From: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx> Subject: mm/munlock: protect the per-CPU pagevec by a local_lock_t The access to mlock_pvec is protected by disabling preemption via get_cpu_var() or implicit by having preemption disabled by the caller (in mlock_page_drain() case). This breaks on PREEMPT_RT since folio_lruvec_lock_irq() acquires a sleeping lock in this section. Create struct mlock_pvec which consits of the local_lock_t and the pagevec. Acquire the local_lock() before accessing the per-CPU pagevec. Replace mlock_page_drain() with a _local() version which is invoked on the local CPU and acquires the local_lock_t and a _remote() version which uses the pagevec from a remote CPU which offline. Link: https://lkml.kernel.org/r/YjizWi9IY0mpvIfb@xxxxxxxxxxxxx Signed-off-by: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx> Acked-by: Hugh Dickins <hughd@xxxxxxxxxx> Cc: Vlastimil Babka <vbabka@xxxxxxx> Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx> Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- mm/internal.h | 6 ++++-- mm/migrate.c | 2 +- mm/mlock.c | 46 ++++++++++++++++++++++++++++++++++++---------- mm/page_alloc.c | 1 + mm/rmap.c | 4 ++-- mm/swap.c | 4 +++- 6 files changed, 47 insertions(+), 16 deletions(-) --- a/mm/internal.h~mm-munlock-protect-the-per-cpu-pagevec-by-a-local_lock_t +++ a/mm/internal.h @@ -456,7 +456,8 @@ static inline void munlock_vma_page(stru } void mlock_new_page(struct page *page); bool need_mlock_page_drain(int cpu); -void mlock_page_drain(int cpu); +void mlock_page_drain_local(void); +void mlock_page_drain_remote(int cpu); extern pmd_t maybe_pmd_mkwrite(pmd_t pmd, struct vm_area_struct *vma); @@ -539,7 +540,8 @@ static inline void munlock_vma_page(stru struct vm_area_struct *vma, bool compound) { } static inline void mlock_new_page(struct page *page) { } static inline bool need_mlock_page_drain(int cpu) { return false; } -static inline void mlock_page_drain(int cpu) { } +static inline void mlock_page_drain_local(void) { } +static inline void mlock_page_drain_remote(int cpu) { } static inline void vunmap_range_noflush(unsigned long start, unsigned long end) { } --- a/mm/migrate.c~mm-munlock-protect-the-per-cpu-pagevec-by-a-local_lock_t +++ a/mm/migrate.c @@ -246,7 +246,7 @@ static bool remove_migration_pte(struct set_pte_at(vma->vm_mm, pvmw.address, pvmw.pte, pte); } if (vma->vm_flags & VM_LOCKED) - mlock_page_drain(smp_processor_id()); + mlock_page_drain_local(); trace_remove_migration_pte(pvmw.address, pte_val(pte), compound_order(new)); --- a/mm/mlock.c~mm-munlock-protect-the-per-cpu-pagevec-by-a-local_lock_t +++ a/mm/mlock.c @@ -28,7 +28,14 @@ #include "internal.h" -static DEFINE_PER_CPU(struct pagevec, mlock_pvec); +struct mlock_pvec { + local_lock_t lock; + struct pagevec vec; +}; + +static DEFINE_PER_CPU(struct mlock_pvec, mlock_pvec) = { + .lock = INIT_LOCAL_LOCK(lock), +}; bool can_do_mlock(void) { @@ -203,18 +210,30 @@ static void mlock_pagevec(struct pagevec pagevec_reinit(pvec); } -void mlock_page_drain(int cpu) +void mlock_page_drain_local(void) { struct pagevec *pvec; - pvec = &per_cpu(mlock_pvec, cpu); + local_lock(&mlock_pvec.lock); + pvec = this_cpu_ptr(&mlock_pvec.vec); + if (pagevec_count(pvec)) + mlock_pagevec(pvec); + local_unlock(&mlock_pvec.lock); +} + +void mlock_page_drain_remote(int cpu) +{ + struct pagevec *pvec; + + WARN_ON_ONCE(cpu_online(cpu)); + pvec = &per_cpu(mlock_pvec.vec, cpu); if (pagevec_count(pvec)) mlock_pagevec(pvec); } bool need_mlock_page_drain(int cpu) { - return pagevec_count(&per_cpu(mlock_pvec, cpu)); + return