[dm-devel] [PATCH 6/8] [persistent-data] Add a transactional array.
Joe Thornber
ejt at redhat.com
Thu Dec 13 20:19:14 UTC 2012
---
drivers/md/persistent-data/Makefile | 1 +
drivers/md/persistent-data/dm-array.c | 818 +++++++++++++++++++++++++++++++++
drivers/md/persistent-data/dm-array.h | 128 ++++++
3 files changed, 947 insertions(+)
create mode 100644 drivers/md/persistent-data/dm-array.c
create mode 100644 drivers/md/persistent-data/dm-array.h
diff --git a/drivers/md/persistent-data/Makefile b/drivers/md/persistent-data/Makefile
index d8e7cb7..ebd8d80 100644
--- a/drivers/md/persistent-data/Makefile
+++ b/drivers/md/persistent-data/Makefile
@@ -1,5 +1,6 @@
obj-$(CONFIG_DM_PERSISTENT_DATA) += dm-persistent-data.o
dm-persistent-data-objs := \
+ dm-array.o \
dm-block-manager.o \
dm-space-map-common.o \
dm-space-map-disk.o \
diff --git a/drivers/md/persistent-data/dm-array.c b/drivers/md/persistent-data/dm-array.c
new file mode 100644
index 0000000..d762caf
--- /dev/null
+++ b/drivers/md/persistent-data/dm-array.c
@@ -0,0 +1,818 @@
+/*
+ * Copyright (C) 2012 Red Hat, Inc.
+ *
+ * This file is released under the GPL.
+ */
+
+#include "dm-array.h"
+#include "dm-space-map.h"
+#include "dm-transaction-manager.h"
+
+#include <linux/export.h>
+#include <linux/device-mapper.h>
+
+#define DM_MSG_PREFIX "array"
+
+/*----------------------------------------------------------------*/
+
+/*
+ * The array is implemented as a fully populated btree, which points to
+ * blocks that contain the packed values. This is more space efficient
+ * than just using a btree since we don't store 1 key per value.
+ */
+struct array_block {
+ __le32 csum;
+ __le32 max_entries;
+ __le32 nr_entries;
+ __le32 value_size;
+ __le64 blocknr; /* Block this node is supposed to live in. */
+} __packed;
+
+/*----------------------------------------------------------------*/
+
+/*
+ * Validator methods. As usual we calculate a checksum, and also write the
+ * block location into the header (paranoia about ssds remapping areas by
+ * mistake).
+ */
+#define CSUM_XOR 595846735
+
+static void array_block_prepare_for_write(struct dm_block_validator *v,
+ struct dm_block *b,
+ size_t block_size)
+{
+ struct array_block *bh_le = dm_block_data(b);
+
+ bh_le->blocknr = cpu_to_le64(dm_block_location(b));
+ bh_le->csum = cpu_to_le32(dm_bm_checksum(&bh_le->max_entries,
+ block_size - sizeof(__le32),
+ CSUM_XOR));
+}
+
+static int array_block_check(struct dm_block_validator *v,
+ struct dm_block *b,
+ size_t block_size)
+{
+ struct array_block *bh_le = dm_block_data(b);
+ __le32 csum_disk;
+
+ if (dm_block_location(b) != le64_to_cpu(bh_le->blocknr)) {
+ DMERR_LIMIT("array_block_check failed: blocknr %llu != wanted %llu",
+ le64_to_cpu(bh_le->blocknr), dm_block_location(b));
+ return -ENOTBLK;
+ }
+
+ csum_disk = cpu_to_le32(dm_bm_checksum(&bh_le->max_entries,
+ block_size - sizeof(__le32),
+ CSUM_XOR));
+ if (csum_disk != bh_le->csum) {
+ DMERR_LIMIT("array_block_check failed: csum %u != wanted %u",
+ le32_to_cpu(csum_disk), le32_to_cpu(bh_le->csum));
+ return -EILSEQ;
+ }
+
+ return 0;
+}
+
+static struct dm_block_validator array_validator = {
+ .name = "array",
+ .prepare_for_write = array_block_prepare_for_write,
+ .check = array_block_check
+};
+
+/*----------------------------------------------------------------*/
+
+/*
+ * Functions for manipulating the array blocks.
+ */
+
+/*
+ * Returns a pointer to a value within an array block.
+ *
+ * index - The index into _this_ specific block.
