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Go Back   Linux Archive > Redhat > Device-mapper Development

 
 
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Old 03-01-2010, 11:23 PM
Mike Snitzer
 
Default dm-multisnap-daniel

From: Mikulas Patocka <mpatocka@redhat.com>

An implementation of snapshot store.
Designed by Daniel Phillips, ported to kernelspace by Fujita Tomonorig.

This implementation plugs as a module into dm-multisnapshot interface.

The interface is almost the same as in Mikulas' exception store. You have to
specify "daniel" instead of "mikulas" as a type of exception store.
The only supported chunk size is 16384 bytes (but the code is general enough and
this restriction may be removed in the future).

Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
---
drivers/md/Kconfig | 14 +
drivers/md/Makefile | 2 +
drivers/md/dm-multisnap-daniel.c | 1711 ++++++++++++++++++++++++++++++++++++++
3 files changed, 1727 insertions(+), 0 deletions(-)
create mode 100644 drivers/md/dm-multisnap-daniel.c

diff --git a/drivers/md/Kconfig b/drivers/md/Kconfig
index 0c3ce3b..c30bf70 100644
--- a/drivers/md/Kconfig
+++ b/drivers/md/Kconfig
@@ -268,6 +268,20 @@ config DM_MULTISNAPSHOT_MIKULAS
A B+-tree-based log-structured storage allowing unlimited
number of snapshots.

