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yaml
---
r: 361518
b: refs/heads/master
c: e2e74d6
h: refs/heads/master
v: v3
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Joe Thornber authored and Alasdair G Kergon committed Mar 20, 2013
1 parent cbc5556 commit dc62c95
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Showing 2 changed files with 89 additions and 51 deletions.
2 changes: 1 addition & 1 deletion [refs]
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Original file line number Diff line number Diff line change
@@ -1,2 +1,2 @@
---
refs/heads/master: 79ed9caffc9fff67aa64fd683e791aa70f1bcb51
refs/heads/master: e2e74d617eadc15f601983270c4f4a6935c5a943
138 changes: 88 additions & 50 deletions trunk/drivers/md/dm-cache-target.c
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Original file line number Diff line number Diff line change
Expand Up @@ -142,6 +142,7 @@ struct cache {
spinlock_t lock;
struct bio_list deferred_bios;
struct bio_list deferred_flush_bios;
struct bio_list deferred_writethrough_bios;
struct list_head quiesced_migrations;
struct list_head completed_migrations;
struct list_head need_commit_migrations;
Expand Down Expand Up @@ -199,6 +200,11 @@ struct per_bio_data {
bool tick:1;
unsigned req_nr:2;
struct dm_deferred_entry *all_io_entry;

/* writethrough fields */
struct cache *cache;
dm_cblock_t cblock;
bio_end_io_t *saved_bi_end_io;
};

struct dm_cache_migration {
Expand Down Expand Up @@ -616,6 +622,56 @@ static void issue(struct cache *cache, struct bio *bio)
spin_unlock_irqrestore(&cache->lock, flags);
}

static void defer_writethrough_bio(struct cache *cache, struct bio *bio)
{
unsigned long flags;

spin_lock_irqsave(&cache->lock, flags);
bio_list_add(&cache->deferred_writethrough_bios, bio);
spin_unlock_irqrestore(&cache->lock, flags);

wake_worker(cache);
}

static void writethrough_endio(struct bio *bio, int err)
{
struct per_bio_data *pb = get_per_bio_data(bio);
bio->bi_end_io = pb->saved_bi_end_io;

if (err) {
bio_endio(bio, err);
return;
}

remap_to_cache(pb->cache, bio, pb->cblock);

/*
* We can't issue this bio directly, since we're in interrupt
* context. So it get's put on a bio list for processing by the
* worker thread.
*/
defer_writethrough_bio(pb->cache, bio);
}

/*
* When running in writethrough mode we need to send writes to clean blocks
* to both the cache and origin devices. In future we'd like to clone the
* bio and send them in parallel, but for now we're doing them in
* series as this is easier.
*/
static void remap_to_origin_then_cache(struct cache *cache, struct bio *bio,
dm_oblock_t oblock, dm_cblock_t cblock)
{
struct per_bio_data *pb = get_per_bio_data(bio);

pb->cache = cache;
pb->cblock = cblock;
pb->saved_bi_end_io = bio->bi_end_io;
bio->bi_end_io = writethrough_endio;

remap_to_origin_clear_discard(pb->cache, bio, oblock);
}

/*----------------------------------------------------------------
* Migration processing
*
Expand Down Expand Up @@ -1077,14 +1133,9 @@ static void process_bio(struct cache *cache, struct prealloc *structs,
inc_hit_counter(cache, bio);
pb->all_io_entry = dm_deferred_entry_inc(cache->all_io_ds);

if (is_writethrough_io(cache, bio, lookup_result.cblock)) {
/*
* No need to mark anything dirty in write through mode.
*/
pb->req_nr == 0 ?
remap_to_cache(cache, bio, lookup_result.cblock) :
remap_to_origin_clear_discard(cache, bio, block);
} else
if (is_writethrough_io(cache, bio, lookup_result.cblock))
remap_to_origin_then_cache(cache, bio, block, lookup_result.cblock);
else
remap_to_cache_dirty(cache, bio, block, lookup_result.cblock);

issue(cache, bio);
Expand All @@ -1093,17 +1144,8 @@ static void process_bio(struct cache *cache, struct prealloc *structs,
case POLICY_MISS:
inc_miss_counter(cache, bio);
pb->all_io_entry = dm_deferred_entry_inc(cache->all_io_ds);

if (pb->req_nr != 0) {
/*
* This is a duplicate writethrough io that is no
* longer needed because the block has been demoted.
*/
bio_endio(bio, 0);
} else {
remap_to_origin_clear_discard(cache, bio, block);
issue(cache, bio);
}
remap_to_origin_clear_discard(cache, bio, block);
issue(cache, bio);
break;

case POLICY_NEW:
Expand Down Expand Up @@ -1224,6 +1266,23 @@ static void process_deferred_flush_bios(struct cache *cache, bool submit_bios)
submit_bios ? generic_make_request(bio) : bio_io_error(bio);
}

