Linux-2.6.12-rc2
Initial git repository build. I'm not bothering with the full history,
even though we have it. We can create a separate "historical" git
archive of that later if we want to, and in the meantime it's about
3.2GB when imported into git - space that would just make the early
git days unnecessarily complicated, when we don't have a lot of good
infrastructure for it.
Let it rip!
diff --git a/drivers/md/dm-exception-store.c b/drivers/md/dm-exception-store.c
new file mode 100644
index 0000000..17212b4
--- /dev/null
+++ b/drivers/md/dm-exception-store.c
@@ -0,0 +1,648 @@
+/*
+ * dm-snapshot.c
+ *
+ * Copyright (C) 2001-2002 Sistina Software (UK) Limited.
+ *
+ * This file is released under the GPL.
+ */
+
+#include "dm.h"
+#include "dm-snap.h"
+#include "dm-io.h"
+#include "kcopyd.h"
+
+#include <linux/mm.h>
+#include <linux/pagemap.h>
+#include <linux/vmalloc.h>
+#include <linux/slab.h>
+
+/*-----------------------------------------------------------------
+ * 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 chunk_size;
+ 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;
+
+ /*
+ * Used to keep track of which metadata area the data in
+ * 'chunk' refers to.
+ */
+ uint32_t current_area;
+
+ /*
+ * The next free chunk for an exception.
+ */
+ uint32_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;
+};
+
+static inline unsigned int sectors_to_pages(unsigned int sectors)
+{
+ return sectors / (PAGE_SIZE >> 9);
+}
+
+static int alloc_area(struct pstore *ps)
+{
+ int r = -ENOMEM;
+ size_t len;
+
+ len = ps->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;
+
+ return 0;
+}
+
+static void free_area(struct pstore *ps)
+{
+ vfree(ps->area);
+}
+
+/*
+ * Read or write a chunk aligned and sized block of data from a device.
+ */
+static int chunk_io(struct pstore *ps, uint32_t chunk, int rw)
+{
+ struct io_region where;
+ unsigned long bits;
+
+ where.bdev = ps->snap->cow->bdev;
+ where.sector = ps->chunk_size * chunk;
+ where.count = ps->chunk_size;
+
+ return dm_io_sync_vm(1, &where, rw, ps->area, &bits);
+}
+
+/*
+ * Read or write a metadata area. Remembering to skip the first
+ * chunk which holds the header.
+ */
+static int area_io(struct pstore *ps, uint32_t area, int rw)
+{
+ int r;
+ uint32_t chunk;
+
+ /* convert a metadata area index to a chunk index */
+ chunk = 1 + ((ps->exceptions_per_area + 1) * area);
+
+ r = chunk_io(ps, chunk, rw);
+ if (r)
+ return r;
+
+ ps->current_area = area;
+ return 0;
+}
+
+static int zero_area(struct pstore *ps, uint32_t area)
+{
+ memset(ps->area, 0, ps->chunk_size << SECTOR_SHIFT);
+ return area_io(ps, area, WRITE);
+}
+
+static int read_header(struct pstore *ps, int *new_snapshot)
+{
+ int r;
+ struct disk_header *dh;
+
+ r = chunk_io(ps, 0, READ);
+ if (r)
+ return r;
+
+ dh = (struct disk_header *) ps->area;
+
+ if (le32_to_cpu(dh->magic) == 0) {
+ *new_snapshot = 1;
+
+ } else if (le32_to_cpu(dh->magic) == SNAP_MAGIC) {
+ *new_snapshot = 0;
+ ps->valid = le32_to_cpu(dh->valid);
+ ps->version = le32_to_cpu(dh->version);
+ ps->chunk_size = le32_to_cpu(dh->chunk_size);
+
+ } else {
+ DMWARN("Invalid/corrupt snapshot");
+ r = -ENXIO;
+ }
+
+ return r;
+}
+
+static int write_header(struct pstore *ps)
+{
+ struct disk_header *dh;
+
+ memset(ps->area, 0, ps->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->chunk_size);
+
+ return chunk_io(ps, 0, WRITE);
+}
+
+/*
+ * Access functions for the disk exceptions, these do the endian conversions.
+ */
+static struct disk_exception *get_exception(struct pstore *ps, uint32_t index)
+{
+ if (index >= ps->exceptions_per_area)
+ return NULL;
+
+ return ((struct disk_exception *) ps->area) + index;
+}
+
+static int read_exception(struct pstore *ps,
+ uint32_t index, struct disk_exception *result)
+{
+ struct disk_exception *e;
+
+ e = get_exception(ps, index);
+ if (!e)
+ return -EINVAL;
+
+ /* copy it */
+ result->old_chunk = le64_to_cpu(e->old_chunk);
+ result->new_chunk = le64_to_cpu(e->new_chunk);
+
+ return 0;
+}
+
+static int write_exception(struct pstore *ps,
+ uint32_t index, struct disk_exception *de)
+{
+ struct disk_exception *e;
+
+ e = get_exception(ps, index);
+ if (!e)
+ return -EINVAL;
+
+ /* copy it */
+ e->old_chunk = cpu_to_le64(de->old_chunk);
+ e->new_chunk = cpu_to_le64(de->new_chunk);
+
+ return 0;
+}
+
+/*
+ * 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 r;
+ unsigned int i;
+ struct disk_exception de;
+
+ /* presume the area is full */
+ *full = 1;
+
+ for (i = 0; i < ps->exceptions_per_area; i++) {
+ r = read_exception(ps, i, &de);
+
+ if (r)
+ return r;
+
+ /*
+ * 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)
+{
+ uint32_t area;
+ int r, full = 1;
+
+ /*
+ * Keeping reading chunks and inserting exceptions until
+ * we find a partially full area.
