Messages in this thread Patches in this message | | | Date | Mon, 21 May 2007 13:48:26 -0700 | From | "Ken Chen" <> | Subject | Re: bug in 2.6.22-rc2: loop mount limited to one single iso image |
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On 5/21/07, Ken Chen <kenchen@google.com> wrote: > The easiest way is to reinstate max_loop and create "max_loop" device > up front at module load time. However, that will lose all the "fancy > on-demand device instantiation feature". > > So I propose we do the following: > > 1. have the module honor "max_loop" parameter and create that many > device upfront on module load (max_loop will also be a hard max) iff > user specify the parameter. > 2. if max_loop is not specified, default create 8 loop device. User > can extent more loop device by create device node themselves and have > kernel automatically instantiate loop device on-demand. > > Is this acceptable? Patch in a bit. >
Could people who has problem with loop device please test this? I tested it on my Ubuntu feisty distribution and it works fine. Though I typically don't use loop device at all.
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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>
diff --git a/drivers/block/loop.c b/drivers/block/loop.c index 5526ead..0aae8d8 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);
@@ -1462,34 +1462,66 @@ static struct kobject *loop_probe(dev_t return kobj; }
-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 MINORBITS, - THIS_MODULE, loop_probe, NULL, NULL); - - if (max_loop) { - printk(KERN_INFO "loop: the max_loop option is obsolete " - "and will be removed in March 2008\n"); - - } - printk(KERN_INFO "loop: module loaded\n"); - return 0; -} - static void __exit loop_exit(void) { + unsigned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"); }
+static int __init loop_init(void) +{ + int i, nr; + unsigned long range; + + /* + * 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) { + nr = max_loop; + range = max_loop; + } else { + nr = 8; + range = 1UL << MINORBITS; + } + + if (register_blkdev(LOOP_MAJOR, "loop")) + return -EIO; + blk_register_region(MKDEV(LOOP_MAJOR, 0), range, + THIS_MODULE, loop_probe, NULL, NULL); + + for (i = 0; i < nr; i++) { + if (!loop_init_one(i)) + goto err; + } + + printk(KERN_INFO "loop: module loaded\n"); + return 0; +err: + loop_exit(); + printk(KERN_INFO "loop: out of memory\n"); + return -ENOMEM; +} + module_init(loop_init); module_exit(loop_exit); diff --git a/drivers/block/loop.c b/drivers/block/loop.c index 5526ead..0aae8d8 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); @@ -1462,34 +1462,66 @@ static struct kobject *loop_probe(dev_t return kobj; } -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); - - if (max_loop) { - printk(KERN_INFO "loop: the max_loop option is obsolete " - "and will be removed in March 2008\n"); - - } - printk(KERN_INFO "loop: module loaded\n"); - return 0; -} - 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"); } +static int __init loop_init(void) +{ + int i, nr; + unsigned long range; + + /* + * 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) { + nr = max_loop; + range = max_loop; + } else { + nr = 8; + range = 1UL << MINORBITS; + } + + if (register_blkdev(LOOP_MAJOR, "loop")) + return -EIO; + blk_register_region(MKDEV(LOOP_MAJOR, 0), range, + THIS_MODULE, loop_probe, NULL, NULL); + + for (i = 0; i < nr; i++) { + if (!loop_init_one(i)) + goto err; + } + + printk(KERN_INFO "loop: module loaded\n"); + return 0; +err: + loop_exit(); + printk(KERN_INFO "loop: out of memory\n"); + return -ENOMEM; +} + module_init(loop_init); module_exit(loop_exit); | |