From a6020ed759404372e8be2b276e85e51735472cc9 Mon Sep 17 00:00:00 2001 From: Lee Schermerhorn Date: Mon, 28 Apr 2008 02:13:14 -0700 Subject: [PATCH] mempolicy: document {set|get}_policy() vm_ops APIs Document mempolicy return value reference semantics assumed by the rest of the mempolicy code for the set_ and get_policy vm_ops in --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 Cc: Christoph Lameter Cc: David Rientjes Cc: Mel Gorman Cc: Andi Kleen Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/mm.h | 18 ++++++++++++++++++ 1 file changed, 18 insertions(+) diff --git a/include/linux/mm.h b/include/linux/mm.h index bc0ad24cf8..8b7f4a5d4f 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -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, -- 2.39.5