linux-kernel - [PATCH 2/4] xen: xen-pciback: Replace GFP_ATOMIC with GFP_KERNEL in pcistub_init

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Message-Id: <1523286233-26392-1-git-send-email-baijiaju1990@gmail.com>
Date:   Mon,  9 Apr 2018 23:03:53 +0800
From:   Jia-Ju Bai <baijiaju1990@...il.com>
To:     boris.ostrovsky@...cle.com, jgross@...e.com,
        gregkh@...uxfoundation.org
Cc:     xen-devel@...ts.xenproject.org, linux-kernel@...r.kernel.org,
        Jia-Ju Bai <baijiaju1990@...il.com>
Subject: [PATCH 2/4] xen: xen-pciback: Replace GFP_ATOMIC with GFP_KERNEL in pcistub_init_device

pcistub_init_device() is never called in atomic context.

The call chain ending up at pcistub_init_device() is:
[1] pcistub_init_device() <- pcistub_seize() <- pcistub_probe()
[2] pcistub_init_device() <- pcistub_init_devices_late() <- 
	xen_pcibk_init()
pcistub_probe() is only set as ".probe" in struct pci_driver.
xen_pcibk_init() is is only set as a parameter of module_init().
These functions are not called in atomic context.

Despite never getting called from atomic context,
pcistub_init_device() calls kzalloc() with GFP_ATOMIC,
which does not sleep for allocation.
GFP_ATOMIC is not necessary and can be replaced with GFP_KERNEL,
which can sleep and improve the possibility of sucessful allocation.

This is found by a static analysis tool named DCNS written by myself.
And I also manually check it.

Signed-off-by: Jia-Ju Bai <baijiaju1990@...il.com>
---
 drivers/xen/xen-pciback/pci_stub.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/xen/xen-pciback/pci_stub.c b/drivers/xen/xen-pciback/pci_stub.c
index 9e480fd..bf8c0d3 100644
--- a/drivers/xen/xen-pciback/pci_stub.c
+++ b/drivers/xen/xen-pciback/pci_stub.c
@@ -364,7 +364,7 @@ static int pcistub_init_device(struct pci_dev *dev)
 	 * here and then to call kfree(pci_get_drvdata(psdev->dev)).
 	 */
 	dev_data = kzalloc(sizeof(*dev_data) +  strlen(DRV_NAME "[]")
-				+ strlen(pci_name(dev)) + 1, GFP_ATOMIC);
+				+ strlen(pci_name(dev)) + 1, GFP_KERNEL);
 	if (!dev_data) {
 		err = -ENOMEM;
 		goto out;
-- 
1.9.1