cpuset,mm: fix no node to alloc memory when changing cpuset's mems
Before applying this patch, cpuset updates task->mems_allowed and
mempolicy by setting all new bits in the nodemask first, and clearing all
old unallowed bits later. But in the way, the allocator may find that
there is no node to alloc memory.
The reason is that cpuset rebinds the task's mempolicy, it cleans the
nodes which the allocater can alloc pages on, for example:
(mpol: mempolicy)
task1 task1's mpol task2
alloc page 1
alloc on node0? NO 1
1 change mems from 1 to 0
1 rebind task1's mpol
0-1 set new bits
0 clear disallowed bits
alloc on node1? NO 0
...
can't alloc page
goto oom
This patch fixes this problem by expanding the nodes range first(set newly
allowed bits) and shrink it lazily(clear newly disallowed bits). So we
use a variable to tell the write-side task that read-side task is reading
nodemask, and the write-side task clears newly disallowed nodes after
read-side task ends the current memory allocation.
[akpm@linux-foundation.org: fix spello]
Signed-off-by: Miao Xie <miaox@cn.fujitsu.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Nick Piggin <npiggin@suse.de>
Cc: Paul Menage <menage@google.com>
Cc: Lee Schermerhorn <lee.schermerhorn@hp.com>
Cc: Hugh Dickins <hugh.dickins@tiscali.co.uk>
Cc: Ravikiran Thirumalai <kiran@scalex86.org>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Christoph Lameter <cl@linux-foundation.org>
Cc: Andi Kleen <andi@firstfloor.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/include/linux/cpuset.h b/include/linux/cpuset.h
index a73454a..20b51ca 100644
--- a/include/linux/cpuset.h
+++ b/include/linux/cpuset.h
@@ -86,9 +86,44 @@
extern void cpuset_print_task_mems_allowed(struct task_struct *p);
+/*
+ * reading current mems_allowed and mempolicy in the fastpath must protected
+ * by get_mems_allowed()
+ */
+static inline void get_mems_allowed(void)
+{
+ current->mems_allowed_change_disable++;
+
+ /*
+ * ensure that reading mems_allowed and mempolicy happens after the
+ * update of ->mems_allowed_change_disable.
+ *
+ * the write-side task finds ->mems_allowed_change_disable is not 0,
+ * and knows the read-side task is reading mems_allowed or mempolicy,
+ * so it will clear old bits lazily.
+ */
+ smp_mb();
+}
+
+static inline void put_mems_allowed(void)
+{
+ /*
+ * ensure that reading mems_allowed and mempolicy before reducing
+ * mems_allowed_change_disable.
+ *
+ * the write-side task will know that the read-side task is still
+ * reading mems_allowed or mempolicy, don't clears old bits in the
+ * nodemask.
+ */
+ smp_mb();
+ --ACCESS_ONCE(current->mems_allowed_change_disable);
+}
+
static inline void set_mems_allowed(nodemask_t nodemask)
{
+ task_lock(current);
current->mems_allowed = nodemask;
+ task_unlock(current);
}
#else /* !CONFIG_CPUSETS */
@@ -187,6 +222,14 @@
{
}
+static inline void get_mems_allowed(void)
+{
+}
+
+static inline void put_mems_allowed(void)
+{
+}
+
#endif /* !CONFIG_CPUSETS */
#endif /* _LINUX_CPUSET_H */
diff --git a/include/linux/sched.h b/include/linux/sched.h
index b55e988..415b8f8 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1421,6 +1421,7 @@
#endif
#ifdef CONFIG_CPUSETS
nodemask_t mems_allowed; /* Protected by alloc_lock */
+ int mems_allowed_change_disable;
int cpuset_mem_spread_rotor;
#endif
#ifdef CONFIG_CGROUPS
diff --git a/kernel/cpuset.c b/kernel/cpuset.c
index db0990a..61d6af7 100644
--- a/kernel/cpuset.c
+++ b/kernel/cpuset.c
@@ -946,16 +946,62 @@
* In order to avoid seeing no nodes if the old and new nodes are disjoint,
* we structure updates as setting all new allowed nodes, then clearing newly
* disallowed ones.
