// SPDX-License-Identifier: GPL-2.0-only /* * Copyright (C) 2001-2002 Sistina Software (UK) Limited. * Copyright (C) 2006-2008 Red Hat GmbH * * This file is released under the GPL. */ #include "dm-exception-store.h" #include <linux/ctype.h> #include <linux/mm.h> #include <linux/pagemap.h> #include <linux/vmalloc.h> #include <linux/export.h> #include <linux/slab.h> #include <linux/dm-io.h> #include <linux/dm-bufio.h> #define DM_MSG_PREFIX … #define DM_CHUNK_SIZE_DEFAULT_SECTORS … #define DM_PREFETCH_CHUNKS … /* *--------------------------------------------------------------- * Persistent snapshots, by persistent we mean that the snapshot * will survive a reboot. *--------------------------------------------------------------- */ /* * We need to store a record of which parts of the origin have * been copied to the snapshot device. The snapshot code * requires that we copy exception chunks to chunk aligned areas * of the COW store. It makes sense therefore, to store the * metadata in chunk size blocks. * * There is no backward or forward compatibility implemented, * snapshots with different disk versions than the kernel will * not be usable. It is expected that "lvcreate" will blank out * the start of a fresh COW device before calling the snapshot * constructor. * * The first chunk of the COW device just contains the header. * After this there is a chunk filled with exception metadata, * followed by as many exception chunks as can fit in the * metadata areas. * * All on disk structures are in little-endian format. The end * of the exceptions info is indicated by an exception with a * new_chunk of 0, which is invalid since it would point to the * header chunk. */ /* * Magic for persistent snapshots: "SnAp" - Feeble isn't it. */ #define SNAP_MAGIC … /* * The on-disk version of the metadata. */ #define SNAPSHOT_DISK_VERSION … #define NUM_SNAPSHOT_HDR_CHUNKS … struct disk_header { … } __packed; struct disk_exception { … } __packed; struct core_exception { … }; struct commit_callback { … }; /* * The top level structure for a persistent exception store. */ struct pstore { … }; static int alloc_area(struct pstore *ps) { … } static void free_area(struct pstore *ps) { … } struct mdata_req { … }; static void do_metadata(struct work_struct *work) { … } /* * Read or write a chunk aligned and sized block of data from a device. */ static int chunk_io(struct pstore *ps, void *area, chunk_t chunk, blk_opf_t opf, int metadata) { … } /* * Convert a metadata area index to a chunk index. */ static chunk_t area_location(struct pstore *ps, chunk_t area) { … } static void skip_metadata(struct pstore *ps) { … } /* * Read or write a metadata area. Remembering to skip the first * chunk which holds the header. */ static int area_io(struct pstore *ps, blk_opf_t opf) { … } static void zero_memory_area(struct pstore *ps) { … } static int zero_disk_area(struct pstore *ps, chunk_t area) { … } static int read_header(struct pstore *ps, int *new_snapshot) { … } static int write_header(struct pstore *ps) { … } /* * Access functions for the disk exceptions, these do the endian conversions. */ static struct disk_exception *get_exception(struct pstore *ps, void *ps_area, uint32_t index) { … } static void read_exception(struct pstore *ps, void *ps_area, uint32_t index, struct core_exception *result) { … } static void write_exception(struct pstore *ps, uint32_t index, struct core_exception *e) { … } static void clear_exception(struct pstore *ps, uint32_t index) { … } /* * Registers the exceptions that are present in the current area. * 'full' is filled in to indicate if the area has been * filled. */ static int insert_exceptions(struct pstore *ps, void *ps_area, int (*callback)(void *callback_context, chunk_t old, chunk_t new), void *callback_context, int *full) { … } static int read_exceptions(struct pstore *ps, int (*callback)(void *callback_context, chunk_t old, chunk_t new), void *callback_context) { … } static struct pstore *get_info(struct dm_exception_store *store) { … } static void persistent_usage(struct dm_exception_store *store, sector_t *total_sectors, sector_t *sectors_allocated, sector_t *metadata_sectors) { … } static void persistent_dtr(struct dm_exception_store *store) { … } static int persistent_read_metadata(struct dm_exception_store *store, int (*callback)(void *callback_context, chunk_t old, chunk_t new), void *callback_context) { … } static int persistent_prepare_exception(struct dm_exception_store *store, struct dm_exception *e) { … } static void persistent_commit_exception(struct dm_exception_store *store, struct dm_exception *e, int valid, void (*callback)(void *, int success), void *callback_context) { … } static int persistent_prepare_merge(struct dm_exception_store *store, chunk_t *last_old_chunk, chunk_t *last_new_chunk) { … } static int persistent_commit_merge(struct dm_exception_store *store, int nr_merged) { … } static void persistent_drop_snapshot(struct dm_exception_store *store) { … } static int persistent_ctr(struct dm_exception_store *store, char *options) { … } static unsigned int persistent_status(struct dm_exception_store *store, status_type_t status, char *result, unsigned int maxlen) { … } static struct dm_exception_store_type _persistent_type = …; static struct dm_exception_store_type _persistent_compat_type = …; int dm_persistent_snapshot_init(void) { … } void dm_persistent_snapshot_exit(void) { … }
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