From 7a9cc6e18b8fe751a41349b188dd468a8317192a Mon Sep 17 00:00:00 2001 From: Michael Holzheu Date: Thu, 6 Jun 2013 09:49:09 +0200 Subject: [PATCH] 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 Signed-off-by: Martin Schwidefsky --- drivers/s390/cio/chsc_sch.c | 20 +++++++++++++++++++- 1 file changed, 19 insertions(+), 1 deletion(-) 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 long chsc_ioctl(struct file *filp, unsigned int cmd, } } +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, -- 2.7.4