diff --git a/Documentation/device-mapper/cache.txt b/Documentation/device-mapper/cache.txt
index ff0841711fd524063e2acf0fa4644ec2fbb4b764..8ae1cf8e94daeb6cf142e24624d0e5f4d99d728b 100644
--- a/Documentation/device-mapper/cache.txt
+++ b/Documentation/device-mapper/cache.txt
@@ -206,6 +206,9 @@ Optional feature arguments are:
in a separate btree, which improves speed of shutting
down the cache.
+ no_discard_passdown : disable passing down discards from the cache
+ to the origin's data device.
+
A policy called 'default' is always registered. This is an alias for
the policy we currently think is giving best all round performance.
diff --git a/drivers/md/dm-cache-target.c b/drivers/md/dm-cache-target.c
index adc529f12b6b830bb192503044ef1bf5f2d8d729..d249cf8ac277e4246d8f398c8aa3b2e46fe90724 100644
--- a/drivers/md/dm-cache-target.c
+++ b/drivers/md/dm-cache-target.c
@@ -353,6 +353,7 @@ struct cache_features {
enum cache_metadata_mode mode;
enum cache_io_mode io_mode;
unsigned metadata_version;
+ bool discard_passdown:1;
};
struct cache_stats {
@@ -1899,7 +1900,11 @@ static bool process_discard_bio(struct cache *cache, struct bio *bio)
b = to_dblock(from_dblock(b) + 1);
}
- bio_endio(bio);
+ if (cache->features.discard_passdown) {
+ remap_to_origin(cache, bio);
+ generic_make_request(bio);
+ } else
+ bio_endio(bio);
return false;
}
@@ -2233,13 +2238,14 @@ static void init_features(struct cache_features *cf)
cf->mode = CM_WRITE;
cf->io_mode = CM_IO_WRITEBACK;
cf->metadata_version = 1;
+ cf->discard_passdown = true;
}
static int parse_features(struct cache_args *ca, struct dm_arg_set *as,
char **error)
{
static const struct dm_arg _args[] = {
- {0, 2, "Invalid number of cache feature arguments"},
+ {0, 3, "Invalid number of cache feature arguments"},
};
int r, mode_ctr = 0;
@@ -2274,6 +2280,9 @@ static int parse_features(struct cache_args *ca, struct dm_arg_set *as,
else if (!strcasecmp(arg, "metadata2"))
cf->metadata_version = 2;
+ else if (!strcasecmp(arg, "no_discard_passdown"))
+ cf->discard_passdown = false;
+
else {
*error = "Unrecognised cache feature requested";
return -EINVAL;
@@ -3119,6 +3128,39 @@ static void cache_resume(struct dm_target *ti)
do_waker(&cache->waker.work);
}
+static void emit_flags(struct cache *cache, char *result,
+ unsigned maxlen, ssize_t *sz_ptr)
+{
+ ssize_t sz = *sz_ptr;
+ struct cache_features *cf = &cache->features;
+ unsigned count = (cf->metadata_version == 2) + !cf->discard_passdown + 1;
+
+ DMEMIT("%u ", count);
+
+ if (cf->metadata_version == 2)
+ DMEMIT("metadata2 ");
+
+ if (writethrough_mode(cache))
+ DMEMIT("writethrough ");
+
+ else if (passthrough_mode(cache))
+ DMEMIT("passthrough ");
+
+ else if (writeback_mode(cache))
+ DMEMIT("writeback ");
+
+ else {
+ DMEMIT("unknown ");
+ DMERR("%s: internal error: unknown io mode: %d",
+ cache_device_name(cache), (int) cf->io_mode);
+ }
+
+ if (!cf->discard_passdown)
+ DMEMIT("no_discard_passdown ");
+
+ *sz_ptr = sz;
+}
+
/*
* Status format:
*
@@ -3185,25 +3227,7 @@ static void cache_status(struct dm_target *ti, status_type_t type,
(unsigned) atomic_read(&cache->stats.promotion),
(unsigned long) atomic_read(&cache->nr_dirty));
- if (cache->features.metadata_version == 2)
- DMEMIT("2 metadata2 ");
- else
- DMEMIT("1 ");
-
- if (writethrough_mode(cache))
- DMEMIT("writethrough ");
-
- else if (passthrough_mode(cache))
- DMEMIT("passthrough ");
-
- else if (writeback_mode(cache))
- DMEMIT("writeback ");
-
- else {
- DMERR("%s: internal error: unknown io mode: %d",
- cache_device_name(cache), (int) cache->features.io_mode);
- goto err;
- }
+ emit_flags(cache, result, maxlen, &sz);
DMEMIT("2 migration_threshold %llu ", (unsigned long long) cache->migration_threshold);
@@ -3432,14 +3456,62 @@ static int cache_iterate_devices(struct dm_target *ti,
return r;
}
+static bool origin_dev_supports_discard(struct block_device *origin_bdev)
+{
+ struct request_queue *q = bdev_get_queue(origin_bdev);
+
+ return q && blk_queue_discard(q);
+}
+
+/*
+ * If discard_passdown was enabled verify that the origin device
+ * supports discards. Disable discard_passdown if not.
