[dm-devel] [PATCH 09/11] [dm-thin] Discard support part 1
Joe Thornber
ejt at redhat.com
Thu Feb 2 16:39:12 UTC 2012
This patch contains a lot of the ground work needed for supporting
discard.
- The thin target now has an endio function, that replaces
shared_read_endio.
- An explicit 'quiesced' flag has been introduced into the new_mapping
structure. Before, this was implicitly indicated by m->list being
empty.
- The map_info->ptr remains constant for the duration of a bio's trip
through thinp. Making it easier to reason about it.
---
drivers/md/dm-thin.c | 125 ++++++++++++++++++++++++++++----------------------
1 files changed, 70 insertions(+), 55 deletions(-)
diff --git a/drivers/md/dm-thin.c b/drivers/md/dm-thin.c
index 922ebf2..c5e3102 100644
--- a/drivers/md/dm-thin.c
+++ b/drivers/md/dm-thin.c
@@ -511,7 +511,7 @@ struct pool {
struct bio_list retry_on_resume_list;
- struct deferred_set ds; /* FIXME: move to thin_c */
+ struct deferred_set shared_read_ds;
struct new_mapping *next_mapping;
mempool_t *mapping_pool;
@@ -606,6 +606,12 @@ static struct pool *__pool_table_lookup_metadata_dev(struct block_device *md_dev
/*----------------------------------------------------------------*/
+struct endio_hook {
+ struct thin_c *tc;
+ struct deferred_entry *shared_read_entry;
+ struct new_mapping *overwrite_mapping;
+};
+
static void __requeue_bio_list(struct thin_c *tc, struct bio_list *master)
{
struct bio *bio;
@@ -616,7 +622,8 @@ static void __requeue_bio_list(struct thin_c *tc, struct bio_list *master)
bio_list_init(master);
while ((bio = bio_list_pop(&bios))) {
- if (dm_get_mapinfo(bio)->ptr == tc)
+ struct endio_hook *h = dm_get_mapinfo(bio)->ptr;
+ if (h->tc == tc)
bio_endio(bio, DM_ENDIO_REQUEUE);
else
bio_list_add(master, bio);
@@ -706,16 +713,11 @@ static void wake_worker(struct pool *pool)
/*
* Bio endio functions.
*/
-struct endio_hook {
- struct thin_c *tc;
- bio_end_io_t *saved_bi_end_io;
- struct deferred_entry *entry;
-};
-
struct new_mapping {
struct list_head list;
- int prepared;
+ unsigned quiesced:1;
+ unsigned prepared:1;
struct thin_c *tc;
dm_block_t virt_block;
@@ -737,7 +739,7 @@ static void __maybe_add_mapping(struct new_mapping *m)
{
struct pool *pool = m->tc->pool;
- if (list_empty(&m->list) && m->prepared) {
+ if (m->quiesced && m->prepared) {
list_add(&m->list, &pool->prepared_mappings);
wake_worker(pool);
}
@@ -760,7 +762,8 @@ static void copy_complete(int read_err, unsigned long write_err, void *context)
static void overwrite_endio(struct bio *bio, int err)
{
unsigned long flags;
- struct new_mapping *m = dm_get_mapinfo(bio)->ptr;
+ struct endio_hook *h = dm_get_mapinfo(bio)->ptr;
+ struct new_mapping *m = h->overwrite_mapping;
struct pool *pool = m->tc->pool;
m->err = err;
@@ -771,31 +774,6 @@ static void overwrite_endio(struct bio *bio, int err)
spin_unlock_irqrestore(&pool->lock, flags);
}
-static void shared_read_endio(struct bio *bio, int err)
-{
- struct list_head mappings;
- struct new_mapping *m, *tmp;