+ */
+ for (area = 0; full; area++) {
+ r = area_io(ps, area, READ);
+ if (r)
+ return r;
+
+ r = insert_exceptions(ps, &full);
+ if (r)
+ return r;
+ }
+
+ return 0;
+}
+
+static inline 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);
+
+ dm_io_put(sectors_to_pages(ps->chunk_size));
+ vfree(ps->callbacks);
+ free_area(ps);
+ kfree(ps);
+}
+
+static int persistent_read_metadata(struct exception_store *store)
+{
+ int r, new_snapshot;
+ struct pstore *ps = get_info(store);
+
+ /*
+ * Read the snapshot header.
+ */
+ r = read_header(ps, &new_snapshot);
+ if (r)
+ return r;
+
+ /*
+ * Do we need to setup a new snapshot ?
+ */
+ if (new_snapshot) {
+ r = write_header(ps);
+ if (r) {
+ DMWARN("write_header failed");
+ return r;
+ }
+
+ r = zero_area(ps, 0);
+ if (r) {
+ DMWARN("zero_area(0) failed");
+ return r;
+ }
+
+ } else {
+ /*
+ * Sanity checks.
+ */
+ if (!ps->valid) {
+ DMWARN("snapshot is marked invalid");
+ return -EINVAL;
+ }
+
+ if (ps->version != SNAPSHOT_DISK_VERSION) {
+ DMWARN("unable to handle snapshot disk version %d",
+ ps->version);
+ return -EINVAL;
+ }
+
+ /*
+ * Read the metadata.
+ */
+ r = read_exceptions(ps);
+ if (r)
+ return r;
+ }
+
+ return 0;
+}
+
+static int persistent_prepare(struct exception_store *store,
+ struct exception *e)
+{
+ struct pstore *ps = get_info(store);
+ uint32_t stride;
+ 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);
+ if ((++ps->next_free % stride) == 1)
+ ps->next_free++;
+
+ atomic_inc(&ps->pending_count);
+ return 0;
+}
+
+static void persistent_commit(struct exception_store *store,
+ struct exception *e,
+ void (*callback) (void *, int success),
+ void *callback_context)
+{
+ int r;
+ 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 no more exceptions in flight, or we have
+ * filled this metadata area we commit the exceptions to
+ * disk.
+ */
+ if (atomic_dec_and_test(&ps->pending_count) ||
+ (ps->current_committed == ps->exceptions_per_area)) {
+ r = area_io(ps, ps->current_area, WRITE);
+ if (r)
+ ps->valid = 0;
+
+ for (i = 0; i < ps->callback_count; i++) {
+ cb = ps->callbacks + i;
+ cb->callback(cb->context, r == 0 ? 1 : 0);
+ }
+
+ ps->callback_count = 0;
+ }
+
+ /*
+ * Have we completely filled the current area ?
+ */
+ if (ps->current_committed == ps->exceptions_per_area) {
+ ps->current_committed = 0;
+ r = zero_area(ps, ps->current_area + 1);
+ if (r)
+ ps->valid = 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, uint32_t chunk_size)
+{
+ int r;
+ struct pstore *ps;
+
+ r = dm_io_get(sectors_to_pages(chunk_size));
+ if (r)
+ return r;
+
+ /* allocate the pstore */
+ ps = kmalloc(sizeof(*ps), GFP_KERNEL);
+ if (!ps) {
+ r = -ENOMEM;
+ goto bad;
+ }
+
+ ps->snap = store->snap;
+ ps->valid = 1;
+ ps->version = SNAPSHOT_DISK_VERSION;
+ ps->chunk_size = chunk_size;
+ ps->exceptions_per_area = (chunk_size << SECTOR_SHIFT) /
+ sizeof(struct disk_exception);
+ ps->next_free = 2; /* skipping the header and first area */
+ ps->current_committed = 0;
+
+ r = alloc_area(ps);
+ if (r)
+ goto bad;
+
+ /*
+ * Allocate space for all the callbacks.
+ */
+ ps->callback_count = 0;
+ atomic_set(&ps->pending_count, 0);
+ ps->callbacks = dm_vcalloc(ps->exceptions_per_area,
+ sizeof(*ps->callbacks));
+
+ if (!ps->callbacks) {
+ r = -ENOMEM;
+ goto bad;
+ }
+
+ 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;
+
+ bad:
+ dm_io_put(sectors_to_pages(chunk_size));
+ if (ps) {
+ if (ps->area)
+ free_area(ps);
+
+ kfree(ps);
+ }
+ return r;
+}
+
+/*-----------------------------------------------------------------
+ * 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 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 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);
+}
+
+int dm_create_transient(struct exception_store *store,
+ struct dm_snapshot *s, int blocksize)
+{
+ struct transient_c *tc;
+
+ memset(store, 0, sizeof(*store));
+ store->destroy = transient_destroy;
+ store->read_metadata = transient_read_metadata;
+ store->prepare_exception = transient_prepare;
+ store->commit_exception = transient_commit;
+ store->fraction_full = transient_fraction_full;
+ store->snap = s;
+
+ tc = kmalloc(sizeof(struct transient_c), GFP_KERNEL);
+ if (!tc)
+ return -ENOMEM;
+
+ tc->next_free = 0;
+ store->context = tc;
+
+ return 0;
+}