+config DM_MULTISNAPSHOT_DANIEL
+ tristate "Daniel's snapshot store"
+ depends on DM_MULTISNAPSHOT
+ ---help---
+ Daniel Philips' exception store. The data structures were
+ designed by Daniel Phillips for Zumastore project, a porting
+ to kernel space was done by Fujita Tomonorig.
+
+ This store has limit of at most 64 snapshots and supports
+ snapshot deletion.
+
+ So far it doesn't support maintaining consistency across
+ crashes; journaling is under development.
+
config DM_MIRROR
tristate "Mirror target"
depends on BLK_DEV_DM
diff --git a/drivers/md/Makefile b/drivers/md/Makefile
index 084d632..836cd95 100644
--- a/drivers/md/Makefile
+++ b/drivers/md/Makefile
@@ -13,6 +13,7 @@ dm-store-mikulas-y += dm-multisnap-mikulas.o dm-multisnap-alloc.o
dm-multisnap-commit.o dm-multisnap-delete.o
dm-multisnap-freelist.o dm-multisnap-io.o
dm-multisnap-snaps.o dm-bufio.o
+dm-store-daniel-y += dm-multisnap-daniel.o
dm-mirror-y += dm-raid1.o
dm-log-userspace-y
+= dm-log-userspace-base.o dm-log-userspace-transfer.o
@@ -49,6 +50,7 @@ obj-$(CONFIG_DM_MULTIPATH_ST) += dm-service-time.o
obj-$(CONFIG_DM_SNAPSHOT) += dm-snapshot.o
obj-$(CONFIG_DM_MULTISNAPSHOT) += dm-multisnapshot.o
obj-$(CONFIG_DM_MULTISNAPSHOT_MIKULAS) += dm-store-mikulas.o
+obj-$(CONFIG_DM_MULTISNAPSHOT_DANIEL) += dm-store-daniel.o
obj-$(CONFIG_DM_MIRROR) += dm-mirror.o dm-log.o dm-region-hash.o
obj-$(CONFIG_DM_LOG_USERSPACE) += dm-log-userspace.o
obj-$(CONFIG_DM_ZERO) += dm-zero.o
diff --git a/drivers/md/dm-multisnap-daniel.c b/drivers/md/dm-multisnap-daniel.c
new file mode 100644
index 0000000..00fd3c0
--- /dev/null
+++ b/drivers/md/dm-multisnap-daniel.c
@@ -0,0 +1,1711 @@
+/*
+ * dm-exception-store.c
+ *
+ * Copyright (C) 2001-2002 Sistina Software (UK) Limited.
+ * Copyright (C) 2006 Red Hat GmbH
+ *
+ * The shared exception code is based on Zumastor (http://zumastor.org/)
+ *
+ * By: Daniel Phillips, Nov 2003 to Mar 2007
+ * (c) 2003, Sistina Software Inc.
+ * (c) 2004, Red Hat Software Inc.
+ * (c) 2005 Daniel Phillips
+ * (c) 2006 - 2007, Google Inc
+ *
+ * This file is released under the GPL.
+ */
+
+#include "dm-multisnap.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_CHUNK_SIZE_DEFAULT_SECTORS 32 /* 16KB */
+
+#define MAX_SNAPSHOTS 64
+
+#define MAX_CHUNK_BUFFERS 128
+
+/*-----------------------------------------------------------------
+ * 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
+
+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;
+
+ /*
+ * for shared exception
+ */
+ __le64 root_tree_chunk;
+ __le64 snapmask; /* Mikulas: don't mix bit_test/set w.r.t. direct reading, it's unportable */
+ __le32 tree_level;
+ __le32 h_nr_journal_chunks;
+};
+
+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 dm_exception_store {
+ struct dm_multisnap *dm;
+
+ void *area;
+
+ struct dm_io_client *io_client;
+
+ unsigned chunk_size;
+ unsigned char chunk_shift;
+
+ int version;
+
+ /*
+ * for shared exception
+ */
+ u64 root_tree_chunk;
+ u64 snapmask;
+ u32 tree_level;
+
+ u32 nr_snapshots;
+
+ chunk_t nr_chunks;
+ chunk_t nr_bitmap_chunks;
+ chunk_t nr_journal_chunks;
+ unsigned long *bitmap;
+ chunk_t cur_bitmap_chunk;
+ chunk_t cur_bitmap_index;
+ chunk_t cur_journal_chunk;
+
+ struct list_head chunk_buffer_list;
+ struct list_head chunk_buffer_dirty_list;
+
+ int header_dirty;
+ int nr_chunk_buffers;
+
+ chunk_t chunk_to_add;
+};
+
+static unsigned sectors_to_pages(unsigned sectors)
+{
+ return DIV_ROUND_UP(sectors, PAGE_SIZE >> 9);
+}
+
+static int alloc_area(struct dm_exception_store *ps)
+{
+ int r = -ENOMEM;
+ size_t len;
+
+ len = ps->chunk_size;
+
+ /*
+ * 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 dm_exception_store *ps)
+{
+ vfree(ps->area);
+ ps->area = NULL;
+}
+
+/*
+ * Read or write a chunk aligned and sized block of data from a device.
+ */
+static int chunk_io(struct dm_exception_store *ps, chunk_t chunk, int rw, void *data)
+{
+ struct dm_io_region where = {
+ .bdev = dm_multisnap_snapshot_bdev(ps->dm),
+ .sector = (ps->chunk_size >> SECTOR_SHIFT) * chunk,
+ .count = (ps->chunk_size >> SECTOR_SHIFT),
+ };
+ struct dm_io_request io_req = {
+ .bi_rw = rw,
+ .mem.type = DM_IO_VMA,
+ .mem.ptr.vma = data,
+ .client = ps->io_client,
+ .notify.fn = NULL,
+ };
+
+ int r = dm_io(&io_req, 1, &where, NULL);
+ if (r) {
+ DM_MULTISNAP_SET_ERROR(ps->dm, r, ("io error when %s %llx: %d",
+ rw == WRITE ? "writing" : "reading",
+ (unsigned long long)chunk, r));
+ }
+ return r;
+}
+
+static int write_header(struct dm_exception_store *ps)
+{
+ struct disk_header *dh;
+
+ memset(ps->area, 0, ps->chunk_size);
+
+ dh = (struct disk_header *) ps->area;
+ dh->magic = cpu_to_le32(SNAP_MAGIC);
+ dh->valid = cpu_to_le32(dm_multisnap_drop_on_error(ps->dm) && dm_multisnap_has_error(ps->dm));
+ dh->version = cpu_to_le32(ps->version);
+ dh->chunk_size = cpu_to_le32(ps->chunk_size >> SECTOR_SHIFT);
+
+ dh->root_tree_chunk = cpu_to_le64(ps->root_tree_chunk);
+ dh->snapmask = cpu_to_le64(ps->snapmask);
+ dh->tree_level = cpu_to_le32(ps->tree_level);
+ dh->h_nr_journal_chunks = cpu_to_le32(ps->nr_journal_chunks);
+
+ ps->header_dirty = 0;
+
+ return chunk_io(ps, 0, WRITE, ps->area);
+}
+
+/*
+ * shared exception code
+ */
+
+#define SNAP_MAGIC 0x70416e53
+#define FIRST_BITMAP_CHUNK 1
+
+struct chunk_buffer {
+ struct list_head list;
+ struct list_head dirty_list;
+ u64 chunk;
+ void *data;
+};
+
+struct node {
+ __le32 count;
+ __le32 unused;
+ struct index_entry {
+ __le64 key; /* note: entries[0].key never accessed */
+ __le64 chunk; /* node sector address goes here */
+ } entries[];
+};
+
+struct leaf {
+ __le16 magic;
+ __le16 version;
+ __le32 count;
+ /* !!! FIXME the code doesn't use the base_chunk properly */
+ __le64 base_chunk;
+ __le64 using_mask;
+
+ struct tree_map {
+ __le32 offset;
+ __le32 rchunk;
+ } map[];
+};
+
+struct exception {
+ __le64 share;
+ __le64 chunk;
+};
+
+static inline struct node *buffer2node(struct chunk_buffer *buffer)
+{
+ return (struct node *)buffer->data;
+}
+
+static inline struct leaf *buffer2leaf(struct chunk_buffer *buffer)
+{
+ return (struct leaf *)buffer->data;
+}
+
+static struct chunk_buffer *alloc_chunk_buffer(struct dm_exception_store *ps)
+{
+ struct chunk_buffer *b;
+
+ /* Mikulas: changed to GFP_NOIO */
+ b = kzalloc(sizeof(*b), GFP_NOIO);
+ if (!b) {
+ DM_MULTISNAP_SET_ERROR(ps->dm, -ENOMEM,
+ ("%s %d: out of memory", __func__, __LINE__));
+ return NULL;
+ }
+
+ /* Mikulas: must use GFP_NOIO; vmalloc without it may deadlock */
+ b->data = __vmalloc(ps->chunk_size, GFP_NOIO | __GFP_HIGHMEM, PAGE_KERNEL);
+ if (!b->data) {
+ kfree(b);
+ DM_MULTISNAP_SET_ERROR(ps->dm, -ENOMEM,
+ ("%s %d: out of memory", __func__, __LINE__));
+ return NULL;
+ }
+
+ memset(b->data, 0, ps->chunk_size);
+
+ list_add(&b->list, &ps->chunk_buffer_list);
+ INIT_LIST_HEAD(&b->dirty_list);
+
+ ps->nr_chunk_buffers++;
+
+ return b;
+}
+
+static void free_chunk_buffer(struct dm_exception_store *ps, struct chunk_buffer *b)
+{
+ list_del(&b->list);
+ vfree(b->data);
+ kfree(b);
+
+ ps->nr_chunk_buffers--;
+}
+
+static int read_new_bitmap_chunk(struct dm_exception_store *ps)
+{
+ chunk_io(ps, ps->cur_bitmap_chunk, WRITE, ps->bitmap);
+
+ ps->cur_bitmap_chunk++;
+ if (ps->cur_bitmap_chunk == ps->nr_bitmap_chunks + FIRST_BITMAP_CHUNK /* --- I couldn't get it working without this. I wonder how it ever worked? --- Mikulas */)
+ ps->cur_bitmap_chunk = FIRST_BITMAP_CHUNK;
+
+ chunk_io(ps, ps->cur_bitmap_chunk, READ, ps->bitmap);
+
+ return 0;
+}
+
+static chunk_t shared_allocate_chunk(struct dm_exception_store *ps)
+{
+ /* !!! FIXME: replace multiply/divide/modulo with bit shifts */
+ unsigned idx;
+ unsigned limit;
+ chunk_t start_chunk;
