diff options
Diffstat (limited to 'drivers/md/dm-exception-store.c')
| -rw-r--r-- | drivers/md/dm-exception-store.c | 749 |
1 files changed, 19 insertions, 730 deletions
diff --git a/drivers/md/dm-exception-store.c b/drivers/md/dm-exception-store.c index 01590f3e0009..dccbfb0e010f 100644 --- a/drivers/md/dm-exception-store.c +++ b/drivers/md/dm-exception-store.c @@ -1,756 +1,45 @@ /* - * 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-snap.h" +#include "dm-exception-store.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; -} -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 exception_store *store) -{ - return (struct pstore *) store->context; -} - -static void persistent_fraction_full(struct 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 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 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 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 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 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 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 exception_store *store) -{ - kfree(store->context); -} - -static int transient_read_metadata(struct exception_store *store) -{ - return 0; -} - -static int transient_prepare(struct 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 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 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 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(); } |