-#include <linux/dm-io.h>
-#include <linux/dm-kcopyd.h>
-
-#define DM_MSG_PREFIX "snapshots"
-#define DM_CHUNK_SIZE_DEFAULT_SECTORS 32 /* 16KB */
-
-/*-----------------------------------------------------------------
- * 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 0x70416e53
-
-/*
- * The on-disk version of the metadata.
- */
-#define SNAPSHOT_DISK_VERSION 1
-
-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;
-};
-
-struct disk_exception {
- uint64_t old_chunk;
- uint64_t new_chunk;
-};
-
-struct commit_callback {
- void (*callback)(void *, int success);
- void *context;
-};
-
-/*
- * The top level structure for a persistent exception store.
- */
-struct pstore {
- struct dm_snapshot *snap; /* up pointer to my snapshot */
- int version;
- int valid;
- uint32_t exceptions_per_area;
-
- /*
- * Now that we have an asynchronous kcopyd there is no
- * need for large chunk sizes, so it wont hurt to have a
- * whole chunks worth of metadata in memory at once.
- */
- void *area;
-
- /*
- * An area of zeros used to clear the next area.
- */
- void *zero_area;
-
- /*
- * Used to keep track of which metadata area the data in
- * 'chunk' refers to.
- */
- chunk_t current_area;
-
- /*
- * The next free chunk for an exception.
- */
- chunk_t next_free;
-
- /*
- * The index of next free exception in the current
- * metadata area.
- */
- uint32_t current_committed;
-
- atomic_t pending_count;
- uint32_t callback_count;
- struct commit_callback *callbacks;
- struct dm_io_client *io_client;
-
- struct workqueue_struct *metadata_wq;
-};
-
-static unsigned sectors_to_pages(unsigned sectors)
-{
- return DIV_ROUND_UP(sectors, PAGE_SIZE >> 9);
-}
-
-static int alloc_area(struct pstore *ps)
-{
- int r = -ENOMEM;
- size_t len;
-
- len = ps->snap->chunk_size << SECTOR_SHIFT;
-
- /*
- * Allocate the chunk_size block of memory that will hold
- * a single metadata area.
- */
- ps->area = vmalloc(len);
- if (!ps->area)
- return r;
-
- ps->zero_area = vmalloc(len);
- if (!ps->zero_area) {
- vfree(ps->area);
- return r;
- }
- memset(ps->zero_area, 0, len);
-
- return 0;
-}
-
-static void free_area(struct pstore *ps)
-{
- vfree(ps->area);
- ps->area = NULL;
- vfree(ps->zero_area);
- ps->zero_area = NULL;
-}
-
-struct mdata_req {
- struct dm_io_region *where;
- struct dm_io_request *io_req;
- struct work_struct work;
- int result;
-};
-
-static void do_metadata(struct work_struct *work)
-{
- struct mdata_req *req = container_of(work, struct mdata_req, work);
-
- req->result = dm_io(req->io_req, 1, req->where, NULL);
-}
-
-/*
- * Read or write a chunk aligned and sized block of data from a device.
- */
-static int chunk_io(struct pstore *ps, chunk_t chunk, int rw, int metadata)
-{
- struct dm_io_region where = {
- .bdev = ps->snap->cow->bdev,
- .sector = ps->snap->chunk_size * chunk,
- .count = ps->snap->chunk_size,
- };
- struct dm_io_request io_req = {
- .bi_rw = rw,
- .mem.type = DM_IO_VMA,
- .mem.ptr.vma = ps->area,
- .client = ps->io_client,
- .notify.fn = NULL,
- };
- struct mdata_req req;
-
- if (!metadata)
- return dm_io(&io_req, 1, &where, NULL);
-
- req.where = &where;
- req.io_req = &io_req;
-
- /*
- * Issue the synchronous I/O from a different thread
- * to avoid generic_make_request recursion.
- */
- INIT_WORK(&req.work, do_metadata);
- queue_work(ps->metadata_wq, &req.work);
- flush_workqueue(ps->metadata_wq);
-
- return req.result;
-}
-
-/*
- * Convert a metadata area index to a chunk index.
- */
-static chunk_t area_location(struct pstore *ps, chunk_t area)
-{
- return 1 + ((ps->exceptions_per_area + 1) * area);
-}
-
-/*
- * Read or write a metadata area. Remembering to skip the first
- * chunk which holds the header.