+ */
+static void *element_at(struct dm_array_info *info, struct array_block *ab,
+ unsigned index)
+{
+ unsigned char *entry = (unsigned char *) (ab + 1);
+ entry += index * info->value_type.size;
+ return entry;
+}
+
+/*
+ * Utility function that calls one of the value_type methods on every value
+ * in an array block.
+ */
+static void on_entries(struct dm_array_info *info, struct array_block *ab,
+ void (*fn)(void *, const void *))
+{
+ unsigned i, nr_entries = le32_to_cpu(ab->nr_entries);
+
+ for (i = 0; i < nr_entries; i++)
+ fn(info->value_type.context, element_at(info, ab, i));
+}
+
+/*
+ * Increment every value in an array block.
+ */
+static void inc_ablock_entries(struct dm_array_info *info, struct array_block *ab)
+{
+ struct dm_btree_value_type *vt = &info->value_type;
+
+ if (vt->inc)
+ on_entries(info, ab, vt->inc);
+}
+
+/*
+ * Decrement every value in an array block.
+ */
+static void dec_ablock_entries(struct dm_array_info *info, struct array_block *ab)
+{
+ struct dm_btree_value_type *vt = &info->value_type;
+
+ if (vt->dec)
+ on_entries(info, ab, vt->dec);
+}
+
+/*
+ * Each array block can hold this many values.
+ */
+static uint32_t calc_max_entries(size_t value_size, size_t block_size)
+{
+ return (block_size - sizeof(struct array_block)) / value_size;
+}
+
+/*
+ * Allocate a new array block. The caller will need to unlock block.
+ */
+static int alloc_ablock(struct dm_array_info *info, size_t block_size,
+ struct dm_block **block, struct array_block **ab)
+{
+ int r;
+
+ r = dm_tm_new_block(info->btree_info.tm, &array_validator, block);
+ if (r)
+ return r;
+
+ (*ab) = dm_block_data(*block);
+ (*ab)->max_entries =
+ cpu_to_le32(calc_max_entries(info->value_type.size, block_size));
+ (*ab)->nr_entries = cpu_to_le32(0);
+ (*ab)->value_size = cpu_to_le32(info->value_type.size);
+
+ return 0;
+}
+
+/*
+ * Pad an array block out with a particular value. Every instance will
+ * cause an increment of the value_type. new_nr must always be more than
+ * the current number of entries.
+ */
+static void fill_ablock(struct dm_array_info *info, struct array_block *ab,
+ const void *value, unsigned new_nr)
+{
+ unsigned i;
+ uint32_t nr_entries;
+ struct dm_btree_value_type *vt = &info->value_type;
+
+ BUG_ON(new_nr > le32_to_cpu(ab->max_entries));
+ BUG_ON(new_nr < le32_to_cpu(ab->nr_entries));
+
+ nr_entries = le32_to_cpu(ab->nr_entries);
+ for (i = nr_entries; i < new_nr; i++) {
+ if (vt->inc)
+ vt->inc(vt->context, value);
+ memcpy(element_at(info, ab, i), value, vt->size);
+ }
+ ab->nr_entries = cpu_to_le32(new_nr);
+}
+
+/*
+ * Remove some entries from the back of an array block. Every value
+ * removed will be decremented. new_nr must be <= the current number of
+ * entries.
+ */
+static void trim_ablock(struct dm_array_info *info, struct array_block *ab,
+ unsigned new_nr)
+{
+ unsigned i;
+ uint32_t nr_entries;
+ struct dm_btree_value_type *vt = &info->value_type;
+
+ BUG_ON(new_nr > le32_to_cpu(ab->max_entries));
+ BUG_ON(new_nr > le32_to_cpu(ab->nr_entries));
+
+ nr_entries = le32_to_cpu(ab->nr_entries);
+ for (i = nr_entries; i > new_nr; i--)
+ if (vt->dec)
+ vt->dec(vt->context, element_at(info, ab, i - 1));
+ ab->nr_entries = cpu_to_le32(new_nr);
+}
+
+/*
+ * Read locks a block, and coerces it to an array block. The caller must
+ * unlock 'block' when finished.
+ */
+static int get_ablock(struct dm_array_info *info, dm_block_t b,
+ struct dm_block **block, struct array_block **ab)
+{
+ int r;
+
+ r = dm_tm_read_lock(info->btree_info.tm, b, &array_validator, block);
+ if (r)
+ return r;
+
+ *ab = dm_block_data(*block);
+ return 0;
+}
+
+/*
+ * Unlocks an array block.
