fs/bcachefs/extents_format.h

1 /* SPDX-License-Identifier: GPL-2.0 */
6  * In extent bkeys, the value is a list of pointers (bch_extent_ptr), optionally
10  * One major determining factor in the format of extents is how we handle and
15  * merely adjust ptr->offset to point to the start of the data that is currently
16  * live. The size field in struct bkey records the current (live) size of the
17  * extent, and is also used to mean "size of region on disk that we point to" in
20  * Thus an extent that is not checksummed or compressed will consist only of a
21  * list of bch_extent_ptrs, with none of the fields in
26  * originally written, and then return only the part of the extent that is
29  * Thus, in addition to the current size of the extent in struct bkey, we need
30  * to store the size of the originally allocated space - this is the
32  * when the extent is trimmed, instead of modifying the offset field of the
33  * pointer, we keep a second smaller offset field - "offset into the original
34  * extent of the currently live region".
40  * same checksum type and compression format - however, when copygc runs later (or
42  * going to rewrite all the pointers at once - one of the replicas may be in a
47  * Thus it will only move a subset of the pointers (or in the case of
51  * fragmentation!) - which necessitates a different bch_extent_crc format for
54  * But in the interests of space efficiency, we don't want to store one
57  * Thus, a bch_extent consists of bch_extent_crc32s, bch_extent_crc64s, and
59  * type of a given entry with a scheme similar to utf8 (except we're encoding a
60  * type, not a size), encoding the type in the position of the first set bit:
62  * bch_extent_crc32	- 0b1
63  * bch_extent_ptr	- 0b10
64  * bch_extent_crc64	- 0b100
78 	x(crc32,		1)		\
81 	x(stripe_ptr,		4)		\
91 /* Compressed/uncompressed size are stored biased by 1: */
98 				_unused:1,
99 				csum_type:4,
100 				compression_type:4;
104 	__u32			compression_type:4,
105 				csum_type:4,
106 				_unused:1,
114 #define CRC32_SIZE_MAX		(1U << 7)
124 				csum_type:4,
125 				compression_type:4,
129 				compression_type:4,
130 				csum_type:4,
140 #define CRC64_SIZE_MAX		(1U << 9)
141 #define CRC64_NONCE_MAX		((1U << 10) - 1)
145 	__u64			type:4,
150 				csum_type:4,
151 				compression_type:4;
153 	__u64			compression_type:4,
154 				csum_type:4,
159 				type:4;
164 #define CRC128_SIZE_MAX		(1U << 13)
165 #define CRC128_NONCE_MAX	((1U << 13) - 1)
168  * @reservation - pointer hasn't been written to, just reserved
172 	__u64			type:1,
173 				cached:1,
174 				unused:1,
175 				unwritten:1,
183 				unwritten:1,
184 				unused:1,
185 				cached:1,
186 				type:1;
194 				redundancy:4,
198 				redundancy:4,
254 LE16_BITMASK(BTREE_PTR_RANGE_UPDATED,	struct bch_btree_ptr_v2, flags, 0, 1);
268 /* Maximum possible size of an entire extent value: */
270 	(1 + BKEY_EXTENT_PTR_U64s_MAX * (BCH_REPLICAS_MAX + 1))
272 /* * Maximum possible size of an entire extent, key + value: */