1 files changed, 109 insertions, 60 deletions

diff --git a/drivers/md/dm-cache-target.c b/drivers/md/dm-cache-target.c
index 0f4e84b15c30..66120bd46d15 100644
--- a/drivers/md/dm-cache-target.c
+++ b/drivers/md/dm-cache-target.c
@@ -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;
@@ -158,7 +159,7 @@ struct cache {
         /*
          * origin_blocks entries, discarded if set.
          */
-        sector_t discard_block_size; /* a power of 2 times sectors per block */
+        uint32_t discard_block_size; /* a power of 2 times sectors per block */
         dm_dblock_t discard_nr_blocks;
         unsigned long *discard_bitset;
 
@@ -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 {
@@ -412,17 +418,24 @@ static bool block_size_is_power_of_two(struct cache *cache)
         return cache->sectors_per_block_shift >= 0;
 }
 
+static dm_block_t block_div(dm_block_t b, uint32_t n)
+{
+        do_div(b, n);
+
+        return b;
+}
+
 static dm_dblock_t oblock_to_dblock(struct cache *cache, dm_oblock_t oblock)
 {
-        sector_t discard_blocks = cache->discard_block_size;
+        uint32_t discard_blocks = cache->discard_block_size;
         dm_block_t b = from_oblock(oblock);
 
         if (!block_size_is_power_of_two(cache))
-                (void) sector_div(discard_blocks, cache->sectors_per_block);
+                discard_blocks = discard_blocks / cache->sectors_per_block;
         else
                 discard_blocks >>= cache->sectors_per_block_shift;
 
-        (void) sector_div(b, discard_blocks);
+        b = block_div(b, discard_blocks);
 
         return to_dblock(b);
 }
@@ -609,6 +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
  *
@@ -1002,7 +1065,7 @@ static void process_discard_bio(struct cache *cache, struct bio *bio)
         dm_block_t end_block = bio->bi_sector + bio_sectors(bio);
         dm_block_t b;
 
-        (void) sector_div(end_block, cache->discard_block_size);
+        end_block = block_div(end_block, cache->discard_block_size);
 
         for (b = start_block; b < end_block; b++)
                 set_discard(cache, to_dblock(b));
@@ -1070,14 +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);
@@ -1086,17 +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:
@@ -1217,6 +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;
@@ -1313,6 +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);
@@ -1331,6 +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);
 
@@ -1756,8 +1825,11 @@ static int create_cache_policy(struct cache *cache, struct cache_args *ca,
         }
 
         r = set_config_values(cache->policy, ca->policy_argc, ca->policy_argv);
-        if (r)
+        if (r) {
+                *error = "Error setting cache policy's config values";
                 dm_cache_policy_destroy(cache->policy);
+                cache->policy = NULL;
+        }
 
         return r;
 }
@@ -1793,8 +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;
@@ -1821,9 +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);
 
@@ -1835,7 +1902,7 @@ static int cache_create(struct cache_args *ca, struct cache **result)
 
         /* FIXME: factor out this whole section */
         origin_blocks = cache->origin_sectors = ca->origin_sectors;
-        (void) sector_div(origin_blocks, ca->block_size);
+        origin_blocks = block_div(origin_blocks, ca->block_size);
         cache->origin_blocks = to_oblock(origin_blocks);
 
         cache->sectors_per_block = ca->block_size;
@@ -1848,7 +1915,7 @@ static int cache_create(struct cache_args *ca, struct cache **result)
                 dm_block_t cache_size = ca->cache_sectors;
 
                 cache->sectors_per_block_shift = -1;
-                (void) sector_div(cache_size, ca->block_size);
+                cache_size = block_div(cache_size, ca->block_size);
                 cache->cache_size = to_cblock(cache_size);
         } else {
                 cache->sectors_per_block_shift = __ffs(ca->block_size);
@@ -1873,6 +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);
@@ -2002,6 +2070,8 @@ static int cache_ctr(struct dm_target *ti, unsigned argc, char **argv)
                 goto out;
 
         r = cache_create(ca, &cache);
+        if (r)
+                goto out;
 
         r = copy_ctr_args(cache, argc - 3, (const char **)argv + 3);
         if (r) {
@@ -2016,20 +2086,6 @@ out:
         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;
@@ -2097,18 +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:
@@ -2319,8 +2369,7 @@ static int cache_preresume(struct dm_target *ti)
         }
 
         if (!cache->loaded_mappings) {
-                r = dm_cache_load_mappings(cache->cmd,
-                                           dm_cache_policy_get_name(cache->policy),
+                r = dm_cache_load_mappings(cache->cmd, cache->policy,
                                            load_mapping, cache);
                 if (r) {
                         DMERR("could not load cache mappings");
@@ -2535,7 +2584,7 @@ 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,