s390/cio: Make /dev/chsc a single-open device
In order to allow serialization of dynamic I/O with this patch
the /dev/chsc character device can only be accessed by one
single opener. Any subsequent open calls are rejected with EBUSY.
Signed-off-by: Michael Holzheu <holzheu@linux.vnet.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
diff --git a/drivers/s390/cio/chsc_sch.c b/drivers/s390/cio/chsc_sch.c
index 190fc84..5fe9f8c 100644
--- a/drivers/s390/cio/chsc_sch.c
+++ b/drivers/s390/cio/chsc_sch.c
@@ -847,9 +847,27 @@
}
}
+static atomic_t chsc_ready_for_use = ATOMIC_INIT(1);
+
+static int chsc_open(struct inode *inode, struct file *file)
+{
+ if (!atomic_dec_and_test(&chsc_ready_for_use)) {
+ atomic_inc(&chsc_ready_for_use);
+ return -EBUSY;
+ }
+ return nonseekable_open(inode, file);
+}
+
+static int chsc_release(struct inode *inode, struct file *filp)
+{
+ atomic_inc(&chsc_ready_for_use);
+ return 0;
+}
+
static const struct file_operations chsc_fops = {
.owner = THIS_MODULE,
- .open = nonseekable_open,
+ .open = chsc_open,
+ .release = chsc_release,
.unlocked_ioctl = chsc_ioctl,
.compat_ioctl = chsc_ioctl,
.llseek = no_llseek,