[PATCH v2] uio:uio_pci_generic:Don't clear master bit when the process does not exit
From: Su Weifeng
Date: Mon Feb 20 2023 - 11:48:08 EST
From: Weifeng Su <suweifeng1@xxxxxxxxxx>
The /dev/uioX device has concurrent operations in a few scenarios.
For example, when a process using the device exits abnormally,
the management program starts the same process to operate the device.
When the process exits and closes the /dev/uioX device,
the master bit of the device is cleared. In this case, if the
new process is issuing commands, I/Os are suspended and cannot be
automatically recovered.
Therefore, reference counting is added to clear the master bit
only when the last process exits.
Signed-off-by: Weifeng Su <suweifeng1@xxxxxxxxxx>
---
The difference between the first patch and the first patch is that
the reference counting operation is performed using the atomic semantics,
just like other drivers under UIO:
cdfa835c6e5e87d145f("uio_hv_generic: defer opening vmbus until first use").
drivers/uio/uio_pci_generic.c | 15 ++++++++++++++-
1 file changed, 14 insertions(+), 1 deletion(-)
diff --git a/drivers/uio/uio_pci_generic.c b/drivers/uio/uio_pci_generic.c
index e03f9b532..df436e3d9 100644
--- a/drivers/uio/uio_pci_generic.c
+++ b/drivers/uio/uio_pci_generic.c
@@ -31,6 +31,7 @@
struct uio_pci_generic_dev {
struct uio_info info;
struct pci_dev *pdev;
+ atomic_t refcnt;
};
static inline struct uio_pci_generic_dev *
@@ -39,10 +40,19 @@ to_uio_pci_generic_dev(struct uio_info *info)
return container_of(info, struct uio_pci_generic_dev, info);
}
+static int open(struct uio_info *info, struct inode *inode)
+{
+ struct uio_pci_generic_dev *gdev = to_uio_pci_generic_dev(info);
+
+ atomic_inc(&gdev->refcnt);
+ return 0;
+}
+
static int release(struct uio_info *info, struct inode *inode)
{
struct uio_pci_generic_dev *gdev = to_uio_pci_generic_dev(info);
+
/*
* This driver is insecure when used with devices doing DMA, but some
* people (mis)use it with such devices.
@@ -51,7 +61,8 @@ static int release(struct uio_info *info, struct inode *inode)
* Note that there's a non-zero chance doing this will wedge the device
* at least until reset.
*/
- pci_clear_master(gdev->pdev);
+ if (atomic_dec_and_test(&gdev->refcnt))
+ pci_clear_master(gdev->pdev);
return 0;
}
@@ -93,7 +104,9 @@ static int probe(struct pci_dev *pdev,
gdev->info.name = "uio_pci_generic";
gdev->info.version = DRIVER_VERSION;
gdev->info.release = release;
+ gdev->info.open = open;
gdev->pdev = pdev;
+ atomic_set(&gdev->refcnt, 0);
if (pdev->irq && (pdev->irq != IRQ_NOTCONNECTED)) {
gdev->info.irq = pdev->irq;
gdev->info.irq_flags = IRQF_SHARED;
--
2.33.0