[dm-devel] [PATCH for-3.15 1/3] dm: add era target
Mike Snitzer
snitzer at redhat.com
Fri Mar 7 00:47:26 UTC 2014
From: Joe Thornber <ejt at redhat.com>
dm-era is a target that behaves similar to the linear target. In
addition it keeps track of which blocks were written within a user
defined period of time called an 'era'. Each era target instance
maintains the current era as a monotonically increasing 32-bit
counter.
Use cases include tracking changed blocks for backup software, and
partially invalidating the contents of a cache to restore cache
coherency after rolling back a vendor snapshot.
dm-era is primarily expected to be paired with the dm-cache target.
Signed-off-by: Joe Thornber <ejt at redhat.com>
Signed-off-by: Mike Snitzer <snitzer at redhat.com>
---
Documentation/device-mapper/era.txt | 107 +++
drivers/md/Kconfig | 11 +
drivers/md/Makefile | 2 +
drivers/md/dm-era-target.c | 1667 +++++++++++++++++++++++++++++++++++
4 files changed, 1787 insertions(+)
create mode 100644 Documentation/device-mapper/era.txt
create mode 100644 drivers/md/dm-era-target.c
diff --git a/Documentation/device-mapper/era.txt b/Documentation/device-mapper/era.txt
new file mode 100644
index 0000000..f1173ed
--- /dev/null
+++ b/Documentation/device-mapper/era.txt
@@ -0,0 +1,107 @@
+Introduction
+============
+
+dm-era is a target that behaves similar to the linear target. In
+addition it keeps track of which blocks were written within a user
+defined period of time called an 'era'. Each era target instance
+maintains the current era as a monotonically increasing 32-bit
+counter.
+
+Use cases include tracking changed blocks for backup software, and
+partially invalidating the contents of a cache to restore cache
+coherency after rolling back a vendor snapshot.
+
+Constructor
+===========
+
+ era <metadata dev> <origin dev> <block size>
+
+ metadata dev : fast device holding the persistent metadata
+ origin dev : device holding data blocks that may change
+ block size : block size of origin data device
+
+Messages
+========
+
+None of the dm messages take any arguments.
+
+checkpoint
+----------
+
+Possibly move to a new era. You shouldn't assume the era has
+incremented. After sending this message, you should check the
+current era via the status line.
+
+take_metadata_snap
+------------------
+
+Create a clone of the metadata, to allow a userland process to read it.
+
+drop_metadata_snap
+------------------
+
+Drop the metadata snapshot.
+
+Status
+======
+
+<metadata block size> <#used metadata blocks>/<#total metadata blocks>
+<current era> <held metadata root | '-'>
+
+metadata block size : Fixed block size for each metadata block in
+ sectors
+#used metadata blocks : Number of metadata blocks used
+#total metadata blocks : Total number of metadata blocks
+current era : The current era
+held metadata root : The location, in blocks, of the metadata root
+ that has been 'held' for userspace read
+ access. '-' indicates there is no held root
+
+Detailed use case
+=================
+
+The scenario of invalidating a cache when rolling back a vendor
+snapshot was the primary use case when developing this target:
+
+Taking a vendor snapshot
+------------------------
+
+- Send a checkpoint message to the era target
+- Make a note of the current era in its status line
+- Take vendor snapshot (the era and snapshot should be forever
+ associated now).
+
+Rolling back to an vendor snapshot
+----------------------------------
+
+- Cache enters passthrough mode (see: dm-cache's docs in cache.txt)
+- Rollback vendor storage
+- Take metadata snapshot
+- Ascertain which blocks have been written since the snapshot was taken
+ by checking each block's era
+- Invalidate those blocks in the caching software
+- Cache returns to writeback/writethrough mode
+
+Memory usage
+============
+
+The target uses a bitset to record writes in the current era. It also
+has a spare bitset ready for switching over to a new era. Other than
+that it uses a few 4k blocks for updating metadata.
+
+ (4 * nr_blocks) bytes + buffers
+
+Resilience
+==========
+
+Metadata is updated on disk before a write to a previously unwritten
+block is performed. As such dm-era should not be effected by a hard
+crash such as power failure.
+
+Userland tools
+==============
+
+Userland tools are found in the increasingly poorly named
+thin-provisioning-tools project:
+
+ https://github.com/jthornber/thin-provisioning-tools
diff --git a/drivers/md/Kconfig b/drivers/md/Kconfig
index 95ad936..5bdedf6 100644
--- a/drivers/md/Kconfig
+++ b/drivers/md/Kconfig
@@ -285,6 +285,17 @@ config DM_CACHE_CLEANER
A simple cache policy that writes back all data to the
origin. Used when decommissioning a dm-cache.
+config DM_ERA
+ tristate "Era target (EXPERIMENTAL)"
+ depends on BLK_DEV_DM
+ default n
+ select DM_PERSISTENT_DATA
+ select DM_BIO_PRISON
+ ---help---
+ dm-era tracks which parts of a block device are written to
+ over time. Useful for maintaining cache coherency when using
+ vendor snapshots.
+
config DM_MIRROR
tristate "Mirror target"
depends on BLK_DEV_DM
diff --git a/drivers/md/Makefile b/drivers/md/Makefile
index f26d832..a2da532 100644
--- a/drivers/md/Makefile
+++ b/drivers/md/Makefile
@@ -14,6 +14,7 @@ dm-thin-pool-y += dm-thin.o dm-thin-metadata.o
dm-cache-y += dm-cache-target.o dm-cache-metadata.o dm-cache-policy.o
dm-cache-mq-y += dm-cache-policy-mq.o
dm-cache-cleaner-y += dm-cache-policy-cleaner.o
+dm-era-y += dm-era-target.o
md-mod-y += md.o bitmap.o
raid456-y += raid5.o
@@ -53,6 +54,7 @@ obj-$(CONFIG_DM_VERITY) += dm-verity.o
obj-$(CONFIG_DM_CACHE) += dm-cache.o
obj-$(CONFIG_DM_CACHE_MQ) += dm-cache-mq.o
obj-$(CONFIG_DM_CACHE_CLEANER) += dm-cache-cleaner.o
+obj-$(CONFIG_DM_ERA) += dm-era.o
ifeq ($(CONFIG_DM_UEVENT),y)
dm-mod-objs += dm-uevent.o
diff --git a/drivers/md/dm-era-target.c b/drivers/md/dm-era-target.c
new file mode 100644
index 0000000..f772351
--- /dev/null
+++ b/drivers/md/dm-era-target.c
@@ -0,0 +1,1667 @@
+#include "dm.h"
+#include "persistent-data/dm-transaction-manager.h"
+#include "persistent-data/dm-bitset.h"
+#include "persistent-data/dm-space-map.h"
+
+#include <linux/dm-io.h>
+#include <linux/dm-kcopyd.h>
+#include <linux/init.h>
+#include <linux/mempool.h>
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/vmalloc.h>
+
+#define DM_MSG_PREFIX "era"
+
+#define SUPERBLOCK_LOCATION 0
+#define SUPERBLOCK_MAGIC 2126579579
+#define SUPERBLOCK_CSUM_XOR 146538381
+#define MIN_ERA_VERSION 1
+#define MAX_ERA_VERSION 1
+#define INVALID_WRITESET_ROOT SUPERBLOCK_LOCATION
+
+/*----------------------------------------------------------------
+ * Writeset
+ *--------------------------------------------------------------*/
+struct writeset_metadata {
+ uint32_t nr_bits;
+ dm_block_t root;
+};
+
+struct writeset {
+ struct writeset_metadata md;
+
+ /*
+ * An in core copy of the bits to save constantly doing look ups on
+ * disk.
