block: Generic bio chaining
This adds a generic mechanism for chaining bio completions. This is
going to be used for a bio_split() replacement, and it turns out to be
very useful in a fair amount of driver code - a fair number of drivers
were implementing this in their own roundabout ways, often painfully.
Note that this means it's no longer to call bio_endio() more than once
on the same bio! This can cause problems for drivers that save/restore
bi_end_io. Arguably they shouldn't be saving/restoring bi_end_io at all
- in all but the simplest cases they'd be better off just cloning the
bio, and immutable biovecs is making bio cloning cheaper. But for now,
we add a bio_endio_nodec() for these cases.
Signed-off-by: Kent Overstreet <kmo@daterainc.com>
Cc: Jens Axboe <axboe@kernel.dk>
diff --git a/drivers/md/dm-thin.c b/drivers/md/dm-thin.c
index a654024..1abb4a2 100644
--- a/drivers/md/dm-thin.c
+++ b/drivers/md/dm-thin.c
@@ -611,8 +611,10 @@
static void process_prepared_mapping_fail(struct dm_thin_new_mapping *m)
{
- if (m->bio)
+ if (m->bio) {
m->bio->bi_end_io = m->saved_bi_end_io;
+ atomic_inc(&m->bio->bi_remaining);
+ }
cell_error(m->tc->pool, m->cell);
list_del(&m->list);
mempool_free(m, m->tc->pool->mapping_pool);
@@ -626,8 +628,10 @@
int r;
bio = m->bio;
- if (bio)
+ if (bio) {
bio->bi_end_io = m->saved_bi_end_io;
+ atomic_inc(&bio->bi_remaining);
+ }
if (m->err) {
cell_error(pool, m->cell);