static void process_deferred_writethrough_bios(struct cache *cache)
{
unsigned long flags;
struct bio_list bios;
struct bio *bio;

bio_list_init(&bios);

spin_lock_irqsave(&cache->lock, flags);
bio_list_merge(&bios, &cache->deferred_writethrough_bios);
bio_list_init(&cache->deferred_writethrough_bios);
spin_unlock_irqrestore(&cache->lock, flags);

while ((bio = bio_list_pop(&bios)))
generic_make_request(bio);
}

static void writeback_some_dirty_blocks(struct cache *cache)
{
int r = 0;
Expand Down Expand Up @@ -1320,6 +1379,7 @@ static int more_work(struct cache *cache)
else
return !bio_list_empty(&cache->deferred_bios) ||
!bio_list_empty(&cache->deferred_flush_bios) ||
!bio_list_empty(&cache->deferred_writethrough_bios) ||
!list_empty(&cache->quiesced_migrations) ||
!list_empty(&cache->completed_migrations) ||
!list_empty(&cache->need_commit_migrations);
Expand All @@ -1338,6 +1398,8 @@ static void do_worker(struct work_struct *ws)

writeback_some_dirty_blocks(cache);

process_deferred_writethrough_bios(cache);

if (commit_if_needed(cache)) {
process_deferred_flush_bios(cache, false);

Expand Down Expand Up @@ -1803,8 +1865,6 @@ static sector_t calculate_discard_block_size(sector_t cache_block_size,

#define DEFAULT_MIGRATION_THRESHOLD (2048 * 100)

static unsigned cache_num_write_bios(struct dm_target *ti, struct bio *bio);

static int cache_create(struct cache_args *ca, struct cache **result)
{
int r = 0;
Expand All @@ -1831,9 +1891,6 @@ static int cache_create(struct cache_args *ca, struct cache **result)

memcpy(&cache->features, &ca->features, sizeof(cache->features));

if (cache->features.write_through)
ti->num_write_bios = cache_num_write_bios;

cache->callbacks.congested_fn = cache_is_congested;
dm_table_add_target_callbacks(ti->table, &cache->callbacks);

Expand Down Expand Up @@ -1883,6 +1940,7 @@ static int cache_create(struct cache_args *ca, struct cache **result)
spin_lock_init(&cache->lock);
bio_list_init(&cache->deferred_bios);
bio_list_init(&cache->deferred_flush_bios);
bio_list_init(&cache->deferred_writethrough_bios);
INIT_LIST_HEAD(&cache->quiesced_migrations);
INIT_LIST_HEAD(&cache->completed_migrations);
INIT_LIST_HEAD(&cache->need_commit_migrations);
Expand Down Expand Up @@ -2028,20 +2086,6 @@ static int cache_ctr(struct dm_target *ti, unsigned argc, char **argv)
return r;
}

static unsigned cache_num_write_bios(struct dm_target *ti, struct bio *bio)
{
int r;
struct cache *cache = ti->private;
dm_oblock_t block = get_bio_block(cache, bio);
dm_cblock_t cblock;

r = policy_lookup(cache->policy, block, &cblock);
if (r < 0)
return 2; /* assume the worst */

return (!r && !is_dirty(cache, cblock)) ? 2 : 1;
}

static int cache_map(struct dm_target *ti, struct bio *bio)
{
struct cache *cache = ti->private;
Expand Down Expand Up @@ -2109,18 +2153,12 @@ static int cache_map(struct dm_target *ti, struct bio *bio)
inc_hit_counter(cache, bio);
pb->all_io_entry = dm_deferred_entry_inc(cache->all_io_ds);

if (is_writethrough_io(cache, bio, lookup_result.cblock)) {
/*
* No need to mark anything dirty in write through mode.
*/
pb->req_nr == 0 ?
remap_to_cache(cache, bio, lookup_result.cblock) :
remap_to_origin_clear_discard(cache, bio, block);
cell_defer(cache, cell, false);
} else {
if (is_writethrough_io(cache, bio, lookup_result.cblock))
remap_to_origin_then_cache(cache, bio, block, lookup_result.cblock);
else
remap_to_cache_dirty(cache, bio, block, lookup_result.cblock);
cell_defer(cache, cell, false);
}

cell_defer(cache, cell, false);
break;

case POLICY_MISS:
Expand Down Expand Up @@ -2547,7 +2585,7 @@ static void cache_io_hints(struct dm_target *ti, struct queue_limits *limits)

static struct target_type cache_target = {
.name = "cache",
.version = {1, 0, 0},
.version = {1, 1, 0},
.module = THIS_MODULE,
.ctr = cache_ctr,
.dtr = cache_dtr,
Expand Down

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