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@linutronix.de
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Acked-by: Hugh Dickins <hughd@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/mm/internal.h b/mm/internal.h
index 58dc6ad..cf16280 100644 (file)
--- a/mm/internal.h
+++ b/mm/internal.h
@@ -456,7 +456,8 @@ static inline void munlock_vma_page(struct page *page,
 }
 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(struct page *page,
                        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)
 {
 }

diff --git a/mm/migrate.c b/mm/migrate.c
index 3d60823..de175e2 100644 (file)
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -246,7 +246,7 @@ static bool remove_migration_pte(struct folio *folio,
                        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));

diff --git a/mm/mlock.c b/mm/mlock.c
index 529fbc1..716caf8 100644 (file)
--- a/mm/mlock.c
+++ b/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 *pvec)
        pagevec_reinit(pvec);
 }
 
-void mlock_page_drain(int cpu)
+void mlock_page_drain_local(void)
+{
+       struct pagevec *pvec;
+
+       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;
 
-       pvec = &per_cpu(mlock_pvec, cpu);
+       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,

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 6c6af86..2db9578 100644 (file)
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -8367,6 +8367,7 @@ static int page_alloc_cpu_dead(unsigned int cpu)
        struct zone *zone;
 
        lru_add_drain_cpu(cpu);
+       mlock_page_drain_remote(cpu);
        drain_pages(cpu);
 
        /*

diff --git a/mm/rmap.c b/mm/rmap.c
index 5cb970d..fedb823 100644 (file)
--- a/mm/rmap.c
+++ b/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 folio *folio, struct vm_area_struct *vma,
                 */
                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);
        }
 

diff --git a/mm/swap.c b/mm/swap.c
index bceff0c..7e320ec 100644 (file)
--- a/mm/swap.c
+++ b/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(void)
        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 *zone)
        lru_add_drain_cpu(smp_processor_id());
        drain_local_pages(zone);
        local_unlock(&lru_pvecs.lock);
+       mlock_page_drain_local();
 }
 
 #ifdef CONFIG_SMP