mm: Start tracking VMAs with maple tree

Start tracking the VMAs with the new maple tree structure in parallel
with the rb_tree.  Add debug and trace events for maple tree operations
and duplicate the rb_tree that is created on forks into the maple tree.

The maple tree is added to the mm_struct including the mm_init struct,
added support in required mm/mmap functions, added tracking in
kernel/fork for process forking, and used to find the unmapped_area and
checked against what the rbtree finds.

Signed-off-by: Liam R. Howlett <Liam.Howlett@Oracle.com>
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>

diff --git a/arch/x86/kernel/tboot.c b/arch/x86/kernel/tboot.c
index f9af561c3cd4fef9ff3b3bbeb53cb8ba03a1524b..859e8d2ea0703ffefe0fc7fca6849880de68e94c 100644 (file)
--- a/arch/x86/kernel/tboot.c
+++ b/arch/x86/kernel/tboot.c
@@ -98,6 +98,7 @@ void __init tboot_probe(void)
 static pgd_t *tboot_pg_dir;
 static struct mm_struct tboot_mm = {
        .mm_rb          = RB_ROOT,
+       .mm_mt          = MTREE_INIT_EXT(mm_mt, MM_MT_FLAGS, tboot_mm.mmap_lock),
        .pgd            = swapper_pg_dir,
        .mm_users       = ATOMIC_INIT(2),
        .mm_count       = ATOMIC_INIT(1),

diff --git a/drivers/firmware/efi/efi.c b/drivers/firmware/efi/efi.c
index ae79c33001297aba6fbf6f6b4dc572b6dc317702..0b40291416cad1347c8b2884632e6d532e68f4ff 100644 (file)
--- a/drivers/firmware/efi/efi.c
+++ b/drivers/firmware/efi/efi.c
@@ -55,6 +55,7 @@ static unsigned long __initdata rt_prop = EFI_INVALID_TABLE_ADDR;
 
 struct mm_struct efi_mm = {
        .mm_rb                  = RB_ROOT,
+       .mm_mt                  = MTREE_INIT_EXT(mm_mt, MM_MT_FLAGS, efi_mm.mmap_lock),
        .mm_users               = ATOMIC_INIT(2),
        .mm_count               = ATOMIC_INIT(1),
        .write_protect_seq      = SEQCNT_ZERO(efi_mm.write_protect_seq),

diff --git a/include/linux/mm.h b/include/linux/mm.h
index a7e4a9e7d807a39bc549bcfc7238e03c4e7237bd..9eae78a155beabae5e8fa9259fcfccd4004ded57 100644 (file)
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -2610,6 +2610,8 @@ extern bool arch_has_descending_max_zone_pfns(void);
 /* nommu.c */
 extern atomic_long_t mmap_pages_allocated;
 extern int nommu_shrink_inode_mappings(struct inode *, size_t, size_t);
+/* maple_tree */
+void vma_store(struct mm_struct *mm, struct vm_area_struct *vma);
 
 /* interval_tree.c */
 void vma_interval_tree_insert(struct vm_area_struct *node,

diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
index c3a6e620960068cddb7818e1a39fac924bfd91fe..d9ce412fca04fcb12bea51a674e6cb023fbf094a 100644 (file)
--- a/include/linux/mm_types.h
+++ b/include/linux/mm_types.h
@@ -8,6 +8,7 @@
 #include <linux/list.h>
 #include <linux/spinlock.h>
 #include <linux/rbtree.h>
+#include <linux/maple_tree.h>
 #include <linux/rwsem.h>
 #include <linux/completion.h>
 #include <linux/cpumask.h>
@@ -467,6 +468,7 @@ struct kioctx_table;
 struct mm_struct {
        struct {
                struct vm_area_struct *mmap;            /* list of VMAs */
+               struct maple_tree mm_mt;
                struct rb_root mm_rb;
                u64 vmacache_seqnum;                   /* per-thread vmacache */
 #ifdef CONFIG_MMU
@@ -655,6 +657,7 @@ struct mm_struct {
        unsigned long cpu_bitmap[];
 };
 
+#define MM_MT_FLAGS    (MT_FLAGS_ALLOC_RANGE | MT_FLAGS_LOCK_EXTERN)
 extern struct mm_struct init_mm;
 