+ */
+ unsigned long *bits;
+};
+
+/*
+ * This does not free off the on disk bitset as this will normally be done
+ * after digesting into the era array.
+ */
+static void writeset_free(struct writeset *ws)
+{
+ vfree(ws->bits);
+}
+
+static int setup_on_disk_bitset(struct dm_disk_bitset *info,
+ unsigned nr_bits, dm_block_t *root)
+{
+ int r;
+
+ r = dm_bitset_empty(info, root);
+ if (r)
+ return r;
+
+ return dm_bitset_resize(info, *root, 0, nr_bits, false, root);
+}
+
+static size_t bitset_size(unsigned nr_bits)
+{
+ return sizeof(unsigned long) * dm_div_up(nr_bits, BITS_PER_LONG);
+}
+
+/*
+ * Allocates memory for the in core bitset.
+ */
+static int writeset_alloc(struct writeset *ws, dm_block_t nr_blocks)
+{
+ ws->md.nr_bits = nr_blocks;
+ ws->md.root = INVALID_WRITESET_ROOT;
+ ws->bits = vzalloc(bitset_size(nr_blocks));
+ if (!ws->bits) {
+ DMERR("%s: couldn't allocate in memory bitset", __func__);
+ return -ENOMEM;
+ }
+
+ return 0;
+}
+
+/*
+ * Wipes the in-core bitset, and creates a new on disk bitset.
+ */
+static int writeset_init(struct dm_disk_bitset *info, struct writeset *ws)
+{
+ int r;
+
+ memset(ws->bits, 0, bitset_size(ws->md.nr_bits));
+
+ r = setup_on_disk_bitset(info, ws->md.nr_bits, &ws->md.root);
+ if (r) {
+ DMERR("%s: setup_on_disk_bitset failed", __func__);
+ return r;
+ }
+
+ return 0;
+}
+
+static bool writeset_marked(struct writeset *ws, dm_block_t block)
+{
+ return test_bit(block, ws->bits);
+}
+
+static int writeset_marked_on_disk(struct dm_disk_bitset *info,
+ struct writeset_metadata *m, dm_block_t block,
+ bool *result)
+{
+ dm_block_t old = m->root;
+
+ /*
+ * The bitset was flushed when it was archived, so we know there'll
+ * be no change to the root.
+ */
+ int r = dm_bitset_test_bit(info, m->root, block, &m->root, result);
+ if (r) {
+ DMERR("%s: dm_bitset_test_bit failed", __func__);
+ return r;
+ }
+
+ BUG_ON(m->root != old);
+
+ return r;
+}
+
+/*
+ * Returns < 0 on error, 0 if the bit wasn't previously set, 1 if it was.
+ */
+static int writeset_test_and_set(struct dm_disk_bitset *info,
+ struct writeset *ws, uint32_t block)
+{
+ int r;
+
+ if (!test_and_set_bit(block, ws->bits)) {
+ r = dm_bitset_set_bit(info, ws->md.root, block, &ws->md.root);
+ if (r) {
+ /* FIXME: fail mode */
+ return r;
+ }
+
+ return 0;
+ }
+
+ return 1;
+}
+
+/*----------------------------------------------------------------
+ * On disk metadata layout
+ *--------------------------------------------------------------*/
+#define SPACE_MAP_ROOT_SIZE 128
+#define UUID_LEN 16
+
+struct writeset_disk {
+ __le32 nr_bits;
+ __le64 root;
+} __packed;
+
+struct superblock_disk {
+ __le32 csum;
+ __le32 flags;
+ __le64 blocknr;
+
+ __u8 uuid[UUID_LEN];
+ __le64 magic;
+ __le32 version;
+
+ __u8 metadata_space_map_root[SPACE_MAP_ROOT_SIZE];
+
+ __le32 data_block_size;
+ __le32 metadata_block_size;
+ __le32 nr_blocks;
+
+ __le32 current_era;
+ struct writeset_disk current_writeset;
+
+ /*
+ * Only these two fields are valid within the metadata snapshot.
+ */
+ __le64 writeset_tree_root;
+ __le64 era_array_root;
+
+ __le64 metadata_snap;
+} __packed;
+
+/*----------------------------------------------------------------
+ * Superblock validation
+ *--------------------------------------------------------------*/
+static void sb_prepare_for_write(struct dm_block_validator *v,
+ struct dm_block *b,
+ size_t sb_block_size)
+{
+ struct superblock_disk *disk = dm_block_data(b);
+
+ disk->blocknr = cpu_to_le64(dm_block_location(b));
+ disk->csum = cpu_to_le32(dm_bm_checksum(&disk->flags,
+ sb_block_size - sizeof(__le32),
+ SUPERBLOCK_CSUM_XOR));
+}
+
+static int check_metadata_version(struct superblock_disk *disk)
+{
+ uint32_t metadata_version = le32_to_cpu(disk->version);
+ if (metadata_version < MIN_ERA_VERSION || metadata_version > MAX_ERA_VERSION) {
+ DMERR("Era metadata version %u found, but only versions between %u and %u supported.",
+ metadata_version, MIN_ERA_VERSION, MAX_ERA_VERSION);
+ return -EINVAL;
+ }
+
+ return 0;
+}
+
+static int sb_check(struct dm_block_validator *v,
+ struct dm_block *b,
+ size_t sb_block_size)
+{
+ struct superblock_disk *disk = dm_block_data(b);
+ __le32 csum_le;
+
+ if (dm_block_location(b) != le64_to_cpu(disk->blocknr)) {
+ DMERR("sb_check failed: blocknr %llu: wanted %llu",
+ le64_to_cpu(disk->blocknr),
+ (unsigned long long)dm_block_location(b));
+ return -ENOTBLK;
+ }
+
+ if (le64_to_cpu(disk->magic) != SUPERBLOCK_MAGIC) {
+ DMERR("sb_check failed: magic %llu: wanted %llu",
+ le64_to_cpu(disk->magic),
+ (unsigned long long) SUPERBLOCK_MAGIC);
+ return -EILSEQ;
+ }
+
+ csum_le = cpu_to_le32(dm_bm_checksum(&disk->flags,
+ sb_block_size - sizeof(__le32),
+ SUPERBLOCK_CSUM_XOR));
+ if (csum_le != disk->csum) {
+ DMERR("sb_check failed: csum %u: wanted %u",
+ le32_to_cpu(csum_le), le32_to_cpu(disk->csum));
+ return -EILSEQ;
+ }
+
+ return check_metadata_version(disk);
+}
+
+static struct dm_block_validator sb_validator = {
+ .name = "superblock",
+ .prepare_for_write = sb_prepare_for_write,
+ .check = sb_check
+};
+
+/*----------------------------------------------------------------
+ * Low level metadata handling
+ *--------------------------------------------------------------*/
+#define DM_ERA_METADATA_BLOCK_SIZE 4096
+#define DM_ERA_METADATA_CACHE_SIZE 64
+#define ERA_MAX_CONCURRENT_LOCKS 5
+
+struct era_metadata {
+ struct block_device *bdev;
+ struct dm_block_manager *bm;
+ struct dm_space_map *sm;
+ struct dm_transaction_manager *tm;
+
+ dm_block_t block_size;
+ uint32_t nr_blocks;
+
+ atomic64_t current_era;
+
+ /*
+ * We preallocate 2 writesets. When an era rolls over we
+ * switch between them. This means the allocation is done at
+ * preresume time, rather than on the io path.
