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Subject[patch 5/6] mempolicy: add MPOL_F_RELATIVE_NODES flag
Adds another optional mode flag, MPOL_F_RELATIVE_NODES, that specifies
nodemasks passed via set_mempolicy() or mbind() should be considered
relative to the current task's mems_allowed.

When the mempolicy is created, the passed nodemask is folded and mapped
onto the current task's mems_allowed. For example, consider a task
using set_mempolicy() to pass MPOL_INTERLEAVE | MPOL_F_RELATIVE_NODES
with a nodemask of 1-3. If current's mems_allowed is 4-7, the effected
nodemask is 5-7 (the second, third, and fourth node of mems_allowed).
If the same task is attached to a cpuset, the mempolicy nodemask is
rebound each time the mems are changed. Some possible rebinds and
results are:

mems result
1-3 1-3
1-7 2-4
1,5-6 1,5-6
1,5-7 5-7

Likewise, the zonelist built for MPOL_BIND acts on the set of zones
assigned to the resultant nodemask from the relative remap.

In the MPOL_PREFERRED case, the preferred node is remapped from the
currently effected nodemask to the relative nodemask.

This mempolicy mode flag was conceived of by Paul Jackson <pj@sgi.com>.

Cc: Paul Jackson <pj@sgi.com>
Cc: Christoph Lameter <clameter@sgi.com>
Cc: Lee Schermerhorn <Lee.Schermerhorn@hp.com>
Cc: Andi Kleen <ak@suse.de>
Signed-off-by: David Rientjes <rientjes@google.com>
---
include/linux/mempolicy.h | 3 ++-
mm/mempolicy.c | 40 ++++++++++++++++++++++++++++++++++++++--
mm/shmem.c | 6 ++++++
3 files changed, 46 insertions(+), 3 deletions(-)
diff --git a/include/linux/mempolicy.h b/include/linux/mempolicy.h
--- a/include/linux/mempolicy.h
+++ b/include/linux/mempolicy.h
@@ -25,12 +25,13 @@ enum {

/* Flags for set_mempolicy */
#define MPOL_F_STATIC_NODES (1 << 15)
+#define MPOL_F_RELATIVE_NODES (1 << 14)

/*
* MPOL_MODE_FLAGS is the union of all possible optional mode flags passed to
* either set_mempolicy() or mbind().
*/
-#define MPOL_MODE_FLAGS (MPOL_F_STATIC_NODES)
+#define MPOL_MODE_FLAGS (MPOL_F_STATIC_NODES | MPOL_F_RELATIVE_NODES)

/* Flags for get_mempolicy */
#define MPOL_F_NODE (1<<0) /* return next IL mode instead of node mask */
diff --git a/mm/mempolicy.c b/mm/mempolicy.c
--- a/mm/mempolicy.c
+++ b/mm/mempolicy.c
@@ -152,7 +152,18 @@ static struct zonelist *bind_zonelist(nodemask_t *nodes)

static inline int mpol_store_user_nodemask(const struct mempolicy *pol)
{
- return !!(pol->flags & MPOL_F_STATIC_NODES);
+ return !!(pol->flags & (MPOL_F_STATIC_NODES | MPOL_F_RELATIVE_NODES));
+}
+
+static nodemask_t mpol_relative_nodemask(const nodemask_t *orig,
+ const nodemask_t *rel)
+{
+ nodemask_t ret;
+ nodemask_t tmp;
+
+ nodes_fold(tmp, *orig, nodes_weight(*rel));
+ nodes_onto(ret, tmp, *rel);
+ return ret;
}

