[05/12] bcache: gc does not work when triggering by manual command

Commit Message

Coly Li Sept. 6, 2017, 6:25 a.m. UTC

From: Tang Junhui <[e-mail]>

I try to execute the following command to trigger gc thread:
[root@localhost internal]# echo 1 > trigger_gc
But it does not work, I debug the code in gc_should_run(), It works only
if in invalidating or sectors_to_gc < 0. So set sectors_to_gc to -1 to
meet the condition when we trigger gc by manual command.

(Code comments aded by Coly Li)

Signed-off-by: Tang Junhui <[e-mail]>
Reviewed-by: Coly Li <[e-mail]>
---
 drivers/md/bcache/sysfs.c | 15 ++++++++++++++-
 1 file changed, 14 insertions(+), 1 deletion(-)

Patch

diff --git a/drivers/md/bcache/sysfs.c b/drivers/md/bcache/sysfs.c
index f90f13616980..09295c07ea88 100644
--- a/drivers/md/bcache/sysfs.c
+++ b/drivers/md/bcache/sysfs.c
@@ -615,8 +615,21 @@  STORE(__bch_cache_set)
 		bch_cache_accounting_clear(&c->accounting);
 	}
 
-	if (attr == &sysfs_trigger_gc)
+	if (attr == &sysfs_trigger_gc) {
+		/*
+		 * Garbage collection thread only works when sectors_to_gc < 0,
+		 * when users write to sysfs entry trigger_gc, most of time
+		 * they want to forcibly triger gargage collection. Here -1 is
+		 * set to c->sectors_to_gc, to make gc_should_run() give a
+		 * chance to permit gc thread to run. "give a chance" means
+		 * before going into gc_should_run(), there is still chance
+		 * that c->sectors_to_gc being set to other positive value. So
+		 * writing sysfs entry trigger_gc won't always make sure gc
+		 * thread takes effect.
+		 */
+		atomic_set(&c->sectors_to_gc, -1);
 		wake_up_gc(c);
+	}
 
 	if (attr == &sysfs_prune_cache) {
 		struct shrink_control sc;