[PATCH v8] erofs-utils: support calculating checksum of erofs blocks
Chao Yu
yuchao0 at huawei.com
Wed Oct 30 13:39:18 AEDT 2019
On 2019/10/28 22:23, Gao Xiang wrote:
> From: Pratik Shinde <pratikshinde320 at gmail.com>
>
> Added code for calculating crc of erofs blocks (4K size).
> For now it calculates checksum of first block. but it can
> be modified to calculate crc for any no. of blocks.
>
> Note that the first 1024 bytes are not checksumed to allow
> for the installation of x86 boot sectors and other oddities.
>
> Fill 'feature_compat' field of erofs_super_block so that it
> can be used on kernel side. also fixing one typo.
>
> Signed-off-by: Pratik Shinde <pratikshinde320 at gmail.com>
> Signed-off-by: Gao Xiang <gaoxiang25 at huawei.com>
> ---
>
> changes since v7:
> - get rid of `chksum_blocks' pointed out by Chao.
>
>
> include/erofs/internal.h | 1 +
> include/erofs/io.h | 8 +++++
> include/erofs_fs.h | 3 +-
> lib/io.c | 27 ++++++++++++++++
> mkfs/main.c | 68 ++++++++++++++++++++++++++++++++++++++++
> 5 files changed, 106 insertions(+), 1 deletion(-)
>
> diff --git a/include/erofs/internal.h b/include/erofs/internal.h
> index 25ce7b54442d..9e2bb9ce33b6 100644
> --- a/include/erofs/internal.h
> +++ b/include/erofs/internal.h
> @@ -52,6 +52,7 @@ struct erofs_sb_info {
> erofs_blk_t meta_blkaddr;
> erofs_blk_t xattr_blkaddr;
>
> + u32 feature_compat;
> u32 feature_incompat;
> u64 build_time;
> u32 build_time_nsec;
> diff --git a/include/erofs/io.h b/include/erofs/io.h
> index 97750478b5ab..e0ca8d949130 100644
> --- a/include/erofs/io.h
> +++ b/include/erofs/io.h
> @@ -19,6 +19,7 @@
> int dev_open(const char *devname);
> void dev_close(void);
> int dev_write(const void *buf, u64 offset, size_t len);
> +int dev_read(void *buf, u64 offset, size_t len);
> int dev_fillzero(u64 offset, size_t len, bool padding);
> int dev_fsync(void);
> int dev_resize(erofs_blk_t nblocks);
> @@ -31,5 +32,12 @@ static inline int blk_write(const void *buf, erofs_blk_t blkaddr,
> blknr_to_addr(nblocks));
> }
>
> +static inline int blk_read(void *buf, erofs_blk_t start,
> + u32 nblocks)
> +{
> + return dev_read(buf, blknr_to_addr(start),
> + blknr_to_addr(nblocks));
> +}
> +
> #endif
>
> diff --git a/include/erofs_fs.h b/include/erofs_fs.h
> index f29aa2516a99..bcc4f0c630ad 100644
> --- a/include/erofs_fs.h
> +++ b/include/erofs_fs.h
> @@ -13,6 +13,8 @@
> #define EROFS_SUPER_MAGIC_V1 0xE0F5E1E2
> #define EROFS_SUPER_OFFSET 1024
>
> +#define EROFS_FEATURE_COMPAT_SB_CHKSUM 0x00000001
> +
> /*
> * Any bits that aren't in EROFS_ALL_FEATURE_INCOMPAT should
> * be incompatible with this kernel version.
> @@ -39,7 +41,6 @@ struct erofs_super_block {
> __u8 uuid[16]; /* 128-bit uuid for volume */
> __u8 volume_name[16]; /* volume name */
> __le32 feature_incompat;
> -
> __u8 reserved2[44];
> };
>
> diff --git a/lib/io.c b/lib/io.c
> index 7f5f94dd6b1e..52f9424d201b 100644
> --- a/lib/io.c
> +++ b/lib/io.c
> @@ -207,3 +207,30 @@ int dev_resize(unsigned int blocks)
> return dev_fillzero(st.st_size, length, true);
> }
>
> +int dev_read(void *buf, u64 offset, size_t len)
> +{
> + int ret;
> +
> + if (cfg.c_dry_run)
> + return 0;
> +
> + if (!buf) {
> + erofs_err("buf is NULL");
> + return -EINVAL;
> + }
> + if (offset >= erofs_devsz || len > erofs_devsz ||
> + offset > erofs_devsz - len) {
> + erofs_err("read posion[%" PRIu64 ", %zd] is too large beyond"
> + "the end of device(%" PRIu64 ").",
> + offset, len, erofs_devsz);
> + return -EINVAL;
> + }
> +
> + ret = pread64(erofs_devfd, buf, len, (off64_t)offset);
> + if (ret != (int)len) {
> + erofs_err("Failed to read data from device - %s:[%" PRIu64 ", %zd].",
> + erofs_devname, offset, len);
> + return -errno;
Minor thing, I notice caller wrap this errno to EIO, so we'd better print errno
here or by caller? Other part looks good to me anyway.
