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authorColy Li <colyli@suse.de>2019-11-13 16:03:24 +0800
committerJens Axboe <axboe@kernel.dk>2019-11-13 15:42:50 -0700
commit9fcc34b1a6dd4b8e5337e2b6ef45e428897eca6b (patch)
treef48581635d520d28d26f7f1cb5969f706c311dab /drivers/md/bcache/btree.c
parentc5fcdedcee4e6ae15c0eb5e0fbe25467e57d2963 (diff)
downloadlinux-9fcc34b1a6dd4b8e5337e2b6ef45e428897eca6b.tar.gz
bcache: at least try to shrink 1 node in bch_mca_scan()
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>
Diffstat (limited to 'drivers/md/bcache/btree.c')
-rw-r--r--drivers/md/bcache/btree.c2
1 files changed, 2 insertions, 0 deletions
diff --git a/drivers/md/bcache/btree.c b/drivers/md/bcache/btree.c
index 48e33ee0d876..3df5fa4a501c 100644
--- a/drivers/md/bcache/btree.c
+++ b/drivers/md/bcache/btree.c
@@ -754,6 +754,8 @@ 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;