ext4: calculate and verify superblock checksum

Calculate and verify the superblock checksum.  Since the UUID and
block group number are embedded in each copy of the superblock, we
need only checksum the entire block.  Refactor some of the code to
eliminate open-coding of the checksum update call.

Signed-off-by: Darrick J. Wong <djwong@us.ibm.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

1 files changed, 10 insertions, 0 deletions

diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index f19192bde094..5adbce519b66 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -1280,6 +1280,9 @@ struct ext4_sb_info {
 
         /* Reference to checksum algorithm driver via cryptoapi */
         struct crypto_shash *s_chksum_driver;
+
+        /* Precomputed FS UUID checksum for seeding other checksums */
+        __u32 s_csum_seed;
 };
 
 static inline struct ext4_sb_info *EXT4_SB(struct super_block *sb)
@@ -2004,6 +2007,10 @@ extern int ext4_group_extend(struct super_block *sb,
 extern int ext4_resize_fs(struct super_block *sb, ext4_fsblk_t n_blocks_count);
 
 /* super.c */
+extern int ext4_superblock_csum_verify(struct super_block *sb,
+                                       struct ext4_super_block *es);
+extern void ext4_superblock_csum_set(struct super_block *sb,
+                                     struct ext4_super_block *es);
 extern void *ext4_kvmalloc(size_t size, gfp_t flags);
 extern void *ext4_kvzalloc(size_t size, gfp_t flags);
 extern void ext4_kvfree(void *ptr);
@@ -2279,6 +2286,9 @@ static inline void ext4_unlock_group(struct super_block *sb,
 
 static inline void ext4_mark_super_dirty(struct super_block *sb)
 {
+        struct ext4_super_block *es = EXT4_SB(sb)->s_es;
+
+        ext4_superblock_csum_set(sb, es);
         if (EXT4_SB(sb)->s_journal == NULL)
                 sb->s_dirt =1;
 }