+ */
+ struct writeset writesets[2];
+ struct writeset *current_writeset;
+
+ dm_block_t writeset_tree_root;
+ dm_block_t era_array_root;
+
+ struct dm_disk_bitset bitset_info;
+ struct dm_btree_info writeset_tree_info;
+ struct dm_array_info era_array_info;
+
+ dm_block_t metadata_snap;
+
+ /*
+ * A flag that is set whenever a writeset has been archived.
+ */
+ atomic_t archived_writesets;
+};
+
+static int superblock_read_lock(struct era_metadata *md,
+ struct dm_block **sblock)
+{
+ return dm_bm_read_lock(md->bm, SUPERBLOCK_LOCATION,
+ &sb_validator, sblock);
+}
+
+static int superblock_lock_zero(struct era_metadata *md,
+ struct dm_block **sblock)
+{
+ return dm_bm_write_lock_zero(md->bm, SUPERBLOCK_LOCATION,
+ &sb_validator, sblock);
+}
+
+static int superblock_lock(struct era_metadata *md,
+ struct dm_block **sblock)
+{
+ return dm_bm_write_lock(md->bm, SUPERBLOCK_LOCATION,
+ &sb_validator, sblock);
+}
+
+/* FIXME: duplication with cache and thin */
+static int superblock_all_zeroes(struct dm_block_manager *bm, bool *result)
+{
+ int r;
+ unsigned i;
+ struct dm_block *b;
+ __le64 *data_le, zero = cpu_to_le64(0);
+ unsigned sb_block_size = dm_bm_block_size(bm) / sizeof(__le64);
+
+ /*
+ * We can't use a validator here - it may be all zeroes.
+ */
+ r = dm_bm_read_lock(bm, SUPERBLOCK_LOCATION, NULL, &b);
+ if (r)
+ return r;
+
+ data_le = dm_block_data(b);
+ *result = true;
+ for (i = 0; i < sb_block_size; i++) {
+ if (data_le[i] != zero) {
+ *result = false;
+ break;
+ }
+ }
+
+ return dm_bm_unlock(b);
+}
+
+/*----------------------------------------------------------------*/
+
+static void ws_pack(const struct writeset_metadata *core, struct writeset_disk *disk)
+{
+ disk->nr_bits = cpu_to_le32(core->nr_bits);
+ disk->root = cpu_to_le64(core->root);
+}
+
+static void ws_unpack(const struct writeset_disk *disk, struct writeset_metadata *core)
+{
+ core->nr_bits = le32_to_cpu(disk->nr_bits);
+ core->root = le64_to_cpu(disk->root);
+}
+
+static void ws_inc(void *context, const void *value)
+{
+ struct era_metadata *md = context;
+ struct writeset_disk ws_d;
+ dm_block_t b;
+
+ memcpy(&ws_d, value, sizeof(ws_d));
+ b = le64_to_cpu(ws_d.root);
+
+ dm_tm_inc(md->tm, b);
+}
+
+static void ws_dec(void *context, const void *value)
+{
+ struct era_metadata *md = context;
+ struct writeset_disk ws_d;
+ dm_block_t b;
+
+ memcpy(&ws_d, value, sizeof(ws_d));
+ b = le64_to_cpu(ws_d.root);
+
+ dm_bitset_del(&md->bitset_info, b);
+}
+
+static int ws_eq(void *context, const void *value1, const void *value2)
+{
+ return !memcmp(value1, value2, sizeof(struct writeset_metadata));
+}
+
+/*----------------------------------------------------------------*/
+
+static void setup_writeset_tree_info(struct era_metadata *md)
+{
+ struct dm_btree_value_type *vt = &md->writeset_tree_info.value_type;
+ md->writeset_tree_info.tm = md->tm;
+ md->writeset_tree_info.levels = 1;
+ vt->context = md;
+ vt->size = sizeof(struct writeset_disk);
+ vt->inc = ws_inc;
+ vt->dec = ws_dec;
+ vt->equal = ws_eq;
+}
+
+static void setup_era_array_info(struct era_metadata *md)
+
+{
+ struct dm_btree_value_type vt;
+ vt.context = NULL;
+ vt.size = sizeof(__le32);
+ vt.inc = NULL;
+ vt.dec = NULL;
+ vt.equal = NULL;
+
+ dm_array_info_init(&md->era_array_info, md->tm, &vt);
+}
+
+static void setup_infos(struct era_metadata *md)
+{
+ dm_disk_bitset_init(md->tm, &md->bitset_info);
+ setup_writeset_tree_info(md);
+ setup_era_array_info(md);
+}
+
+/*----------------------------------------------------------------*/
+
+static int create_fresh_metadata(struct era_metadata *md)
+{
+ int r;
+
+ r = dm_tm_create_with_sm(md->bm, SUPERBLOCK_LOCATION,
+ &md->tm, &md->sm);
+ if (r < 0) {
+ DMERR("dm_tm_create_with_sm failed");
+ return r;
+ }
+
+ setup_infos(md);
+
+ r = dm_btree_empty(&md->writeset_tree_info, &md->writeset_tree_root);
+ if (r) {
+ DMERR("couldn't create new writeset tree");
+ return r;
+ }
+
+ r = dm_array_empty(&md->era_array_info, &md->era_array_root);
+ if (r) {
+ DMERR("couldn't create era array");
+ return r;
+ }
+
+ return 0;
+}
+
+/*
+ * Writes a superblock, including the static fields that don't get updated
+ * with every commit (possible optimisation here). 'md' should be fully
+ * constructed when this is called.
