Re: [NFS] RE: [autofs] multiple servers per automount

[Mike Waychison <Michael.Waychison@Sun.COM>]

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H. Peter Anvin wrote:
> Followup to:  <3F8C1BB6.9010202@sun.com>
> By author:    Mike Waychison <Michael.Waychison@Sun.COM>
> In newsgroup: linux.dev.kernel
> 
>>Here is the quick fix for this in RH 2.1AS kernels:
>>
>>http://www.kernelnewbies.org/kernels/rh21as/SOURCES/linux-2.4.9-moreunnamed.patch
>>
>>It makes unnamed block devices use majors 12, 14, 38, 39, as well as 0. 
>>
>>I don't know if anyone is working out a better scheme for 
>>get_unnamed_dev in 2.6 yet.  It does need to be done though.  A simple 
>>patch for 2.6 would maybe see the unnamed_dev_in_use bitmap grow to 
>>PAGE_SIZE, automatically allowing for 32768 unnamed devices.
>>
> 
> 
> dev_t enlargement, which solves this without a bunch of auxilliary
> majors, should be in 2.6.
> 
> 	-hpa

The problem still remains in 2.6 that we limit the count to 256.  I've 
attached a quick patch that I've compiled and tested.  I don't know if 
there is a better way to handle dynamic assignment of minors (haven't 
kept up to date in that realm), but if there is, then we should probably 
  use it instead.

Mike Waychison

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===== fs/super.c 1.108 vs edited =====
--- 1.108/fs/super.c	Wed Oct  1 15:36:45 2003
+++ edited/fs/super.c	Tue Oct 14 22:52:12 2003
@@ -528,14 +528,22 @@
  * filesystems which don't use real block-devices.  -- jrs
  */
 
-enum {Max_anon = 256};
-static unsigned long unnamed_dev_in_use[Max_anon/(8*sizeof(unsigned long))];
+enum {Max_anon = PAGE_SIZE * 8};
+static void *unnamed_dev_in_use = NULL;
 static spinlock_t unnamed_dev_lock = SPIN_LOCK_UNLOCKED;/* protects the above */
 
 int set_anon_super(struct super_block *s, void *data)
 {
 	int dev;
 	spin_lock(&unnamed_dev_lock);
+
+	if (!unnamed_dev_in_use)
+		unnamed_dev_in_use = (void *)get_zeroed_page(GFP_KERNEL);
+	if (!unnamed_dev_in_use) {
+		spin_unlock(&unnamed_dev_lock);
+		return -ENOMEM;
+	}
+
 	dev = find_first_zero_bit(unnamed_dev_in_use, Max_anon);
 	if (dev == Max_anon) {
 		spin_unlock(&unnamed_dev_lock);