Commit 85ab365f authored by Kent Overstreet's avatar Kent Overstreet
Browse files

bcachefs: Fix deadlock in journal write path 



bch2_journal_write() was incorrectly waiting on earlier journal writes
synchronously; this usually worked because most of the time we'd be
running in the context of a thread that did a journal_buf_put(), but
sometimes we'd be running out of the same workqueue that completes those
prior journal writes.

Additionally, this makes sure to punt to a workqueue before submitting
preflushes - we really don't want to be calling submit_bio() in the main
transaction commit path.

Signed-off-by: default avatarKent Overstreet <kent.overstreet@linux.dev>
parent adfe9357

fs/bcachefs/journal_io.c

+42 −18
Original line number Diff line number Diff line
@@ -1723,7 +1723,7 @@ static void journal_write_endio(struct bio *bio) 
	percpu_ref_put(&ca->io_ref);

}



static CLOSURE_CALLBACK(do_journal_write)

static CLOSURE_CALLBACK(journal_write_submit)

{

	closure_type(w, struct journal_buf, io);

	struct journal *j = container_of(w, struct journal, buf[w->idx]);
@@ -1768,6 +1768,44 @@ static CLOSURE_CALLBACK(do_journal_write) 
	continue_at(cl, journal_write_done, j->wq);

}



static CLOSURE_CALLBACK(journal_write_preflush)

{

	closure_type(w, struct journal_buf, io);

	struct journal *j = container_of(w, struct journal, buf[w->idx]);

	struct bch_fs *c = container_of(j, struct bch_fs, journal);



	if (j->seq_ondisk + 1 != le64_to_cpu(w->data->seq)) {

		spin_lock(&j->lock);

		closure_wait(&j->async_wait, cl);

		spin_unlock(&j->lock);



		continue_at(cl, journal_write_preflush, j->wq);

		return;

	}



	if (w->separate_flush) {

		for_each_rw_member(c, ca) {

			percpu_ref_get(&ca->io_ref);



			struct journal_device *ja = &ca->journal;

			struct bio *bio = &ja->bio[w->idx]->bio;

			bio_reset(bio, ca->disk_sb.bdev,

				  REQ_OP_WRITE|REQ_SYNC|REQ_META|REQ_PREFLUSH);

			bio->bi_end_io		= journal_write_endio;

			bio->bi_private		= ca;

			closure_bio_submit(bio, cl);

		}



		continue_at(cl, journal_write_submit, j->wq);

	} else {

		/*

		 * no need to punt to another work item if we're not waiting on

		 * preflushes

		 */

		journal_write_submit(&cl->work);

	}

}



static int bch2_journal_write_prep(struct journal *j, struct journal_buf *w)

{

	struct bch_fs *c = container_of(j, struct bch_fs, journal);
@@ -2033,23 +2071,9 @@ CLOSURE_CALLBACK(bch2_journal_write) 
		goto err;



	if (!JSET_NO_FLUSH(w->data))

		closure_wait_event(&j->async_wait, j->seq_ondisk + 1 == le64_to_cpu(w->data->seq));



	if (!JSET_NO_FLUSH(w->data) && w->separate_flush) {

		for_each_rw_member(c, ca) {

			percpu_ref_get(&ca->io_ref);



			struct journal_device *ja = &ca->journal;

			struct bio *bio = &ja->bio[w->idx]->bio;

			bio_reset(bio, ca->disk_sb.bdev,

				  REQ_OP_WRITE|REQ_SYNC|REQ_META|REQ_PREFLUSH);

			bio->bi_end_io		= journal_write_endio;

			bio->bi_private		= ca;

			closure_bio_submit(bio, cl);

		}

	}



	continue_at(cl, do_journal_write, j->wq);

		continue_at(cl, journal_write_preflush, j->wq);

	else

		continue_at(cl, journal_write_submit, j->wq);

	return;

no_io:

	continue_at(cl, journal_write_done, j->wq);