Patch "blk-iocost: clamp inuse and skip noops in __propagate_weights()" has been added to the 5.4-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    blk-iocost: clamp inuse and skip noops in __propagate_weights()

to the 5.4-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     blk-iocost-clamp-inuse-and-skip-noops-in-__propagate.patch
and it can be found in the queue-5.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 067fe0a9230c01e1b8fae56fa64133abb3b9f8ba
Author: Tejun Heo <tj@xxxxxxxxxx>
Date:   Tue Sep 1 14:52:35 2020 -0400

    blk-iocost: clamp inuse and skip noops in __propagate_weights()
    
    [ 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>

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];