+ unsigned nr_bits = ps->chunk_shift + 3;
+
+ start_chunk = ps->cur_bitmap_chunk;
+again:
+ if (ps->cur_bitmap_chunk == ps->nr_bitmap_chunks && ps->nr_chunks & ((1 << nr_bits) - 1))
+ limit = ps->nr_chunks & ((1 << nr_bits) - 1);
+ else
+ limit = 1 << nr_bits;
+
+ idx = ext2_find_next_zero_bit(ps->bitmap, limit, ps->cur_bitmap_index);
+ if (idx < limit) {
+ ext2_set_bit(idx, ps->bitmap);
+
+ if (idx == limit - 1) {
+ ps->cur_bitmap_index = 0;
+
+ read_new_bitmap_chunk(ps);
+ } else
+ ps->cur_bitmap_index++;
+ } else {
+ /* chunk_io(ps, ps->cur_bitmap_chunk, WRITE, ps->bitmap); don't write it twice -- Mikulas */
+
+ read_new_bitmap_chunk(ps);
+
+ /* todo: check # free chunks */
+ if (start_chunk == ps->cur_bitmap_chunk) {
+ DM_MULTISNAP_SET_ERROR(ps->dm, -ENOSPC, ("%s %d: fail to find a new chunk", __func__, __LINE__));
+ return 0;
+ }
+
+ goto again;
+ }
+
+ return idx + ((ps->cur_bitmap_chunk - FIRST_BITMAP_CHUNK) << nr_bits);
+}
+
+static int shared_free_chunk(struct dm_exception_store *ps, chunk_t chunk)
+{
+ unsigned bits_per_chunk_shift = ps->chunk_shift + 3;
+ unsigned idx = chunk & ((1 << bits_per_chunk_shift) - 1);
+
+ /* we don't always need to do this... */
+ chunk_io(ps, ps->cur_bitmap_chunk, WRITE, ps->bitmap);
+
+ ps->cur_bitmap_chunk = (chunk >> bits_per_chunk_shift) + FIRST_BITMAP_CHUNK;
+
+ chunk_io(ps, ps->cur_bitmap_chunk, READ, ps->bitmap);
+
+ if (!ext2_test_bit(idx, ps->bitmap)) {
+ DM_MULTISNAP_SET_ERROR(ps->dm, -EFSERROR,
+ ("%s: trying to free free block %lld %lld %u", __func__,
+ (unsigned long long)chunk,
+ (unsigned long long)ps->cur_bitmap_chunk, idx));
+ }
+
+ ext2_clear_bit(idx, ps->bitmap);
+
+ chunk_io(ps, ps->cur_bitmap_chunk, WRITE, ps->bitmap);
+
+ DMINFO("%s %d: free a chunk, %llu", __func__, __LINE__,
+ (unsigned long long)chunk);
+
+ return 0;
+}
+
+static void init_leaf(struct dm_exception_store *ps, struct leaf *leaf)
+{
+ leaf->magic = cpu_to_le16(0x1eaf);
+ leaf->version = 0;
+ leaf->base_chunk = 0;
+ leaf->count = 0;
+ leaf->map[0].offset = cpu_to_le32(ps->chunk_size);
+}
+
+static struct chunk_buffer *new_btree_obj(struct dm_exception_store *ps)
+{
+ u64 chunk;
+ struct chunk_buffer *b;
+
+ b = alloc_chunk_buffer(ps);
+ if (!b)
+ return NULL;
+
+ chunk = shared_allocate_chunk(ps);
+ if (!chunk) {
+ free_chunk_buffer(ps, b);
+ return NULL;
+ }
+
+ b->chunk = chunk;
+
+ return b;
+}
+
+static int shared_create_bitmap(struct dm_exception_store *ps)
+{
+ int i, r, rest, this;
+ chunk_t chunk;
+
+ /* bitmap + superblock */
+ rest = 1 + ps->nr_bitmap_chunks + ps->nr_journal_chunks;
+
+ for (chunk = 0; chunk < ps->nr_bitmap_chunks; chunk++) {
+ memset(ps->area, 0, ps->chunk_size);
+
+ this = min_t(int, rest, ps->chunk_size * 8);
+ if (this) {
+ rest -= this;
+
+ memset(ps->area, 0xff, this / 8);
+
+ for (i = 0; i < this % 8; i++) {
+ /* Mikulas: this produces unaligned accesses
+ char *p = ps->area + (this / 8);
+ ext2_set_bit(i, (unsigned long *)p);*/
+ ext2_set_bit(this - this % 8 + i, (unsigned long *)ps->area);
+ }
+ }
+
+ r = chunk_io(ps, chunk + FIRST_BITMAP_CHUNK, WRITE,
+ ps->area);
+ if (r)
+ return r;
+ }
+
+ return 0;
+}
+
+static struct chunk_buffer *new_leaf(struct dm_exception_store *ps)
+{
+ struct chunk_buffer *cb;
+
+ cb = new_btree_obj(ps);
+ if (cb)
+ init_leaf(ps, cb->data);
+
+ return cb;
+}
+
+static struct chunk_buffer *new_node(struct dm_exception_store *ps)
+{
+ return new_btree_obj(ps);
+}
+
+static int shared_create_btree(struct dm_exception_store *ps)
+{
+ struct chunk_buffer *l, *n;
+ int r;
+
+ r = chunk_io(ps, ps->cur_bitmap_chunk, READ, ps->bitmap);
+ if (r)
+ return r;
+
+ l = new_btree_obj(ps);
+ if (!l)
+ return -ENOMEM;
+ init_leaf(ps, l->data);
+
+ n = new_btree_obj(ps);
+ if (!n)
+ return -ENOMEM;
+
+ buffer2node(n)->count = cpu_to_le32(1);
+ buffer2node(n)->entries[0].chunk = cpu_to_le64(l->chunk);
+
+ chunk_io(ps, l->chunk, WRITE, l->data);
+ chunk_io(ps, n->chunk, WRITE, n->data);
+
+ ps->root_tree_chunk = n->chunk;
+ ps->snapmask = 0;
+ ps->tree_level = 1;
+
+ return 0;
+}
+
+static int shared_create_header(struct dm_exception_store *ps)
+{
+ int r;
+
+ /* 128MB by default, should be configurable. */
+ ps->nr_journal_chunks = (128 * 1024 * 1024) / ps->chunk_size;
+
+ /* Mikulas: if the device is smaller than 128MB, we need something smaller */
+ if (ps->nr_journal_chunks > ps->nr_chunks / 8)
+ ps->nr_journal_chunks = ps->nr_chunks / 8;
+
+ r = shared_create_bitmap(ps);
+ if (r)
+ return r;
+
+ r = shared_create_btree(ps);
+ if (r)
+ return r;
+
+ r = write_header(ps);
+ if (r)
+ return r;
+
+ return r;
+}
+
+static int shared_read_header(struct dm_exception_store *ps, int *new_snapshot)
+{
+ struct disk_header *dh;
+ int r;
+
+ ps->io_client = dm_io_client_create(sectors_to_pages(ps->chunk_size >> SECTOR_SHIFT));
+ if (IS_ERR(ps->io_client)) {
+ r = PTR_ERR(ps->io_client);
+ goto fail_io_client;
+ }
+
+ ps->bitmap = vmalloc(ps->chunk_size);
+ if (!ps->bitmap) {
+ r = -ENOMEM;
+ goto fail_bitmap;
+ }
+
+ r = alloc_area(ps);
+ if (r)
+ goto fail_alloc_area;
+
+
+ r = chunk_io(ps, 0, READ, ps->area);
+ if (r)
+ goto fail_to_read_header;
+
+ 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 fail_to_read_header;
+ }
+
+ *new_snapshot = 0;
+ if (le32_to_cpu(dh->valid))
+ dm_multisnap_set_error(ps->dm, -EINVAL);
+ ps->version = le32_to_cpu(dh->version);
+
+ ps->root_tree_chunk = le64_to_cpu(dh->root_tree_chunk);
+ ps->snapmask = le64_to_cpu(dh->snapmask);
+ ps->tree_level = le32_to_cpu(dh->tree_level);
+ ps->nr_journal_chunks = le32_to_cpu(dh->h_nr_journal_chunks);
+
+ if (ps->chunk_size >> SECTOR_SHIFT != le32_to_cpu(dh->chunk_size)) {
+ DMWARN("Invalid chunk size");
+ r = -ENXIO;
+ goto fail_to_read_header;
+ }
+
+ return 0;
+
+fail_to_read_header:
+ free_area(ps);
+fail_alloc_area:
+ vfree(ps->bitmap);
+ ps->bitmap = NULL;
+fail_bitmap:
+ dm_io_client_destroy(ps->io_client);
+fail_io_client:
+ return r;
+}
+
+static void shared_drop_header(struct dm_exception_store *ps)
+{
+ free_area(ps);
+ vfree(ps->bitmap);
+ ps->bitmap = NULL;
+ dm_io_client_destroy(ps->io_client);
+}
+
+static int shared_read_metadata(struct dm_exception_store *ps, char **error)
+{
+ int i, r, uninitialized_var(new_snapshot);
+ size_t size = i_size_read(dm_multisnap_snapshot_bdev(ps->dm)->bd_inode);
+ chunk_t bitmap_chunk_bytes;
+ unsigned chunk_bytes = ps->chunk_size;
+
+ ps->cur_bitmap_chunk = FIRST_BITMAP_CHUNK;
+ ps->cur_bitmap_index = 0;
+ ps->nr_chunks = size >> ps->chunk_shift;
+
+ INIT_LIST_HEAD(&ps->chunk_buffer_list);
+ INIT_LIST_HEAD(&ps->chunk_buffer_dirty_list);
+ ps->nr_chunk_buffers = 0;
+
+ bitmap_chunk_bytes = DIV_ROUND_UP(ps->nr_chunks, 8);
+ ps->nr_bitmap_chunks = (bitmap_chunk_bytes + chunk_bytes - 1) >> ps->chunk_shift;
+
+ r = shared_read_header(ps, &new_snapshot);
+ if (r) {
+ *error = "Failed to read header";
+ return r;
+ }
+
+ if (new_snapshot)
+ DMINFO("%s %d: creates a new cow device", __func__, __LINE__);
+ else
+ DMINFO("%s %d: loads the cow device", __func__, __LINE__);
+
+ if (new_snapshot) {
+ r = shared_create_header(ps);
+ if (r) {
+ *error = "Failed to create header";
+ goto bad_header;
+ }
+ } else {
+ r = chunk_io(ps, ps->cur_bitmap_chunk, READ, ps->bitmap);
+ if (r) {
+ *error = "Failed to read bitmap";
+ goto bad_header;
+ }
+ }
+
+ for (i = 0; i < MAX_SNAPSHOTS; i++)
+ if (ps->snapmask & 1LL << i)
+ ps->nr_snapshots++;
+
+ return 0;
+
+bad_header:
+ shared_drop_header(ps);
+ return r;
+}
+
+struct etree_path {
+ struct chunk_buffer *buffer;
+ struct index_entry *pnext;
+};
+
+static struct chunk_buffer *btbread(struct dm_exception_store *ps, u64 chunk)
+{
+ struct chunk_buffer *b;
+
+ list_for_each_entry(b, &ps->chunk_buffer_list, list) {
+ if (b->chunk == chunk)