+ */
+static int unlock_ablock(struct dm_array_info *info, struct dm_block *block)
+{
+ return dm_tm_unlock(info->btree_info.tm, block);
+}
+
+/*----------------------------------------------------------------*/
+
+/*
+ * Btree manipulation.
+ */
+
+/*
+ * Looks up an array block in the btree, and then read locks it.
+ *
+ * index is the index of the index of the array_block, (ie. the array index
+ * / max_entries).
+ */
+static int lookup_ablock(struct dm_array_info *info, dm_block_t root,
+ unsigned index, struct dm_block **block,
+ struct array_block **ab)
+{
+ int r;
+ uint64_t key = index;
+ __le64 block_le;
+
+ r = dm_btree_lookup(&info->btree_info, root, &key, &block_le);
+ if (r)
+ return r;
+
+ return get_ablock(info, le64_to_cpu(block_le), block, ab);
+}
+
+/*
+ * Insert an array block into the btree. The block is _not_ unlocked.
+ */
+static int insert_ablock(struct dm_array_info *info, uint64_t index,
+ struct dm_block *block, dm_block_t *root)
+{
+ __le64 block_le = cpu_to_le64(dm_block_location(block));
+
+ __dm_bless_for_disk(block_le);
+ return dm_btree_insert(&info->btree_info, *root, &index, &block_le, root);
+}
+
+/*
+ * Looks up an array block in the btree. Then shadows it, and updates the
+ * btree to point to this new shadow. 'root' is an input/output parameter
+ * for both the current root block, and the new one.
+ */
+static int shadow_ablock(struct dm_array_info *info, dm_block_t *root,
+ unsigned index, struct dm_block **block,
+ struct array_block **ab)
+{
+ int r, inc;
+ uint64_t key = index;
+ dm_block_t b;
+ __le64 block_le;
+
+ /*
+ * lookup
+ */
+ r = dm_btree_lookup(&info->btree_info, *root, &key, &block_le);
+ if (r)
+ return r;
+ b = le64_to_cpu(block_le);
+
+ /*
+ * shadow
+ */
+ r = dm_tm_shadow_block(info->btree_info.tm, b,
+ &array_validator, block, &inc);
+ if (r)
+ return r;
+
+ *ab = dm_block_data(*block);
+ if (inc)
+ inc_ablock_entries(info, *ab);
+
+ /*
+ * Reinsert.
+ *
+ * The shadow op will often be a noop. Only insert if it really
+ * copied data.
+ */
+ if (dm_block_location(*block) != b)
+ r = insert_ablock(info, index, *block, root);
+
+ return r;
+}
+
+static int insert_full_ablocks(struct dm_array_info *info, size_t block_size,
+ unsigned begin_block, unsigned end_block,
+ unsigned max_entries, const void *value,
+ dm_block_t *root)
+{
+ int r;
+ struct dm_block *block;
+ struct array_block *ab;
+
+
+ while (begin_block != end_block) {
+ r = alloc_ablock(info, block_size, &block, &ab);
+ if (r)
+ return r;
+
+ fill_ablock(info, ab, value, le32_to_cpu(ab->max_entries));
+
+ r = insert_ablock(info, begin_block, block, root);
+ if (r) {
+ unlock_ablock(info, block);
+ return r;
+ }
+
+ unlock_ablock(info, block);
+ begin_block++;
+ }
+
+ return 0;
+}
+
+/*
+ * Allocate an new array block, and fill it with some values.
+ */
+static int insert_partial_ablock(struct dm_array_info *info, size_t block_size,
+ unsigned block_index, unsigned nr,
+ const void *value, dm_block_t *root)
+{
+ int r;
+ struct dm_block *block;
+ struct array_block *ab;
+
+ if (nr == 0)
+ return 0;
+
+ r = alloc_ablock(info, block_size, &block, &ab);
+ if (r)
+ return r;
+
+ fill_ablock(info, ab, value, nr);
+ r = insert_ablock(info, block_index, block, root);
+ unlock_ablock(info, block);
+
+ return r;
+}
+
+/*
+ * There are a bunch of functions involved with resizing an array. This
+ * structure holds information that commonly needed by them. Purely here
+ * to reduce parameter count.
+ */
+struct resize {
+ /*
+ * Describes the array.
+ */
+ struct dm_array_info *info;
+
+ /*
+ * The current root of the array. This gets updated.