+ */
+static int prepare_superblock(struct era_metadata *md, struct superblock_disk *disk)
+{
+ int r;
+ size_t metadata_len;
+
+ disk->magic = cpu_to_le64(SUPERBLOCK_MAGIC);
+ disk->flags = cpu_to_le32(0ul);
+
+ /* FIXME: can't keep blanking the uuid (uuid is currently unused though) */
+ memset(disk->uuid, 0, sizeof(disk->uuid));
+ disk->version = cpu_to_le32(MAX_ERA_VERSION);
+
+ r = dm_sm_root_size(md->sm, &metadata_len);
+ if (r < 0)
+ return r;
+
+ r = dm_sm_copy_root(md->sm, &disk->metadata_space_map_root,
+ metadata_len);
+ if (r < 0)
+ return r;
+
+ disk->data_block_size = cpu_to_le32(md->block_size);
+ disk->metadata_block_size = cpu_to_le32(DM_ERA_METADATA_BLOCK_SIZE >> SECTOR_SHIFT);
+ disk->nr_blocks = cpu_to_le32(md->nr_blocks);
+ disk->current_era = cpu_to_le32(atomic64_read(&md->current_era));
+
+ ws_pack(&md->current_writeset->md, &disk->current_writeset);
+ disk->writeset_tree_root = cpu_to_le64(md->writeset_tree_root);
+ disk->era_array_root = cpu_to_le64(md->era_array_root);
+ disk->metadata_snap = cpu_to_le64(md->metadata_snap);
+
+ return 0;
+}
+
+static int write_superblock(struct era_metadata *md)
+{
+ int r;
+ struct dm_block *sblock;
+ struct superblock_disk *disk;
+
+ r = superblock_lock_zero(md, &sblock);
+ if (r)
+ return r;
+
+ disk = dm_block_data(sblock);
+ r = prepare_superblock(md, disk);
+ if (r) {
+ DMERR("%s: prepare_superblock failed", __func__);
+ dm_bm_unlock(sblock); /* FIXME: does this commit? */
+ return r;
+ }
+
+ return dm_tm_commit(md->tm, sblock);
+}
+
+/*
+ * Assumes block_size and the infos are set.
+ */
+static int format_metadata(struct era_metadata *md)
+{
+ int r;
+
+ r = create_fresh_metadata(md);
+ if (r)
+ return r;
+
+ r = write_superblock(md);
+ if (r)
+ return r;
+
+ return 0;
+}
+
+static int open_metadata(struct era_metadata *md)
+{
+ int r;
+ struct dm_block *sblock;
+ struct superblock_disk *disk;
+
+ r = superblock_read_lock(md, &sblock);
+ if (r) {
+ DMERR("couldn't read_lock superblock");
+ return r;
+ }
+
+ disk = dm_block_data(sblock);
+ r = dm_tm_open_with_sm(md->bm, SUPERBLOCK_LOCATION,
+ disk->metadata_space_map_root,
+ sizeof(disk->metadata_space_map_root),
+ &md->tm, &md->sm);
+ if (r) {
+ DMERR("dm_tm_open_with_sm failed");
+ goto bad;
+ }
+
+ setup_infos(md);
+
+ md->block_size = le32_to_cpu(disk->data_block_size);
+ md->nr_blocks = le32_to_cpu(disk->nr_blocks);
+ atomic64_set(&md->current_era, le32_to_cpu(disk->current_era));
+
+ md->writeset_tree_root = le64_to_cpu(disk->writeset_tree_root);
+ md->era_array_root = le64_to_cpu(disk->era_array_root);
+ md->metadata_snap = le64_to_cpu(disk->metadata_snap);
+ atomic_set(&md->archived_writesets, 1);
+
+ return dm_bm_unlock(sblock);
+
+bad:
+ dm_bm_unlock(sblock);
+ return r;
+}
+
+static int open_or_format_metadata(struct era_metadata *md,
+ bool may_format)
+{
+ int r;
+ bool unformatted = false;
+
+ r = superblock_all_zeroes(md->bm, &unformatted);
+ if (r)
+ return r;
+
+ if (unformatted)
+ return may_format ? format_metadata(md) : -EPERM;
+
+ return open_metadata(md);
+}
+
+static int create_persistent_data_objects(struct era_metadata *md,
+ bool may_format)
+{
+ int r;
+
+ md->bm = dm_block_manager_create(md->bdev, DM_ERA_METADATA_BLOCK_SIZE,
+ DM_ERA_METADATA_CACHE_SIZE,
+ ERA_MAX_CONCURRENT_LOCKS);
+ if (IS_ERR(md->bm)) {
+ DMERR("could not create block manager");
+ return PTR_ERR(md->bm);
+ }
+
+ r = open_or_format_metadata(md, may_format);
+ if (r)
+ dm_block_manager_destroy(md->bm);
+
+ return r;
+}
+
+static void destroy_persistent_data_objects(struct era_metadata *md)
+{
+ dm_sm_destroy(md->sm);
+ dm_tm_destroy(md->tm);
+ dm_block_manager_destroy(md->bm);
+}
+
+/*
+ * This waits until all era_map threads have picked up the new filter.
+ */
+static void swap_writeset(struct era_metadata *md, struct writeset *new_writeset)
+{
+ rcu_assign_pointer(md->current_writeset, new_writeset);
+ synchronize_rcu();
+}
+
+/*----------------------------------------------------------------
+ * Writesets get 'digested' into the main era array.
+ *
+ * We're using a coroutine here so the worker thread can do the digestion,
+ * thus avoiding synchronisation of the metadata. Digesting a whole
+ * writeset in one go would cause too much latency.
+ *--------------------------------------------------------------*/
+struct digest {
+ uint32_t era;
+ unsigned nr_bits, current_bit;
+ struct writeset_metadata writeset;
+ __le32 value;
+ struct dm_disk_bitset info;
+
+ int (*step)(struct era_metadata *, struct digest *);
+};
+
+static int metadata_digest_lookup_writeset(struct era_metadata *md,
+ struct digest *d);
+
+static int metadata_digest_remove_writeset(struct era_metadata *md,
+ struct digest *d)
+{
+ int r;
+ uint64_t key = d->era;
+
+ r = dm_btree_remove(&md->writeset_tree_info, md->writeset_tree_root,
+ &key, &md->writeset_tree_root);
+ if (r) {
+ DMERR("%s: dm_btree_remove failed", __func__);
+ return r;
+ }
+
+ d->step = metadata_digest_lookup_writeset;
+ return 0;
+}
+
+#define INSERTS_PER_STEP 100
+
+static int metadata_digest_transcribe_writeset(struct era_metadata *md,
+ struct digest *d)
+{
+ int r;
+ bool marked;
+ unsigned b, e = min(d->current_bit + INSERTS_PER_STEP, d->nr_bits);
+
+ for (b = d->current_bit; b < e; b++) {
+ r = writeset_marked_on_disk(&d->info, &d->writeset, b, &marked);
+ if (r) {
+ DMERR("%s: writeset_marked_on_disk failed", __func__);
+ return r;
+ }
+
+ if (!marked)
+ continue;
+
+ __dm_bless_for_disk(&d->value);
+ r = dm_array_set_value(&md->era_array_info, md->era_array_root,
+ b, &d->value, &md->era_array_root);
+ if (r) {
+ DMERR("%s: dm_array_set_value failed", __func__);
+ return r;
+ }
+ }
+
+ if (b == d->nr_bits)
+ d->step = metadata_digest_remove_writeset;
+ else
+ d->current_bit = b;
+
+ return 0;
+}
+
+static int metadata_digest_lookup_writeset(struct era_metadata *md,
+ struct digest *d)
+{
+ int r;
+ uint64_t key;
+ struct writeset_disk disk;
+
+ r = dm_btree_find_lowest_key(&md->writeset_tree_info,
+ md->writeset_tree_root, &key);
+ if (r < 0)
+ return r;
+
+ d->era = key;
+
+ r = dm_btree_lookup(&md->writeset_tree_info,
+ md->writeset_tree_root, &key, &disk);
+ if (r) {
+ if (r == -ENODATA) {
+ d->step = NULL;
+ return 0;
+ }
+
+ DMERR("%s: dm_btree_lookup failed", __func__);
+ return r;
+ }
+
+ ws_unpack(&disk, &d->writeset);
+ d->value = cpu_to_le32(key);
+
+ d->nr_bits = min(d->writeset.nr_bits, md->nr_blocks);
+ d->current_bit = 0;
+ d->step = metadata_digest_transcribe_writeset;
+
+ return 0;
+}
+
+static int metadata_digest_start(struct era_metadata *md, struct digest *d)
+{
+ if (d->step)
+ return 0;
+
+ memset(d, 0, sizeof(*d));
+
+ /*
+ * We initialise another bitset info to avoid any caching side
+ * effects with the previous one.