+ return b;
+ }
+
+ b = alloc_chunk_buffer(ps);
+ if (!b)
+ return NULL;
+
+ b->chunk = chunk;
+
+ chunk_io(ps, chunk, READ, b->data);
+
+ return b;
+}
+
+static void brelse(struct chunk_buffer *buffer)
+{
+}
+
+static void brelse_dirty(struct dm_exception_store *ps, struct chunk_buffer *b)
+{
+ if (list_empty(&b->dirty_list))
+ list_add(&b->dirty_list, &ps->chunk_buffer_dirty_list);
+}
+
+static void set_buffer_dirty(struct dm_exception_store *ps, struct chunk_buffer *b)
+{
+ if (list_empty(&b->dirty_list))
+ list_add(&b->dirty_list, &ps->chunk_buffer_dirty_list);
+}
+
+static inline struct exception *emap(struct leaf *leaf, unsigned i)
+{
+ return (struct exception *)
+ ((char *)leaf + le32_to_cpu(leaf->map[i].offset));
+}
+
+static int add_exception_to_leaf(struct leaf *leaf, u64 chunk, u64 exception,
+ int snapshot, u64 active)
+{
+ unsigned target = chunk - le64_to_cpu(leaf->base_chunk);
+ u64 mask = 1ULL << snapshot, sharemap;
+ struct exception *ins, *exceptions = emap(leaf, 0);
+ char *maptop = (char *)(&leaf->map[le32_to_cpu(leaf->count) + 1]);
+ unsigned i, j, free = (char *)exceptions - maptop;
+
+ /*
+ * Find the chunk for which we're adding an exception entry.
+ */
+ for (i = 0; i < le32_to_cpu(leaf->count); i++) /* !!! binsearch goes here */
+ if (le32_to_cpu(leaf->map[i].rchunk) >= target)
+ break;
+
+ /*
+ * If we didn't find the chunk, insert a new one at map[i].
+ */
+ if (i == le32_to_cpu(leaf->count) ||
+ le32_to_cpu(leaf->map[i].rchunk) > target) {
+ if (free < sizeof(struct exception) + sizeof(struct tree_map))
+ return -1;
+ ins = emap(leaf, i);
+ memmove(&leaf->map[i+1], &leaf->map[i], maptop - (char *)&leaf->map[i]);
+ leaf->map[i].offset = cpu_to_le32((char *)ins - (char *)leaf);
+ leaf->map[i].rchunk = cpu_to_le32(target);
+ leaf->count = cpu_to_le32(le32_to_cpu(leaf->count) + 1);
+ sharemap = snapshot == -1 ? active : mask;
+ goto insert;
+ }
+
+ if (free < sizeof(struct exception))
+ return -1;
+ /*
+ * Compute the share map from that of each existing exception entry
+ * for this chunk. If we're doing this for a chunk on the origin,
+ * the new exception is shared between those snapshots that weren't
+ * already sharing exceptions for this chunk. (We combine the sharing
+ * that already exists, invert it, then mask off everything but the
+ * active snapshots.)
+ *
+ * If this is a chunk on a snapshot we go through the existing
+ * exception list to turn off sharing with this snapshot (with the
+ * side effect that if the chunk was only shared by this snapshot it
+ * becomes unshared). We then set sharing for this snapshot in the
+ * new exception entry.
+ */
+ if (snapshot == -1) {
+ for (sharemap = 0, ins = emap(leaf, i); ins < emap(leaf, i+1); ins++)
+ sharemap |= le64_to_cpu(ins->share);
+ sharemap = (~sharemap) & active;
+ } else {
+ for (ins = emap(leaf, i); ins < emap(leaf, i+1); ins++) {
+ u64 val = le64_to_cpu(ins->share);
+ if (val & mask) {
+ ins->share = cpu_to_le64(val & ~mask);
+ break;
+ }
+ }
+ sharemap = mask;
+ }
+ ins = emap(leaf, i);
+insert:
+ /*
+ * Insert the new exception entry. These grow from the end of the
+ * block toward the beginning. First move any earlier exceptions up
+ * to make room for the new one, then insert the new entry in the
+ * space freed. Adjust the offsets for all earlier chunks.
+ */
+ memmove(exceptions - 1, exceptions, (char *)ins - (char *)exceptions);
+ ins--;
+ ins->share = cpu_to_le64(sharemap);
+ ins->chunk = cpu_to_le64(exception);
+
+ for (j = 0; j <= i; j++) {
+ u32 val = le32_to_cpu(leaf->map[j].offset);
+ leaf->map[j].offset = cpu_to_le32(val - sizeof(struct exception));
+ }
+
+ return 0;
+}
+
+static void insert_child(struct node *node, struct index_entry *p, u64 child,
+ u64 childkey)
+{
+ size_t count = (char *)(&node->entries[0] + le32_to_cpu(node->count)) -
+ (char *)p;
+ memmove(p + 1, p, count);
+ p->chunk = cpu_to_le64(child);
+ p->key = cpu_to_le64(childkey);
+ node->count = cpu_to_le32(le32_to_cpu(node->count) + 1);
+}
+
+static u64 split_leaf(struct leaf *leaf, struct leaf *leaf2)
+{
+ unsigned i, nhead, ntail, tailsize;
+ u64 splitpoint;
+ char *phead, *ptail;
+
+ nhead = (le32_to_cpu(leaf->count) + 1) / 2;
+ ntail = le32_to_cpu(leaf->count) - nhead;
+
+ /* Should split at middle of data instead of median exception */
+ splitpoint = le32_to_cpu(leaf->map[nhead].rchunk) +
+ le64_to_cpu(leaf->base_chunk);
+
+ phead = (char *)emap(leaf, 0);
+ ptail = (char *)emap(leaf, nhead);
+ tailsize = (char *)emap(leaf, le32_to_cpu(leaf->count)) - ptail;
+
+ /* Copy upper half to new leaf */
+ memcpy(leaf2, leaf, offsetof(struct leaf, map));
+ memcpy(&leaf2->map[0], &leaf->map[nhead], (ntail + 1) * sizeof(struct tree_map));
+ memcpy(ptail - (char *)leaf + (char *)leaf2, ptail, tailsize);
+ leaf2->count = cpu_to_le32(ntail);
+
+ /* Move lower half to top of block */
+ memmove(phead + tailsize, phead, ptail - phead);
+ leaf->count = cpu_to_le32(nhead);
+ for (i = 0; i <= nhead; i++)
+ leaf->map[i].offset =
+ cpu_to_le32(le32_to_cpu(leaf->map[i].offset) + tailsize);
+ leaf->map[nhead].rchunk = 0;
+
+ return splitpoint;
+}
+
+static int add_exception_to_tree(struct dm_exception_store *ps,
+ struct chunk_buffer *leafbuf,
+ u64 target, u64 exception, int snapbit,
+ struct etree_path path[], unsigned levels)
+{
+ struct node *newroot;
+ struct chunk_buffer *newrootbuf, *childbuf;
+ struct leaf *leaf;
+ u64 childkey, childsector;
+ int ret;
+
+ ret = add_exception_to_leaf(buffer2leaf(leafbuf), target,
+ exception, snapbit, ps->snapmask);
+ if (!ret) {
+ brelse_dirty(ps, leafbuf);
+ return 0;
+ }
+
+ /*
+ * There wasn't room to add a new exception to the leaf. Split it.
+ */
+
+ childbuf = new_leaf(ps);
+ if (!childbuf)
+ return -ENOMEM; /* this is the right thing to do? */
+
+ set_buffer_dirty(ps, childbuf);
+
+ childkey = split_leaf(buffer2leaf(leafbuf), buffer2leaf(childbuf));
+ childsector = childbuf->chunk;
+
+ /*
+ * Now add the exception to the appropriate leaf. Childkey has the
+ * first chunk in the new leaf we just created.
+ */
+ if (target < childkey)
+ leaf = buffer2leaf(leafbuf);
+ else
+ leaf = buffer2leaf(childbuf);
+
+ ret = add_exception_to_leaf(leaf, target, exception, snapbit,
+ ps->snapmask);
+ if (ret)
+ return -ENOMEM;
+
+ brelse_dirty(ps, leafbuf);
+ brelse_dirty(ps, childbuf);
+
+ while (levels--) {
+ unsigned half;
+ u64 newkey;
+ struct index_entry *pnext = path[levels].pnext;
+ struct chunk_buffer *parentbuf = path[levels].buffer;
+ struct node *parent = buffer2node(parentbuf);
+ struct chunk_buffer *newbuf;
+ struct node *newnode;
+ int csize = ps->chunk_size;
+ int alloc_per_node = (csize - offsetof(struct node, entries))
+ / sizeof(struct index_entry);
+
+ if (le32_to_cpu(parent->count) < alloc_per_node) {
+ insert_child(parent, pnext, childsector, childkey);
+ set_buffer_dirty(ps, parentbuf);
+ return 0;
+ }
+ /*
+ * Split the node.
+ */
+ half = le32_to_cpu(parent->count) / 2;
+ newkey = le64_to_cpu(parent->entries[half].key);
+ newbuf = new_node(ps);
+ if (!newbuf)
+ return -ENOMEM;
+ set_buffer_dirty(ps, newbuf);
+ newnode = buffer2node(newbuf);
+
+ newnode->count = cpu_to_le32(le32_to_cpu(parent->count) - half);
+ memcpy(&newnode->entries[0], &parent->entries[half],
+ le32_to_cpu(newnode->count) * sizeof(struct index_entry));
+ parent->count = cpu_to_le32(half);
+ /*
+ * If the path entry is in the new node, use that as the
+ * parent.
+ */
+ if (pnext > &parent->entries[half]) {
+ pnext = pnext - &parent->entries[half] + newnode->entries;
+ set_buffer_dirty(ps, parentbuf);
+ parentbuf = newbuf;
+ parent = newnode;
+ } else
+ set_buffer_dirty(ps, newbuf);
+ /*
+ * Insert the child now that we have room in the parent, then