+ */
+ dm_block_t root;
+
+ /*
+ * Metadata block size. Used to calculate the nr entries in an
+ * array block.
+ */
+ size_t block_size;
+
+ /*
+ * Maximum nr entries in an array block.
+ */
+ unsigned max_entries;
+
+ /*
+ * nr of completely full blocks in the array.
+ *
+ * 'old' refers to before the resize, 'new' after.
+ */
+ unsigned old_nr_full_blocks, new_nr_full_blocks;
+
+ /*
+ * Number of entries in the final block. 0 iff only full blocks in
+ * the array.
+ */
+ unsigned old_nr_entries_in_last_block, new_nr_entries_in_last_block;
+
+ /*
+ * The default value used when growing the array.
+ */
+ const void *value;
+};
+
+/*
+ * Removes a consecutive set of array blocks from the btree. The values
+ * in block are decremented as a side effect of the btree remove.
+ *
+ * begin_index - the index of the first array block to remove.
+ * end_index - the one-past-the-end value. ie. this block is not removed.
+ */
+static int drop_blocks(struct resize *resize, unsigned begin_index,
+ unsigned end_index)
+{
+ int r;
+
+ while (begin_index != end_index) {
+ uint64_t key = begin_index++;
+ r = dm_btree_remove(&resize->info->btree_info, resize->root,
+ &key, &resize->root);
+ if (r)
+ return r;
+ }
+
+ return 0;
+}
+
+/*
+ * Calculates how many blocks are needed for the array.
+ */
+static unsigned total_nr_blocks_needed(unsigned nr_full_blocks,
+ unsigned nr_entries_in_last_block)
+{
+ return nr_full_blocks + (nr_entries_in_last_block ? 1 : 0);
+}
+
+/*
+ * Shrink an array.
+ */
+static int shrink(struct resize *resize)
+{
+ int r;
+ unsigned begin, end;
+ struct dm_block *block;
+ struct array_block *ab;
+
+ /*
+ * Lose some blocks from the back?
+ */
+ if (resize->new_nr_full_blocks < resize->old_nr_full_blocks) {
+ begin = total_nr_blocks_needed(resize->new_nr_full_blocks,
+ resize->new_nr_entries_in_last_block);
+ end = total_nr_blocks_needed(resize->old_nr_full_blocks,
+ resize->old_nr_entries_in_last_block);
+
+ r = drop_blocks(resize, begin, end);
+ if (r)
+ return r;
+ }
+
+ /*
+ * Trim the new tail block
+ */
+ if (resize->new_nr_entries_in_last_block) {
+ r = shadow_ablock(resize->info, &resize->root,
+ resize->new_nr_full_blocks, &block, &ab);
+ if (r)
+ return r;
+
+ trim_ablock(resize->info, ab, resize->new_nr_entries_in_last_block);
+ unlock_ablock(resize->info, block);
+ }
+
+ return 0;
+}
+
+/*
+ * Grow an array.
+ */
+static int grow(struct resize *resize)
+{
+ int r;
+ struct dm_block *block;
+ struct array_block *ab;
+
+ if (resize->new_nr_full_blocks > resize->old_nr_full_blocks) {
+ /*
+ * Pad the end of the old block?
+ */
+ if (resize->old_nr_entries_in_last_block > 0) {
+ r = shadow_ablock(resize->info, &resize->root,
+ resize->old_nr_full_blocks, &block, &ab);
+ if (r)
+ return r;
+
+ fill_ablock(resize->info, ab, resize->value, resize->max_entries);
+ unlock_ablock(resize->info, block);
+ }
+
+ /*
+ * Add the full blocks.
+ */
+ r = insert_full_ablocks(resize->info, resize->block_size,
+ resize->old_nr_full_blocks,
+ resize->new_nr_full_blocks,
+ resize->max_entries, resize->value,
+ &resize->root);
+ if (r)
+ return r;
+
+ /*
+ * Add new tail block?
