Hello Andrew,
Please replace v2 with the attached v3 of this patch to address the
issue with building ARCH=um [1].
[1] https://lore.kernel.org/linux-mm/20230718172105.GA1714004@dev-arch.thelio-3990X/T/
Thanks,
Liam
* Liam R. Howlett <Liam.Howlett@xxxxxxxxxx> [230714 15:56]:
> Don't set the lock to the mm lock so that the detached VMA tree does not
> complain about being unlocked when the mmap_lock is dropped prior to
> freeing the tree.
>
> Move the destroying of the detached tree outside the mmap lock all
> together.
>
> Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
> Signed-off-by: Liam R. Howlett <Liam.Howlett@xxxxxxxxxx>
> ---
> mm/mmap.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/mm/mmap.c b/mm/mmap.c
> index 7b70379a8b3e..ab6cb00d377a 100644
> --- a/mm/mmap.c
> +++ b/mm/mmap.c
> @@ -2427,7 +2427,7 @@ do_vmi_align_munmap(struct vma_iterator *vmi, struct vm_area_struct *vma,
> unsigned long locked_vm = 0;
> MA_STATE(mas_detach, &mt_detach, 0, 0);
> mt_init_flags(&mt_detach, vmi->mas.tree->ma_flags & MT_FLAGS_LOCK_MASK);
> - mt_set_external_lock(&mt_detach, &mm->mmap_lock);
> + mt_detach.ma_external_lock = NULL;
>
> /*
> * If we need to split any vma, do it now to save pain later.
> @@ -2545,11 +2545,11 @@ do_vmi_align_munmap(struct vma_iterator *vmi, struct vm_area_struct *vma,
> /* Statistics and freeing VMAs */
> mas_set(&mas_detach, start);
> remove_mt(mm, &mas_detach);
> - __mt_destroy(&mt_detach);
> validate_mm(mm);
> if (unlock)
> mmap_read_unlock(mm);
>
> + __mt_destroy(&mt_detach);
> return 0;
>
> clear_tree_failed:
> --
> 2.39.2
>
>From 099a01955898a852aba26bda8fe85af055e4caf7 Mon Sep 17 00:00:00 2001
From: "Liam R. Howlett" <Liam.Howlett@xxxxxxxxxx>
Date: Wed, 5 Jul 2023 14:47:49 -0400
Subject: [PATCH v3 3/4] mm/mmap: Change detached vma locking scheme
Don't set the lock to the mm lock so that the detached VMA tree does not
complain about being unlocked when the mmap_lock is dropped prior to
freeing the tree.
Introduce mt_on_stack() for setting the external lock to NULL only when
LOCKDEP is used.
Move the destroying of the detached tree outside the mmap lock all
together.
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Liam R. Howlett <Liam.Howlett@xxxxxxxxxx>
---
include/linux/maple_tree.h | 3 +++
mm/mmap.c | 4 ++--
2 files changed, 5 insertions(+), 2 deletions(-)
diff --git a/include/linux/maple_tree.h b/include/linux/maple_tree.h
index 6618c1512886..e278b9598428 100644
--- a/include/linux/maple_tree.h
+++ b/include/linux/maple_tree.h
@@ -187,10 +187,13 @@ typedef struct lockdep_map *lockdep_map_p;
#define mt_set_external_lock(mt, lock) \
(mt)->ma_external_lock = &(lock)->dep_map
+
+#define mt_on_stack(mt) (mt).ma_external_lock = NULL
#else
typedef struct { /* nothing */ } lockdep_map_p;
#define mt_lock_is_held(mt) 1
#define mt_set_external_lock(mt, lock) do { } while (0)
+#define mt_on_stack(mt) do { } while (0)
#endif
/*
diff --git a/mm/mmap.c b/mm/mmap.c
index 7b70379a8b3e..18971ab91633 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -2427,7 +2427,7 @@ do_vmi_align_munmap(struct vma_iterator *vmi, struct vm_area_struct *vma,
unsigned long locked_vm = 0;
MA_STATE(mas_detach, &mt_detach, 0, 0);
mt_init_flags(&mt_detach, vmi->mas.tree->ma_flags & MT_FLAGS_LOCK_MASK);
- mt_set_external_lock(&mt_detach, &mm->mmap_lock);
+ mt_on_stack(mt_detach);
/*
* If we need to split any vma, do it now to save pain later.
@@ -2545,11 +2545,11 @@ do_vmi_align_munmap(struct vma_iterator *vmi, struct vm_area_struct *vma,
/* Statistics and freeing VMAs */
mas_set(&mas_detach, start);
remove_mt(mm, &mas_detach);
- __mt_destroy(&mt_detach);
validate_mm(mm);
if (unlock)
mmap_read_unlock(mm);
+ __mt_destroy(&mt_detach);
return 0;
clear_tree_failed:
--
2.39.2
