PATCH 07/15 Mempolicy: Document {set|get}_policy() vm_ops APIs
Against: 2.6.25-rc8-mm1
Document mempolicy return value reference semantics assumed by
the rest of the mempolicy code for the set_ and get_policy vm_ops
in <linux/mm.h>--where the prototypes are defined--to inform any
future mempolicy vm_op writers what the rest of the subsystem
expects of them.
Signed-off-by: Lee Schermerhorn <lee.schermerhorn@xxxxxx>
include/linux/mm.h | 18 ++++++++++++++++++
1 file changed, 18 insertions(+)
Index: linux-2.6.25-rc8-mm1/include/linux/mm.h
===================================================================
--- linux-2.6.25-rc8-mm1.orig/include/linux/mm.h 2008-04-02 17:09:54.000000000 -0400
+++ linux-2.6.25-rc8-mm1/include/linux/mm.h 2008-04-02 17:47:21.000000000 -0400
@@ -172,7 +172,25 @@ struct vm_operations_struct {
* writable, if an error is returned it will cause a SIGBUS */
int (*page_mkwrite)(struct vm_area_struct *vma, struct page *page);
#ifdef CONFIG_NUMA
+ /*
+ * set_policy() op must add a reference to any non-NULL @new mempolicy
+ * to hold the policy upon return. Caller should pass NULL @new to
+ * remove a policy and fall back to surrounding context--i.e. do not
+ * install a MPOL_DEFAULT policy, nor the task or system default
+ * mempolicy.
+ */
int (*set_policy)(struct vm_area_struct *vma, struct mempolicy *new);
+
+ /*
+ * get_policy() op must add reference [mpol_get()] to any policy at
+ * (vma,addr) marked as MPOL_SHARED. The shared policy infrastructure
+ * in mm/mempolicy.c will do this automatically.
+ * get_policy() must NOT add a ref if the policy at (vma,addr) is not
+ * marked as MPOL_SHARED. vma policies are protected by the mmap_sem.
+ * If no [shared/vma] mempolicy exists at the addr, get_policy() op
+ * must return NULL--i.e., do not "fallback" to task or system default
+ * policy.
+ */
struct mempolicy *(*get_policy)(struct vm_area_struct *vma,
unsigned long addr);
int (*migrate)(struct vm_area_struct *vma, const nodemask_t *from,
--
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