On Sat, Oct 17, 2015 at 09:19:46PM -0400, Theodore Ts'o wrote:
> On Mon, Oct 12, 2015 at 02:54:44PM -0700, Darrick J. Wong wrote:
> > 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@xxxxxxxxxx>
>
> This is what I have in my tree after deconflict with project quota's
> superblock usage.
>
> Cheers,
>
> - Ted
>
>
> commit 8c81bd8f586c46eaf114758a78d82895a2b081c2
> Author: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
> Date: Sat Oct 17 16:16:02 2015 -0400
>
> 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@xxxxxxxxxx>
> Signed-off-by: Theodore Ts'o <tytso@xxxxxxx>
>
> 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 @@ struct ext4_super_block {
> __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 */
I think this is the only change from the previous patch? Looks good to me!
--D
> __le32 s_checksum; /* crc32c(superblock) */
> };
>
> @@ -1584,7 +1585,7 @@ static inline int ext4_encrypted_inode(struct inode *inode)
> #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 @@ static inline int ext4_encrypted_inode(struct inode *inode)
> 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 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent)
> }
>
> /* 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(lazy_itable_init);
> 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,
> };
>
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