From 0cf3d804281822563d469b7c7eb66d08dbfe4009 Mon Sep 17 00:00:00 2001
From: Kay Sievers <kay.sievers@vrfy.org>
Date: Sun, 31 Jul 2011 22:08:04 +0200
Subject: [PATCH] --- yaml --- r: 263131 b: refs/heads/master c:
 d134b00b9acca3fb054d7c88a5f5d562ecbb42d1 h: refs/heads/master i:   263129:
 a2d9c1070fa9a7956a15dd207639fd6a55c05ee6   263127:
 ceb0d1c6cfcca225708e3a77a5d827e38f4d2dea v: v3

---
 [refs]                                    |  2 +-
 trunk/Documentation/kernel-parameters.txt |  9 +++++---
 trunk/drivers/block/Kconfig               | 15 +++++++++++++
 trunk/drivers/block/loop.c                | 27 +++++++++--------------
 4 files changed, 32 insertions(+), 21 deletions(-)

diff --git a/[refs] b/[refs]
index 2b59080b8dea..a69e9b7aab0b 100644
--- a/[refs]
+++ b/[refs]
@@ -1,2 +1,2 @@
 ---
-refs/heads/master: 770fe30a46a12b6fb6b63fbe1737654d28e84844
+refs/heads/master: d134b00b9acca3fb054d7c88a5f5d562ecbb42d1
diff --git a/trunk/Documentation/kernel-parameters.txt b/trunk/Documentation/kernel-parameters.txt
index 4ca93898fbd3..c32851131646 100644
--- a/trunk/Documentation/kernel-parameters.txt
+++ b/trunk/Documentation/kernel-parameters.txt
@@ -1340,9 +1340,12 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
 			it is equivalent to "nosmp", which also disables
 			the IO APIC.
 
-	max_loop=	[LOOP] Maximum number of loopback devices that can
-			be mounted
-			Format: <1-256>
+	max_loop=	[LOOP] The number of loop block devices that get
+	(loop.max_loop)	unconditionally pre-created at init time. The default
+			number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
+			of statically allocating a predefined number, loop
+			devices can be requested on-demand with the
+			/dev/loop-control interface.
 
 	mcatest=	[IA-64]
 
diff --git a/trunk/drivers/block/Kconfig b/trunk/drivers/block/Kconfig
index 717d6e4e18d3..57212c5235e2 100644
--- a/trunk/drivers/block/Kconfig
+++ b/trunk/drivers/block/Kconfig
@@ -256,6 +256,21 @@ config BLK_DEV_LOOP
 
 	  Most users will answer N here.
 
+config BLK_DEV_LOOP_MIN_COUNT
+	int "Number of loop devices to pre-create at init time"
+	depends on BLK_DEV_LOOP
+	default 8
+	help
+	  Static number of loop devices to be unconditionally pre-created
+	  at init time.
+
+	  This default value can be overwritten on the kernel command
+	  line or with module-parameter loop.max_loop.
+
+	  The historic default is 8. If a late 2011 version of losetup(8)
+	  is used, it can be set to 0, since needed loop devices can be
+	  dynamically allocated with the /dev/loop-control interface.
+
 config BLK_DEV_CRYPTOLOOP
 	tristate "Cryptoloop Support"
 	select CRYPTO
diff --git a/trunk/drivers/block/loop.c b/trunk/drivers/block/loop.c
index 5c9edf944879..3defc52f060c 100644
--- a/trunk/drivers/block/loop.c
+++ b/trunk/drivers/block/loop.c
@@ -1793,21 +1793,6 @@ static int __init loop_init(void)
 	struct loop_device *lo;
 	int err;
 
-	/*
-	 * 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.
-	 */
-
 	err = misc_register(&loop_misc);
 	if (err < 0)
 		return err;
@@ -1833,11 +1818,19 @@ static int __init loop_init(void)
 	if (max_loop > 1UL << (MINORBITS - part_shift))
 		return -EINVAL;
 
+	/*
+	 * If max_loop is specified, create that many devices upfront.
+	 * This also becomes a hard limit. If max_loop is not specified,
+	 * create CONFIG_BLK_DEV_LOOP_MIN_COUNT loop devices at module
+	 * init time. Loop devices can be requested on-demand with the
+	 * /dev/loop-control interface, or be instantiated by accessing
+	 * a 'dead' device node.
+	 */
 	if (max_loop) {
 		nr = max_loop;
 		range = max_loop << part_shift;
 	} else {
-		nr = 8;
+		nr = CONFIG_BLK_DEV_LOOP_MIN_COUNT;
 		range = 1UL << MINORBITS;
 	}
 
@@ -1847,7 +1840,7 @@ static int __init loop_init(void)
 	blk_register_region(MKDEV(LOOP_MAJOR, 0), range,
 				  THIS_MODULE, loop_probe, NULL, NULL);
 
-	/* pre-create number devices of devices given by config or max_loop */
+	/* pre-create number of devices given by config or max_loop */
 	mutex_lock(&loop_index_mutex);
 	for (i = 0; i < nr; i++)
 		loop_add(&lo, i);