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 53fd2dbb6e9e91e0223b37609bbcc4333623e9b2..465ca3cfc87e24ee22fbefd347cf9286a6236267 100644 (file)
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -5268,9 +5268,18 @@ 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;