failed-if-.patch
and it can be found in the queue-6.6 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit ae7439e69808383d6238d2eb964cef301f6b9646
Author: Baokun Li <libaokun1@xxxxxxxxxx>
Date:   Thu Jan 4 22:20:35 2024 +0800

    ext4: regenerate buddy after block freeing failed if under fc replay
    
    [ Upstream commit c9b528c35795b711331ed36dc3dbee90d5812d4e ]
    
    This mostly reverts commit 6bd97bf273bd ("ext4: remove redundant
    mb_regenerate_buddy()") and reintroduces mb_regenerate_buddy(). Based on
    code in mb_free_blocks(), fast commit replay can end up marking as free
    blocks that are already marked as such. This causes corruption of the
    buddy bitmap so we need to regenerate it in that case.
    
    Reported-by: Jan Kara <jack@xxxxxxx>
    Fixes: 6bd97bf273bd ("ext4: remove redundant mb_regenerate_buddy()")
    Signed-off-by: Baokun Li <libaokun1@xxxxxxxxxx>
    Reviewed-by: Jan Kara <jack@xxxxxxx>
    Link: https://lore.kernel.org/r/20240104142040.2835097-4-libaokun1@xxxxxxxxxx
    Signed-off-by: Theodore Ts'o <tytso@xxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
index 1fd4ed19060d..529ca47da035 100644
--- a/fs/ext4/mballoc.c
+++ b/fs/ext4/mballoc.c
@@ -1232,6 +1232,24 @@ void ext4_mb_generate_buddy(struct super_block *sb,
 	atomic64_add(period, &sbi->s_mb_generation_time);
 }
 
+static void mb_regenerate_buddy(struct ext4_buddy *e4b)
+{
+	int count;
+	int order = 1;
+	void *buddy;
+
+	while ((buddy = mb_find_buddy(e4b, order++, &count)))
+		mb_set_bits(buddy, 0, count);
+
+	e4b->bd_info->bb_fragments = 0;
+	memset(e4b->bd_info->bb_counters, 0,
+		sizeof(*e4b->bd_info->bb_counters) *
+		(e4b->bd_sb->s_blocksize_bits + 2));
+
+	ext4_mb_generate_buddy(e4b->bd_sb, e4b->bd_buddy,
+		e4b->bd_bitmap, e4b->bd_group, e4b->bd_info);
+}
+
 /* The buddy information is attached the buddy cache inode
  * for convenience. The information regarding each group
  * is loaded via ext4_mb_load_buddy. The information involve
@@ -1920,6 +1938,8 @@ static void mb_free_blocks(struct inode *inode, struct ext4_buddy *e4b,
 			ext4_mark_group_bitmap_corrupted(
 				sb, e4b->bd_group,
 				EXT4_GROUP_INFO_BBITMAP_CORRUPT);
+		} else {
+			mb_regenerate_buddy(e4b);
 		}
 		goto done;
 	}