On Mon, Nov 28, 2022 at 12:16:23PM +0100, Alexander Larsson wrote: > This commit adds the on-disk layout header file of composefs. > > Signed-off-by: Alexander Larsson <alexl@xxxxxxxxxx> > Signed-off-by: Giuseppe Scrivano <gscrivan@xxxxxxxxxx> Add Co-Developed-By: Giuseppe ... ? Full disclosure: I'm not a file system developer but I'll attempt to help with the review of this series. > --- > fs/composefs/cfs.h | 242 +++++++++++++++++++++++++++++++++++++++++++++ > 1 file changed, 242 insertions(+) > create mode 100644 fs/composefs/cfs.h > > diff --git a/fs/composefs/cfs.h b/fs/composefs/cfs.h > new file mode 100644 > index 000000000000..8f001fd28d6b > --- /dev/null > +++ b/fs/composefs/cfs.h > @@ -0,0 +1,242 @@ > +/* SPDX-License-Identifier: GPL-2.0 */ > +/* > + * composefs > + * > + * Copyright (C) 2021 Giuseppe Scrivano > + * Copyright (C) 2022 Alexander Larsson > + * > + * This file is released under the GPL. > + */ > + > +#ifndef _CFS_H > +#define _CFS_H > + > +#include <asm/byteorder.h> > +#include <crypto/sha2.h> > +#include <linux/fs.h> > +#include <linux/stat.h> > +#include <linux/types.h> > + > +#define CFS_VERSION 1 > + > +#define CFS_MAGIC 0xc078629aU > + > +#define CFS_MAX_DIR_CHUNK_SIZE 4096 > +#define CFS_MAX_XATTRS_SIZE 4096 > + > +static inline u16 cfs_u16_to_file(u16 val) > +{ > + return cpu_to_le16(val); > +} > + > +static inline u32 cfs_u32_to_file(u32 val) > +{ > + return cpu_to_le32(val); > +} > + > +static inline u64 cfs_u64_to_file(u64 val) > +{ > + return cpu_to_le64(val); > +} > + > +static inline u16 cfs_u16_from_file(u16 val) > +{ > + return le16_to_cpu(val); > +} > + > +static inline u32 cfs_u32_from_file(u32 val) > +{ > + return le32_to_cpu(val); > +} > + > +static inline u64 cfs_u64_from_file(u64 val) > +{ > + return le64_to_cpu(val); > +} I don't see where the cfs_xxx_{to,from}_file() approach is used in other filesystems. Instead, move the cpu() functions directly into the code. > +static inline int cfs_xdigit_value(char c) > +{ > + if (c >= '0' && c <= '9') > + return c - '0'; > + if (c >= 'A' && c <= 'F') > + return c - 'A' + 10; > + if (c >= 'a' && c <= 'f') > + return c - 'a' + 10; > + return -1; > +} There's some utilities in lib/hexdump.c that you can use. hex_to_bin() will convert a single character and hex2bin() will convert a string for you. > +static inline int cfs_digest_from_payload(const char *payload, > + size_t payload_len, > + u8 digest_out[SHA256_DIGEST_SIZE]) > +{ > + const char *p, *end; > + u8 last_digit = 0; > + int digit = 0; > + size_t n_nibbles = 0; Put in reverse Christmas tree order. > + > + end = payload + payload_len; > + for (p = payload; p != end; p++) { > + /* Skip subdir structure */ > + if (*p == '/') > + continue; > + > + /* Break at (and ignore) extension */ > + if (*p == '.') > + break; A comment would be helpful in this area that shows what the payload is expected to be. > + > + if (n_nibbles == SHA256_DIGEST_SIZE * 2) > + return -1; /* Too long */ return -EINVAL; ? > + > + digit = cfs_xdigit_value(*p); > + if (digit == -1) > + return -1; /* Not hex digit */ -EINVAL here as well > + > + n_nibbles++; > + if ((n_nibbles % 2) == 0) { > + digest_out[n_nibbles / 2 - 1] = > + (last_digit << 4) | digit; > + } > + last_digit = digit; > + } > + > + if (n_nibbles != SHA256_DIGEST_SIZE * 2) > + return -1; /* Too short */ -EINVAL here as well > + > + return 0; > +} > + > +struct cfs_vdata_s { > + u64 off; > + u32 len; > +} __packed; > + > +struct cfs_header_s { > + u8 version; > + u8 unused1; > + u16 unused2; > + > + u32 magic; Should the magic number appear first? > + u64 data_offset; > + u64 root_inode; > + > + u64 unused3[2]; > +} __packed; > + > +enum cfs_inode_flags { > + CFS_INODE_FLAGS_NONE = 0, > + CFS_INODE_FLAGS_PAYLOAD = 1 << 0, > + CFS_INODE_FLAGS_MODE = 1 << 1, > + CFS_INODE_FLAGS_NLINK = 1 << 2, > + CFS_INODE_FLAGS_UIDGID = 1 << 3, > + CFS_INODE_FLAGS_RDEV = 1 << 4, > + CFS_INODE_FLAGS_TIMES = 1 << 5, > + CFS_INODE_FLAGS_TIMES_NSEC = 1 << 6, > + CFS_INODE_FLAGS_LOW_SIZE = 1 << 7, /* Low 32bit of st_size */ > + CFS_INODE_FLAGS_HIGH_SIZE = 1 << 8, /* High 32bit of st_size */ > + CFS_INODE_FLAGS_XATTRS = 1 << 9, > + CFS_INODE_FLAGS_DIGEST = 1 > + << 10, /* fs-verity sha256 digest of content */ Include << 10 on line above Brian