 /* Pointer magic because the dynamic array size confuses some compilers. */

diff --git a/include/trace/events/mmap.h b/include/trace/events/mmap.h
index 4661f7ba07c05e642f5b6cf663c0c8739f994747..f5c1626f3bbb1c9e53e2411c4adb1338be89bcd8 100644 (file)
--- a/include/trace/events/mmap.h
+++ b/include/trace/events/mmap.h
@@ -42,6 +42,77 @@ TRACE_EVENT(vm_unmapped_area,
                __entry->low_limit, __entry->high_limit, __entry->align_mask,
                __entry->align_offset)
 );
+
+TRACE_EVENT(vma_mt_szero,
+       TP_PROTO(struct mm_struct *mm, unsigned long start,
+                unsigned long end),
+
+       TP_ARGS(mm, start, end),
+
+       TP_STRUCT__entry(
+                       __field(struct mm_struct *, mm)
+                       __field(unsigned long, start)
+                       __field(unsigned long, end)
+       ),
+
+       TP_fast_assign(
+                       __entry->mm             = mm;
+                       __entry->start          = start;
+                       __entry->end            = end - 1;
+       ),
+
+       TP_printk("mt_mod %p, (NULL), SNULL, %lu, %lu,",
+                 __entry->mm,
+                 (unsigned long) __entry->start,
+                 (unsigned long) __entry->end
+       )
+);
+
+TRACE_EVENT(vma_store,
+       TP_PROTO(struct mm_struct *mm, struct vm_area_struct *vma),
+
+       TP_ARGS(mm, vma),
+
+       TP_STRUCT__entry(
+                       __field(struct mm_struct *, mm)
+                       __field(struct vm_area_struct *, vma)
+                       __field(unsigned long, vm_start)
+                       __field(unsigned long, vm_end)
+       ),
+
+       TP_fast_assign(
+                       __entry->mm             = mm;
+                       __entry->vma            = vma;
+                       __entry->vm_start       = vma->vm_start;
+                       __entry->vm_end         = vma->vm_end - 1;
+       ),
+
+       TP_printk("mt_mod %p, (%p), STORE, %lu, %lu,",
+                 __entry->mm, __entry->vma,
+                 (unsigned long) __entry->vm_start,
+                 (unsigned long) __entry->vm_end
+       )
+);
+
+
+TRACE_EVENT(exit_mmap,
+       TP_PROTO(struct mm_struct *mm),
+
+       TP_ARGS(mm),
+
+       TP_STRUCT__entry(
+                       __field(struct mm_struct *, mm)
+       ),
+
+       TP_fast_assign(
+                       __entry->mm             = mm;
+       ),
+
+       TP_printk("mt_mod %p, DESTROY\n",
+                 __entry->mm
+       )
+);
+
 #endif
 
 /* This part must be outside protection */

diff --git a/init/main.c b/init/main.c
index bb984ed79de0ea49b9a298c209c0c2f7e6f70941..ed906a15a86ce0f5e3a9c0f69dd476d6bd124299 100644 (file)
--- a/init/main.c
+++ b/init/main.c
@@ -115,6 +115,7 @@ static int kernel_init(void *);
 
 extern void init_IRQ(void);
 extern void radix_tree_init(void);
+extern void maple_tree_init(void);
 
 /*
  * Debug helper: via this flag we know that we are in 'early bootup code'
@@ -997,6 +998,7 @@ asmlinkage __visible void __init __no_sanitize_address start_kernel(void)
                 "Interrupts were enabled *very* early, fixing it\n"))
                local_irq_disable();
        radix_tree_init();
+       maple_tree_init();
 
        /*
         * Set up housekeeping before setting up workqueues to allow the unbound

diff --git a/kernel/fork.c b/kernel/fork.c
index 3244cc56b697d7e3a5b3a87d1ed580fb64db1954..cc9bb95c76789281beb0f326da5eb0bfc4a70682 100644 (file)
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -604,6 +604,9 @@ static __latent_entropy int dup_mmap(struct mm_struct *mm,
                rb_link = &tmp->vm_rb.rb_right;
                rb_parent = &tmp->vm_rb;
 
