Commit e3de0446 authored Jan 24, 2020 by Coly Li Committed by Jens Axboe Jan 23, 2020

bcache: reap from tail of c->btree_cache in bch_mca_scan()



When shrink btree node cache from c->btree_cache in bch_mca_scan(),
no matter the selected node is reaped or not, it will be rotated from
the head to the tail of c->btree_cache list. But in bcache journal
code, when flushing the btree nodes with oldest journal entry, btree
nodes are iterated and slected from the tail of c->btree_cache list in
btree_flush_write(). The list_rotate_left() in bch_mca_scan() will
make btree_flush_write() iterate more nodes in c->btree_list in reverse
order.

This patch just reaps the selected btree node cache, and not move it
from the head to the tail of c->btree_cache list. Then bch_mca_scan()
will not mess up c->btree_cache list to btree_flush_write().

Signed-off-by: Coly Li <colyli@suse.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

parent d5c9c470

drivers/md/bcache/btree.c

+5 −5

Original line number	Diff line number	Diff line
		@@ -747,19 +747,19 @@ static unsigned long bch_mca_scan(struct shrinker *shrink,
		i++;
		}

		for (; (nr--) && i < btree_cache_used; i++) {
		if (list_empty(&c->btree_cache))
		list_for_each_entry_safe_reverse(b, t, &c->btree_cache, list) {
		if (nr <= 0 \|\| i >= btree_cache_used)
		goto out;

		b = list_first_entry(&c->btree_cache, struct btree, list);
		list_rotate_left(&c->btree_cache);

		if (!mca_reap(b, 0, false)) {
		mca_bucket_free(b);
		mca_data_free(b);
		rw_unlock(true, b);
		freed++;
		}

		nr--;
		i++;
		}
		out:
		mutex_unlock(&c->bucket_lock);

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