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loop: preallocate eight loop devices 

The kernel on-demand loop device instantiation breaks several user space
tools as the tools are not ready to cope with the "on-demand feature".  Fix
it by instantiate default 8 loop devices and also reinstate max_loop module
parameter.

Signed-off-by: Ken Chen <kenchen@google.com>
Acked-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Ken Chen 2007-06-08 13:46:44 -07:00 committed by Linus Torvalds
parent c287ef1ff9
commit a47653fc26
1 changed files with 83 additions and 19 deletions
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102
drivers/block/loop.c
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@ -1354,7 +1354,7 @@ static struct block_device_operations lo_fops = {
*/
static int max_loop;
module_param(max_loop, int, 0);
MODULE_PARM_DESC(max_loop, "obsolete, loop device is created on-demand");
MODULE_PARM_DESC(max_loop, "Maximum number of loop devices");
MODULE_LICENSE("GPL");
MODULE_ALIAS_BLOCKDEV_MAJOR(LOOP_MAJOR);
@ -1394,16 +1394,11 @@ int loop_unregister_transfer(int number)
EXPORT_SYMBOL(loop_register_transfer);
EXPORT_SYMBOL(loop_unregister_transfer);
static struct loop_device *loop_init_one(int i)
static struct loop_device *loop_alloc(int i)
{
struct loop_device *lo;
struct gendisk *disk;
list_for_each_entry(lo, &loop_devices, lo_list) {
if (lo->lo_number == i)
return lo;
}
lo = kzalloc(sizeof(*lo), GFP_KERNEL);
if (!lo)
goto out;
@ -1427,8 +1422,6 @@ static struct loop_device *loop_init_one(int i)
disk->private_data = lo;
disk->queue = lo->lo_queue;
sprintf(disk->disk_name, "loop%d", i);
add_disk(disk);
list_add_tail(&lo->lo_list, &loop_devices);
return lo;
out_free_queue:
@ -1439,15 +1432,37 @@ out:
return NULL;
}
static void loop_del_one(struct loop_device *lo)
static void loop_free(struct loop_device *lo)
{
del_gendisk(lo->lo_disk);
blk_cleanup_queue(lo->lo_queue);
put_disk(lo->lo_disk);
list_del(&lo->lo_list);
kfree(lo);
}
static struct loop_device *loop_init_one(int i)
{
struct loop_device *lo;
list_for_each_entry(lo, &loop_devices, lo_list) {
if (lo->lo_number == i)
return lo;
}
lo = loop_alloc(i);
if (lo) {
add_disk(lo->lo_disk);
list_add_tail(&lo->lo_list, &loop_devices);
}
return lo;
}
static void loop_del_one(struct loop_device *lo)
{
del_gendisk(lo->lo_disk);
loop_free(lo);
}
static struct kobject *loop_probe(dev_t dev, int *part, void *data)
{
struct loop_device *lo;
@ -1464,28 +1479,77 @@ static struct kobject *loop_probe(dev_t dev, int *part, void *data)
static int __init loop_init(void)
{
if (register_blkdev(LOOP_MAJOR, "loop"))
return -EIO;
blk_register_region(MKDEV(LOOP_MAJOR, 0), 1UL << MINORBITS,
THIS_MODULE, loop_probe, NULL, NULL);
int i, nr;
unsigned long range;
struct loop_device *lo, *next;
/*
* loop module now has a feature to instantiate underlying device
* structure on-demand, provided that there is an access dev node.
* However, this will not work well with user space tool that doesn't
* know about such "feature". In order to not break any existing
* tool, we do the following:
*
* (1) if max_loop is specified, create that many upfront, and this
* also becomes a hard limit.
* (2) if max_loop is not specified, create 8 loop device on module
* load, user can further extend loop device by create dev node
* themselves and have kernel automatically instantiate actual
* device on-demand.
*/
if (max_loop > 1UL << MINORBITS)
return -EINVAL;
if (max_loop) {
printk(KERN_INFO "loop: the max_loop option is obsolete "
"and will be removed in March 2008\n");
nr = max_loop;
range = max_loop;
} else {
nr = 8;
range = 1UL << MINORBITS;
}
if (register_blkdev(LOOP_MAJOR, "loop"))
return -EIO;
for (i = 0; i < nr; i++) {
lo = loop_alloc(i);
if (!lo)
goto Enomem;
list_add_tail(&lo->lo_list, &loop_devices);
}
/* point of no return */
list_for_each_entry(lo, &loop_devices, lo_list)
add_disk(lo->lo_disk);
blk_register_region(MKDEV(LOOP_MAJOR, 0), range,
THIS_MODULE, loop_probe, NULL, NULL);
printk(KERN_INFO "loop: module loaded\n");
return 0;
Enomem:
printk(KERN_INFO "loop: out of memory\n");
list_for_each_entry_safe(lo, next, &loop_devices, lo_list)
loop_free(lo);
unregister_blkdev(LOOP_MAJOR, "loop");
return -ENOMEM;
}
static void __exit loop_exit(void)
{
unsigned long range;
struct loop_device *lo, *next;
range = max_loop ? max_loop : 1UL << MINORBITS;
list_for_each_entry_safe(lo, next, &loop_devices, lo_list)
loop_del_one(lo);
blk_unregister_region(MKDEV(LOOP_MAJOR, 0), 1UL << MINORBITS);
blk_unregister_region(MKDEV(LOOP_MAJOR, 0), range);
if (unregister_blkdev(LOOP_MAJOR, "loop"))
printk(KERN_WARNING "loop: cannot unregister blkdev\n");
}