+               /* Link the vma into the MT */
+               vma_store(mm, tmp);
+
                mm->map_count++;
                if (!(tmp->vm_flags & VM_WIPEONFORK))
                        retval = copy_page_range(tmp, mpnt);
@@ -1037,6 +1040,8 @@ static struct mm_struct *mm_init(struct mm_struct *mm, struct task_struct *p,
 {
        mm->mmap = NULL;
        mm->mm_rb = RB_ROOT;
+       mt_init_flags(&mm->mm_mt, MM_MT_FLAGS);
+       mt_set_external_lock(&mm->mm_mt, &mm->mmap_lock);
        mm->vmacache_seqnum = 0;
        atomic_set(&mm->mm_users, 1);
        atomic_set(&mm->mm_count, 1);

diff --git a/mm/init-mm.c b/mm/init-mm.c
index b4a6f38fb51ddce7587a94a5df16e54013fd982d..7622ca24eeb75cc410d150436a67a2568068b416 100644 (file)
--- a/mm/init-mm.c
+++ b/mm/init-mm.c
@@ -1,6 +1,7 @@
 // SPDX-License-Identifier: GPL-2.0
 #include <linux/mm_types.h>
 #include <linux/rbtree.h>
+#include <linux/maple_tree.h>
 #include <linux/rwsem.h>
 #include <linux/spinlock.h>
 #include <linux/list.h>
@@ -28,6 +29,7 @@
  */
 struct mm_struct init_mm = {
        .mm_rb          = RB_ROOT,
+       .mm_mt          = MTREE_INIT_EXT(mm_mt, MM_MT_FLAGS, init_mm.mmap_lock),
        .pgd            = swapper_pg_dir,
        .mm_users       = ATOMIC_INIT(2),
        .mm_count       = ATOMIC_INIT(1),

diff --git a/mm/internal.h b/mm/internal.h
index 3b79a5c9427a827e7646dbaf0abfe3b516c60a81..7ec79cef3ea935c9426ffc52a94126acf019bcee 100644 (file)
--- a/mm/internal.h
+++ b/mm/internal.h
@@ -382,6 +382,79 @@ static inline bool is_data_mapping(vm_flags_t flags)
        return (flags & (VM_WRITE | VM_SHARED | VM_STACK)) == VM_WRITE;
 }
 
+/* Maple tree operations using VMAs */
+/*
+ * vma_mas_store() - Store a VMA in the maple tree.
+ * @vma: The vm_area_struct
+ * @mas: The maple state
+ *
+ * Efficient way to store a VMA in the maple tree when the @mas has already
+ * walked to the correct location.
+ *
+ * Note: the end address is inclusive in the maple tree.
+ */
+static inline int vma_mas_store(struct vm_area_struct *vma, struct ma_state *mas)
+{
+       int ret;
+
+#ifdef CONFIG_DEBUG_MAPLE_TREE
+       /* Make sure no VMAs are about to be lost. */
+       MA_STATE(test, mas->tree, vma->vm_start, vma->vm_end - 1);
+       struct vm_area_struct *vma_mas;
+       int count = 0;
+
+       mas_for_each(&test, vma_mas, vma->vm_end - 1) {
+               /* Rule out vma_expand */
+               if ((vma->vm_start != vma_mas->vm_start) &&
+                   (vma->vm_end != vma_mas->vm_end))
+                       count++;
+       }
+
+       BUG_ON(count);
+
+       BUG_ON(mas->min > vma->vm_start);
+       BUG_ON(mas->index > vma->vm_start);
+#endif
+       mas->index = vma->vm_start;
+       mas->last = vma->vm_end - 1;
+       ret = mas_store_gfp(mas, vma, GFP_KERNEL);
+       return ret;
+}
+
+/*
+ * vma_mas_remove() - Remove a VMA from the maple tree.
+ * @vma: The vm_area_struct
+ * @mas: The maple state
+ *
+ * Efficient way to remove a VMA from the maple tree when the @mas has already
+ * been established and points to the correct location.
+ * Note: the end address is inclusive in the maple tree.
+ */
+static inline int vma_mas_remove(struct vm_area_struct *vma, struct ma_state *mas)
+{
+       int ret;
+
+#ifdef CONFIG_DEBUG_MAPLE_TREE
+       /* Make sure no VMAs are about to be lost. */
+       MA_STATE(test, mas->tree, vma->vm_start, vma->vm_end - 1);
+       struct vm_area_struct *vma_mas;
+       int count = 0;
+
+       mas_for_each(&test, vma_mas, vma->vm_end - 1)
+               count++;
+
+       BUG_ON(count != 1);
+
+       BUG_ON(mas->min > vma->vm_start);
+       BUG_ON(mas->index > vma->vm_start);
+       BUG_ON(mas->min > mas->index);
+#endif
+       mas->index = vma->vm_start;
+       mas->last = vma->vm_end - 1;
+       ret = mas_store_gfp(mas, NULL, GFP_KERNEL);
+       return ret;
+}
+
 /* mm/util.c */
 void __vma_link_list(struct mm_struct *mm, struct vm_area_struct *vma,
                struct vm_area_struct *prev);