+ */
+ if (resize->new_nr_entries_in_last_block)
+ r = insert_partial_ablock(resize->info, resize->block_size,
+ resize->new_nr_full_blocks,
+ resize->new_nr_entries_in_last_block,
+ resize->value, &resize->root);
+ } else {
+ if (!resize->old_nr_entries_in_last_block) {
+ r = insert_partial_ablock(resize->info, resize->block_size,
+ resize->new_nr_full_blocks,
+ resize->new_nr_entries_in_last_block,
+ resize->value, &resize->root);
+ } else {
+ r = shadow_ablock(resize->info, &resize->root,
+ resize->old_nr_full_blocks, &block, &ab);
+ if (r)
+ return r;
+
+ fill_ablock(resize->info, ab, resize->value, resize->new_nr_entries_in_last_block);
+ unlock_ablock(resize->info, block);
+ }
+ }
+
+ return r;
+}
+
+/*----------------------------------------------------------------*/
+
+/*
+ * These are the value_type functions for the btree elements, which point
+ * to array blocks.
+ */
+static void block_inc(void *context, const void *value)
+{
+ __le64 block_le;
+ struct dm_array_info *info = context;
+
+ memcpy(&block_le, value, sizeof(block_le));
+ dm_tm_inc(info->btree_info.tm, le64_to_cpu(block_le));
+}
+
+static void block_dec(void *context, const void *value)
+{
+ int r;
+ uint64_t b;
+ __le64 block_le;
+ uint32_t ref_count;
+ struct dm_block *block;
+ struct array_block *ab;
+ struct dm_array_info *info = context;
+
+ memcpy(&block_le, value, sizeof(block_le));
+ b = le64_to_cpu(block_le);
+
+ r = dm_tm_ref(info->btree_info.tm, b, &ref_count);
+ if (r) {
+ DMERR_LIMIT("couldn't get reference count");
+ return;
+ }
+
+ if (ref_count == 1) {
+ /*
+ * We're about to drop the last reference to this ablock.
+ * So we need to decrement the ref count of the contents.
+ */
+ r = get_ablock(info, b, &block, &ab);
+ if (r) {
+ DMERR_LIMIT("couldn't get array block");
+ return;
+ }
+
+ dec_ablock_entries(info, ab);
+ unlock_ablock(info, block);
+ }
+
+ dm_tm_dec(info->btree_info.tm, b);
+}
+
+static int block_equal(void *context, const void *value1, const void *value2)
+{
+ return !memcmp(value1, value2, sizeof(__le64));
+}
+
+/*----------------------------------------------------------------*/
+
+void dm_setup_array_info(struct dm_array_info *info,
+ struct dm_transaction_manager *tm,
+ struct dm_btree_value_type *vt)
+{
+ struct dm_btree_value_type *bvt = &info->btree_info.value_type;
+
+ memcpy(&info->value_type, vt, sizeof(info->value_type));
+ info->btree_info.tm = tm;
+ info->btree_info.levels = 1;
+
+ bvt->context = info;
+ bvt->size = sizeof(__le64);
+ bvt->inc = block_inc;
+ bvt->dec = block_dec;
+ bvt->equal = block_equal;
+}
+EXPORT_SYMBOL_GPL(dm_setup_array_info);
+
+int dm_array_empty(struct dm_array_info *info, dm_block_t *root)
+{
+ return dm_btree_empty(&info->btree_info, root);
+}
+EXPORT_SYMBOL_GPL(dm_array_empty);
+
+static int array_resize(struct dm_array_info *info, dm_block_t root,
+ uint32_t old_size, uint32_t new_size,
+ const void *value, dm_block_t *new_root)
+{
+ int r;
+ struct resize resize;
+
+ if (old_size == new_size)
+ return 0;
+
+ resize.info = info;
+ resize.root = root;
+ resize.block_size = dm_bm_block_size(dm_tm_get_bm(info->btree_info.tm));
+ resize.max_entries = calc_max_entries(info->value_type.size,
+ resize.block_size);
+
+ resize.old_nr_full_blocks = old_size / resize.max_entries;
+ resize.old_nr_entries_in_last_block = old_size % resize.max_entries;
+ resize.new_nr_full_blocks = new_size / resize.max_entries;
+ resize.new_nr_entries_in_last_block = new_size % resize.max_entries;
+ resize.value = value;
+
+ r = ((new_size > old_size) ? grow : shrink)(&resize);
+ if (r)
+ return r;
+
+ *new_root = resize.root;
+ return 0;
+}
+
+int dm_array_resize(struct dm_array_info *info, dm_block_t root,
+ uint32_t old_size, uint32_t new_size,
+ const void *value, dm_block_t *new_root)