+ * climb the path and insert the new child there.
+ */
+ insert_child(parent, pnext, childsector, childkey);
+ set_buffer_dirty(ps, parentbuf);
+ childkey = newkey;
+ childsector = newbuf->chunk;
+ brelse(newbuf);
+ }
+
+ newrootbuf = new_node(ps);
+ if (!newrootbuf)
+ return -ENOMEM;
+
+ newroot = buffer2node(newrootbuf);
+
+ newroot->count = cpu_to_le32(2);
+ newroot->entries[0].chunk = cpu_to_le64(ps->root_tree_chunk);
+ newroot->entries[1].key = cpu_to_le64(childkey);
+ newroot->entries[1].chunk = cpu_to_le64(childsector);
+ ps->root_tree_chunk = newrootbuf->chunk;
+ ps->tree_level++;
+ ps->header_dirty = 1;
+ brelse_dirty(ps, newrootbuf);
+ return 0;
+}
+
+static struct chunk_buffer *probe(struct dm_exception_store *ps, u64 chunk,
+ struct etree_path *path)
+{
+ unsigned i, levels = ps->tree_level;
+ struct node *node;
+ struct chunk_buffer *nodebuf = btbread(ps, ps->root_tree_chunk);
+
+ if (!nodebuf)
+ return NULL;
+ node = buffer2node(nodebuf);
+
+ for (i = 0; i < levels; i++) {
+ struct index_entry *pnext = node->entries,
+ *top = pnext + le32_to_cpu(node->count);
+
+ while (++pnext < top)
+ if (le64_to_cpu(pnext->key) > chunk)
+ break;
+
+ path[i].buffer = nodebuf;
+ path[i].pnext = pnext;
+ nodebuf = btbread(ps, le64_to_cpu((pnext - 1)->chunk));
+ if (!nodebuf)
+ return NULL;
+
+ node = (struct node *)nodebuf->data;
+ }
+ BUG_ON(le16_to_cpu(((struct leaf *)nodebuf->data)->magic) != 0x1eaf);
+ return nodebuf;
+}
+
+static inline struct node *path_node(struct etree_path path[], int level)
+{
+ return buffer2node(path[level].buffer);
+}
+
+/*
+ * Release each buffer in the given path array.
+ */
+static void brelse_path(struct etree_path *path, unsigned levels)
+{
+ unsigned i;
+ for (i = 0; i < levels; i++)
+ brelse(path[i].buffer);
+}
+
+/*
+ * Merge the contents of 'leaf2' into 'leaf.' The leaves are contiguous and
+ * 'leaf2' follows 'leaf.' Move the exception lists in 'leaf' up to make room
+ * for those of 'leaf2,' adjusting the offsets in the map entries, then copy
+ * the map entries and exception lists straight from 'leaf2.'
+ */
+static void merge_leaves(struct leaf *leaf, struct leaf *leaf2)
+{
+ unsigned nhead, ntail, i;
+ unsigned tailsize;
+ char *phead, *ptail;
+
+ nhead = le32_to_cpu(leaf->count);
+ ntail = le32_to_cpu(leaf2->count);
+ tailsize = (char *)emap(leaf2, ntail) - (char *)emap(leaf2, 0);
+ phead = (char *)emap(leaf, 0);
+ ptail = (char *)emap(leaf, nhead);
+
+ /* move data down */
+ memmove(phead - tailsize, phead, ptail - phead);
+
+ /* adjust pointers */
+ for (i = 0; i <= nhead; i++) {
+ u32 val = le32_to_cpu(leaf->map[i].offset);
+ /* also adjust sentinel */
+ leaf->map[i].offset = cpu_to_le32(val - tailsize);
+ }
+
+ /* move data from leaf2 to top */
+ /* data */
+ memcpy(ptail - tailsize, (char *)emap(leaf2, 0), tailsize);
+ /* map */
+ memcpy(&leaf->map[nhead], &leaf2->map[0],
+ (ntail + 1) * sizeof(struct tree_map));
+ leaf->count = cpu_to_le32(le32_to_cpu(leaf->count) + ntail);
+}
+
+/*
+ * Remove the index entry at path[level].pnext-1 by moving entries below it up
+ * into its place. If it wasn't the last entry in the node but it _was_ the
+ * first entry (and we're not at the root), preserve the key by inserting it
+ * into the index entry of the parent node that refers to this node.
+ */
+static void remove_index(struct dm_exception_store *ps, struct etree_path path[], int level)
+{
+ struct node *node = path_node(path, level);
+ /* !!! out of bounds for delete of last from full index */
+ chunk_t pivot = le64_to_cpu((path[level].pnext)->key);
+ int i, count = le32_to_cpu(node->count);
+
+ /* stomps the node count (if 0th key holds count) */
+ memmove(path[level].pnext - 1, path[level].pnext,
+ (char *)&node->entries[count] - (char *)path[level].pnext);
+ node->count = cpu_to_le32(count - 1);
+ --(path[level].pnext);
+ set_buffer_dirty(ps, path[level].buffer);
+
+ /* no pivot for last entry */
+ if (path[level].pnext == node->entries + le32_to_cpu(node->count))
+ return;
+
+ /*
+ * climb up to common parent and set pivot to deleted key
+ * what if index is now empty? (no deleted key)
+ * then some key above is going to be deleted and used to set pivot
+ */
+ if (path[level].pnext == node->entries && level) {
+ /* Keep going up the path if we're at the first index entry. */
+ for (i = level - 1; path[i].pnext - 1 == path_node(path, i)->entries; i--)
+ if (!i) /* If we hit the root, we're done. */
+ return;
+ /*
+ * Found a node where we're not at the first entry.
+ * Set the key here to that of the deleted index
+ * entry.
+ */
+ (path[i].pnext - 1)->key = cpu_to_le64(pivot);
+ set_buffer_dirty(ps, path[i].buffer);
+ }
+}
+
+/*
+ * Returns the number of bytes of free space in the given leaf by computing
+ * the difference between the end of the map entry list and the beginning
+ * of the first set of exceptions.
+ */
+static unsigned leaf_freespace(struct leaf *leaf)
+{
+ /* include sentinel */
+ char *maptop = (char *)(&leaf->map[le32_to_cpu(leaf->count) + 1]);
+ return (char *)emap(leaf, 0) - maptop;
+}
+
+/*
+ * Returns the number of bytes used in the given leaf by computing the number
+ * of bytes used by the map entry list and all sets of exceptions.
+ */
+static unsigned leaf_payload(struct leaf *leaf)
+{
+ int count = le32_to_cpu(leaf->count);
+ int lower = (char *)(&leaf->map[count]) - (char *)leaf->map;
+ int upper = (char *)emap(leaf, count) - (char *)emap(leaf, 0);
+ return lower + upper;
+}
+
+static void check_leaf(struct dm_exception_store *ps, struct leaf *leaf, u64 snapmask)
+{
+ struct exception *p;
+ int i;
+
+ for (i = 0; i < le32_to_cpu(leaf->count); i++) {
+ for (p = emap(leaf, i); p < emap(leaf, i+1); p++) {
+ /* !!! should also check for any zero sharemaps here */
+ if (le64_to_cpu(p->share) & snapmask) {
+ DM_MULTISNAP_SET_ERROR(ps->dm, -EFSERROR,
+ ("nonzero bits %016llx outside snapmask %016llx",
+ (unsigned long long)p->share,
+ (unsigned long long)snapmask));
+ }
+ }
+ }
+}
+
+/*
+ * Remove all exceptions belonging to a given snapshot from the passed leaf.
+ *
+ * This clears the "share" bits on each chunk for the snapshot mask passed
+ * in the delete_info structure. In the process, it compresses out any
+ * exception entries that are entirely unshared and/or unused. In a second
+ * pass, it compresses out any map entries for which there are no exception
+ * entries remaining.
+ */
+static int delete_snapshots_from_leaf(struct dm_exception_store *ps,
+ struct leaf *leaf, u64 snapmask)
+{
+ /* p points just past the last map[] entry in the leaf. */
+ struct exception *p = emap(leaf, le32_to_cpu(leaf->count)), *dest = p;
+ struct tree_map *pmap, *dmap;
+ unsigned i;
+ int ret = 0;
+
+ /* Scan top to bottom clearing snapshot bit and moving
+ * non-zero entries to top of block */
+ /*
+ * p points at each original exception; dest points at the location
+ * to receive an exception that is being moved down in the leaf.
+ * Exceptions that are unshared after clearing the share bit for
+ * the passed snapshot mask are skipped and the associated "exception"
+ * chunk is freed. This operates on the exceptions for one map entry
+ * at a time; when the beginning of a list of exceptions is reached,
+ * the associated map entry offset is adjusted.
+ */
+ for (i = le32_to_cpu(leaf->count); i-- {
+ /*
+ * False the first time through, since i is leaf->count and p
+ * was set to emap(leaf, leaf->count) above.
+ */
+ while (p != emap(leaf, i)) {
+ u64 share = le64_to_cpu((--p)->share);
+ ret |= share & snapmask;
+ /* Unshare with given snapshot(s). */
+ p->share = cpu_to_le64(le64_to_cpu(p->share) & ~snapmask);
+ if (le64_to_cpu(p->share)) /* If still used, keep chunk. */
+ *--dest = *p;
