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s390/cio: Make /dev/chsc a single-open device

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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>
This commit is contained in:
Michael Holzheu 2013-06-06 09:49:09 +02:00 committed by Martin Schwidefsky
parent 64150adf89
commit 7a9cc6e18b
1 changed files with 19 additions and 1 deletions
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20
drivers/s390/cio/chsc_sch.c
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@ -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,