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>

diff --git a/include/linux/maple_tree.h b/include/linux/maple_tree.h
index 6618c15..e278b95 100644 (file)
--- 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 cdbeff0..7bd1caa 100644 (file)
--- 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: