linux-kernel - [PATCH v4 14/40] PCI: hv: Optimize hv_get_dom_num() by using find_and_set

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Date: Thu, 20 Jun 2024 10:56:37 -0700
From: Yury Norov <yury.norov@...il.com>
To: linux-kernel@...r.kernel.org,
	"K. Y. Srinivasan" <kys@...rosoft.com>,
	Haiyang Zhang <haiyangz@...rosoft.com>,
	Wei Liu <wei.liu@...nel.org>,
	Dexuan Cui <decui@...rosoft.com>,
	Lorenzo Pieralisi <lpieralisi@...nel.org>,
	Krzysztof Wilczyński <kw@...ux.com>,
	Rob Herring <robh@...nel.org>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	linux-hyperv@...r.kernel.org,
	linux-pci@...r.kernel.org
Cc: Yury Norov <yury.norov@...il.com>,
	Alexey Klimov <alexey.klimov@...aro.org>,
	Bart Van Assche <bvanassche@....org>,
	Jan Kara <jack@...e.cz>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Matthew Wilcox <willy@...radead.org>,
	Mirsad Todorovac <mirsad.todorovac@....unizg.hr>,
	Rasmus Villemoes <linux@...musvillemoes.dk>,
	Sergey Shtylyov <s.shtylyov@....ru>,
	Michael Kelley <mhklinux@...look.com>
Subject: [PATCH v4 14/40] PCI: hv: Optimize hv_get_dom_num() by using find_and_set_bit()

The function traverses bitmap with for_each_clear_bit() just to allocate
a bit atomically. Simplify it by using dedicated find_and_set_bit().

Signed-off-by: Yury Norov <yury.norov@...il.com>
Reviewed-by: Michael Kelley <mhklinux@...look.com>
Acked-by: Wei Liu <wei.liu@...nel.org>
Acked-by: Bjorn Helgaas <bhelgaas@...gle.com>
---
 drivers/pci/controller/pci-hyperv.c | 8 +++-----
 1 file changed, 3 insertions(+), 5 deletions(-)

diff --git a/drivers/pci/controller/pci-hyperv.c b/drivers/pci/controller/pci-hyperv.c
index 5992280e8110..d8a3ca9a7378 100644
--- a/drivers/pci/controller/pci-hyperv.c
+++ b/drivers/pci/controller/pci-hyperv.c
@@ -37,6 +37,7 @@
  * the PCI back-end driver in Hyper-V.
  */
 
+#include <linux/find_atomic.h>
 #include <linux/kernel.h>
 #include <linux/module.h>
 #include <linux/pci.h>
@@ -3599,12 +3600,9 @@ static u16 hv_get_dom_num(u16 dom)
 	if (test_and_set_bit(dom, hvpci_dom_map) == 0)
 		return dom;
 
-	for_each_clear_bit(i, hvpci_dom_map, HVPCI_DOM_MAP_SIZE) {
-		if (test_and_set_bit(i, hvpci_dom_map) == 0)
-			return i;
-	}
+	i = find_and_set_bit(hvpci_dom_map, HVPCI_DOM_MAP_SIZE);
 
-	return HVPCI_DOM_INVALID;
+	return i < HVPCI_DOM_MAP_SIZE ? i : HVPCI_DOM_INVALID;
 }
 
 /**
-- 
2.43.0