+ */
+ dm_disk_bitset_init(md->tm, &d->info);
+ d->step = metadata_digest_lookup_writeset;
+
+ return 0;
+}
+
+/*----------------------------------------------------------------
+ * High level metadata interface. Target methods should use these, and not
+ * the lower level ones.
+ *--------------------------------------------------------------*/
+static struct era_metadata *metadata_open(struct block_device *bdev,
+ sector_t block_size,
+ bool may_format)
+{
+ int r;
+ struct era_metadata *md = kzalloc(sizeof(*md), GFP_KERNEL);
+
+ if (!md)
+ return NULL;
+
+ md->bdev = bdev;
+ md->block_size = block_size;
+
+ md->writesets[0].md.root = INVALID_WRITESET_ROOT;
+ md->writesets[1].md.root = INVALID_WRITESET_ROOT;
+ md->current_writeset = &md->writesets[0];
+
+ r = create_persistent_data_objects(md, may_format);
+ if (r) {
+ kfree(md);
+ return ERR_PTR(r);
+ }
+
+ return md;
+}
+
+static void metadata_close(struct era_metadata *md)
+{
+ destroy_persistent_data_objects(md);
+ kfree(md);
+}
+
+static int metadata_resize(struct era_metadata *md, void *arg)
+{
+ int r;
+ dm_block_t *new_size = arg;
+ __le32 value;
+
+ writeset_free(&md->writesets[0]);
+ writeset_free(&md->writesets[1]);
+
+ r = writeset_alloc(&md->writesets[0], *new_size);
+ if (r) {
+ DMERR("%s: writeset_alloc failed for writeset 0", __func__);
+ return r;
+ }
+
+ r = writeset_alloc(&md->writesets[1], *new_size);
+ if (r) {
+ DMERR("%s: writeset_alloc failed for writeset 1", __func__);
+ return r;
+ }
+
+ value = cpu_to_le32(0u);
+ __dm_bless_for_disk(&value);
+ r = dm_array_resize(&md->era_array_info, md->era_array_root,
+ md->nr_blocks, *new_size,
+ &value, &md->era_array_root);
+ if (r) {
+ DMERR("%s: dm_array_resize failed", __func__);
+ return r;
+ }
+
+ md->nr_blocks = *new_size;
+ return 0;
+}
+
+static uint32_t metadata_current_era(struct era_metadata *md)
+{
+ return (uint32_t) atomic64_read(&md->current_era);
+}
+
+static int metadata_era_archive(struct era_metadata *md)
+{
+ int r;
+ uint64_t keys[1];
+ struct writeset_disk value;
+
+ r = dm_bitset_flush(&md->bitset_info, md->current_writeset->md.root,
+ &md->current_writeset->md.root);
+ if (r) {
+ DMERR("%s: dm_bitset_flush failed", __func__);
+ return r;
+ }
+
+ ws_pack(&md->current_writeset->md, &value);
+ md->current_writeset->md.root = INVALID_WRITESET_ROOT;
+
+ keys[0] = atomic64_read(&md->current_era);
+ __dm_bless_for_disk(&value);
+ r = dm_btree_insert(&md->writeset_tree_info, md->writeset_tree_root,
+ keys, &value, &md->writeset_tree_root);
+ if (r) {
+ DMERR("%s: couldn't insert writeset into btree", __func__);
+ /* FIXME: fail mode */
+ return r;
+ }
+
+ atomic_set(&md->archived_writesets, 1);
+
+ return 0;
+}
+
+static struct writeset *next_writeset(struct era_metadata *md)
+{
+ return (md->current_writeset == &md->writesets[0]) ?
+ &md->writesets[1] : &md->writesets[0];
+}
+
+static int metadata_new_era(struct era_metadata *md)
+{
+ int r;
+ struct writeset *new_writeset = next_writeset(md);
+
+ r = writeset_init(&md->bitset_info, new_writeset);
+ if (r) {
+ DMERR("%s: writeset_init failed", __func__);
+ return r;
+ }
+
+ swap_writeset(md, new_writeset);
+ atomic64_inc(&md->current_era);
+
+ return 0;
+}
+
+static int metadata_era_rollover(struct era_metadata *md)
+{
+ int r;
+
+ if (md->current_writeset->md.root != INVALID_WRITESET_ROOT) {
+ r = metadata_era_archive(md);
+ if (r) {
+ DMERR("%s: metadata_archive_era failed", __func__);
+ /* FIXME: fail mode? */
+ return r;
+ }
+ }
+
+ r = metadata_new_era(md);
+ if (r) {
+ DMERR("%s: new era failed", __func__);
+ /* FIXME: fail mode */
+ return r;
+ }
+
+ return 0;
+}
+
+static bool metadata_current_marked(struct era_metadata *md, dm_block_t block)
+{
+ bool r;
+ struct writeset *ws;
+
+ rcu_read_lock();
+ ws = rcu_dereference(md->current_writeset);
+ r = writeset_marked(ws, block);
+ rcu_read_unlock();
+
+ return r;
+}
+
+static int metadata_commit(struct era_metadata *md)
+{
+ int r;
+ struct dm_block *sblock;
+
+ if (md->current_writeset->md.root != SUPERBLOCK_LOCATION) {
+ r = dm_bitset_flush(&md->bitset_info, md->current_writeset->md.root,
+ &md->current_writeset->md.root);
+ if (r) {
+ DMERR("%s: bitset flush failed", __func__);
+ return r;
+ }
+ }
+
+ r = dm_tm_pre_commit(md->tm);
+ if (r) {
+ DMERR("%s: pre commit failed", __func__);
+ return r;
+ }
+
+ r = superblock_lock(md, &sblock);
+ if (r) {
+ DMERR("%s: superblock lock failed", __func__);
+ return r;
+ }
+
+ r = prepare_superblock(md, dm_block_data(sblock));
+ if (r) {
+ DMERR("%s: prepare_superblock failed", __func__);
+ dm_bm_unlock(sblock); /* FIXME: does this commit? */
+ return r;
+ }
+
+ return dm_tm_commit(md->tm, sblock);
+}
+
+static int metadata_checkpoint(struct era_metadata *md)
+{
+ /*
+ * For now we just rollover, but later I want to put a check in to
+ * avoid this if the filter is still pretty fresh.
+ */
+ return metadata_era_rollover(md);
+}
+
+/*
+ * Metadata snapshots allow userland to access era data.