diff --git a/mm/mmap.c b/mm/mmap.c
index bfb0ea164a90a96135d80d2ae50b5e52622941c0..c2f1431886d4038634d173040c22c28284aff250 100644 (file)
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -375,7 +375,70 @@ static int browse_rb(struct mm_struct *mm)
        }
        return bug ? -1 : i;
 }
+#if defined(CONFIG_DEBUG_MAPLE_TREE)
+extern void mt_validate(struct maple_tree *mt);
+extern void mt_dump(const struct maple_tree *mt);
 
+/* Validate the maple tree */
+static void validate_mm_mt(struct mm_struct *mm)
+{
+       struct maple_tree *mt = &mm->mm_mt;
+       struct vm_area_struct *vma_mt, *vma = mm->mmap;
+
+       MA_STATE(mas, mt, 0, 0);
+       mas_for_each(&mas, vma_mt, ULONG_MAX) {
+               if (xa_is_zero(vma_mt))
+                       continue;
+
+               if (!vma)
+                       break;
+
+               if ((vma != vma_mt) ||
+                   (vma->vm_start != vma_mt->vm_start) ||
+                   (vma->vm_end != vma_mt->vm_end) ||
+                   (vma->vm_start != mas.index) ||
+                   (vma->vm_end - 1 != mas.last)) {
+                       pr_emerg("issue in %s\n", current->comm);
+                       dump_stack();
+#ifdef CONFIG_DEBUG_VM
+                       dump_vma(vma_mt);
+                       pr_emerg("and next in rb\n");
+                       dump_vma(vma->vm_next);
+#endif
+                       pr_emerg("mt piv: %px %lu - %lu\n", vma_mt,
+                                mas.index, mas.last);
+                       pr_emerg("mt vma: %px %lu - %lu\n", vma_mt,
+                                vma_mt->vm_start, vma_mt->vm_end);
+                       pr_emerg("rb vma: %px %lu - %lu\n", vma,
+                                vma->vm_start, vma->vm_end);
+                       pr_emerg("rb->next = %px %lu - %lu\n", vma->vm_next,
+                                       vma->vm_next->vm_start, vma->vm_next->vm_end);
+
+                       mt_dump(mas.tree);
+                       if (vma_mt->vm_end != mas.last + 1) {
+                               pr_err("vma: %px vma_mt %lu-%lu\tmt %lu-%lu\n",
+                                               mm, vma_mt->vm_start, vma_mt->vm_end,
+                                               mas.index, mas.last);
+                               mt_dump(mas.tree);
+                       }
+                       VM_BUG_ON_MM(vma_mt->vm_end != mas.last + 1, mm);
+                       if (vma_mt->vm_start != mas.index) {
+                               pr_err("vma: %px vma_mt %px %lu - %lu doesn't match\n",
+                                               mm, vma_mt, vma_mt->vm_start, vma_mt->vm_end);
+                               mt_dump(mas.tree);
+                       }
+                       VM_BUG_ON_MM(vma_mt->vm_start != mas.index, mm);
+               }
+               VM_BUG_ON(vma != vma_mt);
+               vma = vma->vm_next;
+
+       }
+       VM_BUG_ON(vma);
+       mt_validate(&mm->mm_mt);
+}
+#else
+#define validate_mm_mt(root) do { } while (0)
+#endif
 static void validate_mm_rb(struct rb_root *root, struct vm_area_struct *ignore)
 {
        struct rb_node *nd;
@@ -430,6 +493,7 @@ static void validate_mm(struct mm_struct *mm)
 }
 #else
 #define validate_mm_rb(root, ignore) do { } while (0)
+#define validate_mm_mt(root) do { } while (0)
 #define validate_mm(mm) do { } while (0)
 #endif
 
