From: heinzm@redhat.com <heinzm@redhat.com>
Date: Wed, 27 Aug 2008 14:16:42 +0200
Subject: [md] add device-mapper dirty region hash file
Message-id: 20080827121637.900954252@redhat.com
O-Subject: [PATCH RHEL5.3 437180 06/11] dm-region_hash.c.patch
Bugzilla: 437180

This patch introduces the device-mapper dirty region hash,
factored out of dm-mirror to allow for sharing it.

Heinz

Signed-off-by: Heinz Mauelshagen <heinzm@redhat.com>

diff --git a/drivers/md/dm-region_hash.c b/drivers/md/dm-region_hash.c
new file mode 100644
index 0000000..7c1ab1f
--- /dev/null
+++ b/drivers/md/dm-region_hash.c
@@ -0,0 +1,644 @@
+/*
+ * Copyright (C) 2003 Sistina Software Limited.
+ * Copyright (C) 2004-2008 Red Hat, Inc. All rights reserved.
+ *
+ * This file is released under the GPL.
+ */
+
+#include "dm.h"
+#include "dm-region_hash.h"
+
+#include <linux/dm-dirty-log.h>
+#include <linux/ctype.h>
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/vmalloc.h>
+
+#define	DM_MSG_PREFIX	"region hash"
+
+/*-----------------------------------------------------------------
+ * Region hash
+ *
+ * The set splits itself up into discrete regions.
+ * Each region can be in one of three states:
+ *
+ * o clean
+ * o dirty,
+ * o nosync.
+ *
+ * There is no need to put clean regions in the hash.
+ *
+ *
+ * In addition to being present in the hash table a region _may_
+ * be present on one of three lists.
+ *
+ *   clean_regions: Regions on this list have no io pending to
+ *   them, they are in sync, we are no longer interested in them,
+ *   they are dull.  rh_update_states() will remove them from the
+ *   hash table.
+ *
+ *   quiesced_regions: These regions have been spun down, ready
+ *   for recovery.  rh_recovery_start() will remove regions from
+ *   this list and hand them to the caller, which will schedule the
+ *   recovery io.
+ *
+ *   recovered_regions: Regions that the caller has successfully
+ *   recovered.  rh_update_states() will now schedule any delayed
+ *   io, up the recovery_count, and remove the region from the hash.
+ *
+ * There are 2 locks:
+ *   A rw spin lock 'hash_lock' protects just the hash table,
+ *   this is never held in write mode from interrupt context,
+ *   which I believe means that we only have to disable irqs when
+ *   doing a write lock.
+ *
+ *   An ordinary spin lock 'region_lock' that protects the three
+ *   lists in the region_hash, with the 'state', 'list' and
+ *   'delayed_bios' fields of the regions.  This is used from irq
+ *   context, so all other uses will have to suspend local irqs.
+ *---------------------------------------------------------------*/
+enum region_hash_flags {
+	RECOVERY,
+};
+
+struct region_hash {
+	unsigned int max_recovery; /* Max # of regions to recover in parallel */
+	unsigned long flags;
+
+	/* Callback function to dispatch queued writes on recovered regions. */
+	void (*dispatch)(void *context, struct bio_list *bios);
+	void *dispatch_context;
+
+	/* Callback function to wakeup callers worker thread. */
+	void (*wake)(void *context);
+	void *wake_context;
+
+	uint32_t region_size;
+	unsigned int region_shift;
+
+	/* holds persistent region state */
+	struct dm_dirty_log *log;
+
+	/* hash table */
+	rwlock_t hash_lock;
+	mempool_t *region_pool;
+	unsigned int mask;
+	unsigned int nr_buckets;
+	unsigned int prime;
+	unsigned int shift;
+	struct list_head *buckets;
+
+	spinlock_t region_lock;
+	struct semaphore recovery_count;
+	struct list_head clean_regions;
+	struct list_head quiesced_regions;
+	struct list_head recovered_regions;
+};
+
+struct region {
+	struct region_hash *rh;	/* FIXME: can we get rid of this ? */
+	region_t key;
+	int state;
+	void *context;	/* Caller context. */
+
+	struct list_head hash_list;
+	struct list_head list;
+
+	atomic_t pending;
+	struct bio_list delayed_bios;
+};
+
+/*
+ * Conversion fns
+ */
+region_t rh_sector_to_region(void *rh, sector_t sector)
+{
+	return sector >> ((struct region_hash*) rh)->region_shift;
+}
+
+region_t rh_bio_to_region(void *rh, struct bio *bio)
+{
+	return rh_sector_to_region(rh, bio->bi_sector);
+}
+
+sector_t rh_region_to_sector(void *rh, region_t region)
+{
+	return region << ((struct region_hash*) rh)->region_shift;
+}
+
+/*
+ * Retrival fns.
