dm: add persistent data library

The persistent-data library offers a re-usable framework for the storage
and management of on-disk metadata in device-mapper targets.

It's used by the thin-provisioning target in the next patch and in an
upcoming hierarchical storage target.

For further information, please read
Documentation/device-mapper/persistent-data.txt

Signed-off-by: Joe Thornber <thornber@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>

1 files changed, 335 insertions, 0 deletions

diff --git a/drivers/md/persistent-data/dm-space-map-disk.c b/drivers/md/persistent-data/dm-space-map-disk.c
new file mode 100644
index 00000000000..aeff7852cf7
--- /dev/null
+++ b/drivers/md/persistent-data/dm-space-map-disk.c
@@ -0,0 +1,335 @@
+/*
+ * Copyright (C) 2011 Red Hat, Inc.
+ *
+ * This file is released under the GPL.
+ */
+
+#include "dm-space-map-checker.h"
+#include "dm-space-map-common.h"
+#include "dm-space-map-disk.h"
+#include "dm-space-map.h"
+#include "dm-transaction-manager.h"
+
+#include <linux/list.h>
+#include <linux/slab.h>
+#include <linux/module.h>
+#include <linux/device-mapper.h>
+
+#define DM_MSG_PREFIX "space map disk"
+
+/*----------------------------------------------------------------*/
+
+/*
+ * Space map interface.
+ */
+struct sm_disk {
+        struct dm_space_map sm;
+
+        struct ll_disk ll;
+        struct ll_disk old_ll;
+
+        dm_block_t begin;
+        dm_block_t nr_allocated_this_transaction;
+};
+
+static void sm_disk_destroy(struct dm_space_map *sm)
+{
+        struct sm_disk *smd = container_of(sm, struct sm_disk, sm);
+
+        kfree(smd);
+}
+
+static int sm_disk_extend(struct dm_space_map *sm, dm_block_t extra_blocks)
+{
+        struct sm_disk *smd = container_of(sm, struct sm_disk, sm);
+
+        return sm_ll_extend(&smd->ll, extra_blocks);
+}
+
+static int sm_disk_get_nr_blocks(struct dm_space_map *sm, dm_block_t *count)
+{
+        struct sm_disk *smd = container_of(sm, struct sm_disk, sm);
+        *count = smd->old_ll.nr_blocks;
+
+        return 0;
+}
+
+static int sm_disk_get_nr_free(struct dm_space_map *sm, dm_block_t *count)
+{
+        struct sm_disk *smd = container_of(sm, struct sm_disk, sm);
+        *count = (smd->old_ll.nr_blocks - smd->old_ll.nr_allocated) - smd->nr_allocated_this_transaction;
+
+        return 0;
+}
+
+static int sm_disk_get_count(struct dm_space_map *sm, dm_block_t b,
+                             uint32_t *result)
+{
+        struct sm_disk *smd = container_of(sm, struct sm_disk, sm);
+        return sm_ll_lookup(&smd->ll, b, result);
+}
+
+static int sm_disk_count_is_more_than_one(struct dm_space_map *sm, dm_block_t b,
+                                          int *result)
+{
+        int r;
+        uint32_t count;
+
+        r = sm_disk_get_count(sm, b, &count);
+        if (r)
+                return r;
+
+        return count > 1;
+}
+
+static int sm_disk_set_count(struct dm_space_map *sm, dm_block_t b,
+                             uint32_t count)
+{
+        int r;
+        uint32_t old_count;
+        enum allocation_event ev;
+        struct sm_disk *smd = container_of(sm, struct sm_disk, sm);
+
+        r = sm_ll_insert(&smd->ll, b, count, &ev);
+        if (!r) {
+                switch (ev) {
+                case SM_NONE:
+                        break;
+
+                case SM_ALLOC:
+                        /*
+                         * This _must_ be free in the prior transaction
+                         * otherwise we've lost atomicity.
+                         */
+                        smd->nr_allocated_this_transaction++;
+                        break;
+
+                case SM_FREE:
+                        /*
+                         * It's only free if it's also free in the last
+                         * transaction.
+                         */
+                        r = sm_ll_lookup(&smd->old_ll, b, &old_count);
+                        if (r)
+                                return r;
+
+                        if (!old_count)
+                                smd->nr_allocated_this_transaction--;
+                        break;
+                }
+        }
+
+        return r;
+}
+
+static int sm_disk_inc_block(struct dm_space_map *sm, dm_block_t b)
+{
+        int r;
+        enum allocation_event ev;
+        struct sm_disk *smd = container_of(sm, struct sm_disk, sm);
+
+        r = sm_ll_inc(&smd->ll, b, &ev);
+        if (!r && (ev == SM_ALLOC))
+                /*
+                 * This _must_ be free in the prior transaction
+                 * otherwise we've lost atomicity.
+                 */
+                smd->nr_allocated_this_transaction++;
+
+        return r;
+}
+
+static int sm_disk_dec_block(struct dm_space_map *sm, dm_block_t b)
+{
+        int r;
+        uint32_t old_count;
+        enum allocation_event ev;
+        struct sm_disk *smd = container_of(sm, struct sm_disk, sm);
+
+        r = sm_ll_dec(&smd->ll, b, &ev);
+        if (!r && (ev == SM_FREE)) {
+                /*
+                 * It's only free if it's also free in the last
