The patch titled
Subject: mm/mmap: change detached vma locking scheme
has been added to the -mm mm-unstable branch. Its filename is
mm-mmap-change-detached-vma-locking-scheme.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-mmap-change-detached-vma-locking-scheme.patch
This patch will later appear in the mm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: "Liam R. Howlett" <Liam.Howlett@xxxxxxxxxx>
Subject: mm/mmap: change detached vma locking scheme
Date: Wed, 5 Jul 2023 14:47:49 -0400
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.
Link: https://lkml.kernel.org/r/20230719183142.ktgcmuj2pnlr3h3s@revolver
Signed-off-by: Liam R. Howlett <Liam.Howlett@xxxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Oliver Sang <oliver.sang@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/linux/maple_tree.h | 3 +++
mm/mmap.c | 4 ++--
2 files changed, 5 insertions(+), 2 deletions(-)
--- a/include/linux/maple_tree.h~mm-mmap-change-detached-vma-locking-scheme
+++ a/include/linux/maple_tree.h
@@ -187,10 +187,13 @@ typedef struct lockdep_map *lockdep_map_
#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
/*
--- a/mm/mmap.c~mm-mmap-change-detached-vma-locking-scheme
+++ a/mm/mmap.c
@@ -2427,7 +2427,7 @@ do_vmi_align_munmap(struct vma_iterator
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
/* 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:
_
Patches currently in -mm which might be from Liam.Howlett@xxxxxxxxxx are
mm-mmap-clean-up-validate_mm-calls.patch
maple_tree-relax-lockdep-checks-for-on-stack-trees.patch
mm-mmap-change-detached-vma-locking-scheme.patch
maple_tree-be-more-strict-about-locking.patch
