Re: [PATCH] PPC64 mmu_context_init needs to run earlier

[Nathan Lynch <nathanl@austin.ibm.com>]

On Tue, 2004-11-02 at 16:10, Linus Torvalds wrote:
> On Tue, 2 Nov 2004, Nathan Lynch wrote:
> > 
> > Using idr_get_new_above in init_new_context lets us get rid of an
> > awkward init function which wasn't running early enough in boot
> > anyway.
> 
> Ok, call me stupid, but what's the difference between
> 
> 	idr_get_new(&mmu_context_idr, NULL, &index);
> 
> and
> 
> 	idr_get_new_above(&mmu_context_idr, NULL, 0, &index);
> 
> because as far as I can tell, they are exactly the same.
> 
> They both just do a "idr_get_new_above_int(idp, ptr, 0)".

Right, bad patch.  I was confused by this bit in idr.c:

/**
 * idr_get_new_above - allocate new idr entry above a start id

into thinking the new entry would be strictly greater than the start id.

Here's another attempt, using 1 instead of 0 for the start id.


Using idr_get_new_above in init_new_context lets us get rid of an
awkward init function which wasn't running early enough in boot
anyway.

Signed-off-by: Nathan Lynch <nathanl@austin.ibm.com>


---


diff -puN arch/ppc64/mm/init.c~ppc64-mmu-context-use-idr_get_new_above
arch/ppc64/mm/init.c
---
linux-2.6.10-rc1-bk12/arch/ppc64/mm/init.c~ppc64-mmu-context-use-idr_get_new_above	2004-11-02 16:28:57.000000000 -0600
+++ linux-2.6.10-rc1-bk12-nathanl/arch/ppc64/mm/init.c	2004-11-02
17:49:08.000000000 -0600
@@ -489,7 +489,7 @@ again:
 		return -ENOMEM;
 
 	spin_lock(&mmu_context_lock);
-	err = idr_get_new(&mmu_context_idr, NULL, &index);
+	err = idr_get_new_above(&mmu_context_idr, NULL, 1, &index);
 	spin_unlock(&mmu_context_lock);
 
 	if (err == -EAGAIN)
@@ -518,19 +518,6 @@ void destroy_context(struct mm_struct *m
 	hugetlb_mm_free_pgd(mm);
 }
 
-static int __init mmu_context_init(void)
-{
-	int index;
-
-	/* Reserve the first (invalid) context*/
-	idr_pre_get(&mmu_context_idr, GFP_KERNEL);
-	idr_get_new(&mmu_context_idr, NULL, &index);
-	BUG_ON(0 != index);
-
-	return 0;
-}
-arch_initcall(mmu_context_init);
-
 /*
  * Do very early mm setup.
  */

_