Messages in this thread Patch in this message | | | From | Greg Kroah-Hartman <> | Subject | [PATCH 5.4 074/191] bcache: at least try to shrink 1 node in bch_mca_scan() | Date | Thu, 2 Jan 2020 23:05:56 +0100 |
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From: Coly Li <colyli@suse.de>
[ Upstream commit 9fcc34b1a6dd4b8e5337e2b6ef45e428897eca6b ]
In bch_mca_scan(), the number of shrinking btree node is calculated by code like this, unsigned long nr = sc->nr_to_scan;
nr /= c->btree_pages; nr = min_t(unsigned long, nr, mca_can_free(c)); variable sc->nr_to_scan is number of objects (here is bcache B+tree nodes' number) to shrink, and pointer variable sc is sent from memory management code as parametr of a callback.
If sc->nr_to_scan is smaller than c->btree_pages, after the above calculation, variable 'nr' will be 0 and nothing will be shrunk. It is frequeently observed that only 1 or 2 is set to sc->nr_to_scan and make nr to be zero. Then bch_mca_scan() will do nothing more then acquiring and releasing mutex c->bucket_lock.
This patch checkes whether nr is 0 after the above calculation, if 0 is the result then set 1 to variable 'n'. Then at least bch_mca_scan() will try to shrink a single B+tree node.
Signed-off-by: Coly Li <colyli@suse.de> Signed-off-by: Jens Axboe <axboe@kernel.dk> Signed-off-by: Sasha Levin <sashal@kernel.org> --- drivers/md/bcache/btree.c | 2 ++ 1 file changed, 2 insertions(+)
diff --git a/drivers/md/bcache/btree.c b/drivers/md/bcache/btree.c index ba434d9ac720..46a8b5a91c38 100644 --- a/drivers/md/bcache/btree.c +++ b/drivers/md/bcache/btree.c @@ -723,6 +723,8 @@ static unsigned long bch_mca_scan(struct shrinker *shrink, * IO can always make forward progress: */ nr /= c->btree_pages; + if (nr == 0) + nr = 1; nr = min_t(unsigned long, nr, mca_can_free(c)); i = 0; -- 2.20.1
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