[PATCH v2 07/11] mm/mempolicy: add userland mempolicy arg structure

[Gregory Price <gourry.memverge@gmail.com>]

This patch adds the new user-api argument structure intended for
set_mempolicy2 and mbind2.

struct mpol_args {
  __u16 mode;
  __u16 mode_flags;
  __s32 home_node;          /* mbind2: policy home node */
  __aligned_u64 *pol_nodes;
  __u64 pol_maxnodes;
  __u64 addr;     /* get_mempolicy: policy address */
  __s32 policy_node;        /* get_mempolicy: policy node info */
  __s32 addr_node;          /* get_mempolicy: memory range policy */
};

This structure is intended to be extensible as new mempolicy extensions
are added.

For example, set_mempolicy_home_node was added to allow vma mempolicies
to have a preferred/home node assigned.  This structure allows the
addition of that setting at the time the mempolicy is set, rather
than requiring additional calls to modify the policy.

Full breakdown of arguments as of this patch:
    mode:         Mempolicy mode (MPOL_DEFAULT, MPOL_INTERLEAVE)

    mode_flags:   Flags previously or'd into mode in set_mempolicy
                  (e.g.: MPOL_F_STATIC_NODES, MPOL_F_RELATIVE_NODES)

    home_node:    for mbind2.  Allows the setting of a policy's home
                  with the use of MPOL_MF_HOME_NODE

    pol_nodes:    Policy nodemask

    pol_maxnodes: Max number of nodes in the policy nodemask

    policy_node:  for get_mempolicy2.  Returns extended information
                  about a policy that was previously reported by
                  passing MPOL_F_NODE to get_mempolicy.  Instead of
                  overriding the mode value, simply add a field.

    addr:         for get_mempolicy2.  Used with MPOL_F_ADDR to run
                  get_mempolicy against the vma the address belongs
                  to instead of the task.

    addr_node:    for get_mempolicy2.  Returns the node the address
                  belongs to.  Previously get_mempolicy() would
                  override the output value of (mode) if MPOL_F_ADDR
                  and MPOL_F_NODE were set.  Instead, we extend
                  mpol_args to do this by default if MPOL_F_ADDR is
                  set and do away with MPOL_F_NODE.

Suggested-by: Frank van der Linden <fvdl@google.com>
Suggested-by: Vinicius Tavares Petrucci <vtavarespetr@micron.com>
Suggested-by: Hasan Al Maruf <Hasan.Maruf@amd.com>
Signed-off-by: Gregory Price <gregory.price@memverge.com>
Co-developed-by: Vinicius Tavares Petrucci <vtavarespetr@micron.com>
Signed-off-by: Vinicius Tavares Petrucci <vtavarespetr@micron.com>
---
 .../admin-guide/mm/numa_memory_policy.rst     | 20 +++++++++++++++++++
 include/uapi/linux/mempolicy.h                | 12 +++++++++++
 2 files changed, 32 insertions(+)

diff --git a/Documentation/admin-guide/mm/numa_memory_policy.rst b/Documentation/admin-guide/mm/numa_memory_policy.rst
index d2c8e712785b..64c5804dc40f 100644
--- a/Documentation/admin-guide/mm/numa_memory_policy.rst
+++ b/Documentation/admin-guide/mm/numa_memory_policy.rst
@@ -482,6 +482,26 @@ closest to which page allocation will come from. Specifying the home node overri
 the default allocation policy to allocate memory close to the local node for an
 executing CPU.
 
+Extended Mempolicy Arguments::
+
+	struct mpol_args {
+		__u16 mode;
+		__u16 mode_flags;
+		__s32 home_node; /* mbind2: policy home node */
+		__aligned_u64 pol_nodes; /* nodemask pointer */
+		__u64 pol_maxnodes;
+		__u64 addr; /* get_mempolicy2: policy address */
+		__s32 policy_node; /* get_mempolicy2: policy node information */
+		__s32 addr_node; /* get_mempolicy2: memory range policy */
+	};
+
+The extended mempolicy argument structure is defined to allow the mempolicy
+interfaces future extensibility without the need for additional system calls.
+
+The core arguments (mode, mode_flags, pol_nodes, and pol_maxnodes) apply to
+all interfaces relative to their non-extended counterparts. Each additional
+field may only apply to specific extended interfaces.  See the respective
+extended interface man page for more details.
 
 Memory Policy Command Line Interface
 ====================================
diff --git a/include/uapi/linux/mempolicy.h b/include/uapi/linux/mempolicy.h
index 1f9bb10d1a47..00a673e30047 100644
--- a/include/uapi/linux/mempolicy.h
+++ b/include/uapi/linux/mempolicy.h
@@ -27,6 +27,18 @@ enum {
 	MPOL_MAX,	/* always last member of enum */
 };
 
+struct mpol_args {
+	/* Basic mempolicy settings */
+	__u16 mode;
+	__u16 mode_flags;
+	__s32 home_node;	/* mbind2: policy home node */
+	__aligned_u64 pol_nodes;
+	__u64 pol_maxnodes;
+	__u64 addr;
+	__s32 policy_node;	/* get_mempolicy: policy node info */
+	__s32 addr_node;	/* get_mempolicy: memory range policy */
+};
+
 /* Flags for set_mempolicy */
 #define MPOL_F_STATIC_NODES	(1 << 15)
 #define MPOL_F_RELATIVE_NODES	(1 << 14)
-- 
2.39.1