[PATCH 5.4 18/24] blk-iocost: clamp inuse and skip noops in __propagate_weights()

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5.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Tejun Heo <tj@xxxxxxxxxx>

[ Upstream commit db84a72af6be422abf2089a5896293590dda5066 ]

__propagate_weights() currently expects the callers to clamp inuse within
[1, active], which is needlessly fragile. The inuse adjustment logic is
going to be revamped, in preparation, let's make __propagate_weights() clamp
inuse on entry.

Also, make it avoid weight updates altogether if neither active or inuse is
changed.

Signed-off-by: Tejun Heo <tj@xxxxxxxxxx>
Signed-off-by: Jens Axboe <axboe@xxxxxxxxx>
Stable-dep-of: 57e420c84f9a ("blk-iocost: Avoid using clamp() on inuse in __propagate_weights()")
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 block/blk-iocost.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/block/blk-iocost.c b/block/blk-iocost.c
index e7d5aafa5e99..75eb90b3241e 100644
--- a/block/blk-iocost.c
+++ b/block/blk-iocost.c
@@ -907,7 +907,10 @@ static void __propagate_active_weight(struct ioc_gq *iocg, u32 active, u32 inuse
 
 	lockdep_assert_held(&ioc->lock);
 
-	inuse = min(active, inuse);
+	inuse = clamp_t(u32, inuse, 1, active);
+
+	if (active == iocg->active && inuse == iocg->inuse)
+		return;
 
 	for (lvl = iocg->level - 1; lvl >= 0; lvl--) {
 		struct ioc_gq *parent = iocg->ancestors[lvl];
-- 
2.39.5







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