- struct endio_hook *h = dm_get_mapinfo(bio)->ptr;
- unsigned long flags;
- struct pool *pool = h->tc->pool;
-
- bio->bi_end_io = h->saved_bi_end_io;
- bio_endio(bio, err);
-
- INIT_LIST_HEAD(&mappings);
- ds_dec(h->entry, &mappings);
-
- spin_lock_irqsave(&pool->lock, flags);
- list_for_each_entry_safe(m, tmp, &mappings, list) {
- list_del(&m->list);
- INIT_LIST_HEAD(&m->list);
- __maybe_add_mapping(m);
- }
- spin_unlock_irqrestore(&pool->lock, flags);
-
- mempool_free(h, pool->endio_hook_pool);
-}
-
/*----------------------------------------------------------------*/
/*
@@ -934,9 +912,7 @@ static int ensure_next_mapping(struct pool *pool)
static struct new_mapping *get_next_mapping(struct pool *pool)
{
struct new_mapping *r = pool->next_mapping;
-
BUG_ON(!pool->next_mapping);
-
pool->next_mapping = NULL;
return r;
@@ -952,6 +928,7 @@ static void schedule_copy(struct thin_c *tc, dm_block_t virt_block,
struct new_mapping *m = get_next_mapping(pool);
INIT_LIST_HEAD(&m->list);
+ m->quiesced = 0;
m->prepared = 0;
m->tc = tc;
m->virt_block = virt_block;
@@ -960,7 +937,8 @@ static void schedule_copy(struct thin_c *tc, dm_block_t virt_block,
m->err = 0;
m->bio = NULL;
- ds_add_work(&pool->ds, &m->list);
+ if (!ds_add_work(&pool->shared_read_ds, &m->list))
+ m->quiesced = 1;
/*
* IO to pool_dev remaps to the pool target's data_dev.
@@ -969,9 +947,10 @@ static void schedule_copy(struct thin_c *tc, dm_block_t virt_block,
* bio immediately. Otherwise we use kcopyd to clone the data first.
*/
if (io_overwrites_block(pool, bio)) {
+ struct endio_hook *h = dm_get_mapinfo(bio)->ptr;
+ h->overwrite_mapping = m;
m->bio = bio;
save_and_set_endio(bio, &m->saved_bi_end_io, overwrite_endio);
- dm_get_mapinfo(bio)->ptr = m;
remap_and_issue(tc, bio, data_dest);
} else {
struct dm_io_region from, to;
@@ -1018,6 +997,7 @@ static void schedule_zero(struct thin_c *tc, dm_block_t virt_block,
struct new_mapping *m = get_next_mapping(pool);
INIT_LIST_HEAD(&m->list);
+ m->quiesced = 1;
m->prepared = 0;
m->tc = tc;
m->virt_block = virt_block;
@@ -1035,9 +1015,10 @@ static void schedule_zero(struct thin_c *tc, dm_block_t virt_block,
process_prepared_mapping(m);
else if (io_overwrites_block(pool, bio)) {
+ struct endio_hook *h = dm_get_mapinfo(bio)->ptr;
+ h->overwrite_mapping = m;
m->bio = bio;
save_and_set_endio(bio, &m->saved_bi_end_io, overwrite_endio);
- dm_get_mapinfo(bio)->ptr = m;
remap_and_issue(tc, bio, data_block);
} else {
@@ -1124,7 +1105,8 @@ static int alloc_data_block(struct thin_c *tc, dm_block_t *result)
*/
static void retry_on_resume(struct bio *bio)
{
- struct thin_c *tc = dm_get_mapinfo(bio)->ptr;
+ struct endio_hook *h = dm_get_mapinfo(bio)->ptr;
+ struct thin_c *tc = h->tc;
struct pool *pool = tc->pool;
unsigned long flags;
@@ -1190,13 +1172,9 @@ static void process_shared_bio(struct thin_c *tc, struct bio *bio,
if (bio_data_dir(bio) == WRITE)
break_sharing(tc, bio, block, &key, lookup_result, cell);
else {
- struct endio_hook *h;
- h = mempool_alloc(pool->endio_hook_pool, GFP_NOIO);
