Hello,
When I wanted to change the state of DRBD from primary to secondary, sometimes
I get the "Device is held open by someone" issue.
I looked into the code drbd_main.c (DRBD Release 8.0.11) and found that the
error is set from the below code.
else if( ns.role == Secondary && mdev->open_cnt )
rv=SS_DeviceInUse;
I put debug logs and found that sometimes "open_cnt" variable is not equal to
zero that results in the error. "open_cnt" variable is incremented and
decremented from the function drbd_open() and drbd_close() respectively. In
function drbd_open(), "open_cnt" variable is handled within locking/unlocking
function to avoid race condition whereas in drbd_close(), no such
locking/unlocking function is there to handle its critical section. Can we
imagine any scenario that due to the absence of locking/unlocking function in
the drbd_close() function, race condition is occurring that results in the
wrong value of "open_cnt" variable.
Here is the code.
STATIC int drbd_close(struct inode *inode, struct file *file)
{
/* do not use *file (May be NULL, in case of a unmount
:-) */
drbd_dev *mdev;
mdev = minor_to_mdev(MINOR(inode->i_rdev));
if(!mdev) return -ENODEV;
/*
printk(KERN_ERR DEVICE_NAME ": close(inode=%p,file=%p)"
"current=%p,minor=%d,wc=%d\n", inode, file,
current, minor,
inode->i_writecount);
*/
mdev->open_cnt--;
return 0;
}
STATIC int drbd_open(struct inode *inode, struct file *file)
{
drbd_dev *mdev;
unsigned long flags;
int rv=0;
mdev = minor_to_mdev(MINOR(inode->i_rdev));
if(!mdev) return -ENODEV;
spin_lock_irqsave(&mdev->req_lock,flags);
/* to have a stable mdev->state.role and no race with
updating open_cnt */
if (mdev->state.role != Primary) {
if (file->f_mode & FMODE_WRITE)
{
rv =
-EROFS;
} else if (!allow_oos) {
rv =
-EMEDIUMTYPE;
}
}
if(!rv) mdev->open_cnt++;
spin_unlock_irqrestore(&mdev->req_lock,flags);
return rv;
}
Thanks in Advance.
Regards,
Satyajit Paul
Software Engineer
India
===============================================================================
Please refer to http://www.aricent.com/legal/email_disclaimer.html
for important disclosures regarding this electronic communication.
===============================================================================
_______________________________________________
drbd-user mailing list
[email protected]
http://lists.linbit.com/mailman/listinfo/drbd-user
