/* SPDX-License-Identifier: GPL-2.0 */ #ifndef _BCACHEFS_EXTENTS_FORMAT_H #define _BCACHEFS_EXTENTS_FORMAT_H /* * In extent bkeys, the value is a list of pointers (bch_extent_ptr), optionally * preceded by checksum/compression information (bch_extent_crc32 or * bch_extent_crc64). * * One major determining factor in the format of extents is how we handle and * represent extents that have been partially overwritten and thus trimmed: * * If an extent is not checksummed or compressed, when the extent is trimmed we * don't have to remember the extent we originally allocated and wrote: we can * merely adjust ptr->offset to point to the start of the data that is currently * live. The size field in struct bkey records the current (live) size of the * extent, and is also used to mean "size of region on disk that we point to" in * this case. * * Thus an extent that is not checksummed or compressed will consist only of a * list of bch_extent_ptrs, with none of the fields in * bch_extent_crc32/bch_extent_crc64. * * When an extent is checksummed or compressed, it's not possible to read only * the data that is currently live: we have to read the entire extent that was * originally written, and then return only the part of the extent that is * currently live. * * Thus, in addition to the current size of the extent in struct bkey, we need * to store the size of the originally allocated space - this is the * compressed_size and uncompressed_size fields in bch_extent_crc32/64. Also, * when the extent is trimmed, instead of modifying the offset field of the * pointer, we keep a second smaller offset field - "offset into the original * extent of the currently live region". * * The other major determining factor is replication and data migration: * * Each pointer may have its own bch_extent_crc32/64. When doing a replicated * write, we will initially write all the replicas in the same format, with the * same checksum type and compression format - however, when copygc runs later (or * tiering/cache promotion, anything that moves data), it is not in general * going to rewrite all the pointers at once - one of the replicas may be in a * bucket on one device that has very little fragmentation while another lives * in a bucket that has become heavily fragmented, and thus is being rewritten * sooner than the rest. * * Thus it will only move a subset of the pointers (or in the case of * tiering/cache promotion perhaps add a single pointer without dropping any * current pointers), and if the extent has been partially overwritten it must * write only the currently live portion (or copygc would not be able to reduce * fragmentation!) - which necessitates a different bch_extent_crc format for * the new pointer. * * But in the interests of space efficiency, we don't want to store one * bch_extent_crc for each pointer if we don't have to. * * Thus, a bch_extent consists of bch_extent_crc32s, bch_extent_crc64s, and * bch_extent_ptrs appended arbitrarily one after the other. We determine the * type of a given entry with a scheme similar to utf8 (except we're encoding a * type, not a size), encoding the type in the position of the first set bit: * * bch_extent_crc32 - 0b1 * bch_extent_ptr - 0b10 * bch_extent_crc64 - 0b100 * * We do it this way because bch_extent_crc32 is _very_ constrained on bits (and * bch_extent_crc64 is the least constrained). * * Then, each bch_extent_crc32/64 applies to the pointers that follow after it, * until the next bch_extent_crc32/64. * * If there are no bch_extent_crcs preceding a bch_extent_ptr, then that pointer * is neither checksummed nor compressed. */ #define BCH_EXTENT_ENTRY_TYPES() \ x(ptr, 0) \ x(crc32, 1) \ x(crc64, 2) \ x(crc128, 3) \ x(stripe_ptr, 4) \ x(rebalance, 5) #define BCH_EXTENT_ENTRY_MAX 6 enum bch_extent_entry_type { #define x(f, n) BCH_EXTENT_ENTRY_##f = n, BCH_EXTENT_ENTRY_TYPES() #undef x }; /* Compressed/uncompressed size are stored biased by 1: */ struct