linux-kernel - [PATCH] s390/zcrypt: optimize memory allocation in online

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Date: Sun, 23 Jun 2024 21:01:49 +0900
From: yskelg@...il.com
To: Harald Freudenberger <freude@...ux.ibm.com>,
	Heiko Carstens <hca@...ux.ibm.com>,
	Vasily Gorbik <gor@...ux.ibm.com>,
	Alexander Gordeev <agordeev@...ux.ibm.com>,
	Christian Borntraeger <borntraeger@...ux.ibm.com>,
	Sven Schnelle <svens@...ux.ibm.com>
Cc: shjy180909@...il.com,
	linux-s390@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Yunseong Kim <yskelg@...il.com>
Subject: [PATCH] s390/zcrypt: optimize memory allocation in online_show()

From: Yunseong Kim <yskelg@...il.com>

Previously, when setting the online state for a card, the code would
allocate memory to store information about all attached queues,
regardless of whether their online state actually changed.
This patch improves efficiency by only allocating memory for the queues
that are truly affected by the online state change.

This allows for a more precise memory allocation (based on maxzqs) which
can reduce memory usage.

Signed-off-by: Yunseong Kim <yskelg@...il.com>
---
 drivers/s390/crypto/zcrypt_card.c | 16 +++++++---------
 1 file changed, 7 insertions(+), 9 deletions(-)

diff --git a/drivers/s390/crypto/zcrypt_card.c b/drivers/s390/crypto/zcrypt_card.c
index 050462d95222..2c80be3f2a00 100644
--- a/drivers/s390/crypto/zcrypt_card.c
+++ b/drivers/s390/crypto/zcrypt_card.c
@@ -88,9 +88,10 @@ static ssize_t online_store(struct device *dev,
 	 * the zqueue objects, we make sure they exist after lock release.
 	 */
 	list_for_each_entry(zq, &zc->zqueues, list)
-		maxzqs++;
+		if (!!zq->online != !!online)
+			maxzqs++;
 	if (maxzqs > 0)
-		zq_uelist = kcalloc(maxzqs + 1, sizeof(*zq_uelist), GFP_ATOMIC);
+		zq_uelist = kcalloc(maxzqs, sizeof(*zq_uelist), GFP_ATOMIC);
 	list_for_each_entry(zq, &zc->zqueues, list)
 		if (zcrypt_queue_force_online(zq, online))
 			if (zq_uelist) {
@@ -98,14 +99,11 @@ static ssize_t online_store(struct device *dev,
 				zq_uelist[i++] = zq;
 			}
 	spin_unlock(&zcrypt_list_lock);
-	if (zq_uelist) {
-		for (i = 0; zq_uelist[i]; i++) {
-			zq = zq_uelist[i];
-			ap_send_online_uevent(&zq->queue->ap_dev, online);
-			zcrypt_queue_put(zq);
-		}
-		kfree(zq_uelist);
+	while (i--) {
+		ap_send_online_uevent(&zq->queue->ap_dev, online);
+		zcrypt_queue_put(zq_uelist[i]);
 	}
+	kfree(zq_uelist);
 
 	return count;
 }
-- 
2.45.2