* Call with cpuset_sem held. May nest a call to the
* lock_cpu_hotplug()/unlock_cpu_hotplug() pair.
*/
+
static void update_cpu_domains(struct cpuset *cur)
{
struct cpuset *c, *par = cur->parent;
return 0;
}
+/*
+ * nearest_exclusive_ancestor() - Returns the nearest mem_exclusive
+ * ancestor to the specified cpuset. Call while holding cpuset_sem.
+ * If no ancestor is mem_exclusive (an unusual configuration), then
+ * returns the root cpuset.
+ */
+static const struct cpuset *nearest_exclusive_ancestor(const struct cpuset *cs)
+{
+ while (!is_mem_exclusive(cs) && cs->parent)
+ cs = cs->parent;
+ return cs;
+}
+
/**
- * cpuset_zone_allowed - is zone z allowed in current->mems_allowed
- * @z: zone in question
+ * cpuset_zone_allowed - Can we allocate memory on zone z's memory node?
+ * @z: is this zone on an allowed node?
+ * @gfp_mask: memory allocation flags (we use __GFP_HARDWALL)
*
- * Is zone z allowed in current->mems_allowed, or is
- * the CPU in interrupt context? (zone is always allowed in this case)
- */
-int cpuset_zone_allowed(struct zone *z)
+ * If we're in interrupt, yes, we can always allocate. If zone
+ * z's node is in our tasks mems_allowed, yes. If it's not a
+ * __GFP_HARDWALL request and this zone's nodes is in the nearest
+ * mem_exclusive cpuset ancestor to this tasks cpuset, yes.
+ * Otherwise, no.
+ *
+ * GFP_USER allocations are marked with the __GFP_HARDWALL bit,
+ * and do not allow allocations outside the current tasks cpuset.
+ * GFP_KERNEL allocations are not so marked, so can escape to the
+ * nearest mem_exclusive ancestor cpuset.
+ *
+ * Scanning up parent cpusets requires cpuset_sem. The __alloc_pages()
+ * routine only calls here with __GFP_HARDWALL bit _not_ set if
+ * it's a GFP_KERNEL allocation, and all nodes in the current tasks
+ * mems_allowed came up empty on the first pass over the zonelist.
+ * So only GFP_KERNEL allocations, if all nodes in the cpuset are
+ * short of memory, might require taking the cpuset_sem semaphore.
+ *
+ * The first loop over the zonelist in mm/page_alloc.c:__alloc_pages()
+ * calls here with __GFP_HARDWALL always set in gfp_mask, enforcing
+ * hardwall cpusets - no allocation on a node outside the cpuset is
+ * allowed (unless in interrupt, of course).
+ *
+ * The second loop doesn't even call here for GFP_ATOMIC requests
+ * (if the __alloc_pages() local variable 'wait' is set). That check
+ * and the checks below have the combined affect in the second loop of
+ * the __alloc_pages() routine that:
+ * in_interrupt - any node ok (current task context irrelevant)
+ * GFP_ATOMIC - any node ok
+ * GFP_KERNEL - any node in enclosing mem_exclusive cpuset ok
+ * GFP_USER - only nodes in current tasks mems allowed ok.
+ **/
+
+int cpuset_zone_allowed(struct zone *z, unsigned int __nocast gfp_mask)
{
- return in_interrupt() ||
- node_isset(z->zone_pgdat->node_id, current->mems_allowed);
+ int node; /* node that zone z is on */
+ const struct cpuset *cs; /* current cpuset ancestors */
+ int allowed = 1; /* is allocation in zone z allowed? */
+
+ if (in_interrupt())
+ return 1;
+ node = z->zone_pgdat->node_id;
+ if (node_isset(node, current->mems_allowed))
+ return 1;
+ if (gfp_mask & __GFP_HARDWALL) /* If hardwall request, stop here */
+ return 0;
+
+ /* Not hardwall and node outside mems_allowed: scan up cpusets */
+ down(&cpuset_sem);
+ cs = current->cpuset;
+ if (!cs)
+ goto done; /* current task exiting */
+ cs = nearest_exclusive_ancestor(cs);
+ allowed = node_isset(node, cs->mems_allowed);
+done:
+ up(&cpuset_sem);
+ return allowed;
+}
+
+/**
+ * cpuset_excl_nodes_overlap - Do we overlap @p's mem_exclusive ancestors?
+ * @p: pointer to task_struct of some other task.
+ *
+ * Description: Return true if the nearest mem_exclusive ancestor
+ * cpusets of tasks @p and current overlap. Used by oom killer to
+ * determine if task @p's memory usage might impact the memory
+ * available to the current task.
+ *
+ * Acquires cpuset_sem - not suitable for calling from a fast path.
+ **/
+
+int cpuset_excl_nodes_overlap(const struct task_struct *p)
+{
+ const struct cpuset *cs1, *cs2; /* my and p's cpuset ancestors */
+ int overlap = 0; /* do cpusets overlap? */
+
+ down(&cpuset_sem);
+ cs1 = current->cpuset;
+ if (!cs1)
+ goto done; /* current task exiting */
+ cs2 = p->cpuset;
+ if (!cs2)
+ goto done; /* task p is exiting */
+ cs1 = nearest_exclusive_ancestor(cs1);
+ cs2 = nearest_exclusive_ancestor(cs2);
+ overlap = nodes_intersects(cs1->mems_allowed, cs2->mems_allowed);
+done:
+ up(&cpuset_sem);
+
+ return overlap;
}
/*
git.samba.org / sfrench / cifs-2.6.git / blobdiff