bch_extent_crc32 { #if defined(__LITTLE_ENDIAN_BITFIELD) __u32 type:2, _compressed_size:7, _uncompressed_size:7, offset:7, _unused:1, csum_type:4, compression_type:4; __u32 csum; #elif defined (__BIG_ENDIAN_BITFIELD) __u32 csum; __u32 compression_type:4, csum_type:4, _unused:1, offset:7, _uncompressed_size:7, _compressed_size:7, type:2; #endif } __packed __aligned(8); #define CRC32_SIZE_MAX (1U << 7) #define CRC32_NONCE_MAX 0 struct bch_extent_crc64 { #if defined(__LITTLE_ENDIAN_BITFIELD) __u64 type:3, _compressed_size:9, _uncompressed_size:9, offset:9, nonce:10, csum_type:4, compression_type:4, csum_hi:16; #elif defined (__BIG_ENDIAN_BITFIELD) __u64 csum_hi:16, compression_type:4, csum_type:4, nonce:10, offset:9, _uncompressed_size:9, _compressed_size:9, type:3; #endif __u64 csum_lo; } __packed __aligned(8); #define CRC64_SIZE_MAX (1U << 9) #define CRC64_NONCE_MAX ((1U << 10) - 1) struct bch_extent_crc128 { #if defined(__LITTLE_ENDIAN_BITFIELD) __u64 type:4, _compressed_size:13, _uncompressed_size:13, offset:13, nonce:13, csum_type:4, compression_type:4; #elif defined (__BIG_ENDIAN_BITFIELD) __u64 compression_type:4, csum_type:4, nonce:13, offset:13, _uncompressed_size:13, _compressed_size:13, type:4; #endif struct bch_csum csum; } __packed __aligned(8); #define CRC128_SIZE_MAX (1U << 13) #define CRC128_NONCE_MAX ((1U << 13) - 1) /* * @reservation - pointer hasn't been written to, just reserved */ struct bch_extent_ptr { #if defined(__LITTLE_ENDIAN_BITFIELD) __u64 type:1, cached:1, unused:1, unwritten:1, offset:44, /* 8 petabytes */ dev:8, gen:8; #elif defined (__BIG_ENDIAN_BITFIELD) __u64 gen:8, dev:8, offset:44, unwritten:1, unused:1, cached:1, type:1; #endif } __packed __aligned(8); struct bch_extent_stripe_ptr { #if defined(__LITTLE_ENDIAN_BITFIELD) __u64 type:5, block:8, redundancy:4, idx:47; #elif defined (__BIG_ENDIAN_BITFIELD) __u64 idx:47, redundancy:4, block:8, type:5; #endif }; struct bch_extent_rebalance { #if defined(__LITTLE_ENDIAN_BITFIELD) __u64 type:6, unused:34, compression:8, /* enum bch_compression_opt */ target:16; #elif defined (__BIG_ENDIAN_BITFIELD) __u64 target:16, compression:8, unused:34, type:6; #endif }; union bch_extent_entry { #if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__ || __BITS_PER_LONG == 64 unsigned long type; #elif __BITS_PER_LONG == 32 struct { unsigned long pad; unsigned long type; }; #else #error edit for your odd byteorder. #endif #define x(f, n) struct bch_extent_##f f; BCH_EXTENT_ENTRY_TYPES() #undef x }; struct bch_btree_ptr { struct bch_val v; __u64 _data[0]; struct bch_extent_ptr start[]; } __packed __aligned(8); struct bch_btree_ptr_v2 { struct bch_val v; __u64 mem_ptr; __le64 seq; __le16 sectors_written; __le16 flags; struct bpos min_key; __u64 _data[0]; struct bch_extent_ptr start[]; } __packed __aligned(8); LE16_BITMASK(BTREE_PTR_RANGE_UPDATED, struct bch_btree_ptr_v2, flags, 0, 1); struct bch_extent { struct bch_val v; __u64 _data[0]; union bch_extent_entry start[]; } __packed __aligned(8); /* Maximum size (in u64s) a single pointer could be: */ #define BKEY_EXTENT_PTR_U64s_MAX\ ((sizeof(struct bch_extent_crc128) + \ sizeof(struct bch_extent_ptr)) / sizeof(__u64)) /* Maximum possible size of an entire extent value: */ #define BKEY_EXTENT_VAL_U64s_MAX \ (1 + BKEY_EXTENT_PTR_U64s_MAX * (BCH_REPLICAS_MAX + 1)) /* * Maximum possible size of an entire extent, key + value: */ #define BKEY_EXTENT_U64s_MAX (BKEY_U64s + BKEY_EXTENT_VAL_U64s_MAX) /* Btree pointers don't carry around checksums: */ #define BKEY_BTREE_PTR_VAL_U64s_MAX \ ((sizeof(struct bch_btree_ptr_v2) + \ sizeof(struct bch_extent_ptr) * BCH_REPLICAS_MAX) / sizeof(__u64)) #define BKEY_BTREE_PTR_U64s_MAX \ (BKEY_U64s + BKEY_BTREE_PTR_VAL_U64s_MAX) struct bch_reservation { struct bch_val v; __le32 generation; __u8 nr_replicas; __u8 pad[3]; } __packed __aligned(8); struct bch_inline_data { struct bch_val v; u8 data[]; }; #endif /* _BCACHEFS_EXTENTS_FORMAT_H */