@@ -674,11 +738,42 @@ static void __vma_link_file(struct vm_area_struct *vma)
        }
 }
 
+/*
+ * vma_mt_szero() - Set a given range to zero.  Used when modifying a
+ * vm_area_struct start or end.
+ *
+ * @mm: The struct_mm
+ * @start: The start address to zero
+ * @end: The end address to zero.
+ */
+static inline void vma_mt_szero(struct mm_struct *mm, unsigned long start,
+                               unsigned long end)
+{
+       MA_STATE(mas, &mm->mm_mt, start, end - 1);
+
+       trace_vma_mt_szero(mm, start, end);
+       mas_store_gfp(&mas, NULL, GFP_KERNEL);
+}
+
+/*
+ * vma_store() - Store a given vm_area_struct in the maple tree.
+ * @mm: The struct_mm
+ * @vma: The vm_area_struct to store in the maple tree.
+ */
+void vma_store(struct mm_struct *mm, struct vm_area_struct *vma)
+{
+       MA_STATE(mas, &mm->mm_mt, vma->vm_start, vma->vm_end - 1);
+
+       trace_vma_store(mm, vma);
+       mas_store_gfp(&mas, vma, GFP_KERNEL);
+}
+
 static void
 __vma_link(struct mm_struct *mm, struct vm_area_struct *vma,
        struct vm_area_struct *prev, struct rb_node **rb_link,
        struct rb_node *rb_parent)
 {
+       vma_store(mm, vma);
        __vma_link_list(mm, vma, prev);
        __vma_link_rb(mm, vma, rb_link, rb_parent);
 }
@@ -751,6 +846,9 @@ int __vma_adjust(struct vm_area_struct *vma, unsigned long start,
        long adjust_next = 0;
        int remove_next = 0;
 
+       validate_mm(mm);
+       validate_mm_mt(mm);
+
        if (next && !insert) {
                struct vm_area_struct *exporter = NULL, *importer = NULL;
 
@@ -876,17 +974,28 @@ again:
        }
 
        if (start != vma->vm_start) {
+               unsigned long old_start = vma->vm_start;
                vma->vm_start = start;
+               if (old_start < start)
+                       vma_mt_szero(mm, old_start, start);
                start_changed = true;
        }
        if (end != vma->vm_end) {
+               unsigned long old_end = vma->vm_end;
                vma->vm_end = end;
+               if (old_end > end)
+                       vma_mt_szero(mm, end, old_end);
                end_changed = true;
        }
+
+       if (end_changed || start_changed)
+               vma_store(mm, vma);
+
        vma->vm_pgoff = pgoff;
        if (adjust_next) {
                next->vm_start += adjust_next;
                next->vm_pgoff += adjust_next >> PAGE_SHIFT;
+               vma_store(mm, next);
        }
 
        if (file) {
@@ -900,6 +1009,8 @@ again:
                /*
                 * vma_merge has merged next into vma, and needs
                 * us to remove next before dropping the locks.
+                * Since we have expanded over this vma, the maple tree will
+                * have overwritten by storing the value
                 */
                if (remove_next != 3)
                        __vma_unlink(mm, next, next);
@@ -1019,6 +1130,7 @@ again:
                uprobe_mmap(insert);
 
        validate_mm(mm);
+       validate_mm_mt(mm);
 
        return 0;
 }
@@ -1166,6 +1278,7 @@ struct vm_area_struct *vma_merge(struct mm_struct *mm,
        struct vm_area_struct *area, *next;
        int err;
 
