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Code Issues Releases Wiki Activity

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: Kent Overstreet <kent.overstreet@linux.dev>
This commit is contained in:
Kent Overstreet 2024-04-19 21:54:32 -04:00
parent adfe9357c3
commit 85ab365f7c
1 changed files with 42 additions and 18 deletions
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60
fs/bcachefs/journal_io.c
View File

@ -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);