| Message ID | 20170405074700.29871-3-vbabka@suse.cz (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Wed 05-04-17 09:46:58, Vlastimil Babka wrote: > The previous patch 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. > > Suggested-by: Michal Hocko <mhocko@suse.com> > Signed-off-by: Vlastimil Babka <vbabka@suse.cz> One could argue that tsk_restore_flags() could be extended to provide tsk_set_flags() and use it for all allocation related PF flags. I do not have a strong opinion on that but explicit API sounds a bit better to me because is easier to follow (at least for me). If others think that generic API would be better then I won't have any objections. Anyway this looks good to me. Acked-by: Michal Hocko <mhocko@suse.com> > --- > 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 9daabe138c99..2b24a6974847 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 b84e6ffbe756..037e32dccd7a 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -3288,15 +3288,15 @@ __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; > @@ -3443,12 +3443,13 @@ __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; > @@ -3458,7 +3459,7 @@ __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 58615bb27f2f..ff63b91a0f48 100644 > --- a/mm/vmscan.c > +++ b/mm/vmscan.c > @@ -2992,6 +2992,7 @@ 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) | > @@ -3018,9 +3019,9 @@ 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); > > @@ -3544,8 +3545,9 @@ 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; > @@ -3554,7 +3556,7 @@ 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; > } > @@ -3719,6 +3721,7 @@ 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)), > @@ -3736,7 +3739,8 @@ 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; > @@ -3752,7 +3756,8 @@ 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; > } > -- > 2.12.2
On April 05, 2017 3:47 PM Vlastimil Babka wrote: > > The previous patch 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. > > Suggested-by: Michal Hocko <mhocko@suse.com> > Signed-off-by: Vlastimil Babka <vbabka@suse.cz> > --- Acked-by: Hillf Danton <hillf.zj@alibaba-inc.com>
diff --git a/include/linux/sched/mm.h b/include/linux/sched/mm.h index 9daabe138c99..2b24a6974847 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 b84e6ffbe756..037e32dccd7a 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -3288,15 +3288,15 @@ __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; @@ -3443,12 +3443,13 @@ __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; @@ -3458,7 +3459,7 @@ __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 58615bb27f2f..ff63b91a0f48 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -2992,6 +2992,7 @@ 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) | @@ -3018,9 +3019,9 @@ 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); @@ -3544,8 +3545,9 @@ 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; @@ -3554,7 +3556,7 @@ 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; } @@ -3719,6 +3721,7 @@ 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)), @@ -3736,7 +3739,8 @@ 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; @@ -3752,7 +3756,8 @@ 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; }
The previous patch 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. Suggested-by: Michal Hocko <mhocko@suse.com> Signed-off-by: Vlastimil Babka <vbabka@suse.cz> --- include/linux/sched/mm.h | 12 ++++++++++++ mm/page_alloc.c | 11 ++++++----- mm/vmscan.c | 17 +++++++++++------ 3 files changed, 29 insertions(+), 11 deletions(-)