+       validate_mm_mt(mm);
        /*
         * We later require that vma->vm_flags == vm_flags,
         * so this tests vma->vm_flags & VM_SPECIAL, too.
@@ -1241,6 +1354,7 @@ struct vm_area_struct *vma_merge(struct mm_struct *mm,
                khugepaged_enter_vma_merge(area, vm_flags);
                return area;
        }
+       validate_mm_mt(mm);
 
        return NULL;
 }
@@ -1722,6 +1836,7 @@ unsigned long mmap_region(struct file *file, unsigned long addr,
        struct rb_node **rb_link, *rb_parent;
        unsigned long charged = 0;
 
+       validate_mm_mt(mm);
        /* Check against address space limit. */
        if (!may_expand_vm(mm, vm_flags, len >> PAGE_SHIFT)) {
                unsigned long nr_pages;
@@ -1869,6 +1984,7 @@ out:
 
        vma_set_page_prot(vma);
 
+       validate_mm_mt(mm);
        return addr;
 
 unmap_and_free_vma:
@@ -1885,6 +2001,7 @@ free_vma:
 unacct_error:
        if (charged)
                vm_unacct_memory(charged);
+       validate_mm_mt(mm);
        return error;
 }
 
@@ -1901,12 +2018,21 @@ static unsigned long unmapped_area(struct vm_unmapped_area_info *info)
        struct mm_struct *mm = current->mm;
        struct vm_area_struct *vma;
        unsigned long length, low_limit, high_limit, gap_start, gap_end;
+       unsigned long gap;
+       MA_STATE(mas, &mm->mm_mt, 0, 0);
 
        /* Adjust search length to account for worst case alignment overhead */
        length = info->length + info->align_mask;
        if (length < info->length)
                return -ENOMEM;
 
+       rcu_read_lock();
+       mas_empty_area_rev(&mas, info->low_limit, info->high_limit - 1,
+                          length);
+       rcu_read_unlock();
+       gap = mas.index;
+       gap += (info->align_offset - gap) & info->align_mask;
+
        /* Adjust search limits by the desired length */
        if (info->high_limit < length)
                return -ENOMEM;
@@ -1988,20 +2114,39 @@ found:
 
        VM_BUG_ON(gap_start + info->length > info->high_limit);
        VM_BUG_ON(gap_start + info->length > gap_end);
+
+       VM_BUG_ON(gap != gap_start);
        return gap_start;
 }
 
+static inline unsigned long top_area_aligned(struct vm_unmapped_area_info *info,
+                                            unsigned long end)
+{
+       return (end - info->length - info->align_offset) & (~info->align_mask);
+}
+
 static unsigned long unmapped_area_topdown(struct vm_unmapped_area_info *info)
 {
        struct mm_struct *mm = current->mm;
-       struct vm_area_struct *vma;
+       struct vm_area_struct *vma = NULL;
        unsigned long length, low_limit, high_limit, gap_start, gap_end;
+       unsigned long gap;
+
+       MA_STATE(mas, &mm->mm_mt, 0, 0);
+       validate_mm_mt(mm);
 
        /* Adjust search length to account for worst case alignment overhead */
        length = info->length + info->align_mask;
        if (length < info->length)
                return -ENOMEM;
 
+       rcu_read_lock();
+       mas_empty_area_rev(&mas, info->low_limit, info->high_limit - 1,
+                  length);
+       rcu_read_unlock();
+       gap = (mas.index + info->align_mask) & ~info->align_mask;
+       gap -= info->align_offset & info->align_mask;
+
        /*
         * Adjust search limits by the desired length.
         * See implementation comment at top of unmapped_area().
@@ -2087,6 +2232,32 @@ found_highest:
 
        VM_BUG_ON(gap_end < info->low_limit);
        VM_BUG_ON(gap_end < gap_start);
+
+       if (gap != gap_end) {
+               pr_err("%s: %px Gap was found: mt %lu gap_end %lu\n", __func__,
+                      mm, gap, gap_end);
+               pr_err("window was %lu - %lu size %lu\n", info->high_limit,
+                      info->low_limit, length);
+               pr_err("mas.min %lu max %lu mas.last %lu\n", mas.min, mas.max,
+                      mas.last);
+               pr_err("mas.index %lu align mask %lu offset %lu\n", mas.index,
+                      info->align_mask, info->align_offset);
+               pr_err("rb_find_vma find on %lu => %px (%px)\n", mas.index,
+                      find_vma(mm, mas.index), vma);
+#if defined(CONFIG_DEBUG_MAPLE_TREE)
+               mt_dump(&mm->mm_mt);
+#endif
+               {
+                       struct vm_area_struct *dv = mm->mmap;
+
+                       while (dv) {
+                               printk("vma %px %lu-%lu\n", dv, dv->vm_start, dv->vm_end);
+                               dv = dv->vm_next;
+                       }
+               }
+               VM_BUG_ON(gap != gap_end);
+       }
+
        return gap_end;
 }
 
