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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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