+ */
+static void disable_passdown_if_not_supported(struct cache *cache)
+{
+ struct block_device *origin_bdev = cache->origin_dev->bdev;
+ struct queue_limits *origin_limits = &bdev_get_queue(origin_bdev)->limits;
+ const char *reason = NULL;
+ char buf[BDEVNAME_SIZE];
+
+ if (!cache->features.discard_passdown)
+ return;
+
+ if (!origin_dev_supports_discard(origin_bdev))
+ reason = "discard unsupported";
+
+ else if (origin_limits->max_discard_sectors < cache->sectors_per_block)
+ reason = "max discard sectors smaller than a block";
+
+ if (reason) {
+ DMWARN("Origin device (%s) %s: Disabling discard passdown.",
+ bdevname(origin_bdev, buf), reason);
+ cache->features.discard_passdown = false;
+ }
+}
+
static void set_discard_limits(struct cache *cache, struct queue_limits *limits)
{
+ struct block_device *origin_bdev = cache->origin_dev->bdev;
+ struct queue_limits *origin_limits = &bdev_get_queue(origin_bdev)->limits;
+
+ if (!cache->features.discard_passdown) {
+ /* No passdown is done so setting own virtual limits */
+ limits->max_discard_sectors = min_t(sector_t, cache->discard_block_size * 1024,
+ cache->origin_sectors);
+ limits->discard_granularity = cache->discard_block_size << SECTOR_SHIFT;
+ return;
+ }
+
/*
- * FIXME: these limits may be incompatible with the cache device
+ * cache_iterate_devices() is stacking both origin and fast device limits
+ * but discards aren't passed to fast device, so inherit origin's limits.
*/
- limits->max_discard_sectors = min_t(sector_t, cache->discard_block_size * 1024,
- cache->origin_sectors);
- limits->discard_granularity = cache->discard_block_size << SECTOR_SHIFT;
+ limits->max_discard_sectors = origin_limits->max_discard_sectors;
+ limits->max_hw_discard_sectors = origin_limits->max_hw_discard_sectors;
+ limits->discard_granularity = origin_limits->discard_granularity;
+ limits->discard_alignment = origin_limits->discard_alignment;
+ limits->discard_misaligned = origin_limits->discard_misaligned;
}
static void cache_io_hints(struct dm_target *ti, struct queue_limits *limits)
@@ -3456,6 +3528,8 @@ static void cache_io_hints(struct dm_target *ti, struct queue_limits *limits)
blk_limits_io_min(limits, cache->sectors_per_block << SECTOR_SHIFT);
blk_limits_io_opt(limits, cache->sectors_per_block << SECTOR_SHIFT);
}
+
+ disable_passdown_if_not_supported(cache);
set_discard_limits(cache, limits);
}
@@ -3463,7 +3537,7 @@ static void cache_io_hints(struct dm_target *ti, struct queue_limits *limits)
static struct target_type cache_target = {
.name = "cache",
- .version = {2, 0, 0},
+ .version = {2, 1, 0},
.module = THIS_MODULE,
.ctr = cache_ctr,
.dtr = cache_dtr,