[dm-devel] [for-3.19 PATCH 16/17] dm thin: direct dispatch when breaking sharing
Mike Snitzer
snitzer at redhat.com
Fri Oct 17 06:07:06 UTC 2014
From: Joe Thornber <ejt at redhat.com>
This use of direct submission in process_shared_bio() reduces latency
for submitting bios in the shared cell by avoiding adding those bios to
the deferred list and waiting for the next iteration of the worker.
Signed-off-by: Joe Thornber <ejt at redhat.com>
Signed-off-by: Mike Snitzer <snitzer at redhat.com>
---
drivers/md/dm-thin.c | 66 +++++++++++++++++++++++++++++++++++++++++-----------
1 file changed, 53 insertions(+), 13 deletions(-)
diff --git a/drivers/md/dm-thin.c b/drivers/md/dm-thin.c
index 3e1f40d..b585c0d 100644
--- a/drivers/md/dm-thin.c
+++ b/drivers/md/dm-thin.c
@@ -1357,11 +1357,49 @@ static void break_sharing(struct thin_c *tc, struct bio *bio, dm_block_t block,
}
}
+static void __remap_and_issue_shared_cell(void *context,
+ struct dm_bio_prison_cell *cell)
+{
+ struct remap_info *info = context;
+ struct bio *bio;
+
+ while ((bio = bio_list_pop(&cell->bios))) {
+ if ((bio_data_dir(bio) == WRITE) ||
+ (bio->bi_rw & (REQ_DISCARD | REQ_FLUSH | REQ_FUA)))
+ thin_defer_bio(info->tc, bio);
+ else {
+ struct dm_thin_endio_hook *h = dm_per_bio_data(bio, sizeof(struct dm_thin_endio_hook));;
+
+ h->shared_read_entry = dm_deferred_entry_inc(info->tc->pool->shared_read_ds);
+ inc_all_io_entry(info->tc->pool, bio);
+ bio_list_add(&info->bios, bio);
+ }
+ }
+}
+
+static void remap_and_issue_shared_cell(struct thin_c *tc,
+ struct dm_bio_prison_cell *cell,
+ dm_block_t block)
+{
+ struct bio *bio;
+ struct remap_info info;
+
+ info.tc = tc;
+ bio_list_init(&info.bios);
+
+ cell_visit_release(tc->pool, __remap_and_issue_shared_cell,
+ &info, cell);
+
+ while ((bio = bio_list_pop(&info.bios)))
+ remap_and_issue(tc, bio, block);
+}
+
static void process_shared_bio(struct thin_c *tc, struct bio *bio,
dm_block_t block,
- struct dm_thin_lookup_result *lookup_result)
+ struct dm_thin_lookup_result *lookup_result,
+ struct dm_bio_prison_cell *virt_cell)
{
- struct dm_bio_prison_cell *cell;
+ struct dm_bio_prison_cell *data_cell;
struct pool *pool = tc->pool;
struct dm_cell_key key;
@@ -1370,19 +1408,23 @@ static void process_shared_bio(struct thin_c *tc, struct bio *bio,
* of being broken so we have nothing further to do here.
*/
build_data_key(tc->td, lookup_result->block, &key);
- if (bio_detain(pool, &key, bio, &cell))
+ if (bio_detain(pool, &key, bio, &data_cell)) {
+ cell_defer_no_holder(tc, virt_cell);
return;
+ }
- if (bio_data_dir(bio) == WRITE && bio->bi_iter.bi_size)
- break_sharing(tc, bio, block, &key, lookup_result, cell);
- else {
+ if (bio_data_dir(bio) == WRITE && bio->bi_iter.bi_size) {
+ break_sharing(tc, bio, block, &key, lookup_result, data_cell);
+ cell_defer_no_holder(tc, virt_cell);
+ } else {
struct dm_thin_endio_hook *h = dm_per_bio_data(bio, sizeof(struct dm_thin_endio_hook));
h->shared_read_entry = dm_deferred_entry_inc(pool->shared_read_ds);
inc_all_io_entry(pool, bio);
- cell_defer_no_holder(tc, cell);
+ remap_and_issue(tc, bio, block);
- remap_and_issue(tc, bio, lookup_result->block);
+ remap_and_issue_shared_cell(tc, data_cell, lookup_result->block);
+ remap_and_issue_shared_cell(tc, virt_cell, lookup_result->block);
}
}
@@ -1446,11 +1488,9 @@ static void process_cell(struct thin_c *tc, struct dm_bio_prison_cell *cell)
r = dm_thin_find_block(tc->td, block, 1, &lookup_result);
switch (r) {
case 0:
- if (lookup_result.shared) {
- process_shared_bio(tc, bio, block, &lookup_result);
- // FIXME: we can't remap because we're waiting on a commit
- cell_defer_no_holder(tc, cell); /* FIXME: pass this cell into process_shared? */
- } else {
+ if (lookup_result.shared)
+ process_shared_bio(tc, bio, block, &lookup_result, cell);
+ else {
inc_all_io_entry(pool, bio);
remap_and_issue(tc, bio, lookup_result.block);
inc_remap_and_issue_cell(tc, cell, lookup_result.block);
--
1.9.3
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