+ __dm_written_to_disk(value)
+{
+ int r = array_resize(info, root, old_size, new_size, value, new_root);
+ __dm_unbless_for_disk(value);
+ return r;
+}
+EXPORT_SYMBOL_GPL(dm_array_resize);
+
+int dm_array_del(struct dm_array_info *info, dm_block_t root)
+{
+ return dm_btree_del(&info->btree_info, root);
+}
+EXPORT_SYMBOL_GPL(dm_array_del);
+
+int dm_array_get(struct dm_array_info *info, dm_block_t root,
+ uint32_t index, void *value_le)
+{
+ int r;
+ struct dm_block *block;
+ struct array_block *ab;
+ size_t block_size;
+ unsigned entry, max_entries;
+
+ block_size = dm_bm_block_size(dm_tm_get_bm(info->btree_info.tm));
+ max_entries = calc_max_entries(info->value_type.size, block_size);
+
+ r = lookup_ablock(info, root, index / max_entries, &block, &ab);
+ if (r)
+ return r;
+
+ entry = index % max_entries;
+ if (entry >= le32_to_cpu(ab->nr_entries))
+ r = -ENODATA;
+ else
+ memcpy(value_le, element_at(info, ab, entry),
+ info->value_type.size);
+
+ unlock_ablock(info, block);
+ return r;
+}
+EXPORT_SYMBOL_GPL(dm_array_get);
+
+static int array_set(struct dm_array_info *info, dm_block_t root,
+ uint32_t index, const void *value, dm_block_t *new_root)
+{
+ int r;
+ struct dm_block *block;
+ struct array_block *ab;
+ size_t block_size;
+ unsigned max_entries;
+ unsigned entry;
+ void *old_value;
+ struct dm_btree_value_type *vt = &info->value_type;
+
+ block_size = dm_bm_block_size(dm_tm_get_bm(info->btree_info.tm));
+ max_entries = calc_max_entries(info->value_type.size, block_size);
+
+ r = shadow_ablock(info, &root, index / max_entries, &block, &ab);
+ if (r)
+ return r;
+ *new_root = root;
+
+ entry = index % max_entries;
+ if (entry >= le32_to_cpu(ab->nr_entries)) {
+ r = -ENODATA;
+ goto out;
+ }
+
+ old_value = element_at(info, ab, entry);
+ if (vt->dec &&
+ (!vt->equal || !vt->equal(vt->context, old_value, value))) {
+ vt->dec(vt->context, old_value);
+ if (vt->inc)
+ vt->inc(vt->context, value);
+ }
+
+ memcpy(old_value, value, info->value_type.size);
+
+out:
+ unlock_ablock(info, block);
+ return r;
+}
+
+int dm_array_set(struct dm_array_info *info, dm_block_t root,
+ uint32_t index, const void *value, dm_block_t *new_root)
+ __dm_written_to_disk(value)
+{
+ int r;
+
+ r = array_set(info, root, index, value, new_root);
+ __dm_unbless_for_disk(value);
+ return r;
+}
+EXPORT_SYMBOL_GPL(dm_array_set);
+
+struct walk_info {
+ struct dm_array_info *info;
+ int (*fn)(void *context, uint64_t key, void *leaf);
+ void *context;
+};
+
+static int walk_ablock(void *context, uint64_t *keys, void *leaf)
+{
+ struct walk_info *wi = context;
+
+ int r;
+ unsigned i;
+ __le64 block_le;
+ unsigned nr_entries, max_entries;
+ struct dm_block *block;
+ struct array_block *ab;
+
+ memcpy(&block_le, leaf, sizeof(block_le));
+ r = get_ablock(wi->info, le64_to_cpu(block_le), &block, &ab);
+ if (r)
+ return r;
+
+ max_entries = le32_to_cpu(ab->max_entries);
+ nr_entries = le32_to_cpu(ab->nr_entries);
+ for (i = 0; i < nr_entries; i++) {
+ r = wi->fn(wi->context, keys[0] * max_entries + i,
+ element_at(wi->info, ab, i));
+
+ if (r)
+ break;
+ }
+
+ unlock_ablock(wi->info, block);
+ return r;
+}
+
+int dm_array_walk(struct dm_array_info *info, dm_block_t root,
+ int (*fn)(void *, uint64_t key, void *leaf),
+ void *context)
+{
+ struct walk_info wi;
+
+ wi.info = info;
+ wi.fn = fn;
+ wi.context = context;
+
+ return dm_btree_walk(&info->btree_info, root, walk_ablock, &wi);
+}
+EXPORT_SYMBOL_GPL(dm_array_walk);
+
+/*----------------------------------------------------------------*/
diff --git a/drivers/md/persistent-data/dm-array.h b/drivers/md/persistent-data/dm-array.h
new file mode 100644
index 0000000..0fb868d
--- /dev/null
+++ b/drivers/md/persistent-data/dm-array.h
@@ -0,0 +1,128 @@
+/*
+ * Copyright (C) 2012 Red Hat, Inc.