pagevec_count(&per_cpu(mlock_pvec.vec, cpu)); } /** @@ -223,7 +242,10 @@ bool need_mlock_page_drain(int cpu) */ void mlock_folio(struct folio *folio) { - struct pagevec *pvec = &get_cpu_var(mlock_pvec); + struct pagevec *pvec; + + local_lock(&mlock_pvec.lock); + pvec = this_cpu_ptr(&mlock_pvec.vec); if (!folio_test_set_mlocked(folio)) { int nr_pages = folio_nr_pages(folio); @@ -236,7 +258,7 @@ void mlock_folio(struct folio *folio) if (!pagevec_add(pvec, mlock_lru(&folio->page)) || folio_test_large(folio) || lru_cache_disabled()) mlock_pagevec(pvec); - put_cpu_var(mlock_pvec); + local_unlock(&mlock_pvec.lock); } /** @@ -245,9 +267,11 @@ void mlock_folio(struct folio *folio) */ void mlock_new_page(struct page *page) { - struct pagevec *pvec = &get_cpu_var(mlock_pvec); + struct pagevec *pvec; int nr_pages = thp_nr_pages(page); + local_lock(&mlock_pvec.lock); + pvec = this_cpu_ptr(&mlock_pvec.vec); SetPageMlocked(page); mod_zone_page_state(page_zone(page), NR_MLOCK, nr_pages); __count_vm_events(UNEVICTABLE_PGMLOCKED, nr_pages); @@ -256,7 +280,7 @@ void mlock_new_page(struct page *page) if (!pagevec_add(pvec, mlock_new(page)) || PageHead(page) || lru_cache_disabled()) mlock_pagevec(pvec); - put_cpu_var(mlock_pvec); + local_unlock(&mlock_pvec.lock); } /** @@ -265,8 +289,10 @@ void mlock_new_page(struct page *page) */ void munlock_page(struct page *page) { - struct pagevec *pvec = &get_cpu_var(mlock_pvec); + struct pagevec *pvec; + local_lock(&mlock_pvec.lock); + pvec = this_cpu_ptr(&mlock_pvec.vec); /* * TestClearPageMlocked(page) must be left to __munlock_page(), * which will check whether the page is multiply mlocked. @@ -276,7 +302,7 @@ void munlock_page(struct page *page) if (!pagevec_add(pvec, page) || PageHead(page) || lru_cache_disabled()) mlock_pagevec(pvec); - put_cpu_var(mlock_pvec); + local_unlock(&mlock_pvec.lock); } static int mlock_pte_range(pmd_t *pmd, unsigned long addr, --- a/mm/page_alloc.c~mm-munlock-protect-the-per-cpu-pagevec-by-a-local_lock_t +++ a/mm/page_alloc.c @@ -8367,6 +8367,7 @@ static int page_alloc_cpu_dead(unsigned struct zone *zone; lru_add_drain_cpu(cpu); + mlock_page_drain_remote(cpu); drain_pages(cpu); /* --- a/mm/rmap.c~mm-munlock-protect-the-per-cpu-pagevec-by-a-local_lock_t +++ a/mm/rmap.c @@ -1683,7 +1683,7 @@ discard: */ page_remove_rmap(subpage, vma, folio_test_hugetlb(folio)); if (vma->vm_flags & VM_LOCKED) - mlock_page_drain(smp_processor_id()); + mlock_page_drain_local(); folio_put(folio); } @@ -1961,7 +1961,7 @@ static bool try_to_migrate_one(struct fo */ page_remove_rmap(subpage, vma, folio_test_hugetlb(folio)); if (vma->vm_flags & VM_LOCKED) - mlock_page_drain(smp_processor_id()); + mlock_page_drain_local(); folio_put(folio); } --- a/mm/swap.c~mm-munlock-protect-the-per-cpu-pagevec-by-a-local_lock_t +++ a/mm/swap.c @@ -624,7 +624,6 @@ void lru_add_drain_cpu(int cpu) pagevec_lru_move_fn(pvec, lru_lazyfree_fn); activate_page_drain(cpu); - mlock_page_drain(cpu); } /** @@ -706,6 +705,7 @@ void lru_add_drain(void) local_lock(&lru_pvecs.lock); lru_add_drain_cpu(smp_processor_id()); local_unlock(&lru_pvecs.lock); + mlock_page_drain_local(); } /* @@ -720,6 +720,7 @@ static void lru_add_and_bh_lrus_drain(vo lru_add_drain_cpu(smp_processor_id()); local_unlock(&lru_pvecs.lock); invalidate_bh_lrus_cpu(); + mlock_page_drain_local(); } void lru_add_drain_cpu_zone(struct zone *zone) @@ -728,6 +729,7 @@ void lru_add_drain_cpu_zone(struct zone lru_add_drain_cpu(smp_processor_id()); drain_local_pages(zone); local_unlock(&lru_pvecs.lock); + mlock_page_drain_local(); } #ifdef CONFIG_SMP _
