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SubjectRe: + loop-preallocate-eight-loop-devices.patch added to -mm tree
Date
Ken Chen wrote:
> On 5/21/07, Ken Chen <kenchen@google.com> wrote:
...
> tested, like this?

Ken, your patch below works for me. Are you going to send this
on to Linus?

> diff --git a/drivers/block/loop.c b/drivers/block/loop.c
> index 5526ead..0ed5470 100644
> --- a/drivers/block/loop.c
> +++ b/drivers/block/loop.c
> @@ -1354,7 +1354,7 @@ #endif
> */
> 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
> 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
> 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
>
> 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");
> }



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