Improvement for [md PATCH 15/15] MD: use per-cpu counter for writes_pending
From: NeilBrown <hidden>
Date: 2017-03-22 01:55:13
Subsystem:
software raid (multiple disks) support, the rest · Maintainers:
Song Liu, Yu Kuai, Linus Torvalds
__ref_is_percpu() is documented as an internal interface, so best not to use it. We don't really need it, as ->sync_checkers is always 0 when the writes_pending is in per-cpu mode. So change to test ->sync_checkers, and update comments to match. Signed-off-by: NeilBrown <redacted> --- drivers/md/md.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/drivers/md/md.c b/drivers/md/md.c
index adf2b5bdfd67..b76ac563115e 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c@@ -2266,8 +2266,8 @@ static bool set_in_sync(struct mddev *mddev) percpu_ref_is_zero(&mddev->writes_pending)) { mddev->in_sync = 1; /* - * Ensure in_sync is visible before switch back - * to percpu + * Ensure ->in_sync is visible before we clear + * ->sync_checkers. */ smp_mb(); set_bit(MD_SB_CHANGE_CLEAN, &mddev->sb_flags);
@@ -7920,7 +7920,7 @@ void md_write_start(struct mddev *mddev, struct bio *bi) smp_mb(); /* Match smp_mb in set_in_sync() */ if (mddev->safemode == 1) mddev->safemode = 0; - if (mddev->in_sync || !__ref_is_percpu(&mddev->writes_pending, ¬used)) { + if (mddev->in_sync || !mddev->sync_checkers) { spin_lock(&mddev->lock); if (mddev->in_sync) { mddev->in_sync = 0;
--
2.12.0
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