linux-kernel - [PATCH 5.10 80/86] ext4: force overhead calculation if the s_overhead

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Date:   Tue, 26 Apr 2022 10:21:48 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Theodore Tso <tytso@....edu>,
        stable@...nel.org
Subject: [PATCH 5.10 80/86] ext4: force overhead calculation if the s_overhead_cluster makes no sense

From: Theodore Ts'o <tytso@....edu>

commit 85d825dbf4899a69407338bae462a59aa9a37326 upstream.

If the file system does not use bigalloc, calculating the overhead is
cheap, so force the recalculation of the overhead so we don't have to
trust the precalculated overhead in the superblock.

Signed-off-by: Theodore Ts'o <tytso@....edu>
Cc: stable@...nel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 fs/ext4/super.c |   15 ++++++++++++---
 1 file changed, 12 insertions(+), 3 deletions(-)

--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -4933,9 +4933,18 @@ no_journal:
 	 * Get the # of file system overhead blocks from the
 	 * superblock if present.
 	 */
-	if (es->s_overhead_clusters)
-		sbi->s_overhead = le32_to_cpu(es->s_overhead_clusters);
-	else {
+	sbi->s_overhead = le32_to_cpu(es->s_overhead_clusters);
+	/* ignore the precalculated value if it is ridiculous */
+	if (sbi->s_overhead > ext4_blocks_count(es))
+		sbi->s_overhead = 0;
+	/*
+	 * If the bigalloc feature is not enabled recalculating the
+	 * overhead doesn't take long, so we might as well just redo
+	 * it to make sure we are using the correct value.
+	 */
+	if (!ext4_has_feature_bigalloc(sb))
+		sbi->s_overhead = 0;
+	if (sbi->s_overhead == 0) {
 		err = ext4_calculate_overhead(sb);
 		if (err)
 			goto failed_mount_wq;