/*
- * dm-exception-store.c
- *
* Copyright (C) 2001-2002 Sistina Software (UK) Limited.
- * Copyright (C) 2006 Red Hat GmbH
+ * Copyright (C) 2006-2008 Red Hat GmbH
*
* This file is released under the GPL.
*/
#include "dm-exception-store.h"
-#include "dm-snap.h"
#include <linux/mm.h>
#include <linux/pagemap.h>
#include <linux/vmalloc.h>
#include <linux/slab.h>
-#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;
-}
+#include <linux/device-mapper.h>
-static void read_exception(struct pstore *ps,
- uint32_t index, struct disk_exception *result)
-{
- struct disk_exception *e = get_exception(ps, index);
-
- /* copy it */
- result->old_chunk = le64_to_cpu(e->old_chunk);
- result->new_chunk = le64_to_cpu(e->new_chunk);
-}
-
-static void write_exception(struct pstore *ps,
- uint32_t index, struct disk_exception *de)
-{
- struct disk_exception *e = get_exception(ps, index);
-
- /* copy it */
- e->old_chunk = cpu_to_le64(de->old_chunk);
- e->new_chunk = cpu_to_le64(de->new_chunk);
-}
+#define DM_MSG_PREFIX "snapshot exception stores"
-/*
- * 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, int *full)
+int dm_exception_store_init(void)
{
int r;
- unsigned int i;
- struct disk_exception de;
-
- /* presume the area is full */
- *full = 1;
-
- for (i = 0; i < ps->exceptions_per_area; i++) {
- read_exception(ps, i, &de);
-
- /*
- * If the new_chunk is pointing at the start of
- * the COW device, where the first metadata area
- * is we know that we've hit the end of the
- * exceptions. Therefore the area is not full.
- */
- if (de.new_chunk == 0LL) {
- ps->current_committed = i;
- *full = 0;
- break;
- }
-
- /*
- * Keep track of the start of the free chunks.
- */
- if (ps->next_free <= de.new_chunk)
- ps->next_free = de.new_chunk + 1;
-
- /*
- * Otherwise we add the exception to the snapshot.
- */
- r = dm_add_exception(ps->snap, de.old_chunk, de.new_chunk);
- if (r)
- return r;
- }
-
- return 0;
-}
-
-static int read_exceptions(struct pstore *ps)
-{
- int r, full = 1;
-
- /*
- * Keeping reading chunks and inserting exceptions until
- * we find a partially full area.
- */
- for (ps->current_area = 0; full; ps->current_area++) {
- r = area_io(ps, READ);
- if (r)
- return r;
- r = insert_exceptions(ps, &full);
- if (r)
- return r;
+ r = dm_transient_snapshot_init();
+ if (r) {
+ DMERR("Unable to register transient exception store type.");
+ goto transient_fail;
}
- ps->current_area--;
-
- return 0;
-}
-
-static struct pstore *get_info(struct dm_exception_store *store)
-{
- return (struct pstore *) store->context;
-}
-
-static void persistent_fraction_full(struct dm_exception_store *store,
- sector_t *numerator, sector_t *denominator)
-{
- *numerator = get_info(store)->next_free * store->snap->chunk_size;
- *denominator = get_dev_size(store->snap->cow->bdev);
-}
-
-static void persistent_destroy(struct dm_exception_store *store)
-{
- struct pstore *ps = get_info(store);
-
- destroy_workqueue(ps->metadata_wq);
- dm_io_client_destroy(ps->io_client);
- vfree(ps->callbacks);
- free_area(ps);
- kfree(ps);
-}
-
-static int persistent_read_metadata(struct dm_exception_store *store)
-{
- int r, uninitialized_var(new_snapshot);
- struct pstore *ps = get_info(store);
-
- /*
- * Read the snapshot header.
- */
- r = read_header(ps, &new_snapshot);
- if (r)
- return r;
-
- /*
- * Now we know correct chunk_size, complete the initialisation.
- */
- ps->exceptions_per_area = (ps->snap->chunk_size << SECTOR_SHIFT) /
- sizeof(struct disk_exception);
- ps->callbacks = dm_vcalloc(ps->exceptions_per_area,
- sizeof(*ps->callbacks));
- if (!ps->callbacks)
- return -ENOMEM;
-
- /*
- * Do we need to setup a new snapshot ?
- */
- if (new_snapshot) {
- r = write_header(ps);
- if (r) {
- DMWARN("write_header failed");
- return r;
- }
-
- ps->current_area = 0;
- zero_memory_area(ps);
- r = zero_disk_area(ps, 0);
- if (r) {
- DMWARN("zero_disk_area(0) failed");
- return r;
- }
- } else {
- /*
- * Sanity checks.
- */
- if (ps->version != SNAPSHOT_DISK_VERSION) {
- DMWARN("unable to handle snapshot disk version %d",
- ps->version);
- return -EINVAL;
- }
-
- /*
- * Metadata are valid, but snapshot is invalidated
- */
- if (!ps->valid)
- return 1;
-
- /*
- * Read the metadata.
- */
- r = read_exceptions(ps);
- if (r)
- return r;
+ r = dm_persistent_snapshot_init();
+ if (r) {
+ DMERR("Unable to register persistent exception store type");
+ goto persistent_fail;
}
return 0;
-}
-
-static int persistent_prepare(struct dm_exception_store *store,
- struct dm_snap_exception *e)
-{
- struct pstore *ps = get_info(store);
- uint32_t stride;
- chunk_t next_free;
- sector_t size = get_dev_size(store->snap->cow->bdev);
-
- /* Is there enough room ? */
- if (size < ((ps->next_free + 1) * store->snap->chunk_size))
- return -ENOSPC;
- e->new_chunk = ps->next_free;
-
- /*
- * Move onto the next free pending, making sure to take
- * into account the location of the metadata chunks.
