Commit da415a09 authored by Nicholas Swenson's avatar Nicholas Swenson Committed by Kent Overstreet
Browse files

bcache: Fix moving_gc deadlocking with a foreground write 



Deadlock happened because a foreground write slept, waiting for a bucket
to be allocated. Normally the gc would mark buckets available for invalidation.
But the moving_gc was stuck waiting for outstanding writes to complete.
These writes used the bcache_wq, the same queue foreground writes used.

This fix gives moving_gc its own work queue, so it was still finish moving
even if foreground writes are stuck waiting for allocation. It also makes
work queue a parameter to the data_insert path, so moving_gc can use its
workqueue for writes.

Signed-off-by: default avatarNicholas Swenson <nks@daterainc.com>
Signed-off-by: default avatarKent Overstreet <kmo@daterainc.com>
parent 90db6919

drivers/md/bcache/bcache.h

+2 −0
Original line number Diff line number Diff line
@@ -628,6 +628,8 @@ struct cache_set { 
	/* Number of moving GC bios in flight */

	struct semaphore	moving_in_flight;



	struct workqueue_struct	*moving_gc_wq;



	struct btree		*root;



#ifdef CONFIG_BCACHE_DEBUG

drivers/md/bcache/movinggc.c

+3 −2
Original line number Diff line number Diff line
@@ -115,7 +115,7 @@ static void write_moving(struct closure *cl) 
		closure_call(&op->cl, bch_data_insert, NULL, cl);

	}



	continue_at(cl, write_moving_finish, system_wq);

	continue_at(cl, write_moving_finish, op->wq);

}



static void read_moving_submit(struct closure *cl)
@@ -125,7 +125,7 @@ static void read_moving_submit(struct closure *cl) 


	bch_submit_bbio(bio, io->op.c, &io->w->key, 0);



	continue_at(cl, write_moving, system_wq);

	continue_at(cl, write_moving, io->op.wq);

}



static void read_moving(struct cache_set *c)
@@ -160,6 +160,7 @@ static void read_moving(struct cache_set *c) 
		io->w		= w;

		io->op.inode	= KEY_INODE(&w->key);

		io->op.c	= c;

		io->op.wq	= c->moving_gc_wq;



		moving_init(io);

		bio = &io->bio.bio;

drivers/md/bcache/request.c

+7 −6
Original line number Diff line number Diff line
@@ -248,7 +248,7 @@ static void bch_data_insert_keys(struct closure *cl) 
		atomic_dec_bug(journal_ref);



	if (!op->insert_data_done)

		continue_at(cl, bch_data_insert_start, bcache_wq);

		continue_at(cl, bch_data_insert_start, op->wq);



	bch_keylist_free(&op->insert_keys);

	closure_return(cl);
@@ -297,7 +297,7 @@ static void bch_data_invalidate(struct closure *cl) 
	op->insert_data_done = true;

	bio_put(bio);

out:

	continue_at(cl, bch_data_insert_keys, bcache_wq);

	continue_at(cl, bch_data_insert_keys, op->wq);

}



static void bch_data_insert_error(struct closure *cl)
@@ -340,7 +340,7 @@ static void bch_data_insert_endio(struct bio *bio, int error) 
		if (op->writeback)

			op->error = error;

		else if (!op->replace)

			set_closure_fn(cl, bch_data_insert_error, bcache_wq);

			set_closure_fn(cl, bch_data_insert_error, op->wq);

		else

			set_closure_fn(cl, NULL, NULL);

	}
@@ -376,7 +376,7 @@ static void bch_data_insert_start(struct closure *cl) 
		if (bch_keylist_realloc(&op->insert_keys,

					3 + (op->csum ? 1 : 0),

					op->c))

			continue_at(cl, bch_data_insert_keys, bcache_wq);

			continue_at(cl, bch_data_insert_keys, op->wq);



		k = op->insert_keys.top;

		bkey_init(k);
@@ -413,7 +413,7 @@ static void bch_data_insert_start(struct closure *cl) 
	} while (n != bio);



	op->insert_data_done = true;

	continue_at(cl, bch_data_insert_keys, bcache_wq);

	continue_at(cl, bch_data_insert_keys, op->wq);

err:

	/* bch_alloc_sectors() blocks if s->writeback = true */

	BUG_ON(op->writeback);
@@ -442,7 +442,7 @@ err: 
		bio_put(bio);



		if (!bch_keylist_empty(&op->insert_keys))

			continue_at(cl, bch_data_insert_keys, bcache_wq);

			continue_at(cl, bch_data_insert_keys, op->wq);

		else

			closure_return(cl);

	}
@@ -824,6 +824,7 @@ static inline struct search *search_alloc(struct bio *bio, 
	s->iop.error		= 0;

	s->iop.flags		= 0;

	s->iop.flush_journal	= (bio->bi_rw & (REQ_FLUSH|REQ_FUA)) != 0;

	s->iop.wq		= bcache_wq;



	return s;

}

drivers/md/bcache/request.h

+1 −0
Original line number Diff line number Diff line
@@ -7,6 +7,7 @@ struct data_insert_op { 
	struct closure		cl;

	struct cache_set	*c;

	struct bio		*bio;

	struct workqueue_struct *wq;



	unsigned		inode;

	uint16_t		write_point;

drivers/md/bcache/super.c

+3 −0
Original line number Diff line number Diff line
@@ -1356,6 +1356,8 @@ static void cache_set_free(struct closure *cl) 
	bch_bset_sort_state_free(&c->sort);

	free_pages((unsigned long) c->uuids, ilog2(bucket_pages(c)));



	if (c->moving_gc_wq)

		destroy_workqueue(c->moving_gc_wq);

	if (c->bio_split)

		bioset_free(c->bio_split);

	if (c->fill_iter)
@@ -1522,6 +1524,7 @@ struct cache_set *bch_cache_set_alloc(struct cache_sb *sb) 
	    !(c->fill_iter = mempool_create_kmalloc_pool(1, iter_size)) ||

	    !(c->bio_split = bioset_create(4, offsetof(struct bbio, bio))) ||

	    !(c->uuids = alloc_bucket_pages(GFP_KERNEL, c)) ||

	    !(c->moving_gc_wq = create_workqueue("bcache_gc")) ||

	    bch_journal_alloc(c) ||

	    bch_btree_cache_alloc(c) ||

	    bch_open_buckets_alloc(c) ||

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