From: Andi Kleen <ak@muc.de>

> Andi, how come policy_vma() calls ->set_policy under i_shared_sem?

I think this can be actually dropped now.  In an earlier version I did walk
the vma shared list to change the policies of other mappings to the same
shared memory region.  This turned out too complicated with all the corner
cases, so I eventually gave in and added ->get_policy to the fast path. 
Also there is still the mmap_sem which prevents races in the same MM.  

Patch to remove it attached.  Also adds documentation and removes the bogus
__alloc_page_vma() prototype noticed by hch.


---

 25-akpm/Documentation/numastat.txt |   22 ++++++++++++++++++++++
 25-akpm/include/linux/gfp.h        |    3 ---
 25-akpm/mm/mempolicy.c             |    4 ----
 3 files changed, 22 insertions(+), 7 deletions(-)

diff -puN Documentation/numastat.txt~numa-api-docs-policy_vma-fix Documentation/numastat.txt
--- 25/Documentation/numastat.txt~numa-api-docs-policy_vma-fix	Wed Apr 21 14:10:22 2004
+++ 25-akpm/Documentation/numastat.txt	Wed Apr 21 14:10:22 2004
@@ -0,0 +1,22 @@
+
+Numa policy hit/miss statistics
+
+/sys/devices/system/node/node*/numastat
+
+All units are pages. Hugepages have separate counters.
+
+numa_hit			A process wanted to allocate memory from this node,
+					and succeeded.
+numa_miss			A process wanted to allocate memory from this node,
+					but ended up with memory from another.
+numa_foreign		A process wanted to allocate on another node,
+				    but ended up with memory from this one.
+local_node			A process ran on this node and got memory from it.
+other_node			A process ran on this node and got memory from another node.
+interleave_hit 		Interleaving wanted to allocate from this node
+					and succeeded.
+
+For easier reading you can use the numastat utility from the numactl package
+(ftp://ftp.suse.com/pub/people/ak/numa/numactl*). Note that it only works
+well right now on machines with a small number of CPUs.
+
diff -puN include/linux/gfp.h~numa-api-docs-policy_vma-fix include/linux/gfp.h
--- 25/include/linux/gfp.h~numa-api-docs-policy_vma-fix	Wed Apr 21 14:10:22 2004
+++ 25-akpm/include/linux/gfp.h	Wed Apr 21 14:10:22 2004
@@ -96,9 +96,6 @@ alloc_pages(unsigned int gfp_mask, unsig
 
 	return alloc_pages_current(gfp_mask, order);
 }
-extern struct page *__alloc_page_vma(unsigned gfp_mask,
-			struct vm_area_struct *vma, unsigned long off);
-
 extern struct page *alloc_page_vma(unsigned gfp_mask,
 			struct vm_area_struct *vma, unsigned long addr);
 #else
diff -puN mm/mempolicy.c~numa-api-docs-policy_vma-fix mm/mempolicy.c
--- 25/mm/mempolicy.c~numa-api-docs-policy_vma-fix	Wed Apr 21 14:10:22 2004
+++ 25-akpm/mm/mempolicy.c	Wed Apr 21 14:10:22 2004
@@ -295,8 +295,6 @@ static int policy_vma(struct vm_area_str
 		 vma->vm_ops, vma->vm_file,
 		 vma->vm_ops ? vma->vm_ops->set_policy : NULL);
 
-	if (vma->vm_file)
-		down(&vma->vm_file->f_mapping->i_shared_sem);
 	if (vma->vm_ops && vma->vm_ops->set_policy)
 		err = vma->vm_ops->set_policy(vma, new);
 	if (!err) {
@@ -304,8 +302,6 @@ static int policy_vma(struct vm_area_str
 		vma->vm_policy = new;
 		mpol_free(old);
 	}
-	if (vma->vm_file)
-		up(&vma->vm_file->f_mapping->i_shared_sem);
 	return err;
 }
 

_