From 02fdb25fb41c563a3afbd4a97469c527a6c5abbf Mon Sep 17 00:00:00 2001
From: "Liam R. Howlett" <Liam.Howlett@oracle.com>
Date: Wed, 5 Jul 2023 14:47:49 -0400
Subject: [PATCH] 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.
Link: https://lkml.kernel.org/r/20230719183142.ktgcmuj2pnlr3h3s@revolver
Signed-off-by: Liam R. Howlett <Liam.Howlett@oracle.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Oliver Sang <oliver.sang@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---
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 6618c15128867..e278b95984282 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 cdbeff089049a..7bd1caa09dddf 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -2428,7 +2428,7 @@ 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.
@@ -2546,11 +2546,11 @@ 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:
--
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