[dm-devel] [PATCH 6/6] dm cache: add cache block invalidation support
Mike Snitzer
snitzer at redhat.com
Mon Nov 11 17:20:48 UTC 2013
From: Joe Thornber <ejt at redhat.com>
Cache block invalidation is removing an entry from the cache without
writing it back. Cache blocks can be invalidated via the
'invalidate_cblocks' message, which takes an arbitrary number of cblock
ranges:
invalidate_cblocks [<cblock>|<cblock begin>-<cblock end>]*
E.g.
dmsetup message my_cache 0 invalidate_cblocks 2345 3456-4567 5678-6789
Signed-off-by: Joe Thornber <ejt at redhat.com>
Signed-off-by: Mike Snitzer <snitzer at redhat.com>
---
Documentation/device-mapper/cache.txt | 12 ++-
drivers/md/dm-cache-target.c | 225 ++++++++++++++++++++++++++++++++-
2 files changed, 233 insertions(+), 4 deletions(-)
diff --git a/Documentation/device-mapper/cache.txt b/Documentation/device-mapper/cache.txt
index ff6639f..fc9d2df 100644
--- a/Documentation/device-mapper/cache.txt
+++ b/Documentation/device-mapper/cache.txt
@@ -244,12 +244,22 @@ The message format is:
E.g.
dmsetup message my_cache 0 sequential_threshold 1024
+
+Invalidation is removing an entry from the cache without writing it
+back. Cache blocks can be invalidated via the invalidate_cblocks
+message, which takes an arbitrary number of cblock ranges.
+
+ invalidate_cblocks [<cblock>|<cblock begin>-<cblock end>]*
+
+E.g.
+ dmsetup message my_cache 0 invalidate_cblocks 2345 3456-4567 5678-6789
+
Examples
========
The test suite can be found here:
-https://github.com/jthornber/thinp-test-suite
+https://github.com/jthornber/device-mapper-test-suite
dmsetup create my_cache --table '0 41943040 cache /dev/mapper/metadata \
/dev/mapper/ssd /dev/mapper/origin 512 1 writeback default 0'
diff --git a/drivers/md/dm-cache-target.c b/drivers/md/dm-cache-target.c
index 8c02177..41e664b 100644
--- a/drivers/md/dm-cache-target.c
+++ b/drivers/md/dm-cache-target.c
@@ -150,6 +150,25 @@ struct cache_stats {
atomic_t discard_count;
};
+/*
+ * Defines a range of cblocks, begin to (end - 1) are in the range. end is
+ * the one-past-the-end value.
+ */
+struct cblock_range {
+ dm_cblock_t begin;
+ dm_cblock_t end;
+};
+
+struct invalidation_request {
+ struct list_head list;
+ struct cblock_range *cblocks;
+
+ atomic_t complete;
+ int err;
+
+ wait_queue_head_t result_wait;
+};
+
struct cache {
struct dm_target *ti;
struct dm_target_callbacks callbacks;
@@ -241,6 +260,7 @@ struct cache {
bool need_tick_bio:1;
bool sized:1;
+ bool invalidate:1;
bool commit_requested:1;
bool loaded_mappings:1;
bool loaded_discards:1;
@@ -251,6 +271,12 @@ struct cache {
struct cache_features features;
struct cache_stats stats;
+
+ /*
+ * Invalidation fields.
+ */
+ spinlock_t invalidation_lock;
+ struct list_head invalidation_requests;
};
struct per_bio_data {
@@ -283,6 +309,7 @@ struct dm_cache_migration {
bool demote:1;
bool promote:1;
bool requeue_holder:1;
+ bool invalidate:1;
struct dm_bio_prison_cell *old_ocell;
struct dm_bio_prison_cell *new_ocell;
@@ -904,8 +931,11 @@ static void migration_success_post_commit(struct dm_cache_migration *mg)
list_add_tail(&mg->list, &cache->quiesced_migrations);
spin_unlock_irqrestore(&cache->lock, flags);
- } else
+ } else {
+ if (mg->invalidate)
+ policy_remove_mapping(cache->policy, mg->old_oblock);
cleanup_migration(mg);
+ }
} else {
if (mg->requeue_holder)
@@ -1115,6 +1145,7 @@ static void promote(struct cache *cache, struct prealloc *structs,
mg->demote = false;
mg->promote = true;
mg->requeue_holder = true;
+ mg->invalidate = false;
mg->cache = cache;
mg->new_oblock = oblock;
mg->cblock = cblock;
@@ -1137,6 +1168,7 @@ static void writeback(struct cache *cache, struct prealloc *structs,
mg->demote = false;
mg->promote = false;
mg->requeue_holder = true;
+ mg->invalidate = false;
mg->cache = cache;
mg->old_oblock = oblock;
mg->cblock = cblock;
@@ -1161,6 +1193,7 @@ static void demote_then_promote(struct cache *cache, struct prealloc *structs,
mg->demote = true;
mg->promote = true;
mg->requeue_holder = true;
+ mg->invalidate = false;
mg->cache = cache;
mg->old_oblock = old_oblock;
mg->new_oblock = new_oblock;
@@ -1188,6 +1221,7 @@ static void invalidate(struct cache *cache, struct prealloc *structs,
mg->demote = true;
mg->promote = false;
mg->requeue_holder = true;
+ mg->invalidate = true;
mg->cache = cache;
mg->old_oblock = oblock;
mg->cblock = cblock;
@@ -1525,6 +1559,58 @@ static void writeback_some_dirty_blocks(struct cache *cache)
}
/*----------------------------------------------------------------
+ * Invalidations.
+ * Dropping something from the cache *without* writing back.
+ *--------------------------------------------------------------*/
+
+static void process_invalidation_request(struct cache *cache, struct invalidation_request *req)
+{
+ int r = 0;
+ uint64_t begin = from_cblock(req->cblocks->begin);
+ uint64_t end = from_cblock(req->cblocks->end);
+
+ while (begin != end) {
+ r = policy_remove_cblock(cache->policy, to_cblock(begin));
+ if (!r) {
+ r = dm_cache_remove_mapping(cache->cmd, to_cblock(begin));
+ if (r)
+ break;
+
+ } else if (r == -ENODATA) {
+ /* harmless, already unmapped */
+ r = 0;
+
+ } else {
+ DMERR("policy_remove_cblock failed");
+ break;
+ }
+
+ begin++;
+ }
+
+ cache->commit_requested = true;
+
+ req->err = r;
+ atomic_set(&req->complete, 1);
+
+ wake_up(&req->result_wait);
+}
+
+static void process_invalidation_requests(struct cache *cache)
+{
+ struct list_head list;
+ struct invalidation_request *req, *tmp;
+
+ INIT_LIST_HEAD(&list);
+ spin_lock(&cache->invalidation_lock);
+ list_splice_init(&cache->invalidation_requests, &list);
+ spin_unlock(&cache->invalidation_lock);
+
+ list_for_each_entry_safe (req, tmp, &list, list)
+ process_invalidation_request(cache, req);
+}
+
+/*----------------------------------------------------------------
* Main worker loop
*--------------------------------------------------------------*/
static bool is_quiescing(struct cache *cache)
@@ -1593,7 +1679,8 @@ static int more_work(struct cache *cache)
!bio_list_empty(&cache->deferred_writethrough_bios) ||
!list_empty(&cache->quiesced_migrations) ||
!list_empty(&cache->completed_migrations) ||
- !list_empty(&cache->need_commit_migrations);
+ !list_empty(&cache->need_commit_migrations) ||
+ cache->invalidate;
}
static void do_worker(struct work_struct *ws)
@@ -1605,6 +1692,7 @@ static void do_worker(struct work_struct *ws)
writeback_some_dirty_blocks(cache);
process_deferred_writethrough_bios(cache);
process_deferred_bios(cache);
+ process_invalidation_requests(cache);
}
process_migrations(cache, &cache->quiesced_migrations, issue_copy);
@@ -2271,6 +2359,7 @@ static int cache_create(struct cache_args *ca, struct cache **result)
cache->need_tick_bio = true;
cache->sized = false;
+ cache->invalidate = false;
cache->commit_requested = false;
cache->loaded_mappings = false;
cache->loaded_discards = false;
@@ -2284,6 +2373,9 @@ static int cache_create(struct cache_args *ca, struct cache **result)
atomic_set(&cache->stats.commit_count, 0);
atomic_set(&cache->stats.discard_count, 0);
+ spin_lock_init(&cache->invalidation_lock);
+ INIT_LIST_HEAD(&cache->invalidation_requests);
+
*result = cache;
return 0;
@@ -2833,7 +2925,128 @@ err:
}
/*
- * Supports <key> <value>.
+ * A cache block range can take two forms:
+ *
+ * i) A single cblock, eg. '3456'
+ * ii) A begin and end cblock with dots between, eg. 123-234
+ */
+static int parse_cblock_range(struct cache *cache, const char *str,
+ struct cblock_range *result)
+{
+ char dummy;
+ uint64_t b, e;
+ int r;
+
+ /*
+ * Try and parse form (ii) first.
+ */
+ r = sscanf(str, "%llu-%llu%c", &b, &e, &dummy);
+ if (r < 0)
+ return r;
+
+ if (r == 2) {
+ result->begin = to_cblock(b);
+ result->end = to_cblock(e);
+ return 0;
+ }
+
+ /*
+ * That didn't work, try form (i).
+ */
+ r = sscanf(str, "%llu%c", &b, &dummy);
+ if (r < 0)
+ return r;
+
+ if (r == 1) {
+ result->begin = to_cblock(b);
+ result->end = to_cblock(from_cblock(result->begin) + 1u);
+ return 0;
+ }
+
+ DMERR("invalid cblock range '%s'", str);
+ return -EINVAL;
+}
+
+static int validate_cblock_range(struct cache *cache, struct cblock_range *range)
+{
+ uint64_t b = from_cblock(range->begin);
+ uint64_t e = from_cblock(range->end);
+ uint64_t n = from_cblock(cache->cache_size);
+
+ if (b >= n) {
+ DMERR("begin cblock out of range: %llu >= %llu", b, n);
+ return -EINVAL;
+ }
+
+ if (e > n) {
+ DMERR("end cblock out of range: %llu > %llu", e, n);
+ return -EINVAL;
+ }
+
+ if (b >= e) {
+ DMERR("invalid cblock range: %llu >= %llu", b, e);
+ return -EINVAL;
+ }
+
+ return 0;
+}
+
+static int request_invalidation(struct cache *cache, struct cblock_range *range)
+{
+ struct invalidation_request req;
+
+ INIT_LIST_HEAD(&req.list);
+ req.cblocks = range;
+ atomic_set(&req.complete, 0);
+ req.err = 0;
+ init_waitqueue_head(&req.result_wait);
+
+ spin_lock(&cache->invalidation_lock);
+ list_add(&req.list, &cache->invalidation_requests);
+ spin_unlock(&cache->invalidation_lock);
+ wake_worker(cache);
+
+ wait_event(req.result_wait, atomic_read(&req.complete));
+ return req.err;
+}
+
+static int process_invalidate_cblocks_message(struct cache *cache, unsigned count,
+ const char **cblock_ranges)
+{
+ int r = 0;
+ unsigned i;
+ struct cblock_range range;
+
+ if (!passthrough_mode(&cache->features)) {
+ DMERR("cache has to be in passthrough mode for invalidation");
+ return -EPERM;
+ }
+
+ for (i = 0; i < count; i++) {
+ r = parse_cblock_range(cache, cblock_ranges[i], &range);
+ if (r)
+ break;
+
+ r = validate_cblock_range(cache, &range);
+ if (r)
+ break;
+
+ /*
+ * Pass begin and end origin blocks to the worker and wake it.
+ */
+ r = request_invalidation(cache, &range);
+ if (r)
+ break;
+ }
+
+ return r;
+}
+
+/*
+ * Supports
+ * "<key> <value>"
+ * and
+ * "invalidate_cblocks [(<begin>)|(<begin>-<end>)]*
*
* The key migration_threshold is supported by the cache target core.
*/
@@ -2841,6 +3054,12 @@ static int cache_message(struct dm_target *ti, unsigned argc, char **argv)
{
struct cache *cache = ti->private;
+ if (!argc)
+ return -EINVAL;
+
+ if (!strcmp(argv[0], "invalidate_cblocks"))
+ return process_invalidate_cblocks_message(cache, argc - 1, (const char **) argv + 1);
+
if (argc != 2)
return -EINVAL;
--
1.7.4.4
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