+ else
+ shared_free_chunk(ps, le64_to_cpu(p->chunk));
+ /* dirty_buffer_count_check(sb); */
+ }
+ leaf->map[i].offset = cpu_to_le32((char *)dest - (char *)leaf);
+ }
+ /* Remove empties from map */
+ /*
+ * This runs through the map entries themselves, skipping entries
+ * with matching offsets. If all the exceptions for a given map
+ * entry are skipped, its offset will be set to that of the following
+ * map entry (since the dest pointer will not have moved).
+ */
+ dmap = pmap = &leaf->map[0];
+ for (i = 0; i < le32_to_cpu(leaf->count); i++, pmap++)
+ if (le32_to_cpu(pmap->offset) != le32_to_cpu((pmap + 1)->offset))
+ *dmap++ = *pmap;
+ /*
+ * There is always a phantom map entry after the last, that has the
+ * offset of the end of the leaf and, of course, no chunk number.
+ */
+ dmap->offset = pmap->offset;
+ dmap->rchunk = 0; /* tidy up */
+ leaf->count = cpu_to_le32(dmap - &leaf->map[0]);
+ check_leaf(ps, leaf, snapmask);
+
+ return ret;
+}
+
+/*
+ * Return true if path[level].pnext points at the end of the list of index
+ * entries.
+ */
+static inline int finished_level(struct etree_path path[], int level)
+{
+ struct node *node = path_node(path, level);
+ return path[level].pnext == node->entries + le32_to_cpu(node->count);
+}
+
+/*
+ * Copy the index entries in 'node2' into 'node.'
+ */
+static void merge_nodes(struct node *node, struct node *node2)
+{
+ memcpy(&node->entries[le32_to_cpu(node->count)],
+ &node2->entries[0],
+ le32_to_cpu(node2->count) * sizeof(struct index_entry));
+ node->count = cpu_to_le32(le32_to_cpu(node->count) + le32_to_cpu(node2->count));
+}
+
+static void brelse_free(struct dm_exception_store *ps, struct chunk_buffer *buffer)
+{
+ shared_free_chunk(ps, buffer->chunk);
+ free_chunk_buffer(ps, buffer);
+}
+
+/*
+ * Delete all chunks in the B-tree for the snapshot(s) indicated by the
+ * passed snapshot mask, beginning at the passed chunk.
+ *
+ * Walk the tree (a stack-based inorder traversal) starting with the passed
+ * chunk, calling delete_snapshots_from_leaf() on each leaf to remove chunks
+ * associated with the snapshot(s) we're removing. As leaves and nodes become
+ * sparsely filled, merge them with their neighbors. When we reach the root
+ * we've finished the traversal; if there are empty levels (that is, level(s)
+ * directly below the root that only contain a single node), remove those
+ * empty levels until either the second level is no longer empty or we only
+ * have one level remaining.
+ */
+static int delete_tree_range(struct dm_exception_store *ps, u64 snapmask, chunk_t resume)
+{
+ int levels = ps->tree_level, level = levels - 1;
+ struct etree_path path[levels], hold[levels];
+ struct chunk_buffer *leafbuf, *prevleaf = NULL;
+ unsigned i;
+
+ /* can be initializer if not dynamic array (change it?) */
+ for (i = 0; i < levels; i++)
+ hold[i] = (struct etree_path){ };
+ /*
+ * Find the B-tree leaf with the chunk we were passed. Often
+ * this will be chunk 0.
+ */
+ leafbuf = probe(ps, resume, path);
+ if (!leafbuf)
+ return -ENOMEM;
+
+ while (1) { /* in-order leaf walk */
+ if (delete_snapshots_from_leaf(ps, buffer2leaf(leafbuf), snapmask))
+ set_buffer_dirty(ps, leafbuf);
+ /*
+ * If we have a previous leaf (i.e. we're past the first),
+ * try to merge the current leaf with it.
+ */
+ if (prevleaf) { /* try to merge this leaf with prev */
+ struct leaf *this = buffer2leaf(leafbuf);
+ struct leaf *prev = buffer2leaf(prevleaf);
+
+ /*
+ * If there's room in the previous leaf for this leaf,
+ * merge this leaf into the previous leaf and remove
+ * the index entry that points to this leaf.
+ */
+ if (leaf_payload(this) <= leaf_freespace(prev)) {
+ merge_leaves(prev, this);
+ remove_index(ps, path, level);
+ set_buffer_dirty(ps, prevleaf);
+ brelse_free(ps, leafbuf);
+ /* dirty_buffer_count_check(sb); */
+ goto keep_prev_leaf;
+ }
+ brelse(prevleaf);
+ }
+ prevleaf = leafbuf; /* Save leaf for next time through. */
+keep_prev_leaf:
+ /*
+ * If we've reached the end of the index entries in the B-tree
+ * node at the current level, try to merge the node referred
+ * to at this level of the path with a prior node. Repeat
+ * this process at successively higher levels up the path; if
+ * we reach the root, clean up and exit. If we don't reach
+ * the root, we've reached a node with multiple entries;
+ * rebuild the path from the next index entry to the next
+ * leaf.
+ */
+ if (finished_level(path, level)) {
+ do { /* pop and try to merge finished nodes */
+ /*
+ * If we have a previous node at this level
+ * (again, we're past the first node), try to
+ * merge the current node with it.
+ */
+ if (hold[level].buffer) {
+ struct node *this = path_node(path, level);
+ struct node *prev = path_node(hold, level);
+ int csize = ps->chunk_size;
+ int alloc_per_node =
+ (csize - offsetof(struct node, entries))
+ / sizeof(struct index_entry);
+
+ /*
+ * If there's room in the previous node
+ * for the entries in this node, merge
+ * this node into the previous node and
+ * remove the index entry that points
+ * to this node.
+ */
+ if (le32_to_cpu(this->count) <=
+ alloc_per_node - le32_to_cpu(prev->count)) {
+ merge_nodes(prev, this);
+ remove_index(ps, path, level - 1);
+ set_buffer_dirty(ps, hold[level].buffer);
+ brelse_free(ps, path[level].buffer);
+/* dirty_buffer_count_check(sb); */
+ goto keep_prev_node;
+ }
+ brelse(hold[level].buffer);
+ }
+ /* Save the node for the next time through. */
+ hold[level].buffer = path[level].buffer;
+keep_prev_node:
+ /*
+ * If we're at the root, we need to clean up
+ * and return. First, though, try to reduce
+ * the number of levels. If the tree at the
+ * root has been reduced to only the nodes in
+ * our path, eliminate nodes with only one
+ * entry until we either have a new root node
+ * with multiple entries or we have only one
+ * level remaining in the B-tree.
+ */
+ if (!level) { /* remove levels if possible */
+ /*
+ * While above the first level and the
+ * root only has one entry, point the
+ * root at the (only) first-level node,
+ * reduce the number of levels and
+ * shift the path up one level.
+ */
+ while (levels > 1 &&
+ le32_to_cpu(path_node(hold, 0)->count) == 1) {
+ /* Point root at the first level. */
+ ps->root_tree_chunk = hold[1].buffer->chunk;
+ brelse_free(ps, hold[0].buffer);
+/* dirty_buffer_count_check(sb); */
+ levels = --ps->tree_level;
+ memcpy(hold, hold + 1, levels * sizeof(hold[0]));
+ ps->header_dirty = 1;
+ }
+ brelse(prevleaf);
+ brelse_path(hold, levels);
+
+/* if (dirty_buffer_count) */
+/* commit_transaction(sb, 0); */
+ ps->snapmask &= ~snapmask;
+ ps->header_dirty = 1;
+ return 0;
+ }
+
+ level--;
+ } while (finished_level(path, level));
+ /*
+ * Now rebuild the path from where we are (one entry
+ * past the last leaf we processed, which may have
+ * been adjusted in operations above) down to the node
+ * above the next leaf.
+ */
+ do { /* push back down to leaf level */
+ struct chunk_buffer *nodebuf;
+
+ nodebuf = btbread(ps,
+ le64_to_cpu(path[level++].pnext++->chunk));
+ if (!nodebuf) {
+ brelse_path(path, level - 1); /* anything else needs to be freed? */
+ return -ENOMEM;
+ }
+ path[level].buffer = nodebuf;
+ path[level].pnext = buffer2node(nodebuf)->entries;
+ } while (level < levels - 1);
+ }
+
+ /* dirty_buffer_count_check(sb); */
+ /*
+ * Get the leaf indicated in the next index entry in the node
+ * at this level.
+ */
+ leafbuf = btbread(ps, le64_to_cpu(path[level].pnext++->chunk));
+ if (!leafbuf) {
+ brelse_path(path, level);
+ return -ENOMEM;
+ }
+ }
+}
+
+static int origin_chunk_unique(struct leaf *leaf, u64 chunk, u64 snapmask)
+{
+ u64 using = 0;
+ u64 i, target = chunk - le64_to_cpu(leaf->base_chunk);