+ */
+region_t rh_get_region_key(void *reg)
+{
+	return ((struct region *)reg)->key;
+}
+
+sector_t rh_get_region_size(void *rh)
+{
+	return ((struct region_hash *)rh)->region_size;
+}
+
+/* Squirrel a context with a region. */
+void *rh_reg_get_context(void *reg)
+{
+	return ((struct region*) reg)->context;
+}
+
+void rh_reg_set_context(void *reg, void *context)
+{
+	((struct region*) reg)->context = context;
+}
+
+/*
+ * Region struct allocation/free.
+ */
+static void *region_alloc(unsigned int gfp_mask, void *pool_data)
+{
+	return kmalloc(sizeof(struct region), gfp_mask);
+}
+
+static void region_free(void *element, void *pool_data)
+{
+	kfree(element);
+}
+
+#define MIN_REGIONS 64
+int rh_init(void **region_hash,
+	    unsigned int max_recovery,
+
+            void (*dispatch)(void *dispatch_context, struct bio_list *bios),
+	    void *dispatch_context,
+            void (*wake)(void *wake_context),
+	    void *wake_context,
+	    struct dm_dirty_log *log, uint32_t region_size,
+	    region_t nr_regions)
+{
+	unsigned int nr_buckets, max_buckets;
+	unsigned hash_primes[] = {
+		/* Table of primes for rh_hash/table size optimization. */
+		3, 7, 13, 27, 53, 97, 193, 389, 769,
+		1543, 3079, 6151, 12289, 24593,
+	};
+	size_t i;
+	struct region_hash *rh;
+
+	if (region_size & (region_size - 1)) {
+		DMERR("region size must be 2^^n");
+		return -EINVAL;
+	}
+
+	rh = kmalloc(sizeof(*rh), GFP_KERNEL);
+	if (!rh) {
+		DMERR("unable to allocate region hash memory");
+		return -ENOMEM;
+	}
+
+	rh->max_recovery = max_recovery;
+	rh->dispatch = dispatch;
+	rh->dispatch_context = dispatch_context;
+	rh->wake = wake;
+	rh->wake_context = wake_context;
+	rh->log = log;
+	rh->region_size = region_size;
+	rh->region_shift = ffs(region_size) - 1;
+	rwlock_init(&rh->hash_lock);
+
+	/* Calculate a suitable number of buckets for our hash table. */
+	max_buckets = nr_regions >> 6;
+	for (nr_buckets = 128u; nr_buckets < max_buckets; nr_buckets <<= 1);
+	nr_buckets >>= 1;
+	rh->mask = rh->nr_buckets = nr_buckets;
+	rh->mask--;
+	rh->shift = ffs(nr_buckets);
+	rh->prime = hash_primes[rh->shift - 1];
+	if (rh->prime > ARRAY_SIZE(hash_primes) - 2)
+		rh->prime = ARRAY_SIZE(hash_primes) - 1;
+
+	rh->buckets = vmalloc(nr_buckets * sizeof(*rh->buckets));
+	if (!rh->buckets) {
+		DMERR("unable to allocate region hash bucket memory");
+		vfree(rh);
+		return -ENOMEM;
+	}
+
+	for (i = 0; i < nr_buckets; i++)
+		INIT_LIST_HEAD(rh->buckets + i);
+
+	spin_lock_init(&rh->region_lock);
+	sema_init(&rh->recovery_count, 0);
+	INIT_LIST_HEAD(&rh->clean_regions);
+	INIT_LIST_HEAD(&rh->quiesced_regions);
+	INIT_LIST_HEAD(&rh->recovered_regions);
+
+	rh->region_pool = mempool_create(MIN_REGIONS, region_alloc,
+					 region_free, NULL);
+	if (!rh->region_pool) {
+		vfree(rh->buckets);
+		vfree(rh);
+		return -ENOMEM;
+	}
+
+	*region_hash = rh;
+
+	return 0;
+}
+
+void rh_exit(void *v)
