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 0d2242d41ce2f8969aa86e8d3bda731e90abcdda..fa21d818031907530741d152c61203470357bf2a 100644 (file)
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -4788,9 +4788,18 @@ 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;