From: Vlastimil Babka <vbabka@xxxxxxx>
Subject: mm: introduce memalloc_noreclaim_{save,restore}
The previous patch ("mm: prevent potential recursive reclaim due to
clearing PF_MEMALLOC") has shown that simply setting and clearing
PF_MEMALLOC in current->flags can result in wrongly clearing a
pre-existing PF_MEMALLOC flag and potentially lead to recursive reclaim.
Let's introduce helpers that support proper nesting by saving the previous
stat of the flag, similar to the existing memalloc_noio_* and
memalloc_nofs_* helpers. Convert existing setting/clearing of PF_MEMALLOC
within mm to the new helpers.
There are no known issues with the converted code, but the change makes it
more robust.
Link: http://lkml.kernel.org/r/20170405074700.29871-3-vbabka@xxxxxxx
Signed-off-by: Vlastimil Babka <vbabka@xxxxxxx>
Suggested-by: Michal Hocko <mhocko@xxxxxxxx>
Acked-by: Michal Hocko <mhocko@xxxxxxxx>
Acked-by: Hillf Danton <hillf.zj@xxxxxxxxxxxxxxx>
Cc: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx>
Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
Cc: Andrey Ryabinin <aryabinin@xxxxxxxxxxxxx>
Cc: Boris Brezillon <boris.brezillon@xxxxxxxxxxxxxxxxxx>
Cc: Chris Leech <cleech@xxxxxxxxxx>
Cc: "David S. Miller" <davem@xxxxxxxxxxxxx>
Cc: Eric Dumazet <edumazet@xxxxxxxxxx>
Cc: Josef Bacik <jbacik@xxxxxx>
Cc: Lee Duncan <lduncan@xxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxx>
Cc: Richard Weinberger <richard@xxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/linux/sched/mm.h | 12 ++++++++++++
mm/page_alloc.c | 11 ++++++-----
mm/vmscan.c | 17 +++++++++++------
3 files changed, 29 insertions(+), 11 deletions(-)
diff -puN include/linux/sched/mm.h~mm-introduce-memalloc_noreclaim_saverestore include/linux/sched/mm.h
--- a/include/linux/sched/mm.h~mm-introduce-memalloc_noreclaim_saverestore
+++ a/include/linux/sched/mm.h
@@ -191,4 +191,16 @@ static inline void memalloc_nofs_restore
current->flags = (current->flags & ~PF_MEMALLOC_NOFS) | flags;
}
+static inline unsigned int memalloc_noreclaim_save(void)
+{
+ unsigned int flags = current->flags & PF_MEMALLOC;
+ current->flags |= PF_MEMALLOC;
+ return flags;
+}
+
+static inline void memalloc_noreclaim_restore(unsigned int flags)
+{
+ current->flags = (current->flags & ~PF_MEMALLOC) | flags;
+}
+
#endif /* _LINUX_SCHED_MM_H */
diff -puN mm/page_alloc.c~mm-introduce-memalloc_noreclaim_saverestore mm/page_alloc.c
--- a/mm/page_alloc.c~mm-introduce-memalloc_noreclaim_saverestore
+++ a/mm/page_alloc.c
@@ -3283,15 +3283,15 @@ __alloc_pages_direct_compact(gfp_t gfp_m
enum compact_priority prio, enum compact_result *compact_result)
{
struct page *page;
- unsigned int noreclaim_flag = current->flags & PF_MEMALLOC;
+ unsigned int noreclaim_flag;
if (!order)
return NULL;
- current->flags |= PF_MEMALLOC;
+ noreclaim_flag = memalloc_noreclaim_save();
*compact_result = try_to_compact_pages(gfp_mask, order, alloc_flags, ac,
prio);
- current->flags = (current->flags & ~PF_MEMALLOC) | noreclaim_flag;
+ memalloc_noreclaim_restore(noreclaim_flag);
if (*compact_result <= COMPACT_INACTIVE)
return NULL;
@@ -3438,12 +3438,13 @@ __perform_reclaim(gfp_t gfp_mask, unsign
{
struct reclaim_state reclaim_state;