- *
- * Called with task's alloc_lock held
*/
static void cpuset_change_task_nodemask(struct task_struct *tsk,
nodemask_t *newmems)
{
+repeat:
+ /*
+ * Allow tasks that have access to memory reserves because they have
+ * been OOM killed to get memory anywhere.
+ */
+ if (unlikely(test_thread_flag(TIF_MEMDIE)))
+ return;
+ if (current->flags & PF_EXITING) /* Let dying task have memory */
+ return;
+
+ task_lock(tsk);
nodes_or(tsk->mems_allowed, tsk->mems_allowed, *newmems);
- mpol_rebind_task(tsk, &tsk->mems_allowed, MPOL_REBIND_ONCE);
- mpol_rebind_task(tsk, newmems, MPOL_REBIND_ONCE);
+ mpol_rebind_task(tsk, newmems, MPOL_REBIND_STEP1);
+
+
+ /*
+ * ensure checking ->mems_allowed_change_disable after setting all new
+ * allowed nodes.
+ *
+ * the read-side task can see an nodemask with new allowed nodes and
+ * old allowed nodes. and if it allocates page when cpuset clears newly
+ * disallowed ones continuous, it can see the new allowed bits.
+ *
+ * And if setting all new allowed nodes is after the checking, setting
+ * all new allowed nodes and clearing newly disallowed ones will be done
+ * continuous, and the read-side task may find no node to alloc page.
+ */
+ smp_mb();
+
+ /*
+ * Allocation of memory is very fast, we needn't sleep when waiting
+ * for the read-side.
+ */
+ while (ACCESS_ONCE(tsk->mems_allowed_change_disable)) {
+ task_unlock(tsk);
+ if (!task_curr(tsk))
+ yield();
+ goto repeat;
+ }
+
+ /*
+ * ensure checking ->mems_allowed_change_disable before clearing all new
+ * disallowed nodes.
+ *
+ * if clearing newly disallowed bits before the checking, the read-side
+ * task may find no node to alloc page.
+ */
+ smp_mb();
+
+ mpol_rebind_task(tsk, newmems, MPOL_REBIND_STEP2);
tsk->mems_allowed = *newmems;
+ task_unlock(tsk);
}
/*
@@ -978,9 +1024,7 @@
cs = cgroup_cs(scan->cg);
guarantee_online_mems(cs, newmems);
- task_lock(p);
cpuset_change_task_nodemask(p, newmems);
- task_unlock(p);
NODEMASK_FREE(newmems);
@@ -1383,9 +1427,7 @@
err = set_cpus_allowed_ptr(tsk, cpus_attach);
WARN_ON_ONCE(err);
- task_lock(tsk);
cpuset_change_task_nodemask(tsk, to);
- task_unlock(tsk);
cpuset_update_task_spread_flag(cs, tsk);
}
diff --git a/kernel/exit.c b/kernel/exit.c
index eabca5a..019a284 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -1002,8 +1002,10 @@
exit_notify(tsk, group_dead);
#ifdef CONFIG_NUMA
+ task_lock(tsk);
mpol_put(tsk->mempolicy);
tsk->mempolicy = NULL;
+ task_unlock(tsk);
#endif
#ifdef CONFIG_FUTEX
if (unlikely(current->pi_state_cache))
diff --git a/mm/filemap.c b/mm/filemap.c
index d6f4f07..88d7196 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -461,9 +461,15 @@
#ifdef CONFIG_NUMA
struct page *__page_cache_alloc(gfp_t gfp)
{
+ int n;
+ struct page *page;
+
if (cpuset_do_page_mem_spread()) {
- int n = cpuset_mem_spread_node();
- return alloc_pages_exact_node(n, gfp, 0);
+ get_mems_allowed();
+ n = cpuset_mem_spread_node();
+ page = alloc_pages_exact_node(n, gfp, 0);
+ put_mems_allowed();
+ return page;
}
return alloc_pages(gfp, 0);
}