+{
+	unsigned int h;
+	struct region *reg, *tmp;
+	struct region_hash *rh = v;
+
+	BUG_ON(!list_empty(&rh->quiesced_regions));
+
+	for (h = 0; h < rh->nr_buckets; h++) {
+		list_for_each_entry_safe(reg, tmp, rh->buckets + h, hash_list) {
+			BUG_ON(atomic_read(&reg->pending));
+			mempool_free(reg, rh->region_pool);
+		}
+	}
+
+	dm_dirty_log_destroy(rh->log);
+
+	if (rh->region_pool)
+		mempool_destroy(rh->region_pool);
+
+	vfree(rh->buckets);
+	kfree(rh);
+}
+
+static inline unsigned int rh_hash(struct region_hash *rh, region_t region)
+{
+	return (unsigned int) ((region * rh->prime) >> rh->shift) & rh->mask;
+}
+
+static struct region *__rh_lookup(struct region_hash *rh, region_t region)
+{
+	struct region *reg;
+	struct list_head *bucket = rh->buckets + rh_hash(rh, region);
+
+	list_for_each_entry(reg, bucket, hash_list) {
+		if (reg->key == region)
+			return reg;
+	}
+
+	return NULL;
+}
+
+static void __rh_insert(struct region_hash *rh, struct region *reg)
+{
+	unsigned int h = rh_hash(rh, reg->key);
+	list_add(&reg->hash_list, rh->buckets + h);
+}
+
+static struct region *__rh_alloc(struct region_hash *rh, region_t region)
+{
+	struct region *reg, *nreg;
+
+	read_unlock(&rh->hash_lock);
+
+	nreg = mempool_alloc(rh->region_pool, GFP_NOIO);
+	nreg->state = rh->log->type->in_sync(rh->log, region, 1) ?
+		      RH_CLEAN : RH_NOSYNC;
+	nreg->rh = rh;
+	nreg->key = region;
+
+	INIT_LIST_HEAD(&nreg->list);
+
+	atomic_set(&nreg->pending, 0);
+	bio_list_init(&nreg->delayed_bios);
+
+	write_lock_irq(&rh->hash_lock);
+
+	reg = __rh_lookup(rh, region);
+	if (reg)
+		/* we lost the race */
+		mempool_free(nreg, rh->region_pool);
+	else {
+		__rh_insert(rh, nreg);
+		if (nreg->state == RH_CLEAN) {
+			spin_lock(&rh->region_lock);
+			list_add(&nreg->list, &rh->clean_regions);
+			spin_unlock(&rh->region_lock);
+		}
+		reg = nreg;
+	}
+
+	write_unlock_irq(&rh->hash_lock);
+	read_lock(&rh->hash_lock);
+
+	return reg;
+}
+
+static inline struct region *__rh_find(struct region_hash *rh, region_t region)
+{
+	struct region *reg;
+
+	reg = __rh_lookup(rh, region);
+	if (!reg)
+		reg = __rh_alloc(rh, region);
+
+	return reg;
+}
+
+int rh_state(void *v, region_t region, int may_block)
+{
+	int r = 0;
+	struct region *reg;
+	struct region_hash *rh = v;
+
+	read_lock(&rh->hash_lock);
+	reg = __rh_lookup(rh, region);
+	if (reg)
+		r = reg->state;
+	read_unlock(&rh->hash_lock);
+
+	if (r)
+		return r;
+
+	/*
+	 * The region wasn't in the hash, so we fall back to the dirty log.
+	 */
+	r = rh->log->type->in_sync(rh->log, region, may_block);
+
+	/*
+	 * Any error from the dirty log (eg. -EWOULDBLOCK) gets
+	 * taken as a RH_NOSYNC
+	 */
+	return r == 1 ? RH_CLEAN : RH_NOSYNC;
+}
+
+void rh_update_states(void *v)
+{
+	struct region *reg, *next;
+	struct region_hash *rh = v;
+	LIST_HEAD(clean);
+	LIST_HEAD(recovered);
+
+	/*
+	 * Quickly grab the lists.