+ struct endio_hook *h = dm_get_mapinfo(bio)->ptr;
- h->tc = tc;
- h->entry = ds_inc(&pool->ds);
- save_and_set_endio(bio, &h->saved_bi_end_io, shared_read_endio);
- dm_get_mapinfo(bio)->ptr = h;
+ h->shared_read_entry = ds_inc(&pool->shared_read_ds);
cell_release_singleton(cell, bio);
remap_and_issue(tc, bio, lookup_result->block);
@@ -1320,7 +1298,9 @@ static void process_deferred_bios(struct pool *pool)
spin_unlock_irqrestore(&pool->lock, flags);
while ((bio = bio_list_pop(&bios))) {
- struct thin_c *tc = dm_get_mapinfo(bio)->ptr;
+ struct endio_hook *h = dm_get_mapinfo(bio)->ptr;
+ struct thin_c *tc = h->tc;
+
/*
* If we've got no free new_mapping structs, and processing
* this bio might require one, we pause until there are some
@@ -1405,6 +1385,18 @@ static void thin_defer_bio(struct thin_c *tc, struct bio *bio)
wake_worker(pool);
}
+static struct endio_hook *thin_hook_bio(struct thin_c *tc, struct bio *bio)
+{
+ struct pool *pool = tc->pool;
+ struct endio_hook *h = mempool_alloc(pool->endio_hook_pool, GFP_NOIO);
+
+ h->tc = tc;
+ h->shared_read_entry = NULL;
+ h->overwrite_mapping = NULL;
+
+ return h;
+}
+
/*
* Non-blocking function called from the thin target's map function.
*/
@@ -1417,11 +1409,7 @@ static int thin_bio_map(struct dm_target *ti, struct bio *bio,
struct dm_thin_device *td = tc->td;
struct dm_thin_lookup_result result;
- /*
- * Save the thin context for easy access from the deferred bio later.
- */
- map_context->ptr = tc;
-
+ map_context->ptr = thin_hook_bio(tc, bio);
if (bio->bi_rw & (REQ_FLUSH | REQ_FUA)) {
thin_defer_bio(tc, bio);
return DM_MAPIO_SUBMITTED;
@@ -1601,7 +1589,7 @@ static struct pool *pool_create(struct mapped_device *pool_md,
pool->low_water_triggered = 0;
pool->no_free_space = 0;
bio_list_init(&pool->retry_on_resume_list);
- ds_init(&pool->ds);
+ ds_init(&pool->shared_read_ds);
pool->next_mapping = NULL;
pool->mapping_pool =
@@ -2392,6 +2380,32 @@ static int thin_map(struct dm_target *ti, struct bio *bio,
return thin_bio_map(ti, bio, map_context);
}
+static int thin_endio(struct dm_target *ti,
+ struct bio *bio, int err,
+ union map_info *map_context)
+{
+ unsigned long flags;
+ struct endio_hook *h = map_context->ptr;
+ struct list_head work;
+ struct new_mapping *m, *tmp;
+ struct pool *pool = h->tc->pool;
+
+ if (h->shared_read_entry) {
+ INIT_LIST_HEAD(&work);
+ ds_dec(h->shared_read_entry, &work);
+
+ spin_lock_irqsave(&pool->lock, flags);
+ list_for_each_entry_safe(m, tmp, &work, list) {
+ list_del(&m->list);
+ m->quiesced = 1;
+ __maybe_add_mapping(m);
+ }
+ spin_unlock_irqrestore(&pool->lock, flags);
+ }
+
+ return 0;
+}
+
static void thin_postsuspend(struct dm_target *ti)
{
if (dm_noflush_suspending(ti))
@@ -2477,6 +2491,7 @@ static struct target_type thin_target = {
.ctr = thin_ctr,
.dtr = thin_dtr,
.map = thin_map,
+ .end_io = thin_endio,
.postsuspend = thin_postsuspend,
.status = thin_status,
.iterate_devices = thin_iterate_devices,
--
1.7.5.4
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