ext4: fix a BUG in mb_mark_used during trim.

[mirror_ubuntu-bionic-kernel.git] / fs / ext4 / mballoc.c

diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
index cdc84953f1d416ae533566929a82df0c70d270b3..a5837a837a8bfea8e835563054c99b6fde0897e4 100644 (file)
--- a/fs/ext4/mballoc.c
+++ b/fs/ext4/mballoc.c
@@ -4870,10 +4870,15 @@ int ext4_trim_fs(struct super_block *sb, struct fstrim_range *range)
                        break;
                }
 
-               if (len >= EXT4_BLOCKS_PER_GROUP(sb))
-                       len -= (EXT4_BLOCKS_PER_GROUP(sb) - first_block);
-               else
+               /*
+                * For all the groups except the last one, last block will
+                * always be EXT4_BLOCKS_PER_GROUP(sb), so we only need to
+                * change it for the last group in which case start +
+                * len < EXT4_BLOCKS_PER_GROUP(sb).
+                */
+               if (first_block + len < EXT4_BLOCKS_PER_GROUP(sb))
                        last_block = first_block + len;
+               len -= last_block - first_block;
 
                if (e4b.bd_info->bb_free >= minlen) {
                        cnt = ext4_trim_all_free(sb, &e4b, first_block,