+	 */
+	write_lock_irq(&rh->hash_lock);
+	spin_lock(&rh->region_lock);
+	if (!list_empty(&rh->clean_regions)) {
+		list_splice(&rh->clean_regions, &clean);
+		INIT_LIST_HEAD(&rh->clean_regions);
+
+		list_for_each_entry(reg, &clean, list)
+			list_del(&reg->hash_list);
+	}
+
+	if (!list_empty(&rh->recovered_regions)) {
+		list_splice(&rh->recovered_regions, &recovered);
+		INIT_LIST_HEAD(&rh->recovered_regions);
+
+		list_for_each_entry(reg, &recovered, list)
+			list_del(&reg->hash_list);
+	}
+
+	spin_unlock(&rh->region_lock);
+	write_unlock_irq(&rh->hash_lock);
+
+	/*
+	 * All the regions on the recovered and clean lists have
+	 * now been pulled out of the system, so no need to do
+	 * any more locking.
+	 */
+	list_for_each_entry_safe (reg, next, &recovered, list) {
+		if (reg->state != RH_ERROR)
+			rh->log->type->clear_region(rh->log, reg->key);
+
+		rh->log->type->set_region_sync(rh->log, reg->key,
+					       reg->state != RH_ERROR);
+		up(&rh->recovery_count);
+		if (reg->delayed_bios.head)
+			rh->dispatch(rh->dispatch_context, &reg->delayed_bios);
+
+		mempool_free(reg, rh->region_pool);
+	}
+
+	list_for_each_entry_safe(reg, next, &clean, list) {
+		rh->log->type->clear_region(rh->log, reg->key);
+		mempool_free(reg, rh->region_pool);
+	}
+
+	rh_flush(rh);
+}
+
+void rh_inc(void *v, region_t region)
+{
+	struct region *reg;
+	struct region_hash *rh = v;
+
+	read_lock(&rh->hash_lock);
+	reg = __rh_find(rh, region);
+	if (reg->state == RH_CLEAN) {
+		rh->log->type->mark_region(rh->log, reg->key);
+
+		spin_lock_irq(&rh->region_lock);
+		reg->state = RH_DIRTY;
+		list_del_init(&reg->list);	/* Take off the clean list. */
+		spin_unlock_irq(&rh->region_lock);
+	}
+
+	atomic_inc(&reg->pending);
+	read_unlock(&rh->hash_lock);
+}
+
+void rh_inc_pending(void *v, struct bio_list *bios)
+{
+	struct bio *bio;
+	struct region_hash *rh = v;
+
+	for (bio = bios->head; bio; bio = bio->bi_next)
+		rh_inc(rh, rh_bio_to_region(rh, bio));
+}
+
+void rh_dec(void *v, region_t region)
+{
+	unsigned long flags;
+	struct region *reg;
+	struct region_hash *rh = v;
+
+	read_lock(&rh->hash_lock);
+	reg = __rh_lookup(rh, region);
+	read_unlock(&rh->hash_lock);
+
+	BUG_ON(!reg);
+
+	if (atomic_dec_and_test(&reg->pending)) {
+		spin_lock_irqsave(&rh->region_lock, flags);
+		if (reg->state == RH_RECOVERING) {
+			list_add_tail(&reg->list, &rh->quiesced_regions);
+		} else {
+			reg->state = RH_CLEAN;
+			list_add(&reg->list, &rh->clean_regions);
+		}
+		spin_unlock_irqrestore(&rh->region_lock, flags);
+	}
+}
+
+/*
+ * Starts quiescing a region in preparation for recovery.
+ */
+static int __rh_recovery_prepare(struct region_hash *rh)
+{
+	int r;
+	struct region *reg;
+	region_t region;
+
+	/*
+	 * Ask the dirty log what's next.
+	 */
+	r = rh->log->type->get_resync_work(rh->log, &region);
+	if (r <= 0)
+		return r;
+
+	/*
+	 * Get this region, and start it quiescing
+	 * by setting the recovering flag.