@@ -2300,7 +2471,6 @@ struct vm_area_struct *find_vma(struct mm_struct *mm, unsigned long addr)
                vmacache_update(addr, vma);
        return vma;
 }
-
 EXPORT_SYMBOL(find_vma);
 
 /*
@@ -2381,6 +2551,7 @@ int expand_upwards(struct vm_area_struct *vma, unsigned long address)
        unsigned long gap_addr;
        int error = 0;
 
+       validate_mm_mt(mm);
        if (!(vma->vm_flags & VM_GROWSUP))
                return -EFAULT;
 
@@ -2457,6 +2628,7 @@ int expand_upwards(struct vm_area_struct *vma, unsigned long address)
        anon_vma_unlock_write(vma->anon_vma);
        khugepaged_enter_vma_merge(vma, vma->vm_flags);
        validate_mm(mm);
+       validate_mm_mt(mm);
        return error;
 }
 #endif /* CONFIG_STACK_GROWSUP || CONFIG_IA64 */
@@ -2471,6 +2643,7 @@ int expand_downwards(struct vm_area_struct *vma,
        struct vm_area_struct *prev;
        int error = 0;
 
+       validate_mm(mm);
        address &= PAGE_MASK;
        if (address < mmap_min_addr)
                return -EPERM;
@@ -2524,6 +2697,8 @@ int expand_downwards(struct vm_area_struct *vma,
                                anon_vma_interval_tree_pre_update_vma(vma);
                                vma->vm_start = address;
                                vma->vm_pgoff -= grow;
+                               /* Overwrite old entry in mtree. */
+                               vma_store(mm, vma);
                                anon_vma_interval_tree_post_update_vma(vma);
                                vma_gap_update(vma);
                                spin_unlock(&mm->page_table_lock);
@@ -2665,6 +2840,7 @@ detach_vmas_to_be_unmapped(struct mm_struct *mm, struct vm_area_struct *vma,
 
        insertion_point = (prev ? &prev->vm_next : &mm->mmap);
        vma->vm_prev = NULL;
+       vma_mt_szero(mm, vma->vm_start, end);
        do {
                vma_rb_erase(vma, &mm->mm_rb);
                mm->map_count--;
@@ -2703,6 +2879,7 @@ int __split_vma(struct mm_struct *mm, struct vm_area_struct *vma,
 {
        struct vm_area_struct *new;
        int err;
+       validate_mm_mt(mm);
 
        if (vma->vm_ops && vma->vm_ops->may_split) {
                err = vma->vm_ops->may_split(vma, addr);
@@ -2755,6 +2932,7 @@ int __split_vma(struct mm_struct *mm, struct vm_area_struct *vma,
        mpol_put(vma_policy(new));
  out_free_vma:
        vm_area_free(new);
+       validate_mm_mt(mm);
        return err;
 }
 
@@ -3026,6 +3204,7 @@ static int do_brk_flags(unsigned long addr, unsigned long len, unsigned long fla
        pgoff_t pgoff = addr >> PAGE_SHIFT;
        int error;
        unsigned long mapped_addr;
+       validate_mm_mt(mm);
 
        /* Until we need other flags, refuse anything except VM_EXEC. */
        if ((flags & (~VM_EXEC)) != 0)
@@ -3083,6 +3262,7 @@ out:
        if (flags & VM_LOCKED)
                mm->locked_vm += (len >> PAGE_SHIFT);
        vma->vm_flags |= VM_SOFTDIRTY;
+       validate_mm_mt(mm);
        return 0;
 }
 
@@ -3153,6 +3333,13 @@ void exit_mmap(struct mm_struct *mm)
                mmap_write_unlock(mm);
        }
 