/* Create a new policy */
@@ -173,7 +184,12 @@ static struct mempolicy *mpol_new(unsigned short mode, unsigned short flags,
return ERR_PTR(-ENOMEM);
atomic_set(&policy->refcnt, 1);
cpuset_update_task_memory_state();
- nodes_and(cpuset_context_nmask, *nodes, cpuset_current_mems_allowed);
+ if (flags & MPOL_F_RELATIVE_NODES)
+ cpuset_context_nmask = mpol_relative_nodemask(nodes,
+ &cpuset_current_mems_allowed);
+ else
+ nodes_and(cpuset_context_nmask, *nodes,
+ cpuset_current_mems_allowed);
switch (mode) {
case MPOL_INTERLEAVE:
if (nodes_empty(*nodes) || nodes_empty(cpuset_context_nmask))
@@ -898,6 +914,9 @@ asmlinkage long sys_mbind(unsigned long start, unsigned long len,
mode &= ~MPOL_MODE_FLAGS;
if (mode >= MPOL_MAX)
return -EINVAL;
+ if ((mode_flags & MPOL_F_STATIC_NODES) &&
+ (mode_flags & MPOL_F_RELATIVE_NODES))
+ return -EINVAL;
err = get_nodes(&nodes, nmask, maxnode);
if (err)
return err;
@@ -916,6 +935,8 @@ asmlinkage long sys_set_mempolicy(int mode, unsigned long __user *nmask,
mode &= ~MPOL_MODE_FLAGS;
if ((unsigned int)mode >= MPOL_MAX)
return -EINVAL;
+ if ((flags & MPOL_F_STATIC_NODES) && (flags & MPOL_F_RELATIVE_NODES))
+ return -EINVAL;
err = get_nodes(&nodes, nmask, maxnode);
if (err)
return err;
@@ -1747,10 +1768,12 @@ static void mpol_rebind_policy(struct mempolicy *pol,
{
nodemask_t tmp;
int static_nodes;
+ int relative_nodes;

if (!pol)
return;
static_nodes = pol->flags & MPOL_F_STATIC_NODES;
+ relative_nodes = pol->flags & MPOL_F_RELATIVE_NODES;
if (!mpol_store_user_nodemask(pol) &&
nodes_equal(pol->w.cpuset_mems_allowed, *newmask))
return;
@@ -1761,6 +1784,9 @@ static void mpol_rebind_policy(struct mempolicy *pol,
case MPOL_INTERLEAVE:
if (static_nodes)
nodes_and(tmp, pol->w.user_nodemask, *newmask);
+ else if (relative_nodes)
+ tmp = mpol_relative_nodemask(&pol->w.user_nodemask,
+ newmask);
else {
nodes_remap(tmp, pol->v.nodes,
pol->w.cpuset_mems_allowed, *newmask);
@@ -1783,6 +1809,11 @@ static void mpol_rebind_policy(struct mempolicy *pol,
pol->v.preferred_node = node;
else
pol->v.preferred_node = -1;
+ } else if (relative_nodes) {
+ tmp = mpol_relative_nodemask(&pol->w.user_nodemask,
+ newmask);
+ pol->v.preferred_node = node_remap(pol->v.preferred_node,
+ pol->w.cpuset_mems_allowed, tmp);
} else {
pol->v.preferred_node = node_remap(pol->v.preferred_node,
pol->w.cpuset_mems_allowed, *newmask);
@@ -1794,6 +1825,9 @@ static void mpol_rebind_policy(struct mempolicy *pol,

if (static_nodes)
nodes_and(tmp, pol->w.user_nodemask, *newmask);
+ else if (relative_nodes)
+ tmp = mpol_relative_nodemask(&pol->w.user_nodemask,
+ newmask);
else {
nodemask_t nodes;
struct zone **z;
@@ -1911,6 +1945,8 @@ static inline int mpol_to_str(char *buffer, int maxlen, struct mempolicy *pol)

if (flags & MPOL_F_STATIC_NODES)
p += sprintf(p, "%sstatic", need_bar++ ? "|" : "");
+ if (flags & MPOL_F_RELATIVE_NODES)
+ p += sprintf(p, "%srelative", need_bar++ ? "|" : "");
}

if (!nodes_empty(nodes)) {
diff --git a/mm/shmem.c b/mm/shmem.c
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -1131,6 +1131,12 @@ static int shmem_parse_mpol(char *value, unsigned short *policy,
if (flags) {
if (!strcmp(flags, "static"))
*mode_flags |= MPOL_F_STATIC_NODES;
+ if (!strcmp(flags, "relative"))
+ *mode_flags |= MPOL_F_RELATIVE_NODES;
+
+ if ((*mode_flags & MPOL_F_STATIC_NODES) &&
+ (*mode_flags & MPOL_F_RELATIVE_NODES))
+ err = 1;
}
out:
/* Restore string for error message */

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