From: "Liam R. Howlett" <Liam.Howlett@xxxxxxxxxx>
Use the maple tree in RCU mode for VMA tracking. This is necessary for
the use of per-VMA locking. RCU mode is enabled by default but disabled
when exiting an mm and for the new tree during a fork.
Also enable RCU for the tree used in munmap operations to ensure the
nodes remain valid for readers.
Signed-off-by: Liam R. Howlett <Liam.Howlett@xxxxxxxxxx>
Signed-off-by: Suren Baghdasaryan <surenb@xxxxxxxxxx>
---
include/linux/mm_types.h | 3 ++-
kernel/fork.c | 3 +++
mm/mmap.c | 4 +++-
3 files changed, 8 insertions(+), 2 deletions(-)
diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
index 3cd60243c625..3fd5305dbbf9 100644
--- a/include/linux/mm_types.h
+++ b/include/linux/mm_types.h
@@ -768,7 +768,8 @@ struct mm_struct {
unsigned long cpu_bitmap[];
};
-#define MM_MT_FLAGS (MT_FLAGS_ALLOC_RANGE | MT_FLAGS_LOCK_EXTERN)
+#define MM_MT_FLAGS (MT_FLAGS_ALLOC_RANGE | MT_FLAGS_LOCK_EXTERN | \
+ MT_FLAGS_USE_RCU)
extern struct mm_struct init_mm;
/* Pointer magic because the dynamic array size confuses some compilers. */
diff --git a/kernel/fork.c b/kernel/fork.c
index 5e3029ea8e1e..5f23d5e03362 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -617,6 +617,7 @@ static __latent_entropy int dup_mmap(struct mm_struct *mm,
if (retval)
goto out;
+ mt_clear_in_rcu(vmi.mas.tree);
for_each_vma(old_vmi, mpnt) {
struct file *file;
@@ -700,6 +701,8 @@ static __latent_entropy int dup_mmap(struct mm_struct *mm,
retval = arch_dup_mmap(oldmm, mm);
loop_out:
vma_iter_free(&vmi);
+ if (!retval)
+ mt_set_in_rcu(vmi.mas.tree);
out:
mmap_write_unlock(mm);
flush_tlb_mm(oldmm);
diff --git a/mm/mmap.c b/mm/mmap.c
index 20f21f0949dd..06c0f6686de8 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -2277,7 +2277,8 @@ do_vmi_align_munmap(struct vma_iterator *vmi, struct vm_area_struct *vma,
int count = 0;
int error = -ENOMEM;
MA_STATE(mas_detach, &mt_detach, 0, 0);
- mt_init_flags(&mt_detach, MT_FLAGS_LOCK_EXTERN);
+ mt_init_flags(&mt_detach, vmi->mas.tree->ma_flags &
+ (MT_FLAGS_LOCK_MASK | MT_FLAGS_USE_RCU));
mt_set_external_lock(&mt_detach, &mm->mmap_lock);
/*
@@ -3042,6 +3043,7 @@ void exit_mmap(struct mm_struct *mm)
*/
set_bit(MMF_OOM_SKIP, &mm->flags);
mmap_write_lock(mm);
+ mt_clear_in_rcu(&mm->mm_mt);
free_pgtables(&tlb, &mm->mm_mt, vma, FIRST_USER_ADDRESS,
USER_PGTABLES_CEILING);
tlb_finish_mmu(&tlb);
--
2.39.1
