[PATCH-v2] erofs-utils:code for calculating crc checksum of erofs blocks.
Gao Xiang
hsiangkao at aol.com
Tue Oct 15 10:45:17 AEDT 2019
Hi Pratik,
Some nitpick comments... Let me know if you have other thoughts
On Mon, Oct 14, 2019 at 08:29:43PM +0530, Pratik Shinde wrote:
> Added code for calculating crc of erofs blocks (4K size).for now it calculates
> checksum of first block. but can modified to calculate crc for any no. of blocks
>
> modified patch based on review comments.
>
> Signed-off-by: Pratik Shinde <pratikshinde320 at gmail.com>
> ---
> include/erofs/internal.h | 1 +
> include/erofs/io.h | 8 +++++
> lib/io.c | 27 +++++++++++++++++
> mkfs/main.c | 76 ++++++++++++++++++++++++++++++++++++++++++++++++
> 4 files changed, 112 insertions(+)
>
> diff --git a/include/erofs/internal.h b/include/erofs/internal.h
> index 5384946..53335bc 100644
> --- a/include/erofs/internal.h
> +++ b/include/erofs/internal.h
> @@ -55,6 +55,7 @@ struct erofs_sb_info {
> u32 feature_incompat;
> u64 build_time;
> u32 build_time_nsec;
> + u32 feature;
> };
>
> /* global sbi */
> diff --git a/include/erofs/io.h b/include/erofs/io.h
> index 9775047..e0ca8d9 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/lib/io.c b/lib/io.c
> index 7f5f94d..52f9424 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;
> + }
> + return 0;
> +}
> diff --git a/mkfs/main.c b/mkfs/main.c
> index 91a018f..baaf02a 100644
> --- a/mkfs/main.c
> +++ b/mkfs/main.c
> @@ -22,6 +22,10 @@
>
> #define EROFS_SUPER_END (EROFS_SUPER_OFFSET + sizeof(struct erofs_super_block))
>
> +/* number of blocks for calculating checksum */
> +#define EROFS_CKSUM_BLOCKS 1
> +#define EROFS_FEATURE_SB_CHKSUM 0x0001
How about Moving EROFS_FEATURE_SB_CHKSUM to erofs_fs.h since it's
an on-disk definition,
> +
> static void usage(void)
> {
> fprintf(stderr, "usage: [options] FILE DIRECTORY\n\n");
> @@ -85,6 +89,10 @@ static int parse_extended_opts(const char *opts)
> return -EINVAL;
> cfg.c_force_inodeversion = FORCE_INODE_EXTENDED;
> }
> +
> + if (MATCH_EXTENTED_OPT("nocrc", token, keylen)) {
> + sbi.feature &= ~EROFS_FEATURE_SB_CHKSUM;
> + }
> }
> return 0;
> }
> @@ -180,6 +188,7 @@ int erofs_mkfs_update_super_block(struct erofs_buffer_head *bh,
> .meta_blkaddr = sbi.meta_blkaddr,
> .xattr_blkaddr = 0,
> .feature_incompat = cpu_to_le32(sbi.feature_incompat),
> + .checksum = 0
> };
> const unsigned int sb_blksize =
> round_up(EROFS_SUPER_END, EROFS_BLKSIZ);
> @@ -202,6 +211,70 @@ int erofs_mkfs_update_super_block(struct erofs_buffer_head *bh,
> return 0;
> }
>
> +#define CRCPOLY 0x82F63B78
> +static inline u32 crc32c(u32 seed, unsigned char const *in, size_t len)
> +{
> + int i;
> + u32 crc = seed;
> +
> + while (len--) {
> + crc ^= *in++;
> + for (i = 0; i < 8; i++) {
> + crc = (crc >> 1) ^ ((crc & 1) ? CRCPOLY : 0);
> + }
> + }
> + return crc;
> +}
> +
> +/* calculate checksum for first n blocks */
> +u32 erofs_calc_blk_checksum(erofs_blk_t nblks, u32 *crc)
> +{
> + char *buf;
> + int err = 0;
> +
> + buf = malloc(nblks * EROFS_BLKSIZ);
> + err = blk_read(buf, 0, nblks);
> + if (err) {
> + erofs_err("Failed to calculate erofs checksum - %s",
> + erofs_strerror(err));
> + return err;
> + }
> + *crc = crc32c(0, (const unsigned char *)buf, nblks * EROFS_BLKSIZ);
> + free(buf);
> + return 0;
> +}
> +
> +void erofs_write_checksum()
How about naming write_sb_checksum?
My idea is that this is a checksum in super block (rather than
a checksum only for super block [0th block])
Let me know if you have another thought...
> +{
> + struct erofs_super_block *sb;
> + char buf[EROFS_BLKSIZ];
> + int ret = 0;
> + u32 crc;
> +
> + ret = erofs_calc_blk_checksum(EROFS_CKSUM_BLOCKS, &crc);
> + if (ret) {
> + return;
> + }
> + ret = blk_read(buf, 0, 1);
> + if (ret) {
> + erofs_err("error reading super-block structure");
> + return;
> + }
> +
> + sb = (struct erofs_super_block *)((u8 *)buf + EROFS_SUPER_OFFSET);
> + if (le32_to_cpu(sb->magic) != EROFS_SUPER_MAGIC_V1) {
> + erofs_err("not an erofs image");
As the previous comments, I am little care about these print messages
since users will only see this and "error reading super-block structure"
"not an erofs image" makes confused for them... (They don't know what
the internal process is doing)
BTW, it looks good to me as a whole... Do you have some time on
kernel side as well? :)
Thanks,
Gao Xiang
> + return;
> + }
> + sb->checksum = cpu_to_le32(crc);
> + ret = blk_write(buf, 0, 1);
> + if (ret) {
> + erofs_err("error writing 0th block to disk - %s",
> + erofs_strerror(ret));
> + return;
> + }
> +}
> +
> int main(int argc, char **argv)
> {
> int err = 0;
> @@ -217,6 +290,7 @@ int main(int argc, char **argv)
>
> cfg.c_legacy_compress = false;
> sbi.feature_incompat = EROFS_FEATURE_INCOMPAT_LZ4_0PADDING;
> + sbi.feature = EROFS_FEATURE_SB_CHKSUM;
>
> err = mkfs_parse_options_cfg(argc, argv);
> if (err) {
> @@ -301,6 +375,8 @@ int main(int argc, char **argv)
> err = -EIO;
> else
> err = dev_resize(nblocks);
> + if (sbi.feature & EROFS_FEATURE_SB_CHKSUM)
> + erofs_write_checksum();
> exit:
> z_erofs_compress_exit();
> dev_close();
> --
> 2.9.3
>
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