+ *
+ * This file is released under the GPL.
+ */
+#ifndef _LINUX_DM_ARRAY_H
+#define _LINUX_DM_ARRAY_H
+
+#include "dm-btree.h"
+
+/*----------------------------------------------------------------*/
+
+/*
+ * The dm-array is a persistent version of an array. It packs the data
+ * more efficiently than a btree which will result in less disk space use,
+ * and a performance boost. The get and set operations are still O(ln(n)),
+ * but with a much smaller constant.
+ *
+ * The value type structure is reused from the btree type to support proper
+ * reference counting of values.
+ *
+ * The arrays implicitly know their length, and bounds are checked for
+ * lookups and updates. It doesn't store this in an accessible place
+ * because it would waste a whole metadata block. Make sure you store the
+ * size along with the array root in your encompassing data.
+ */
+
+/*
+ * Describes an array. Don't initialise this structure yourself, use the
+ * setup function below.
+ */
+struct dm_array_info {
+ struct dm_transaction_manager *tm;
+ struct dm_btree_value_type value_type;
+ struct dm_btree_info btree_info;
+};
+
+/*
+ * Sets up a dm_array_info structure.
+ *
+ * info - the structure being filled in.
+ * tm - the transaction manager that should supervise this structure.
+ * vt - describes the leaf values.
+ */
+void dm_setup_array_info(struct dm_array_info *info,
+ struct dm_transaction_manager *tm,
+ struct dm_btree_value_type *vt);
+
+/*
+ * Initialise an empty array, zero length array.
+ *
+ * info - describes the array
+ * root - on success this will be filled out with the root block
+ */
+int dm_array_empty(struct dm_array_info *info, dm_block_t *root);
+
+/*
+ * Resizes the array.
+ *
+ * info - describes the array
+ * root - the root block of the array on disk
+ * old_size - yes, the caller is responsible for remembering the size of the array
+ * new_size - can be bigger or smaller than old_size
+ * value - if we're growing the array the new entries will have this value
+ * new_root - on success, points to the new root block
+ *
+ * If growing the inc function for value will be called the appropriate
+ * number of times. So if the caller is holding a reference they may want
+ * to drop it.
+ */
+int dm_array_resize(struct dm_array_info *info, dm_block_t root,
+ uint32_t old_size, uint32_t new_size,
+ const void *value, dm_block_t *new_root)
+ __dm_written_to_disk(value);
+
+/*
+ * Frees a whole array. The value_type's decrement operation will be called
+ * for all values in the array
+ */
+int dm_array_del(struct dm_array_info *info, dm_block_t root);
+
+/*
+ * Lookup a value in the array
+ *
+ * info - describes the array
+ * root - root block of the array
+ * index - array index
+ * value - the value to be read. Will be in on disk format of course.
+ *
+ * -ENODATA will be returned if the index is out of bounds.
+ */
+int dm_array_get(struct dm_array_info *info, dm_block_t root,
+ uint32_t index, void *value);
+
+/*
+ * Set an entry in the array.
+ *
+ * info - describes the array
+ * root - root block of the array
+ * index - array index
+ * value - value to be written to disk. Make sure you bless this before
+ * calling.
+ * new_root - the new root block
+ *
+ * The old value being overwritten will be decremented, the new value
+ * incremented.
+ *
+ * -ENODATA will be returned if the index is out of bounds.
+ */
+int dm_array_set(struct dm_array_info *info, dm_block_t root,
+ uint32_t index, const void *value, dm_block_t *new_root)
+ __dm_written_to_disk(value);
+
+/*
+ * Walk through all the entries in an array.
+ *
+ * info - describes the array
+ * root - root block of the array
+ * fn - called back for every element
+ * context - passed to the callback
+ */
+int dm_array_walk(struct dm_array_info *info, dm_block_t root,
+ int (*fn)(void *, uint64_t key, void *leaf),
+ void *context);
+
+/*----------------------------------------------------------------*/
+
+#endif
--
1.7.10.4
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