+       /*
+        * Actually taking the mmap semaphore here costs 3% performance on
+        * a large machine:
+        * https://lore.kernel.org/lkml/20170725151754.3txp44a2kbffsxdg@node.shutemov.name/
+        * Lockdep will complain about not holding the mmap_lock, so we lie.
+        */
+       rwsem_acquire(&mm->mmap_lock.dep_map, 0, 0, _THIS_IP_);
        if (mm->locked_vm)
                unlock_range(mm->mmap, ULONG_MAX);
 
@@ -3181,6 +3368,11 @@ void exit_mmap(struct mm_struct *mm)
                vma = remove_vma(vma);
                cond_resched();
        }
+
+       trace_exit_mmap(mm);
+       __mt_destroy(&mm->mm_mt);
+       rwsem_release(&mm->mmap_lock.dep_map, _THIS_IP_);
+
        vm_unacct_memory(nr_accounted);
 }
 
@@ -3192,10 +3384,25 @@ int insert_vm_struct(struct mm_struct *mm, struct vm_area_struct *vma)
 {
        struct vm_area_struct *prev;
        struct rb_node **rb_link, *rb_parent;
+       unsigned long start = vma->vm_start;
+       struct vm_area_struct *overlap = NULL;
 
        if (find_vma_links(mm, vma->vm_start, vma->vm_end,
                           &prev, &rb_link, &rb_parent))
                return -ENOMEM;
+
+       overlap = mt_find(&mm->mm_mt, &start, vma->vm_end - 1);
+       if (overlap) {
+
+               pr_err("Found vma ending at %lu\n", start - 1);
+               pr_err("vma : %lu => %lu-%lu\n", (unsigned long)overlap,
+                               overlap->vm_start, overlap->vm_end - 1);
+#if defined(CONFIG_DEBUG_MAPLE_TREE)
+               mt_dump(&mm->mm_mt);
+#endif
+               BUG();
+       }
+
        if ((vma->vm_flags & VM_ACCOUNT) &&
             security_vm_enough_memory_mm(mm, vma_pages(vma)))
                return -ENOMEM;
@@ -3235,7 +3442,9 @@ struct vm_area_struct *copy_vma(struct vm_area_struct **vmap,
        struct vm_area_struct *new_vma, *prev;
        struct rb_node **rb_link, *rb_parent;
        bool faulted_in_anon_vma = true;
+       unsigned long index = addr;
 
+       validate_mm_mt(mm);
        /*
         * If anonymous vma has not yet been faulted, update new pgoff
         * to match new location, to increase its chance of merging.
@@ -3247,6 +3456,8 @@ struct vm_area_struct *copy_vma(struct vm_area_struct **vmap,
 
        if (find_vma_links(mm, addr, addr + len, &prev, &rb_link, &rb_parent))
                return NULL;    /* should never get here */
+       if (mt_find(&mm->mm_mt, &index, addr+len - 1))
+               BUG();
        new_vma = vma_merge(mm, prev, addr, addr + len, vma->vm_flags,
                            vma->anon_vma, vma->vm_file, pgoff, vma_policy(vma),
                            vma->vm_userfaultfd_ctx);
@@ -3290,6 +3501,7 @@ struct vm_area_struct *copy_vma(struct vm_area_struct **vmap,
                vma_link(mm, new_vma, prev, rb_link, rb_parent);
                *need_rmap_locks = false;
        }
+       validate_mm_mt(mm);
        return new_vma;
 
 out_free_mempol:
@@ -3297,6 +3509,7 @@ out_free_mempol:
 out_free_vma:
        vm_area_free(new_vma);
 out:
+       validate_mm_mt(mm);
        return NULL;
 }
 
@@ -3433,6 +3646,7 @@ static struct vm_area_struct *__install_special_mapping(
        int ret;
        struct vm_area_struct *vma;
 
+       validate_mm_mt(mm);
        vma = vm_area_alloc(mm);
        if (unlikely(vma == NULL))
                return ERR_PTR(-ENOMEM);
@@ -3454,10 +3668,12 @@ static struct vm_area_struct *__install_special_mapping(
 
        perf_event_mmap(vma);
 
+       validate_mm_mt(mm);
        return vma;
 
 out:
        vm_area_free(vma);
+       validate_mm_mt(mm);
        return ERR_PTR(ret);
 }