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* [PATCH-v4] erofs-utils:code for calculating crc checksum of erofs blocks
@ 2019-10-19  9:58 Pratik Shinde
  0 siblings, 0 replies; only message in thread
From: Pratik Shinde @ 2019-10-19  9:58 UTC (permalink / raw)
  To: linux-erofs, bluce.liguifu, miaoxie, fangwei1

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

Fill 'feature_compat' field of erofs_super_block so that it
can be used on kernel side.
.
Signed-off-by: Pratik Shinde <pratikshinde320@gmail.com>
---
 include/erofs/internal.h |  1 +
 include/erofs/io.h       |  8 ++++++
 include/erofs_fs.h       |  5 ++--
 lib/io.c                 | 27 ++++++++++++++++++
 mkfs/main.c              | 71 ++++++++++++++++++++++++++++++++++++++++++++++++
 5 files changed, 110 insertions(+), 2 deletions(-)

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/include/erofs_fs.h b/include/erofs_fs.h
index f29aa25..9eda6c2 100644
--- a/include/erofs_fs.h
+++ b/include/erofs_fs.h
@@ -19,6 +19,7 @@
  */
 #define EROFS_FEATURE_INCOMPAT_LZ4_0PADDING	0x00000001
 #define EROFS_ALL_FEATURE_INCOMPAT		EROFS_FEATURE_INCOMPAT_LZ4_0PADDING
+#define EROFS_FEATURE_SB_CHKSUM	0x0001
 
 /* 128-byte erofs on-disk super block */
 struct erofs_super_block {
@@ -39,8 +40,8 @@ struct erofs_super_block {
 	__u8 uuid[16];          /* 128-bit uuid for volume */
 	__u8 volume_name[16];   /* volume name */
 	__le32 feature_incompat;
-
-	__u8 reserved2[44];
+	__le32 chksum_blocks;	/* number of blocks used for checksum */
+	__u8 reserved2[40];
 };
 
 /*
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..fa793a9 100644
--- a/mkfs/main.c
+++ b/mkfs/main.c
@@ -22,6 +22,9 @@
 
 #define EROFS_SUPER_END (EROFS_SUPER_OFFSET + sizeof(struct erofs_super_block))
 
+/* number of blocks for calculating checksum */
+#define EROFS_CKSUM_BLOCKS	1
+
 static void usage(void)
 {
 	fprintf(stderr, "usage: [options] FILE DIRECTORY\n\n");
@@ -85,6 +88,10 @@ 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 +187,9 @@ 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),
+		.feature_compat = cpu_to_le32(sb.feature),
+		.checksum = 0,
+		.chksum_blocks = cpu_to_le32(EROFS_CKSUM_BLOCKS)
 	};
 	const unsigned int sb_blksize =
 		round_up(EROFS_SUPER_END, EROFS_BLKSIZ);
@@ -202,6 +212,64 @@ 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) {
+		return err;
+	}
+	*crc = crc32c(0, (const unsigned char *)buf, nblks * EROFS_BLKSIZ);
+	free(buf);
+	return 0;
+}
+
+void erofs_write_sb_checksum()
+{
+	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) {
+		return;
+	}
+
+	sb = (struct erofs_super_block *)((u8 *)buf + EROFS_SUPER_OFFSET);
+	if (le32_to_cpu(sb->magic) != EROFS_SUPER_MAGIC_V1) {
+		return;
+	}
+	sb->checksum = cpu_to_le32(crc);
+	ret = blk_write(buf, 0, 1);
+	if (ret) {
+		return;
+	}
+}
+
 int main(int argc, char **argv)
 {
 	int err = 0;
@@ -217,6 +285,7 @@ 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 +370,8 @@ int main(int argc, char **argv)
 		err = -EIO;
 	else
 		err = dev_resize(nblocks);
+	if (sbi.feature & EROFS_FEATURE_SB_CHKSUM)
+		erofs_write_sb_checksum();
 exit:
 	z_erofs_compress_exit();
 	dev_close();
-- 
2.9.3


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2019-10-19  9:58 [PATCH-v4] erofs-utils:code for calculating crc checksum of erofs blocks Pratik Shinde

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