int progress;
+ unsigned int noreclaim_flag;
cond_resched();
/* We now go into synchronous reclaim */
cpuset_memory_pressure_bump();
- current->flags |= PF_MEMALLOC;
+ noreclaim_flag = memalloc_noreclaim_save();
lockdep_set_current_reclaim_state(gfp_mask);
reclaim_state.reclaimed_slab = 0;
current->reclaim_state = &reclaim_state;
@@ -3453,7 +3454,7 @@ __perform_reclaim(gfp_t gfp_mask, unsign
current->reclaim_state = NULL;
lockdep_clear_current_reclaim_state();
- current->flags &= ~PF_MEMALLOC;
+ memalloc_noreclaim_restore(noreclaim_flag);
cond_resched();
diff -puN mm/vmscan.c~mm-introduce-memalloc_noreclaim_saverestore mm/vmscan.c
--- a/mm/vmscan.c~mm-introduce-memalloc_noreclaim_saverestore
+++ a/mm/vmscan.c
@@ -3036,6 +3036,7 @@ unsigned long try_to_free_mem_cgroup_pag
struct zonelist *zonelist;
unsigned long nr_reclaimed;
int nid;
+ unsigned int noreclaim_flag;
struct scan_control sc = {
.nr_to_reclaim = max(nr_pages, SWAP_CLUSTER_MAX),
.gfp_mask = (current_gfp_context(gfp_mask) & GFP_RECLAIM_MASK) |
@@ -3062,9 +3063,9 @@ unsigned long try_to_free_mem_cgroup_pag
sc.gfp_mask,
sc.reclaim_idx);
- current->flags |= PF_MEMALLOC;
+ noreclaim_flag = memalloc_noreclaim_save();
nr_reclaimed = do_try_to_free_pages(zonelist, &sc);
- current->flags &= ~PF_MEMALLOC;
+ memalloc_noreclaim_restore(noreclaim_flag);
trace_mm_vmscan_memcg_reclaim_end(nr_reclaimed);
@@ -3589,8 +3590,9 @@ unsigned long shrink_all_memory(unsigned
struct zonelist *zonelist = node_zonelist(numa_node_id(), sc.gfp_mask);
struct task_struct *p = current;
unsigned long nr_reclaimed;
+ unsigned int noreclaim_flag;
- p->flags |= PF_MEMALLOC;
+ noreclaim_flag = memalloc_noreclaim_save();
lockdep_set_current_reclaim_state(sc.gfp_mask);
reclaim_state.reclaimed_slab = 0;
p->reclaim_state = &reclaim_state;
@@ -3599,7 +3601,7 @@ unsigned long shrink_all_memory(unsigned
p->reclaim_state = NULL;
lockdep_clear_current_reclaim_state();
- p->flags &= ~PF_MEMALLOC;
+ memalloc_noreclaim_restore(noreclaim_flag);
return nr_reclaimed;
}
@@ -3764,6 +3766,7 @@ static int __node_reclaim(struct pglist_
struct task_struct *p = current;
struct reclaim_state reclaim_state;
int classzone_idx = gfp_zone(gfp_mask);
+ unsigned int noreclaim_flag;
struct scan_control sc = {
.nr_to_reclaim = max(nr_pages, SWAP_CLUSTER_MAX),
.gfp_mask = (gfp_mask = current_gfp_context(gfp_mask)),
@@ -3781,7 +3784,8 @@ static int __node_reclaim(struct pglist_
* and we also need to be able to write out pages for RECLAIM_WRITE
* and RECLAIM_UNMAP.
*/
- p->flags |= PF_MEMALLOC | PF_SWAPWRITE;
+ noreclaim_flag = memalloc_noreclaim_save();
+ p->flags |= PF_SWAPWRITE;
lockdep_set_current_reclaim_state(gfp_mask);
reclaim_state.reclaimed_slab = 0;
p->reclaim_state = &reclaim_state;
@@ -3797,7 +3801,8 @@ static int __node_reclaim(struct pglist_
}
p->reclaim_state = NULL;
- current->flags &= ~(PF_MEMALLOC | PF_SWAPWRITE);
+ current->flags &= ~PF_SWAPWRITE;
+ memalloc_noreclaim_restore(noreclaim_flag);
lockdep_clear_current_reclaim_state();
return sc.nr_reclaimed >= nr_pages;
}
_
--
To unsubscribe from this list: send the line "unsubscribe mm-commits" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
