ext4: force overhead calculation if the s_overhead_cluster makes no sense

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@mit.edu>
Cc: stable@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index 859f508b7873a79413d86a7c4a6cd74e0ae5958c..c13879bd21683f1a356912d8f78e7d0fdb9469d6 100644 (file)
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -4514,9 +4514,18 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent)
         * 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;