+ * nearest_exclusive_ancestor() - Returns the nearest mem_exclusive
+ * ancestor to the specified cpuset. Call holding callback_mutex.
+ * 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_softwall - Can we allocate on zone z's memory node?
+ * @z: is this zone on an allowed node?
+ * @gfp_mask: memory allocation flags
+ *
+ * If we're in interrupt, yes, we can always allocate. If
+ * __GFP_THISNODE is set, 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.
+ *
+ * If __GFP_HARDWALL is set, cpuset_zone_allowed_softwall()
+ * reduces to cpuset_zone_allowed_hardwall(). Otherwise,
+ * cpuset_zone_allowed_softwall() might sleep, and might allow a zone
+ * from an enclosing cpuset.
+ *
+ * cpuset_zone_allowed_hardwall() only handles the simpler case of
+ * hardwall cpusets, and never sleeps.
+ *
+ * The __GFP_THISNODE placement logic is really handled elsewhere,
+ * by forcibly using a zonelist starting at a specified node, and by
+ * (in get_page_from_freelist()) refusing to consider the zones for
+ * any node on the zonelist except the first. By the time any such
+ * calls get to this routine, we should just shut up and say 'yes'.
+ *
+ * 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 enclosing mem_exclusive ancestor cpuset.
+ *
+ * Scanning up parent cpusets requires callback_mutex. 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 callback_mutex
+ * mutex.
+ *
+ * The first call here from mm/page_alloc:get_page_from_freelist()
+ * has __GFP_HARDWALL set in gfp_mask, enforcing hardwall cpusets,
+ * so no allocation on a node outside the cpuset is allowed (unless
+ * in interrupt, of course).
+ *
+ * The second pass through get_page_from_freelist() doesn't even call
+ * here for GFP_ATOMIC calls. For those calls, the __alloc_pages()
+ * variable 'wait' is not set, and the bit ALLOC_CPUSET is not set
+ * in alloc_flags. That logic and the checks below have the combined
+ * affect 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.
+ *
+ * Rule:
+ * Don't call cpuset_zone_allowed_softwall if you can't sleep, unless you
+ * pass in the __GFP_HARDWALL flag set in gfp_flag, which disables
+ * the code that might scan up ancestor cpusets and sleep.
+ */
+
+int __cpuset_zone_allowed_softwall(struct zone *z, gfp_t gfp_mask)
+{
+ int node; /* node that zone z is on */
+ const struct cpuset *cs; /* current cpuset ancestors */
+ int allowed; /* is allocation in zone z allowed? */
+
+ if (in_interrupt() || (gfp_mask & __GFP_THISNODE))
+ return 1;
+ node = zone_to_nid(z);
+ might_sleep_if(!(gfp_mask & __GFP_HARDWALL));
+ if (node_isset(node, current->mems_allowed))
+ return 1;
+ if (gfp_mask & __GFP_HARDWALL) /* If hardwall request, stop here */
+ return 0;
+
+ if (current->flags & PF_EXITING) /* Let dying task have memory */
+ return 1;
+
+ /* Not hardwall and node outside mems_allowed: scan up cpusets */
+ mutex_lock(&callback_mutex);
+
+ task_lock(current);
+ cs = nearest_exclusive_ancestor(current->cpuset);
+ task_unlock(current);
+
+ allowed = node_isset(node, cs->mems_allowed);
+ mutex_unlock(&callback_mutex);
+ return allowed;
+}
+
+/*
+ * cpuset_zone_allowed_hardwall - Can we allocate on zone z's memory node?
+ * @z: is this zone on an allowed node?
+ * @gfp_mask: memory allocation flags
+ *
+ * If we're in interrupt, yes, we can always allocate.
+ * If __GFP_THISNODE is set, yes, we can always allocate. If zone
+ * z's node is in our tasks mems_allowed, yes. Otherwise, no.
+ *
+ * The __GFP_THISNODE placement logic is really handled elsewhere,
+ * by forcibly using a zonelist starting at a specified node, and by
+ * (in get_page_from_freelist()) refusing to consider the zones for
+ * any node on the zonelist except the first. By the time any such
+ * calls get to this routine, we should just shut up and say 'yes'.
