On 5/21/07, Ken Chen <[email protected]> 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.
---
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 <[email protected]>
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- printk(KERN_INFO "loop: the max_loop option is obsolete "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);
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