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 4c9e6bb..54d42b0 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -465,11 +465,13 @@
struct page *page = NULL;
struct mempolicy *mpol;
nodemask_t *nodemask;
- struct zonelist *zonelist = huge_zonelist(vma, address,
- htlb_alloc_mask, &mpol, &nodemask);
+ struct zonelist *zonelist;
struct zone *zone;
struct zoneref *z;
+ get_mems_allowed();
+ zonelist = huge_zonelist(vma, address,
+ htlb_alloc_mask, &mpol, &nodemask);
/*
* A child process with MAP_PRIVATE mappings created by their parent
* have no page reserves. This check ensures that reservations are
@@ -477,11 +479,11 @@
*/
if (!vma_has_reserves(vma) &&
h->free_huge_pages - h->resv_huge_pages == 0)
- return NULL;
+ goto err;
/* If reserves cannot be used, ensure enough pages are in the pool */
if (avoid_reserve && h->free_huge_pages - h->resv_huge_pages == 0)
- return NULL;
+ goto err;;
for_each_zone_zonelist_nodemask(zone, z, zonelist,
MAX_NR_ZONES - 1, nodemask) {
@@ -500,7 +502,9 @@
break;
}
}
+err:
mpol_cond_put(mpol);
+ put_mems_allowed();
return page;
}
diff --git a/mm/mempolicy.c b/mm/mempolicy.c
index 8a993db..721b2b3 100644
--- a/mm/mempolicy.c
+++ b/mm/mempolicy.c
@@ -1639,6 +1639,8 @@
* to the struct mempolicy for conditional unref after allocation.
* If the effective policy is 'BIND, returns a pointer to the mempolicy's
* @nodemask for filtering the zonelist.
+ *
+ * Must be protected by get_mems_allowed()
*/
struct zonelist *huge_zonelist(struct vm_area_struct *vma, unsigned long addr,
gfp_t gfp_flags, struct mempolicy **mpol,
@@ -1684,6 +1686,7 @@
if (!(mask && current->mempolicy))
return false;
+ task_lock(current);
mempolicy = current->mempolicy;
switch (mempolicy->mode) {
case MPOL_PREFERRED:
@@ -1703,6 +1706,7 @@
default:
BUG();
}
+ task_unlock(current);
return true;
}
@@ -1750,13 +1754,17 @@
{
struct mempolicy *pol = get_vma_policy(current, vma, addr);
struct zonelist *zl;
+ struct page *page;
+ get_mems_allowed();
if (unlikely(pol->mode == MPOL_INTERLEAVE)) {
unsigned nid;
nid = interleave_nid(pol, vma, addr, PAGE_SHIFT);
mpol_cond_put(pol);
- return alloc_page_interleave(gfp, 0, nid);
+ page = alloc_page_interleave(gfp, 0, nid);
+ put_mems_allowed();
+ return page;
}
zl = policy_zonelist(gfp, pol);
if (unlikely(mpol_needs_cond_ref(pol))) {
@@ -1766,12 +1774,15 @@
struct page *page = __alloc_pages_nodemask(gfp, 0,
zl, policy_nodemask(gfp, pol));
__mpol_put(pol);
+ put_mems_allowed();
return page;
}
/*
* fast path: default or task policy
*/
- return __alloc_pages_nodemask(gfp, 0, zl, policy_nodemask(gfp, pol));
+ page = __alloc_pages_nodemask(gfp, 0, zl, policy_nodemask(gfp, pol));
+ put_mems_allowed();
+ return page;
}
/**
@@ -1796,18 +1807,23 @@
struct page *alloc_pages_current(gfp_t gfp, unsigned order)
{
struct mempolicy *pol = current->mempolicy;
+ struct page *page;
if (!pol || in_interrupt() || (gfp & __GFP_THISNODE))
pol = &default_policy;
+ get_mems_allowed();
/*
* No reference counting needed for current->mempolicy
* nor system default_policy
*/