+ */
+static int metadata_take_snap(struct era_metadata *md)
+{
+ int r, inc;
+ struct dm_block *clone;
+
+ if (md->metadata_snap != SUPERBLOCK_LOCATION) {
+ DMERR("%s: metadata snapshot already exists", __func__);
+ return -EINVAL;
+ }
+
+ r = metadata_era_rollover(md);
+ if (r) {
+ DMERR("%s: era rollover failed", __func__);
+ return r;
+ }
+
+ r = metadata_commit(md);
+ if (r) {
+ DMERR("%s: pre commit failed", __func__);
+ return r;
+ }
+
+ r = dm_sm_inc_block(md->sm, SUPERBLOCK_LOCATION);
+ if (r) {
+ DMERR("%s: couldn't increment superblock", __func__);
+ return r;
+ }
+
+ r = dm_tm_shadow_block(md->tm, SUPERBLOCK_LOCATION,
+ &sb_validator, &clone, &inc);
+ if (r) {
+ DMERR("%s: couldn't shadow superblock", __func__);
+ dm_sm_dec_block(md->sm, SUPERBLOCK_LOCATION);
+ return r;
+ }
+ BUG_ON(!inc);
+
+ r = dm_sm_inc_block(md->sm, md->writeset_tree_root);
+ if (r) {
+ DMERR("%s: couldn't inc writeset tree root", __func__);
+ dm_tm_unlock(md->tm, clone);
+ return r;
+ }
+
+ r = dm_sm_inc_block(md->sm, md->era_array_root);
+ if (r) {
+ DMERR("%s: couldn't inc era tree root", __func__);
+ dm_sm_dec_block(md->sm, md->writeset_tree_root);
+ dm_tm_unlock(md->tm, clone);
+ return r;
+ }
+
+ md->metadata_snap = dm_block_location(clone);
+
+ r = dm_tm_unlock(md->tm, clone);
+ if (r) {
+ DMERR("%s: couldn't unlock clone", __func__);
+ md->metadata_snap = SUPERBLOCK_LOCATION;
+ return r;
+ }
+
+ return 0;
+}
+
+static dm_block_t metadata_snap_root(struct era_metadata *md)
+{
+ return md->metadata_snap;
+}
+
+static int metadata_drop_snap(struct era_metadata *md)
+{
+ int r;
+ dm_block_t location;
+ struct dm_block *clone;
+ struct superblock_disk *disk;
+
+ if (md->metadata_snap == SUPERBLOCK_LOCATION) {
+ DMERR("%s: no snap to drop", __func__);
+ return -EINVAL;
+ }
+
+ r = dm_tm_read_lock(md->tm, md->metadata_snap, &sb_validator, &clone);
+ if (r) {
+ DMERR("%s: couldn't read lock superblock clone", __func__);
+ return r;
+ }
+
+ /*
+ * Whatever happens now we'll commit with no record of the metadata
+ * snap.
+ */
+ md->metadata_snap = SUPERBLOCK_LOCATION;
+
+ disk = dm_block_data(clone);
+ r = dm_btree_del(&md->writeset_tree_info,
+ le64_to_cpu(disk->writeset_tree_root));
+ if (r) {
+ DMERR("%s: error deleting writeset tree clone", __func__);
+ dm_tm_unlock(md->tm, clone);
+ return r;
+ }
+
+ r = dm_array_del(&md->era_array_info, le64_to_cpu(disk->era_array_root));
+ if (r) {
+ DMERR("%s: error deleting era array clone", __func__);
+ dm_tm_unlock(md->tm, clone);
+ return r;
+ }
+
+ location = dm_block_location(clone);
+ dm_tm_unlock(md->tm, clone);
+
+ return dm_sm_dec_block(md->sm, location);
+}
+
+/*----------------------------------------------------------------*/
+
+struct era {
+ struct dm_target *ti;
+ struct dm_target_callbacks callbacks;
+
+ struct dm_dev *metadata_dev;
+ struct dm_dev *origin_dev;
+
+ uint32_t block_size;
+ dm_block_t nr_blocks;
+ unsigned sectors_per_block_shift;
+ struct era_metadata *md;
+
+ struct workqueue_struct *wq;
+ struct work_struct worker;
+
+ spinlock_t deferred_lock;
+ struct bio_list deferred_bios;
+
+ spinlock_t rpc_lock;
+ struct list_head rpc_calls;
+
+ struct digest digest;
+ atomic_t suspended;
+};
+
+struct rpc {
+ struct list_head list;
+
+ int (*fn0)(struct era_metadata *);
+ int (*fn1)(struct era_metadata *, void *);
+ void *arg;
+ int result;
+
+ wait_queue_head_t wait;
+ atomic_t complete;
+};
+
+/*----------------------------------------------------------------
+ * Remapping.
+ *---------------------------------------------------------------*/
+static dm_block_t get_block(struct era *era, struct bio *bio)
+{
+ return bio->bi_iter.bi_sector >> era->sectors_per_block_shift;
+}
+
+static void remap_to_origin(struct era *era, struct bio *bio)
+{
+ bio->bi_bdev = era->origin_dev->bdev;
+}
+
+/*----------------------------------------------------------------
+ * Worker thread
+ *--------------------------------------------------------------*/
+static void wake_worker(struct era *era)
+{
+ if (!atomic_read(&era->suspended))
+ queue_work(era->wq, &era->worker);
+}
+
+static void process_old_eras(struct era *era)
+{
+ int r;
+
+ if (!era->digest.step)
+ return;
+
+ r = era->digest.step(era->md, &era->digest);
+ if (r < 0) {
+ DMERR("%s: digest step failed, stopping digestion", __func__);
+ era->digest.step = NULL;
+
+ } else if (era->digest.step)
+ wake_worker(era);
+}
+
+static void process_deferred_bios(struct era *era)
+{
+ int r;
+ unsigned long flags;
+ struct bio_list deferred_bios, marked_bios;
+ struct bio *bio;
+ bool commit_needed = false;
+ bool failed = false;
+
+ bio_list_init(&deferred_bios);
+ bio_list_init(&marked_bios);
+
+ spin_lock_irqsave(&era->deferred_lock, flags);
+ bio_list_merge(&deferred_bios, &era->deferred_bios);
+ bio_list_init(&era->deferred_bios);
+ spin_unlock_irqrestore(&era->deferred_lock, flags);
+
+ while ((bio = bio_list_pop(&deferred_bios))) {
+ r = writeset_test_and_set(&era->md->bitset_info,
+ era->md->current_writeset,
+ get_block(era, bio));
+ if (r < 0) {
+ /*
+ * This is bad news, we need to rollback.
+ * FIXME: finish.
