Commit 7b6759b1 authored by Kent Overstreet's avatar Kent Overstreet
Browse files

bcachefs: Fix livelock in journal_entry_open() 



When the journal is low on space, we might do discards from
journal_res_get() -> journal_entry_open().

Make sure we set j->can_discard correctly, so that if we're low on space
but not because discards aren't keeping up we don't livelock.

Fixes: 8e4d2803 ("bcachefs: Don't aggressively discard the journal")
Signed-off-by: default avatarKent Overstreet <kent.overstreet@linux.dev>
parent b1c71cb4

fs/bcachefs/journal_reclaim.c

+12 −5
Original line number Diff line number Diff line
@@ -17,6 +17,8 @@ 
#include <linux/kthread.h>

#include <linux/sched/mm.h>



static bool __should_discard_bucket(struct journal *, struct journal_device *);



/* Free space calculations: */



static unsigned journal_space_from(struct journal_device *ja,
@@ -203,8 +205,7 @@ void bch2_journal_space_available(struct journal *j) 
		       ja->bucket_seq[ja->dirty_idx_ondisk] < j->last_seq_ondisk)

			ja->dirty_idx_ondisk = (ja->dirty_idx_ondisk + 1) % ja->nr;



		if (ja->discard_idx != ja->dirty_idx_ondisk)

			can_discard = true;

		can_discard |= __should_discard_bucket(j, ja);



		max_entry_size = min_t(unsigned, max_entry_size, ca->mi.bucket_size);

		nr_online++;
@@ -264,13 +265,19 @@ void bch2_journal_space_available(struct journal *j) 


/* Discards - last part of journal reclaim: */



static bool should_discard_bucket(struct journal *j, struct journal_device *ja)

static bool __should_discard_bucket(struct journal *j, struct journal_device *ja)

{

	spin_lock(&j->lock);

	unsigned min_free = max(4, ja->nr / 8);



	bool ret = bch2_journal_dev_buckets_available(j, ja, journal_space_discarded) < min_free &&

	return bch2_journal_dev_buckets_available(j, ja, journal_space_discarded) <

		min_free &&

		ja->discard_idx != ja->dirty_idx_ondisk;

}



static bool should_discard_bucket(struct journal *j, struct journal_device *ja)

{

	spin_lock(&j->lock);

	bool ret = __should_discard_bucket(j, ja);

	spin_unlock(&j->lock);



	return ret;