I developing a "filter" for block device (Linux, Ubuntu 16), during initialization of the filter-driver I have tried to the queue pointer for the backend (existen device), a body of the bdev_get_queue macro show cool comment "this never NULL", but I go the NULL for the bd_disk field of the struct block_device.
What I'm need to check additionally?
static int __init dua_init(void)
{
int status;
struct request_queue *backend_queue = NULL;
struct super_block *sb = NULL;
printk(KERN_NOTICE __MODULE__ ": Initialize the driver ...\n");
if ( IS_ERR(backend_bdev = lookup_bdev(dudrv_bckend, FMODE_READ)) )
{
status = PTR_ERR(backend_bdev);
printk(KERN_ERR __MODULE__ ": lookup_bdev(%s) -> %d\n", dudrv_bckend, status);
return status;
}
$DELAY(1);
if ( sb = freeze_bdev(backend_bdev) )
$TRACE(": freeze I/O on block device %s ...", dudrv_bckend);
$DELAY(1);
$TRACE(" %p ", backend_bdev->bd_disk);
$DELAY(1);
backend_queue = bdev_get_queue(backend_bdev);
$TRACE(" -- ");
$DELAY(1);
if ( backend_make_request_fn != backend_queue->make_request_fn )
{
backend_make_request_fn = backend_queue->make_request_fn;
backend_queue->make_request_fn = dua_make_request_fn;
$TRACE(": Change for %s request_fn = %p -> %p, ", dudrv_bckend, backend_make_request_fn, backend_queue->make_request_fn);
}
else {
printk(KERN_NOTICE __MODULE__ ": I/O request process has been set.\n");
}
$TRACE(" -- ");
/* unlock filesystem */
$DELAY(1);
if ( sb )
if (status = thaw_bdev(backend_bdev, sb))
printk(KERN_NOTICE __MODULE__ ": thaw_bdev() -> %d\n", status);
printk(KERN_NOTICE __MODULE__ ": End the driver initialization.\n");
return 0;
}
Update1: what is the difference between queue's pointer is supposed to be returned by the bdev_get_queue and struct block_device.bd_queue ?