+ */
+ failed = true;
+
+ } else if (r == 0)
+ commit_needed = true;
+
+ bio_list_add(&marked_bios, bio);
+ }
+
+ if (commit_needed) {
+ r = metadata_commit(era->md);
+ if (r)
+ failed = true;
+ }
+
+ if (failed)
+ while ((bio = bio_list_pop(&marked_bios)))
+ bio_io_error(bio);
+ else
+ while ((bio = bio_list_pop(&marked_bios)))
+ generic_make_request(bio);
+}
+
+static void process_rpc_calls(struct era *era)
+{
+ int r;
+ bool need_commit = false;
+ struct list_head calls;
+ struct rpc *rpc, *tmp;
+
+ INIT_LIST_HEAD(&calls);
+ spin_lock(&era->rpc_lock);
+ list_splice_init(&era->rpc_calls, &calls);
+ spin_unlock(&era->rpc_lock);
+
+ list_for_each_entry_safe(rpc, tmp, &calls, list) {
+ rpc->result = rpc->fn0 ? rpc->fn0(era->md) : rpc->fn1(era->md, rpc->arg);
+ need_commit = true;
+ }
+
+ if (need_commit) {
+ r = metadata_commit(era->md);
+ if (r)
+ list_for_each_entry_safe(rpc, tmp, &calls, list)
+ rpc->result = r;
+ }
+
+ list_for_each_entry_safe(rpc, tmp, &calls, list) {
+ atomic_set(&rpc->complete, 1);
+ wake_up(&rpc->wait);
+ }
+}
+
+static void kick_off_digest(struct era *era)
+{
+ if (atomic_read(&era->md->archived_writesets)) {
+ atomic_set(&era->md->archived_writesets, 0);
+ metadata_digest_start(era->md, &era->digest);
+ }
+}
+
+static void do_work(struct work_struct *ws)
+{
+ struct era *era = container_of(ws, struct era, worker);
+
+ kick_off_digest(era);
+ process_old_eras(era);
+ process_deferred_bios(era);
+ process_rpc_calls(era);
+}
+
+static void defer_bio(struct era *era, struct bio *bio)
+{
+ spin_lock(&era->deferred_lock);
+ bio_list_add(&era->deferred_bios, bio);
+ spin_unlock(&era->deferred_lock);
+
+ wake_worker(era);
+}
+
+/*
+ * Make an rpc call to the worker to change the metadata.
+ */
+static int perform_rpc(struct era *era, struct rpc *rpc)
+{
+ rpc->result = 0;
+ init_waitqueue_head(&rpc->wait);
+ atomic_set(&rpc->complete, 0);
+
+ spin_lock(&era->rpc_lock);
+ list_add(&rpc->list, &era->rpc_calls);
+ spin_unlock(&era->rpc_lock);
+
+ wake_worker(era);
+ wait_event(rpc->wait, atomic_read(&rpc->complete));
+
+ return rpc->result;
+}
+
+static int in_worker0(struct era *era, int (*fn)(struct era_metadata *))
+{
+ struct rpc rpc;
+ rpc.fn0 = fn;
+ rpc.fn1 = NULL;
+
+ return perform_rpc(era, &rpc);
+}
+
+static int in_worker1(struct era *era,
+ int (*fn)(struct era_metadata *, void *), void *arg)
+{
+ struct rpc rpc;
+ rpc.fn0 = NULL;
+ rpc.fn1 = fn;
+ rpc.arg = arg;
+
+ return perform_rpc(era, &rpc);
+}
+
+static void start_worker(struct era *era)
+{
+ atomic_set(&era->suspended, 0);
+}
+
+static void stop_worker(struct era *era)
+{
+ atomic_set(&era->suspended, 1);
+ flush_workqueue(era->wq);
+}
+
+/*----------------------------------------------------------------
+ * Target methods
+ *--------------------------------------------------------------*/
+static int dev_is_congested(struct dm_dev *dev, int bdi_bits)
+{
+ struct request_queue *q = bdev_get_queue(dev->bdev);
+ return bdi_congested(&q->backing_dev_info, bdi_bits);
+}
+
+static int era_is_congested(struct dm_target_callbacks *cb, int bdi_bits)
+{
+ struct era *era = container_of(cb, struct era, callbacks);
+ return dev_is_congested(era->origin_dev, bdi_bits);
+}
+
+static void era_destroy(struct era *era)
+{
+ metadata_close(era->md);
+
+ if (era->wq)
+ destroy_workqueue(era->wq);
+
+ if (era->origin_dev)
+ dm_put_device(era->ti, era->origin_dev);
+
+ if (era->metadata_dev)
+ dm_put_device(era->ti, era->metadata_dev);
+
+ kfree(era);
+}
+
+static dm_block_t calc_nr_blocks(struct era *era)
+{
+ return dm_sector_div_up(era->ti->len, era->block_size);
+}
+
+/*
+ * <metadata dev> <data dev> <data block size (sectors)>
+ */
+static int era_ctr(struct dm_target *ti, unsigned argc, char **argv)
+{
+ int r;
+ char dummy;
+ struct era *era;
+ struct era_metadata *md;
+
+ if (argc != 3) {
+ ti->error = "Invalid argument count";
+ return -EINVAL;
+ }
+
+ era = kzalloc(sizeof(*era), GFP_KERNEL);
+ if (!era) {
+ ti->error = "Error allocating era structure";
+ return -ENOMEM;
+ }
+
+ era->ti = ti;
+
+ r = dm_get_device(ti, argv[0], FMODE_READ | FMODE_WRITE, &era->metadata_dev);
+ if (r) {
+ ti->error = "Error opening metadata device";
+ era_destroy(era);
+ return -EINVAL;
+ }
+
+ r = dm_get_device(ti, argv[1], FMODE_READ | FMODE_WRITE, &era->origin_dev);
+ if (r) {
+ ti->error = "Error opening data device";
+ era_destroy(era);
+ return -EINVAL;
+ }
+
+ r = sscanf(argv[2], "%u%c", &era->block_size, &dummy);
+ if (r != 1) {
+ ti->error = "Error parsing block size";
+ era_destroy(era);
+ return -EINVAL;
+ }
+ era->sectors_per_block_shift = __ffs(era->block_size);
+
+ r = dm_set_target_max_io_len(ti, era->block_size);
+ if (r) {
+ ti->error = "could not set max io len";
+ era_destroy(era);
+ return -EINVAL;
+ }
+
+ md = metadata_open(era->metadata_dev->bdev, era->block_size, true);
+ if (IS_ERR(md)) {
+ ti->error = "Error reading metadata";
+ era_destroy(era);
+ return PTR_ERR(md);
+ }
+ era->md = md;
+
+ era->nr_blocks = calc_nr_blocks(era);
+
+ r = metadata_resize(era->md, &era->nr_blocks);
+ if (r) {
+ ti->error = "couldn't resize metadata";
+ era_destroy(era);
+ return -ENOMEM;
+ }
+
+ era->wq = alloc_ordered_workqueue("dm-" DM_MSG_PREFIX, WQ_MEM_RECLAIM);
+ if (!era->wq) {
+ ti->error = "could not create workqueue for metadata object";
+ era_destroy(era);
+ return -ENOMEM;
+ }
+ INIT_WORK(&era->worker, do_work);
+
+ spin_lock_init(&era->deferred_lock);
+ bio_list_init(&era->deferred_bios);
+
+ spin_lock_init(&era->rpc_lock);
+ INIT_LIST_HEAD(&era->rpc_calls);
+
+ ti->private = era;
+ ti->num_flush_bios = 1;
+ ti->flush_supported = true;
+
+ ti->num_discard_bios = 1;
+ ti->discards_supported = true;
+ era->callbacks.congested_fn = era_is_congested;
+ dm_table_add_target_callbacks(ti->table, &era->callbacks);
+
+ return 0;
+}
+
+static void era_dtr(struct dm_target *ti)
+{
+ era_destroy(ti->private);
+}
+
+static int era_map(struct dm_target *ti, struct bio *bio)
+{
+ struct era *era = ti->private;
+ dm_block_t block = get_block(era, bio);
+
+ /*
+ * All bios get remapped to the origin device. We do this now, but
+ * it may not get issued until later. Depending on whether the
+ * block is marked in this era.