+ struct exception const *p;
+
+ for (i = 0; i < le32_to_cpu(leaf->count); i++)
+ if (le32_to_cpu(leaf->map[i].rchunk) == target)
+ goto found;
+ return !snapmask;
+found:
+ for (p = emap(leaf, i); p < emap(leaf, i+1); p++)
+ using |= le64_to_cpu(p->share);
+
+ return !(~using & snapmask);
+}
+
+static int snapshot_chunk_unique(struct leaf *leaf, u64 chunk, int snapbit,
+ chunk_t *exception)
+{
+ u64 mask = 1LL << snapbit;
+ unsigned i, target = chunk - le64_to_cpu(leaf->base_chunk);
+ struct exception const *p;
+
+ for (i = 0; i < le32_to_cpu(leaf->count); i++)
+ if (le32_to_cpu(leaf->map[i].rchunk) == target)
+ goto found;
+ return 0;
+found:
+ for (p = emap(leaf, i); p < emap(leaf, i+1); p++)
+ /* shared if more than one bit set including this one */
+ if ((le64_to_cpu(p->share) & mask)) {
+ *exception = le64_to_cpu(p->chunk);
+ return !(le64_to_cpu(p->share) & ~mask);
+ }
+ return 0;
+}
+
+static int shared_init(struct dm_multisnap *dm, struct dm_exception_store **sp,
+ unsigned argc, char **argv, char **error)
+{
+ int r;
+ struct dm_exception_store *ps;
+
+ ps = kzalloc(sizeof(struct dm_exception_store), GFP_KERNEL);
+ if (!ps) {
+ *error = "Could not allocate private area";
+ r = -ENOMEM;
+ goto bad_private;
+ }
+ *sp = ps;
+
+ ps->dm = dm;
+ ps->chunk_size = dm_multisnap_chunk_size(dm);
+ ps->chunk_shift = ffs(ps->chunk_size) - 1;
+
+ if (argc != 0) {
+ *error = "Bad number of arguments";
+ r = -EINVAL;
+ goto bad_arguments;
+ }
+
+ if (ps->chunk_size != DM_CHUNK_SIZE_DEFAULT_SECTORS << SECTOR_SHIFT) {
+ *error = "Unsupported chunk size";
+ r = -EINVAL;
+ goto bad_arguments;
+ }
+
+ ps->area = NULL;
+
+ r = shared_read_metadata(ps, error);
+ if (r)
+ goto bad_metadata;
+
+ return 0;
+
+bad_metadata:
+bad_arguments:
+ kfree(ps);
+bad_private:
+ return r;
+}
+
+static void shared_destroy(struct dm_exception_store *ps)
+{
+ struct chunk_buffer *bb, *n;
+
+ list_for_each_entry_safe(bb, n, &ps->chunk_buffer_list, list)
+ free_chunk_buffer(ps, bb);
+
+ shared_drop_header(ps);
+
+ kfree(ps);
+}
+
+static int shared_allocate_snapid(struct dm_exception_store *ps,
+ snapid_t *snapid, int snap_of_snap, snapid_t master)
+{
+ int i;
+
+ if (snap_of_snap) {
+ DMERR("shared_allocate_snapid: this exception store doesn't support snapshots of snapshots");
+ return -EOPNOTSUPP;
+ }
+
+ for (i = 0; i < MAX_SNAPSHOTS; i++)
+ if (!(ps->snapmask & 1LL << i)) {
+ *snapid = i;
+ return 0;
+ }
+
+ DMERR("shared_allocate_snapid: limit of 64 snapshots reached");
+ return -ENOSPC;
+}
+
+static int shared_create_snapshot(struct dm_exception_store *ps, snapid_t snapid)
+{
+ if (snapid >= MAX_SNAPSHOTS) {
+ DMERR("shared_create_snapshot: invalid snapshot id %llx",
+ (unsigned long long)snapid);
+ return -EINVAL;
+ }
+ if (ps->snapmask & 1LL << snapid) {
+ DMERR("shared_create_snapshot: snapshot with id %llx already exists",
+ (unsigned long long)snapid);
+ return -EINVAL;
+ }
+ ps->snapmask |= 1LL << snapid;
+ ps->nr_snapshots++;
+ write_header(ps);
+ return 0;
+}
+
+static void shared_commit(struct dm_exception_store *ps);
+
+static int shared_delete_snapshot(struct dm_exception_store *ps, snapid_t idx)
+{
+ int r;
+
+ if (ps->snapmask & 1LL << idx) {
+ u64 mask;
+ DMINFO("%s %d: delete %uth snapshot.",
+ __func__, __LINE__, (int)idx);
+
+ mask = 1ULL << idx;
+
+ r = delete_tree_range(ps, mask, 0);
+ if (!r) {
+ ps->snapmask &= ~(1LL << idx);
+ ps->nr_snapshots--;
+ }
+
+ write_header(ps);
+
+ shared_commit(ps);
+ } else {
+ BUG(); /* checked in the caller */
+ }
+
+ return r;
+}
+
+static snapid_t shared_get_next_snapid(struct dm_exception_store *ps, snapid_t snapid)
+{
+ for (; snapid < MAX_SNAPSHOTS; snapid++)
+ if ((ps->snapmask >> snapid) & 1)
+ return snapid;
+ return DM_SNAPID_T_ORIGIN;
+}
+
+static int shared_find_snapshot_chunk(struct dm_exception_store *ps, snapid_t snapid,
+ chunk_t chunk, int write, chunk_t *result)
+{
+ unsigned levels = ps->tree_level;
+ struct etree_path path[levels + 1];
+ struct chunk_buffer *leafbuf;
+
+ leafbuf = probe(ps, (u64)chunk, path);
+ if (!leafbuf) /* should make the snapshot invalid */
+ return -1;
+
+ return snapshot_chunk_unique(buffer2leaf(leafbuf), chunk, snapid, result);
+}
+
+static void shared_reset_query(struct dm_exception_store *ps)
+{
+}
+
+static int shared_query_next_remap(struct dm_exception_store *ps, chunk_t chunk)
+{
+ unsigned levels = ps->tree_level;
+ struct etree_path path[levels + 1];
+ struct chunk_buffer *leafbuf;
+
+ leafbuf = probe(ps, (u64)chunk, path);
+ if (!leafbuf) /* should make the snapshot invalid */
+ return -1;
+
+ ps->chunk_to_add = chunk;
+
+ return !origin_chunk_unique(buffer2leaf(leafbuf), chunk, ps->snapmask);
+}
+
+static void shared_add_next_remap(struct dm_exception_store *ps,
+ union chunk_descriptor *cd, chunk_t *new_chunk)
+{
+ struct chunk_buffer *cb;
+ struct etree_path path[ps->tree_level + 1];
+ chunk_t chunk = ps->chunk_to_add;
+ int ret;
+
+ /*
+ * Mikulas: TODO: we could set just bits that we are really relocating.
+ * But setting more bits won't cause incorrect behavior, it'll just
+ * temporarily block access to already remapped snapshots.
+ */
+ cd->bitmask = ps->snapmask;
+
+ cb = probe(ps, chunk, path);
+ if (!cb)
+ return;
+
+ ret = origin_chunk_unique(buffer2leaf(cb), chunk, ps->snapmask);
+ if (ret) {
+ DM_MULTISNAP_SET_ERROR(ps->dm, -EFSERROR,
+ ("%s %d: bug %llu %d", __func__, __LINE__,
+ (unsigned long long)chunk, ret));
+ return;
+ }
+
+ *new_chunk = shared_allocate_chunk(ps);
+ if (!*new_chunk)
+ return;
+
+ add_exception_to_tree(ps, cb, chunk, *new_chunk, -1, path,
+ ps->tree_level);
+
+ /*DMINFO("%s %d: allocated new chunk, %llu", __func__, __LINE__,
+ (unsigned long long)*new_chunk);*/
+}
+
+static int shared_check_conflict(struct dm_exception_store *ps,
+ union chunk_descriptor *cd, snapid_t snapid)
+{
+ return !!(cd->bitmask & (1LL << snapid));
+}
+
+static void shared_commit(struct dm_exception_store *ps)
+{
+ struct chunk_buffer *b, *n;
+
+ /* Write bitmap */
+ chunk_io(ps, ps->cur_bitmap_chunk, WRITE, ps->bitmap);
+
+ list_for_each_entry_safe(b, n, &ps->chunk_buffer_dirty_list,
+ dirty_list) {
+
+ list_del_init(&b->dirty_list);
+ list_move_tail(&b->list, &ps->chunk_buffer_list);
+
+ /* todo: can be async */
+ chunk_io(ps, b->chunk, WRITE, b->data);
+ }
+
+ if (ps->header_dirty)
+ write_header(ps);
+
+ list_for_each_entry_safe(b, n, &ps->chunk_buffer_list, list) {
+ if (ps->nr_chunk_buffers < MAX_CHUNK_BUFFERS)
+ break;
+
+ free_chunk_buffer(ps, b);
+ }
+}
+
+struct dm_multisnap_exception_store dm_multisnap_daniel_store = {
+ .name = "daniel",
+ .module = THIS_MODULE,
+ .init_exception_store = shared_init,
+ .exit_exception_store = shared_destroy,
+ .allocate_snapid = shared_allocate_snapid,
+ .create_snapshot = shared_create_snapshot,
+ .delete_snapshot = shared_delete_snapshot,
+ .get_next_snapid = shared_get_next_snapid,
+ .find_snapshot_chunk = shared_find_snapshot_chunk,
+ .reset_query = shared_reset_query,
+ .query_next_remap = shared_query_next_remap,
+ .add_next_remap = shared_add_next_remap,
+ .check_conflict = shared_check_conflict,
+ .commit = shared_commit,
+};
+
+static int __init dm_multisnapshot_daniel_module_init(void)
+{
+ return dm_multisnap_register_exception_store(&dm_multisna p_daniel_store);
+}
+
+static void __exit dm_multisnapshot_daniel_module_exit(void)
+{
+ dm_multisnap_unregister_exception_store(&dm_multis nap_daniel_store);
+}
+
+module_init(dm_multisnapshot_daniel_module_init);
+module_exit(dm_multisnapshot_daniel_module_exit);
+
+MODULE_DESCRIPTION(DM_NAME " multisnapshot Fujita/Daniel's exceptions store");
+MODULE_AUTHOR("Fujita Tomonorig, Daniel Phillips");
+MODULE_LICENSE("GPL");
--
1.6.5.2