if (pol->mode == MPOL_INTERLEAVE)
- return alloc_page_interleave(gfp, order, interleave_nodes(pol));
- return __alloc_pages_nodemask(gfp, order,
+ page = alloc_page_interleave(gfp, order, interleave_nodes(pol));
+ else
+ page = __alloc_pages_nodemask(gfp, order,
policy_zonelist(gfp, pol), policy_nodemask(gfp, pol));
+ put_mems_allowed();
+ return page;
}
EXPORT_SYMBOL(alloc_pages_current);
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 596180f..f7da2a2 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -1990,10 +1990,13 @@
if (unlikely(!zonelist->_zonerefs->zone))
return NULL;
+ get_mems_allowed();
/* The preferred zone is used for statistics later */
first_zones_zonelist(zonelist, high_zoneidx, nodemask, &preferred_zone);
- if (!preferred_zone)
+ if (!preferred_zone) {
+ put_mems_allowed();
return NULL;
+ }
/* First allocation attempt */
page = get_page_from_freelist(gfp_mask|__GFP_HARDWALL, nodemask, order,
@@ -2003,6 +2006,7 @@
page = __alloc_pages_slowpath(gfp_mask, order,
zonelist, high_zoneidx, nodemask,
preferred_zone, migratetype);
+ put_mems_allowed();
trace_mm_page_alloc(page, order, gfp_mask, migratetype);
return page;
diff --git a/mm/slab.c b/mm/slab.c
index 50a73fc..02786e1 100644
--- a/mm/slab.c
+++ b/mm/slab.c
@@ -3217,10 +3217,12 @@
if (in_interrupt() || (flags & __GFP_THISNODE))
return NULL;
nid_alloc = nid_here = numa_node_id();
+ get_mems_allowed();
if (cpuset_do_slab_mem_spread() && (cachep->flags & SLAB_MEM_SPREAD))
nid_alloc = cpuset_mem_spread_node();
else if (current->mempolicy)
nid_alloc = slab_node(current->mempolicy);
+ put_mems_allowed();
if (nid_alloc != nid_here)
return ____cache_alloc_node(cachep, flags, nid_alloc);
return NULL;
@@ -3247,6 +3249,7 @@
if (flags & __GFP_THISNODE)
return NULL;
+ get_mems_allowed();
zonelist = node_zonelist(slab_node(current->mempolicy), flags);
local_flags = flags & (GFP_CONSTRAINT_MASK|GFP_RECLAIM_MASK);
@@ -3302,6 +3305,7 @@
}
}
}
+ put_mems_allowed();
return obj;
}
diff --git a/mm/slub.c b/mm/slub.c
index e46e312..26f0cb9 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -1360,6 +1360,7 @@
get_cycles() % 1024 > s->remote_node_defrag_ratio)
return NULL;
+ get_mems_allowed();
zonelist = node_zonelist(slab_node(current->mempolicy), flags);
for_each_zone_zonelist(zone, z, zonelist, high_zoneidx) {
struct kmem_cache_node *n;
@@ -1369,10 +1370,13 @@
if (n && cpuset_zone_allowed_hardwall(zone, flags) &&
n->nr_partial > s->min_partial) {
page = get_partial_node(n);
- if (page)
+ if (page) {
+ put_mems_allowed();
return page;
+ }
}
}
+ put_mems_allowed();
#endif
return NULL;
}
diff --git a/mm/vmscan.c b/mm/vmscan.c
index 3ff3311..f2c367c 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -1774,6 +1774,7 @@
enum zone_type high_zoneidx = gfp_zone(sc->gfp_mask);
unsigned long writeback_threshold;
+ get_mems_allowed();
delayacct_freepages_start();
if (scanning_global_lru(sc))
@@ -1857,6 +1858,7 @@
mem_cgroup_record_reclaim_priority(sc->mem_cgroup, priority);
delayacct_freepages_end();
+ put_mems_allowed();
return ret;
}