+                 * transaction.
+                 */
+                r = sm_ll_lookup(&smd->old_ll, b, &old_count);
+                if (r)
+                        return r;
+
+                if (!old_count)
+                        smd->nr_allocated_this_transaction--;
+        }
+
+        return r;
+}
+
+static int sm_disk_new_block(struct dm_space_map *sm, dm_block_t *b)
+{
+        int r;
+        enum allocation_event ev;
+        struct sm_disk *smd = container_of(sm, struct sm_disk, sm);
+
+        /* FIXME: we should loop round a couple of times */
+        r = sm_ll_find_free_block(&smd->old_ll, smd->begin, smd->old_ll.nr_blocks, b);
+        if (r)
+                return r;
+
+        smd->begin = *b + 1;
+        r = sm_ll_inc(&smd->ll, *b, &ev);
+        if (!r) {
+                BUG_ON(ev != SM_ALLOC);
+                smd->nr_allocated_this_transaction++;
+        }
+
+        return r;
+}
+
+static int sm_disk_commit(struct dm_space_map *sm)
+{
+        int r;
+        dm_block_t nr_free;
+        struct sm_disk *smd = container_of(sm, struct sm_disk, sm);
+
+        r = sm_disk_get_nr_free(sm, &nr_free);
+        if (r)
+                return r;
+
+        r = sm_ll_commit(&smd->ll);
+        if (r)
+                return r;
+
+        memcpy(&smd->old_ll, &smd->ll, sizeof(smd->old_ll));
+        smd->begin = 0;
+        smd->nr_allocated_this_transaction = 0;
+
+        r = sm_disk_get_nr_free(sm, &nr_free);
+        if (r)
+                return r;
+
+        return 0;
+}
+
+static int sm_disk_root_size(struct dm_space_map *sm, size_t *result)
+{
+        *result = sizeof(struct disk_sm_root);
+
+        return 0;
+}
+
+static int sm_disk_copy_root(struct dm_space_map *sm, void *where_le, size_t max)
+{
+        struct sm_disk *smd = container_of(sm, struct sm_disk, sm);
+        struct disk_sm_root root_le;
+
+        root_le.nr_blocks = cpu_to_le64(smd->ll.nr_blocks);
+        root_le.nr_allocated = cpu_to_le64(smd->ll.nr_allocated);
+        root_le.bitmap_root = cpu_to_le64(smd->ll.bitmap_root);
+        root_le.ref_count_root = cpu_to_le64(smd->ll.ref_count_root);
+
+        if (max < sizeof(root_le))
+                return -ENOSPC;
+
+        memcpy(where_le, &root_le, sizeof(root_le));
+
+        return 0;
+}
+
+/*----------------------------------------------------------------*/
+
+static struct dm_space_map ops = {
+        .destroy = sm_disk_destroy,
+        .extend = sm_disk_extend,
+        .get_nr_blocks = sm_disk_get_nr_blocks,
+        .get_nr_free = sm_disk_get_nr_free,
+        .get_count = sm_disk_get_count,
+        .count_is_more_than_one = sm_disk_count_is_more_than_one,
+        .set_count = sm_disk_set_count,
+        .inc_block = sm_disk_inc_block,
+        .dec_block = sm_disk_dec_block,
+        .new_block = sm_disk_new_block,
+        .commit = sm_disk_commit,
+        .root_size = sm_disk_root_size,
+        .copy_root = sm_disk_copy_root
+};
+
+static struct dm_space_map *dm_sm_disk_create_real(
+        struct dm_transaction_manager *tm,
+        dm_block_t nr_blocks)
+{
+        int r;
+        struct sm_disk *smd;
+
+        smd = kmalloc(sizeof(*smd), GFP_KERNEL);
+        if (!smd)
+                return ERR_PTR(-ENOMEM);
+
+        smd->begin = 0;
+        smd->nr_allocated_this_transaction = 0;
+        memcpy(&smd->sm, &ops, sizeof(smd->sm));
+
+        r = sm_ll_new_disk(&smd->ll, tm);
+        if (r)
+                goto bad;
+
+        r = sm_ll_extend(&smd->ll, nr_blocks);
+        if (r)
+                goto bad;
+
+        r = sm_disk_commit(&smd->sm);
+        if (r)
+                goto bad;
+
+        return &smd->sm;
+
+bad:
+        kfree(smd);
+        return ERR_PTR(r);
+}
+
+struct dm_space_map *dm_sm_disk_create(struct dm_transaction_manager *tm,
+                                       dm_block_t nr_blocks)
+{
+        struct dm_space_map *sm = dm_sm_disk_create_real(tm, nr_blocks);
+        return dm_sm_checker_create_fresh(sm);
+}
+EXPORT_SYMBOL_GPL(dm_sm_disk_create);
+
+static struct dm_space_map *dm_sm_disk_open_real(
+        struct dm_transaction_manager *tm,
+        void *root_le, size_t len)
+{
+        int r;
+        struct sm_disk *smd;
+
+        smd = kmalloc(sizeof(*smd), GFP_KERNEL);
+        if (!smd)
+                return ERR_PTR(-ENOMEM);
+
+        smd->begin = 0;
+        smd->nr_allocated_this_transaction = 0;
+        memcpy(&smd->sm, &ops, sizeof(smd->sm));
+
+        r = sm_ll_open_disk(&smd->ll, tm, root_le, len);
+        if (r)
+                goto bad;
+
+        r = sm_disk_commit(&smd->sm);
+        if (r)
+                goto bad;
+
+        return &smd->sm;
+
+bad:
+        kfree(smd);
+        return ERR_PTR(r);
+}
+
+struct dm_space_map *dm_sm_disk_open(struct dm_transaction_manager *tm,
+                                     void *root_le, size_t len)
+{
+        return dm_sm_checker_create(
+                dm_sm_disk_open_real(tm, root_le, len));
+}
+EXPORT_SYMBOL_GPL(dm_sm_disk_open);
+
+/*----------------------------------------------------------------*/