FAILED: patch "[PATCH] ext4: avoid bb_free and bb_fragments inconsistency in" failed to apply to 5.4-stable tree

The patch below does not apply to the 5.4-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-5.4.y
git checkout FETCH_HEAD
git cherry-pick -x 2331fd4a49864e1571b4f50aa3aa1536ed6220d0
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2024021910-handbrake-gave-712f@gregkh' --subject-prefix 'PATCH 5.4.y' HEAD^..

Possible dependencies:

2331fd4a4986 ("ext4: avoid bb_free and bb_fragments inconsistency in mb_free_blocks()") c9b528c35795 ("ext4: regenerate buddy after block freeing failed if under fc replay") 196e402adf2e ("ext4: improve cr 0 / cr 1 group scanning")
4b68f6df1059 ("ext4: add MB_NUM_ORDERS macro")
a6c75eaf1103 ("ext4: add mballoc stats proc file")
b237e3044450 ("ext4: add ability to return parsed options from parse_options") 67d251860461 ("ext4: drop s_mb_bal_lock and convert protected fields to atomic") 6bd97bf273bd ("ext4: remove redundant mb_regenerate_buddy()") a72b38eebea4 ("ext4: handle dax mount option collision")
99c880decf27 ("ext4: cleanup fast commit mount options")
0f0672ffb61a ("ext4: add a mount opt to forcefully turn fast commits on") 8016e29f4362 ("ext4: fast commit recovery path")
5b849b5f96b4 ("jbd2: fast commit recovery path")
aa75f4d3daae ("ext4: main fast-commit commit path")
ff780b91efe9 ("jbd2: add fast commit machinery")
6866d7b3f2bb ("ext4 / jbd2: add fast commit initialization")
995a3ed67fc8 ("ext4: add fast_commit feature and handling for extended mount options") 2d069c0889ef ("ext4: use common helpers in all places reading metadata buffers") d9befedaafcf ("ext4: clear buffer verified flag if read meta block from disk") 15ed2851b0f4 ("ext4: remove unused argument from ext4_(inc|dec)_count")

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 2331fd4a49864e1571b4f50aa3aa1536ed6220d0 Mon Sep 17 00:00:00 2001
From: Baokun Li <[email protected]>
Date: Thu, 4 Jan 2024 22:20:36 +0800
Subject: [PATCH] ext4: avoid bb_free and bb_fragments inconsistency in
mb_free_blocks()

After updating bb_free in mb_free_blocks, it is possible to return without updating bb_fragments because the block being freed is found to have already been freed, which leads to inconsistency between bb_free and bb_fragments.

Since the group may be unlocked in ext4_grp_locked_error(), this can lead to problems such as dividing by zero when calculating the average fragment length. Hence move the update of bb_free to after the block double-free check guarantees that the corresponding statistics are updated only after the core block bitmap is modified.

index c97ad0e77831..fa351aa323dc 100644
@@ -1909,11 +1909,6 @@ static void mb_free_blocks(struct inode *inode, struct ext4_buddy *e4b,
 	mb_check_buddy(e4b);
 	mb_free_blocks_double(inode, e4b, first, count);
 
-	this_cpu_inc(discard_pa_seq);
-	e4b->bd_info->bb_free += count;
-	if (first < e4b->bd_info->bb_first_free)
-		e4b->bd_info->bb_first_free = first;
-
 	/* access memory sequentially: check left neighbour,
 	 * clear range and then check right neighbour
 	 */

@@ -1927,23 +1922,31 @@ static void mb_free_blocks(struct inode *inode, struct ext4_buddy *e4b,
 		struct ext4_sb_info *sbi = EXT4_SB(sb);
 		ext4_fsblk_t blocknr;
 
+		/*
+		 * Fastcommit replay can free already freed blocks which
+		 * corrupts allocation info. Regenerate it.
+		 */
+		if (sbi->s_mount_state & EXT4_FC_REPLAY) {
+			mb_regenerate_buddy(e4b);
+			goto check;
+		}
+
 		blocknr = ext4_group_first_block_no(sb, e4b->bd_group);
 		blocknr += EXT4_C2B(sbi, block);
-		if (!(sbi->s_mount_state & EXT4_FC_REPLAY)) {
-			ext4_grp_locked_error(sb, e4b->bd_group,
-					      inode ? inode->i_ino : 0,
-					      blocknr,
-					      "freeing already freed block (bit %u); block bitmap corrupt.",
-					      block);
-			ext4_mark_group_bitmap_corrupted(
-				sb, e4b->bd_group,
+		ext4_grp_locked_error(sb, e4b->bd_group,
+				      inode ? inode->i_ino : 0, blocknr,
+				      "freeing already freed block (bit %u); block bitmap corrupt.",
+				      block);
+		ext4_mark_group_bitmap_corrupted(sb, e4b->bd_group,
 				EXT4_GROUP_INFO_BBITMAP_CORRUPT);
-		} else {
-			mb_regenerate_buddy(e4b);
-		}
-		goto done;
+		return;
 	}
 
+	this_cpu_inc(discard_pa_seq);
+	e4b->bd_info->bb_free += count;
+	if (first < e4b->bd_info->bb_first_free)
+		e4b->bd_info->bb_first_free = first;
+
 	/* let's maintain fragments counter */
 	if (left_is_free && right_is_free)
 		e4b->bd_info->bb_fragments--;

@@ -1968,9 +1971,9 @@ static void mb_free_blocks(struct inode *inode, struct ext4_buddy *e4b,
 	if (first <= last)
 		mb_buddy_mark_free(e4b, first >> 1, last >> 1);
 
-done:
 	mb_set_largest_free_order(sb, e4b->bd_info);
 	mb_update_avg_fragment_size(sb, e4b->bd_info);
+check:
 	mb_check_buddy(e4b);
 }