+ */
+ remap_to_origin(era, bio);
+
+ if (bio_data_dir(bio) == WRITE &&
+ !metadata_current_marked(era->md, block)) {
+ defer_bio(era, bio);
+ return DM_MAPIO_SUBMITTED;
+ }
+
+ return DM_MAPIO_REMAPPED;
+}
+
+static void era_postsuspend(struct dm_target *ti)
+{
+ int r;
+ struct era *era = ti->private;
+
+ r = in_worker0(era, metadata_era_archive);
+ if (r) {
+ DMERR("%s: couldn't archive current era", __func__);
+ /* FIXME: fail mode */
+ }
+
+ stop_worker(era);
+}
+
+static int era_preresume(struct dm_target *ti)
+{
+ int r;
+ struct era *era = ti->private;
+ dm_block_t new_size = calc_nr_blocks(era);
+
+ if (era->nr_blocks != new_size) {
+ r = in_worker1(era, metadata_resize, &new_size);
+ if (r)
+ return r;
+
+ era->nr_blocks = new_size;
+ }
+
+ start_worker(era);
+
+ r = in_worker0(era, metadata_new_era);
+ if (r) {
+ DMERR("%s: metadata_era_rollover failed", __func__);
+ return r;
+ }
+
+ return 0;
+}
+
+/*
+ * Status format:
+ *
+ * <metadata block size> <#used metadata blocks>/<#total metadata blocks>
+ * <current era> <held metadata root | '-'>
+ */
+static void era_status(struct dm_target *ti, status_type_t type,
+ unsigned status_flags, char *result, unsigned maxlen)
+{
+ int r;
+ struct era *era = ti->private;
+ ssize_t sz = 0;
+ dm_block_t snap;
+ dm_block_t nr_md_free, nr_md_total;
+ char buf[BDEVNAME_SIZE];
+
+ switch (type) {
+ case STATUSTYPE_INFO:
+ /*
+ * FIXME: do we need to protect this?
+ */
+ r = dm_sm_get_nr_free(era->md->sm, &nr_md_free);
+ if (r) {
+ DMERR("dm_sm_get_nr_free returned %d", r);
+ goto err;
+ }
+
+ r = dm_sm_get_nr_blocks(era->md->sm, &nr_md_total);
+ if (r) {
+ DMERR("dm_pool_get_metadata_dev_size returned %d", r);
+ goto err;
+ }
+
+ DMEMIT("%u %llu/%llu %u",
+ (unsigned) (DM_ERA_METADATA_BLOCK_SIZE >> SECTOR_SHIFT),
+ (unsigned long long) (nr_md_total - nr_md_free),
+ (unsigned long long) nr_md_total,
+ (unsigned) metadata_current_era(era->md));
+
+ snap = metadata_snap_root(era->md);
+ if (snap != SUPERBLOCK_LOCATION)
+ DMEMIT(" %llu", snap);
+ else
+ DMEMIT(" -");
+ break;
+
+ case STATUSTYPE_TABLE:
+ format_dev_t(buf, era->metadata_dev->bdev->bd_dev);
+ DMEMIT("%s ", buf);
+ format_dev_t(buf, era->origin_dev->bdev->bd_dev);
+ DMEMIT("%s %u", buf, era->block_size);
+ break;
+ }
+
+ return;
+
+err:
+ DMEMIT("Error");
+}
+
+static int era_message(struct dm_target *ti, unsigned argc, char **argv)
+{
+ struct era *era = ti->private;
+
+ if (argc != 1) {
+ DMERR("incorrect number of message arguments");
+ return -EINVAL;
+ }
+
+ if (!strcasecmp(argv[0], "checkpoint"))
+ return in_worker0(era, metadata_checkpoint);
+
+ if (!strcasecmp(argv[0], "take_metadata_snap"))
+ return in_worker0(era, metadata_take_snap);
+
+ if (!strcasecmp(argv[0], "drop_metadata_snap"))
+ return in_worker0(era, metadata_drop_snap);
+
+ DMERR("unsupported message '%s'", argv[0]);
+ return -EINVAL;
+}
+
+static sector_t get_dev_size(struct dm_dev *dev)
+{
+ return i_size_read(dev->bdev->bd_inode) >> SECTOR_SHIFT;
+}
+
+static int era_iterate_devices(struct dm_target *ti,
+ iterate_devices_callout_fn fn, void *data)
+{
+ struct era *era = ti->private;
+ return fn(ti, era->origin_dev, 0, get_dev_size(era->origin_dev), data);
+}
+
+static int era_merge(struct dm_target *ti, struct bvec_merge_data *bvm,
+ struct bio_vec *biovec, int max_size)
+{
+ struct era *era = ti->private;
+ struct request_queue *q = bdev_get_queue(era->origin_dev->bdev);
+
+ if (!q->merge_bvec_fn)
+ return max_size;
+
+ bvm->bi_bdev = era->origin_dev->bdev;
+
+ return min(max_size, q->merge_bvec_fn(q, bvm, biovec));
+}
+
+static void era_io_hints(struct dm_target *ti, struct queue_limits *limits)
+{
+ struct era *era = ti->private;
+ uint64_t io_opt_sectors = limits->io_opt >> SECTOR_SHIFT;
+
+ /*
+ * If the system-determined stacked limits are compatible with the
+ * cache's blocksize (io_opt is a factor) do not override them.
+ */
+ if (io_opt_sectors < era->block_size ||
+ do_div(io_opt_sectors, era->block_size)) {
+ blk_limits_io_min(limits, 0);
+ blk_limits_io_opt(limits, era->block_size << SECTOR_SHIFT);
+ }
+}
+
+/*----------------------------------------------------------------*/
+
+static struct target_type era_target = {
+ .name = "era",
+ .version = {1, 0, 0},
+ .module = THIS_MODULE,
+ .ctr = era_ctr,
+ .dtr = era_dtr,
+ .map = era_map,
+ .postsuspend = era_postsuspend,
+ .preresume = era_preresume,
+ .status = era_status,
+ .message = era_message,
+ .iterate_devices = era_iterate_devices,
+ .merge = era_merge,
+ .io_hints = era_io_hints
+};
+
+static int __init dm_era_init(void)
+{
+ int r;
+
+ r = dm_register_target(&era_target);
+ if (r) {
+ DMERR("era target registration failed: %d", r);
+ return r;
+ }
+
+ return 0;
+}
+
+static void __exit dm_era_exit(void)
+{
+ dm_unregister_target(&era_target);
+}
+
+module_init(dm_era_init);
+module_exit(dm_era_exit);
+
+MODULE_DESCRIPTION(DM_NAME " era target");
+MODULE_AUTHOR("Joe Thornber <ejt at redhat.com>");
+MODULE_LICENSE("GPL");
--
1.8.1.4
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