- */
-static int area_io(struct pstore *ps, int rw)
-{
- int r;
- chunk_t chunk;
-
- chunk = area_location(ps, ps->current_area);
-
- r = chunk_io(ps, chunk, rw, 0);
- if (r)
- return r;
-
- return 0;
-}
-
-static void zero_memory_area(struct pstore *ps)
-{
- memset(ps->area, 0, ps->snap->chunk_size << SECTOR_SHIFT);
-}
-
-static int zero_disk_area(struct pstore *ps, chunk_t area)
-{
- struct dm_io_region where = {
- .bdev = ps->snap->cow->bdev,
- .sector = ps->snap->chunk_size * area_location(ps, area),
- .count = ps->snap->chunk_size,
- };
- struct dm_io_request io_req = {
- .bi_rw = WRITE,
- .mem.type = DM_IO_VMA,
- .mem.ptr.vma = ps->zero_area,
- .client = ps->io_client,
- .notify.fn = NULL,
- };
-
- return dm_io(&io_req, 1, &where, NULL);
-}
-
-static int read_header(struct pstore *ps, int *new_snapshot)
-{
- int r;
- struct disk_header *dh;
- chunk_t chunk_size;
- int chunk_size_supplied = 1;
-
- /*
- * Use default chunk size (or hardsect_size, if larger) if none supplied
- */
- if (!ps->snap->chunk_size) {
- ps->snap->chunk_size = max(DM_CHUNK_SIZE_DEFAULT_SECTORS,
- bdev_hardsect_size(ps->snap->cow->bdev) >> 9);
- ps->snap->chunk_mask = ps->snap->chunk_size - 1;
- ps->snap->chunk_shift = ffs(ps->snap->chunk_size) - 1;
- chunk_size_supplied = 0;
- }
-
- ps->io_client = dm_io_client_create(sectors_to_pages(ps->snap->
- chunk_size));
- if (IS_ERR(ps->io_client))
- return PTR_ERR(ps->io_client);
-
- r = alloc_area(ps);
- if (r)
- return r;
-
- r = chunk_io(ps, 0, READ, 1);
- if (r)
- goto bad;
-
- dh = (struct disk_header *) ps->area;
-
- if (le32_to_cpu(dh->magic) == 0) {
- *new_snapshot = 1;
- return 0;
- }
-
- if (le32_to_cpu(dh->magic) != SNAP_MAGIC) {
- DMWARN("Invalid or corrupt snapshot");
- r = -ENXIO;
- goto bad;
- }
-
- *new_snapshot = 0;
- ps->valid = le32_to_cpu(dh->valid);
- ps->version = le32_to_cpu(dh->version);
- chunk_size = le32_to_cpu(dh->chunk_size);
-
- if (!chunk_size_supplied || ps->snap->chunk_size == chunk_size)
- return 0;
-
- DMWARN("chunk size %llu in device metadata overrides "
- "table chunk size of %llu.",
- (unsigned long long)chunk_size,
- (unsigned long long)ps->snap->chunk_size);
-
- /* We had a bogus chunk_size. Fix stuff up. */
- free_area(ps);
-
- ps->snap->chunk_size = chunk_size;
- ps->snap->chunk_mask = chunk_size - 1;
- ps->snap->chunk_shift = ffs(chunk_size) - 1;
-
- r = dm_io_client_resize(sectors_to_pages(ps->snap->chunk_size),
- ps->io_client);
- if (r)
- return r;
-
- r = alloc_area(ps);
- return r;
-
-bad:
- free_area(ps);
- return r;
-}
-
-static int write_header(struct pstore *ps)
-{
- struct disk_header *dh;
-
- memset(ps->area, 0, ps->snap->chunk_size << SECTOR_SHIFT);
-
- dh = (struct disk_header *) ps->area;
- dh->magic = cpu_to_le32(SNAP_MAGIC);
- dh->valid = cpu_to_le32(ps->valid);
- dh->version = cpu_to_le32(ps->version);
- dh->chunk_size = cpu_to_le32(ps->snap->chunk_size);
-
- return chunk_io(ps, 0, WRITE, 1);
-}
-
-/*
- * Access functions for the disk exceptions, these do the endian conversions.
- */
-static struct disk_exception *get_exception(struct pstore *ps, uint32_t index)
-{
- BUG_ON(index >= ps->exceptions_per_area);
-
- return ((struct disk_exception *) ps->area) + index;
-}