| // Copyright (C) 2020 The Android Open Source Project |
| // |
| // Licensed under the Apache License, Version 2.0 (the "License"); |
| // you may not use this file except in compliance with the License. |
| // You may obtain a copy of the License at |
| // |
| // http://www.apache.org/licenses/LICENSE-2.0 |
| // |
| // Unless required by applicable law or agreed to in writing, software |
| // distributed under the License is distributed on an "AS IS" BASIS, |
| // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| // See the License for the specific language governing permissions and |
| // limitations under the License. |
| |
| #pragma once |
| |
| namespace android { |
| namespace snapshot { |
| |
| #define DM_USER_REQ_MAP_READ 0 |
| #define DM_USER_REQ_MAP_WRITE 1 |
| |
| #define DM_USER_RESP_SUCCESS 0 |
| #define DM_USER_RESP_ERROR 1 |
| #define DM_USER_RESP_UNSUPPORTED 2 |
| |
| // Kernel COW header fields |
| static constexpr uint32_t SNAP_MAGIC = 0x70416e53; |
| |
| static constexpr uint32_t SNAPSHOT_DISK_VERSION = 1; |
| |
| static constexpr uint32_t NUM_SNAPSHOT_HDR_CHUNKS = 1; |
| |
| static constexpr uint32_t SNAPSHOT_VALID = 1; |
| |
| /* |
| * The basic unit of block I/O is a sector. It is used in a number of contexts |
| * in Linux (blk, bio, genhd). The size of one sector is 512 = 2**9 |
| * bytes. Variables of type sector_t represent an offset or size that is a |
| * multiple of 512 bytes. Hence these two constants. |
| */ |
| static constexpr uint32_t SECTOR_SHIFT = 9; |
| |
| typedef __u64 sector_t; |
| typedef sector_t chunk_t; |
| |
| static constexpr uint32_t CHUNK_SIZE = 8; |
| static constexpr uint32_t CHUNK_SHIFT = (__builtin_ffs(CHUNK_SIZE) - 1); |
| |
| static constexpr uint32_t BLOCK_SIZE = 4096; |
| static constexpr uint32_t BLOCK_SHIFT = (__builtin_ffs(BLOCK_SIZE) - 1); |
| |
| // This structure represents the kernel COW header. |
| // All the below fields should be in Little Endian format. |
| struct disk_header { |
| uint32_t magic; |
| |
| /* |
| * Is this snapshot valid. There is no way of recovering |
| * an invalid snapshot. |
| */ |
| uint32_t valid; |
| |
| /* |
| * Simple, incrementing version. no backward |
| * compatibility. |
| */ |
| uint32_t version; |
| |
| /* In sectors */ |
| uint32_t chunk_size; |
| } __packed; |
| |
| // A disk exception is a mapping of old_chunk to new_chunk |
| // old_chunk is the chunk ID of a dm-snapshot device. |
| // new_chunk is the chunk ID of the COW device. |
| struct disk_exception { |
| uint64_t old_chunk; |
| uint64_t new_chunk; |
| } __packed; |
| |
| // Control structures to communicate with dm-user |
| // It comprises of header and a payload |
| struct dm_user_header { |
| __u64 seq; |
| __u64 type; |
| __u64 flags; |
| __u64 sector; |
| __u64 len; |
| } __attribute__((packed)); |
| |
| struct dm_user_payload { |
| __u8 buf[]; |
| }; |
| |
| // Message comprising both header and payload |
| struct dm_user_message { |
| struct dm_user_header header; |
| struct dm_user_payload payload; |
| }; |
| |
| } // namespace snapshot |
| } // namespace android |