+	 */
+	read_lock(&rh->hash_lock);
+	reg = __rh_find(rh, region);
+	read_unlock(&rh->hash_lock);
+
+	spin_lock_irq(&rh->region_lock);
+
+	reg->state = RH_RECOVERING;
+
+	/* Already quiesced ? */
+	list_del_init(&reg->list);
+	if (!atomic_read(&reg->pending))
+		list_add(&reg->list, &rh->quiesced_regions);
+
+	spin_unlock_irq(&rh->region_lock);
+
+	return 1;
+}
+
+int rh_recovery_prepare(void *v)
+{
+	struct region_hash *rh = v;
+
+	if (test_bit(RECOVERY, &rh->flags)) {
+		while (!down_trylock(&rh->recovery_count)) {
+			if (__rh_recovery_prepare(rh) <= 0) {
+				up(&rh->recovery_count);
+				return -ENOENT;
+			}
+		}
+	}
+
+	return 0;
+}
+
+/*
+ * Returns any quiesced regions.
+ */
+void *rh_recovery_start(void *v)
+{
+	struct region *reg = NULL;
+	struct region_hash *rh = v;
+
+	spin_lock_irq(&rh->region_lock);
+	if (!list_empty(&rh->quiesced_regions)) {
+		reg = list_entry(rh->quiesced_regions.next,
+				 struct region, list);
+		list_del_init(&reg->list); /* Remove from the quiesced list. */
+	}
+	spin_unlock_irq(&rh->region_lock);
+
+	return (void*) reg;
+}
+
+/*
+ * Put region on list of recovered ones.
+ */
+void rh_recovery_end(void *v, int error)
+{
+	struct region *reg = v;
+	struct region_hash *rh = reg->rh;
+
+	if (error)
+		reg->state = RH_ERROR;
+
+	spin_lock_irq(&rh->region_lock);
+	list_add(&reg->list, &rh->recovered_regions);
+	spin_unlock_irq(&rh->region_lock);
+}
+
+void rh_flush(void *v)
+{
+	struct region_hash *rh = v;
+
+	rh->log->type->flush(rh->log);
+}
+
+void rh_delay_by_region(void *v, struct bio *bio, region_t region)
+{
+	struct region_hash *rh = v;
+	struct region *reg;
+
+	read_lock(&rh->hash_lock);
+	reg = __rh_find(rh, region);
+	bio_list_add(&reg->delayed_bios, bio);
+	read_unlock(&rh->hash_lock);
+}
+
+void rh_delay(void *v, struct bio *bio)
+{
+	return rh_delay_by_region(v, bio, rh_bio_to_region(v, bio));
+}
+
+void rh_stop_recovery(void *v)
+{
+	int i;
+	struct region_hash *rh = v;
+
+	clear_bit(RECOVERY, &rh->flags);
+	rh->wake(rh->wake_context);
+
+	/* wait for any recovering regions */
+	for (i = 0; i < rh->max_recovery; i++)
+		down(&rh->recovery_count);
+}
+
+void rh_start_recovery(void *v)
+{
+	int i;
+	struct region_hash *rh = v;
+
+	set_bit(RECOVERY, &rh->flags);
+	for (i = 0; i < rh->max_recovery; i++)
+		up(&rh->recovery_count);
+
+	rh->wake(rh->wake_context);
+}
+
+EXPORT_SYMBOL(rh_bio_to_region);
+EXPORT_SYMBOL(rh_sector_to_region);
+EXPORT_SYMBOL(rh_region_to_sector);
+EXPORT_SYMBOL(rh_init);
+EXPORT_SYMBOL(rh_exit);
+EXPORT_SYMBOL(rh_state);
+EXPORT_SYMBOL(rh_update_states);
+EXPORT_SYMBOL(rh_flush);
+EXPORT_SYMBOL(rh_inc);
+EXPORT_SYMBOL(rh_inc_pending);
+EXPORT_SYMBOL(rh_dec);
+EXPORT_SYMBOL(rh_delay);
+EXPORT_SYMBOL(rh_delay_by_region);
+EXPORT_SYMBOL(rh_recovery_prepare);
+EXPORT_SYMBOL(rh_recovery_start);
+EXPORT_SYMBOL(rh_recovery_end);
+EXPORT_SYMBOL(rh_stop_recovery);
+EXPORT_SYMBOL(rh_start_recovery);
+EXPORT_SYMBOL(rh_reg_get_context);
+EXPORT_SYMBOL(rh_reg_set_context);
+EXPORT_SYMBOL(rh_get_region_key);
+EXPORT_SYMBOL(rh_get_region_size);
+
+MODULE_DESCRIPTION(DM_NAME " region hash");
+MODULE_AUTHOR("Heinz Mauelshagen <hjm@redhat.com>");
+MODULE_LICENSE("GPL");