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Old 03-01-2010, 11:57 PM
FUJITA Tomonori
 
Default dm-multisnap-daniel

On Mon, 1 Mar 2010 19:23:58 -0500
Mike Snitzer <snitzer@redhat.com> wrote:

> From: Mikulas Patocka <mpatocka@redhat.com>
>
> An implementation of snapshot store.
> Designed by Daniel Phillips, ported to kernelspace by Fujita Tomonorig.

Thanks for putting my name here, however, I prefer "Fujita Tomonori"


> This implementation plugs as a module into dm-multisnapshot interface.
>
> The interface is almost the same as in Mikulas' exception store. You have to
> specify "daniel" instead of "mikulas" as a type of exception store.
> The only supported chunk size is 16384 bytes (but the code is general enough and
> this restriction may be removed in the future).
>
> Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
> ---
> drivers/md/Kconfig | 14 +
> drivers/md/Makefile | 2 +
> drivers/md/dm-multisnap-daniel.c | 1711 ++++++++++++++++++++++++++++++++++++++
> 3 files changed, 1727 insertions(+), 0 deletions(-)
> create mode 100644 drivers/md/dm-multisnap-daniel.c
>
> diff --git a/drivers/md/Kconfig b/drivers/md/Kconfig
> index 0c3ce3b..c30bf70 100644
> --- a/drivers/md/Kconfig
> +++ b/drivers/md/Kconfig
> @@ -268,6 +268,20 @@ config DM_MULTISNAPSHOT_MIKULAS
> A B+-tree-based log-structured storage allowing unlimited
> number of snapshots.
>
> +config DM_MULTISNAPSHOT_DANIEL
> + tristate "Daniel's snapshot store"
> + depends on DM_MULTISNAPSHOT
> + ---help---
> + Daniel Philips' exception store. The data structures were
> + designed by Daniel Phillips for Zumastore project, a porting
> + to kernel space was done by Fujita Tomonorig.

s/Tomonorig/Tomonori/;


(snip)

> +static int __init dm_multisnapshot_daniel_module_init(void)
> +{
> + return dm_multisnap_register_exception_store(&dm_multisna p_daniel_store);
> +}
> +
> +static void __exit dm_multisnapshot_daniel_module_exit(void)
> +{
> + dm_multisnap_unregister_exception_store(&dm_multis nap_daniel_store);
> +}
> +
> +module_init(dm_multisnapshot_daniel_module_init);
> +module_exit(dm_multisnapshot_daniel_module_exit);
> +
> +MODULE_DESCRIPTION(DM_NAME " multisnapshot Fujita/Daniel's exceptions store");
> +MODULE_AUTHOR("Fujita Tomonorig, Daniel Phillips");

s/Tomonorig/Tomonori/;

> +MODULE_LICENSE("GPL");


Thanks,

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