- */
- stride = (ps->exceptions_per_area + 1);
- next_free = ++ps->next_free;
- if (sector_div(next_free, stride) == 1)
- ps->next_free++;
-
- atomic_inc(&ps->pending_count);
- return 0;
-}
-
-static void persistent_commit(struct dm_exception_store *store,
- struct dm_snap_exception *e,
- void (*callback) (void *, int success),
- void *callback_context)
-{
- unsigned int i;
- struct pstore *ps = get_info(store);
- struct disk_exception de;
- struct commit_callback *cb;
-
- de.old_chunk = e->old_chunk;
- de.new_chunk = e->new_chunk;
- write_exception(ps, ps->current_committed++, &de);
-
- /*
- * Add the callback to the back of the array. This code
- * is the only place where the callback array is
- * manipulated, and we know that it will never be called
- * multiple times concurrently.
- */
- cb = ps->callbacks + ps->callback_count++;
- cb->callback = callback;
- cb->context = callback_context;
-
- /*
- * If there are exceptions in flight and we have not yet
- * filled this metadata area there's nothing more to do.
- */
- if (!atomic_dec_and_test(&ps->pending_count) &&
- (ps->current_committed != ps->exceptions_per_area))
- return;
-
- /*
- * If we completely filled the current area, then wipe the next one.
- */
- if ((ps->current_committed == ps->exceptions_per_area) &&
- zero_disk_area(ps, ps->current_area + 1))
- ps->valid = 0;
-
- /*
- * Commit exceptions to disk.
- */
- if (ps->valid && area_io(ps, WRITE))
- ps->valid = 0;
-
- /*
- * Advance to the next area if this one is full.
- */
- if (ps->current_committed == ps->exceptions_per_area) {
- ps->current_committed = 0;
- ps->current_area++;
- zero_memory_area(ps);
- }
-
- for (i = 0; i < ps->callback_count; i++) {
- cb = ps->callbacks + i;
- cb->callback(cb->context, ps->valid);
- }
-
- ps->callback_count = 0;
-}
-
-static void persistent_drop(struct dm_exception_store *store)
-{
- struct pstore *ps = get_info(store);
-
- ps->valid = 0;
- if (write_header(ps))
- DMWARN("write header failed");
-}
-
-int dm_create_persistent(struct dm_exception_store *store)
-{
- struct pstore *ps;
-
- /* allocate the pstore */
- ps = kmalloc(sizeof(*ps), GFP_KERNEL);
- if (!ps)
- return -ENOMEM;
-
- ps->snap = store->snap;
- ps->valid = 1;
- ps->version = SNAPSHOT_DISK_VERSION;
- ps->area = NULL;
- ps->next_free = 2; /* skipping the header and first area */
- ps->current_committed = 0;
-
- ps->callback_count = 0;
- atomic_set(&ps->pending_count, 0);
- ps->callbacks = NULL;
-
- ps->metadata_wq = create_singlethread_workqueue("ksnaphd");
- if (!ps->metadata_wq) {
- kfree(ps);
- DMERR("couldn't start header metadata update thread");
- return -ENOMEM;
- }
-
- store->destroy = persistent_destroy;
- store->read_metadata = persistent_read_metadata;
- store->prepare_exception = persistent_prepare;
- store->commit_exception = persistent_commit;
- store->drop_snapshot = persistent_drop;
- store->fraction_full = persistent_fraction_full;
- store->context = ps;
-
- return 0;
-}
-
-/*-----------------------------------------------------------------
- * Implementation of the store for non-persistent snapshots.
- *---------------------------------------------------------------*/
-struct transient_c {
- sector_t next_free;
-};
-
-static void transient_destroy(struct dm_exception_store *store)
-{
- kfree(store->context);
-}
-
-static int transient_read_metadata(struct dm_exception_store *store)
-{
- return 0;
-}
-
-static int transient_prepare(struct dm_exception_store *store,
- struct dm_snap_exception *e)
-{
- struct transient_c *tc = (struct transient_c *) store->context;
- sector_t size = get_dev_size(store->snap->cow->bdev);
-
- if (size < (tc->next_free + store->snap->chunk_size))
- return -1;
-
- e->new_chunk = sector_to_chunk(store->snap, tc->next_free);
- tc->next_free += store->snap->chunk_size;
-
- return 0;
-}
-
-static void transient_commit(struct dm_exception_store *store,
- struct dm_snap_exception *e,
- void (*callback) (void *, int success),
- void *callback_context)
-{
- /* Just succeed */
- callback(callback_context, 1);
-}
-
-static void transient_fraction_full(struct dm_exception_store *store,
- sector_t *numerator, sector_t *denominator)
-{
- *numerator = ((struct transient_c *) store->context)->next_free;
- *denominator = get_dev_size(store->snap->cow->bdev);
+persistent_fail:
+ dm_persistent_snapshot_exit();
+transient_fail:
+ return r;
}
-int dm_create_transient(struct dm_exception_store *store)
+void dm_exception_store_exit(void)
{
- struct transient_c *tc;
-
- store->destroy = transient_destroy;
- store->read_metadata = transient_read_metadata;
- store->prepare_exception = transient_prepare;
- store->commit_exception = transient_commit;
- store->drop_snapshot = NULL;
- store->fraction_full = transient_fraction_full;
-
- tc = kmalloc(sizeof(struct transient_c), GFP_KERNEL);
- if (!tc)
- return -ENOMEM;
-
- tc->next_free = 0;
- store->context = tc;
-
- return 0;
+ dm_persistent_snapshot_exit();
+ dm_transient_snapshot_exit();
}
Code Review / linux-2.6.git / blobdiff