From 499118e966f1d2150bd66647c8932343c4e9a0b8 Mon Sep 17 00:00:00 2001 From: Vlastimil Babka Date: Mon, 8 May 2017 15:59:50 -0700 Subject: [PATCH] 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@suse.cz Signed-off-by: Vlastimil Babka Suggested-by: Michal Hocko Acked-by: Michal Hocko Acked-by: Hillf Danton Cc: Mel Gorman Cc: Johannes Weiner Cc: Andrey Ryabinin Cc: Boris Brezillon Cc: Chris Leech Cc: "David S. Miller" Cc: Eric Dumazet Cc: Josef Bacik Cc: Lee Duncan Cc: Michal Hocko Cc: Richard Weinberger Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/sched/mm.h | 12 ++++++++++++ mm/page_alloc.c | 11 ++++++----- mm/vmscan.c | 17 +++++++++++------ 3 files changed, 29 insertions(+), 11 deletions(-) diff --git a/include/linux/sched/mm.h b/include/linux/sched/mm.h index 9daabe1..2b24a69 100644 --- a/include/linux/sched/mm.h +++ b/include/linux/sched/mm.h @@ -191,4 +191,16 @@ static inline void memalloc_nofs_restore(unsigned int flags) 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 --git a/mm/page_alloc.c b/mm/page_alloc.c index 1daf509..f9e450c 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -3283,15 +3283,15 @@ __alloc_pages_direct_compact(gfp_t gfp_mask, unsigned int order, 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, unsigned int order, { 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, unsigned int order, current->reclaim_state = NULL; lockdep_clear_current_reclaim_state(); - current->flags &= ~PF_MEMALLOC; + memalloc_noreclaim_restore(noreclaim_flag); cond_resched(); diff --git a/mm/vmscan.c b/mm/vmscan.c index 4e7ed65..2f45c05 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -3036,6 +3036,7 @@ unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *memcg, 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_pages(struct mem_cgroup *memcg, 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 long nr_to_reclaim) 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 long nr_to_reclaim) 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_data *pgdat, gfp_t gfp_mask, unsigned in 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_data *pgdat, gfp_t gfp_mask, unsigned in * 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_data *pgdat, gfp_t gfp_mask, unsigned in } 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; } -- 2.7.4