diff options
| -rw-r--r-- | fs/ext4/super.c | 11 |
1 files changed, 11 insertions, 0 deletions
diff --git a/fs/ext4/super.c b/fs/ext4/super.c index 41953b86ffe3..593eb123b3c7 100644 --- a/fs/ext4/super.c +++ b/fs/ext4/super.c @@ -201,7 +201,18 @@ void ext4_superblock_csum_set(struct super_block *sb) if (!ext4_has_metadata_csum(sb)) return; + /* + * Locking the superblock prevents the scenario + * where: + * 1) a first thread pauses during checksum calculation. + * 2) a second thread updates the superblock, recalculates + * the checksum, and updates s_checksum + * 3) the first thread resumes and finishes its checksum calculation + * and updates s_checksum with a potentially stale or torn value. + */ + lock_buffer(EXT4_SB(sb)->s_sbh); es->s_checksum = ext4_superblock_csum(sb, es); + unlock_buffer(EXT4_SB(sb)->s_sbh); } ext4_fsblk_t ext4_block_bitmap(struct super_block *sb, |