Reviewed-by: Chao Yu <yuchao0 at huawei.com>
Thanks,
> + }
> + return 0;
> +}
> diff --git a/mkfs/main.c b/mkfs/main.c
> index ab57896e9ca8..eeb6ccc55b82 100644
> --- a/mkfs/main.c
> +++ b/mkfs/main.c
> @@ -109,6 +109,12 @@ static int parse_extended_opts(const char *opts)
> return -EINVAL;
> cfg.c_force_inodeversion = FORCE_INODE_EXTENDED;
> }
> +
> + if (MATCH_EXTENTED_OPT("nosbcrc", token, keylen)) {
> + if (vallen)
> + return -EINVAL;
> + sbi.feature_compat &= ~EROFS_FEATURE_COMPAT_SB_CHKSUM;
> + }
> }
> return 0;
> }
> @@ -218,6 +224,8 @@ int erofs_mkfs_update_super_block(struct erofs_buffer_head *bh,
> .meta_blkaddr = sbi.meta_blkaddr,
> .xattr_blkaddr = sbi.xattr_blkaddr,
> .feature_incompat = cpu_to_le32(sbi.feature_incompat),
> + .feature_compat = cpu_to_le32(sbi.feature_compat &
> + ~EROFS_FEATURE_COMPAT_SB_CHKSUM),
> };
> const unsigned int sb_blksize =
> round_up(EROFS_SUPER_END, EROFS_BLKSIZ);
> @@ -240,6 +248,62 @@ int erofs_mkfs_update_super_block(struct erofs_buffer_head *bh,
> return 0;
> }
>
> +#define CRC32C_POLY_LE 0x82F63B78
> +static inline u32 crc32c(u32 crc, const u8 *in, size_t len)
> +{
> + int i;
> +
> + while (len--) {
> + crc ^= *in++;
> + for (i = 0; i < 8; i++)
> + crc = (crc >> 1) ^ ((crc & 1) ? CRC32C_POLY_LE : 0);
> + }
> + return crc;
> +}
> +
> +static int erofs_superblock_csum_set(void)
> +{
> + int ret;
> + u8 buf[EROFS_BLKSIZ];
> + u32 crc;
> + struct erofs_super_block *sb;
> +
> + ret = blk_read(buf, 0, 1);
> + if (ret) {
> + erofs_err("failed to read superblock to fill checksum");
> + return -EIO;
> + }
> +
> + /*
> + * skip the first 1024 bytes, to allow for the installation
> + * of x86 boot sectors and other oddities.
> + */
> + sb = (struct erofs_super_block *)(buf + EROFS_SUPER_OFFSET);
> +
> + if (le32_to_cpu(sb->magic) != EROFS_SUPER_MAGIC_V1) {
> + erofs_err("internal error: not an erofs valid image");
> + return -EFAULT;
> + }
> +
> + /* turn on checksum feature */
> + sb->feature_compat = cpu_to_le32(le32_to_cpu(sb->feature_compat) |
> + EROFS_FEATURE_COMPAT_SB_CHKSUM);
> + crc = crc32c(~0, (u8 *)sb, EROFS_BLKSIZ - EROFS_SUPER_OFFSET);
> +
> + /* set up checksum field to erofs_super_block */
> + sb->checksum = cpu_to_le32(crc);
> +
> + ret = blk_write(buf, 0, 1);
> + if (ret) {
> + erofs_err("failed to write checksumed superblock: %s",
> + erofs_strerror(ret));
> + return ret;
> + }
> +
> + erofs_info("superblock checksum 0x%08x written", crc);
> + return 0;
> +}
> +
> int main(int argc, char **argv)
> {
> int err = 0;
> @@ -255,6 +319,7 @@ int main(int argc, char **argv)
>
> cfg.c_legacy_compress = false;
> sbi.feature_incompat = EROFS_FEATURE_INCOMPAT_LZ4_0PADDING;
> + sbi.feature_compat = EROFS_FEATURE_COMPAT_SB_CHKSUM;
>
> err = mkfs_parse_options_cfg(argc, argv);
> if (err) {
> @@ -337,6 +402,9 @@ int main(int argc, char **argv)
> err = -EIO;
> else
> err = dev_resize(nblocks);
> +
> + if (!err && (sbi.feature_compat & EROFS_FEATURE_COMPAT_SB_CHKSUM))
> + err = erofs_superblock_csum_set();
> exit:
> z_erofs_compress_exit();
> dev_close();
>
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