bcache: introduce force_wake_up_gc()

Garbage collection thread starts to work when c->sectors_to_gc is
negative value, otherwise nothing will happen even the gc thread is
woken up by wake_up_gc().

force_wake_up_gc() sets c->sectors_to_gc to -1 before calling
wake_up_gc(), then gc thread may have chance to run if no one else sets
c->sectors_to_gc to a positive value before gc_should_run().

This routine can be called where the gc thread is woken up and required
to run in force.

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

1 files changed, 2 insertions, 15 deletions

diff --git a/drivers/md/bcache/sysfs.c b/drivers/md/bcache/sysfs.c
index 9d5fe12f0c9c..c09748497cdc 100644
--- a/drivers/md/bcache/sysfs.c
+++ b/drivers/md/bcache/sysfs.c
@@ -742,21 +742,8 @@ STORE(__bch_cache_set)
 		bch_cache_accounting_clear(&c->accounting);
 	}
 
-	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_trigger_gc)
+		force_wake_up_gc(c);
 
 	if (attr == &sysfs_prune_cache) {
 		struct shrink_control sc;