+ *
+ * Unlike the cpuset_zone_allowed_softwall() variant, above,
+ * this variant requires that the zone be in the current tasks
+ * mems_allowed or that we're in interrupt. It does not scan up the
+ * cpuset hierarchy for the nearest enclosing mem_exclusive cpuset.
+ * It never sleeps.
+ */
+
+int __cpuset_zone_allowed_hardwall(struct zone *z, gfp_t gfp_mask)
+{
+ int node; /* node that zone z is on */
+
+ if (in_interrupt() || (gfp_mask & __GFP_THISNODE))
+ return 1;
+ node = zone_to_nid(z);
+ if (node_isset(node, current->mems_allowed))
+ return 1;
+ return 0;
+}
+
+/**
+ * cpuset_lock - lock out any changes to cpuset structures
+ *
+ * The out of memory (oom) code needs to mutex_lock cpusets
+ * from being changed while it scans the tasklist looking for a
+ * task in an overlapping cpuset. Expose callback_mutex via this
+ * cpuset_lock() routine, so the oom code can lock it, before
+ * locking the task list. The tasklist_lock is a spinlock, so
+ * must be taken inside callback_mutex.
+ */
+
+void cpuset_lock(void)
+{
+ mutex_lock(&callback_mutex);
+}
+
+/**
+ * cpuset_unlock - release lock on cpuset changes
+ *
+ * Undo the lock taken in a previous cpuset_lock() call.
+ */
+
+void cpuset_unlock(void)
+{
+ mutex_unlock(&callback_mutex);
+}
+
+/**
+ * cpuset_mem_spread_node() - On which node to begin search for a page
+ *
+ * If a task is marked PF_SPREAD_PAGE or PF_SPREAD_SLAB (as for
+ * tasks in a cpuset with is_spread_page or is_spread_slab set),
+ * and if the memory allocation used cpuset_mem_spread_node()
+ * to determine on which node to start looking, as it will for
+ * certain page cache or slab cache pages such as used for file
+ * system buffers and inode caches, then instead of starting on the
+ * local node to look for a free page, rather spread the starting
+ * node around the tasks mems_allowed nodes.
+ *
+ * We don't have to worry about the returned node being offline
+ * because "it can't happen", and even if it did, it would be ok.
+ *
+ * The routines calling guarantee_online_mems() are careful to
+ * only set nodes in task->mems_allowed that are online. So it
+ * should not be possible for the following code to return an
+ * offline node. But if it did, that would be ok, as this routine
+ * is not returning the node where the allocation must be, only
+ * the node where the search should start. The zonelist passed to
+ * __alloc_pages() will include all nodes. If the slab allocator
+ * is passed an offline node, it will fall back to the local node.
+ * See kmem_cache_alloc_node().
+ */
+
+int cpuset_mem_spread_node(void)
+{
+ int node;
+
+ node = next_node(current->cpuset_mem_spread_rotor, current->mems_allowed);
+ if (node == MAX_NUMNODES)
+ node = first_node(current->mems_allowed);
+ current->cpuset_mem_spread_rotor = node;
+ return node;
+}
+EXPORT_SYMBOL_GPL(cpuset_mem_spread_node);
+
+/**
+ * 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.
+ *
+ * Call while holding callback_mutex.
+ **/
+
+int cpuset_excl_nodes_overlap(const struct task_struct *p)
+{
+ const struct cpuset *cs1, *cs2; /* my and p's cpuset ancestors */
+ int overlap = 1; /* do cpusets overlap? */
+
+ task_lock(current);
+ if (current->flags & PF_EXITING) {
+ task_unlock(current);
+ goto done;
+ }
+ cs1 = nearest_exclusive_ancestor(current->cpuset);
+ task_unlock(current);
+
+ task_lock((struct task_struct *)p);
+ if (p->flags & PF_EXITING) {
+ task_unlock((struct task_struct *)p);
+ goto done;
+ }
+ cs2 = nearest_exclusive_ancestor(p->cpuset);
+ task_unlock((struct task_struct *)p);
+
+ overlap = nodes_intersects(cs1->mems_allowed, cs2->mems_allowed);
+done:
+ return overlap;
+}
+
+/*
+ * Collection of memory_pressure is suppressed unless
+ * this flag is enabled by writing "1" to the special
+ * cpuset file 'memory_pressure_enabled' in the root cpuset.