ext4: store checksum seed in superblock
Allow the filesystem to store the metadata checksum seed in the
superblock and add an incompat feature to say that we're using it.
This enables tune2fs to change the UUID on a mounted metadata_csum
FS without having to (racy!) rewrite all disk metadata.
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index 320f10e..cd832b9 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -1184,7 +1184,8 @@
__u8 s_encrypt_pw_salt[16]; /* Salt used for string2key algorithm */
__le32 s_lpf_ino; /* Location of the lost+found inode */
__le32 s_prj_quota_inum; /* inode for tracking project quota */
- __le32 s_reserved[99]; /* Padding to the end of the block */
+ __le32 s_checksum_seed; /* crc32c(uuid) if csum_seed set */
+ __le32 s_reserved[98]; /* Padding to the end of the block */
__le32 s_checksum; /* crc32c(superblock) */
};
@@ -1584,7 +1585,7 @@
#define EXT4_FEATURE_INCOMPAT_FLEX_BG 0x0200
#define EXT4_FEATURE_INCOMPAT_EA_INODE 0x0400 /* EA in inode */
#define EXT4_FEATURE_INCOMPAT_DIRDATA 0x1000 /* data in dirent */
-#define EXT4_FEATURE_INCOMPAT_BG_USE_META_CSUM 0x2000 /* use crc32c for bg */
+#define EXT4_FEATURE_INCOMPAT_CSUM_SEED 0x2000
#define EXT4_FEATURE_INCOMPAT_LARGEDIR 0x4000 /* >2GB or 3-lvl htree */
#define EXT4_FEATURE_INCOMPAT_INLINE_DATA 0x8000 /* data in inode */
#define EXT4_FEATURE_INCOMPAT_ENCRYPT 0x10000
@@ -1613,7 +1614,8 @@
EXT4_FEATURE_INCOMPAT_FLEX_BG| \
EXT4_FEATURE_INCOMPAT_MMP | \
EXT4_FEATURE_INCOMPAT_INLINE_DATA | \
- EXT4_FEATURE_INCOMPAT_ENCRYPT)
+ EXT4_FEATURE_INCOMPAT_ENCRYPT | \
+ EXT4_FEATURE_INCOMPAT_CSUM_SEED)
#define EXT4_FEATURE_RO_COMPAT_SUPP (EXT4_FEATURE_RO_COMPAT_SPARSE_SUPER| \
EXT4_FEATURE_RO_COMPAT_LARGE_FILE| \
EXT4_FEATURE_RO_COMPAT_GDT_CSUM| \
diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index 7ef3fa5..43c0cc8 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -3196,7 +3196,9 @@
}
/* Precompute checksum seed for all metadata */
- if (ext4_has_metadata_csum(sb))
+ if (EXT4_HAS_INCOMPAT_FEATURE(sb, EXT4_FEATURE_INCOMPAT_CSUM_SEED))
+ sbi->s_csum_seed = le32_to_cpu(es->s_checksum_seed);
+ else if (ext4_has_metadata_csum(sb))
sbi->s_csum_seed = ext4_chksum(sbi, ~0, es->s_uuid,
sizeof(es->s_uuid));
diff --git a/fs/ext4/sysfs.c b/fs/ext4/sysfs.c
index 62bef0f..1b57c72 100644
--- a/fs/ext4/sysfs.c
+++ b/fs/ext4/sysfs.c
@@ -224,12 +224,14 @@
EXT4_ATTR_FEATURE(batched_discard);
EXT4_ATTR_FEATURE(meta_bg_resize);
EXT4_ATTR_FEATURE(encryption);
+EXT4_ATTR_FEATURE(metadata_csum_seed);
static struct attribute *ext4_feat_attrs[] = {
ATTR_LIST(lazy_itable_init),
ATTR_LIST(batched_discard),
ATTR_LIST(meta_bg_resize),
ATTR_LIST(encryption),
+ ATTR_LIST(metadata_csum_seed),
NULL,
};