mm: remove rb tree.

Remove the RB tree and start using the maple tree for vm_area_struct
tracking.

Drop validate_mm() calls in expand_upwards() and expand_downwards() as the
lock is not held.

Signed-off-by: Liam R. Howlett <Liam.Howlett@Oracle.com>
Signed-off-by: Alexandre Frade <kernel@xanmod.org>

arch/x86/kernel/tboot.c

@@ -95,7 +95,6 @@ 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),

drivers/firmware/efi/efi.c

@@ -57,7 +57,6 @@ static unsigned long __initdata mem_reserve = EFI_INVALID_TABLE_ADDR;
 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),

include/linux/mm.h

@@ -2630,8 +2630,6 @@ extern int __split_vma(struct mm_struct *, struct vm_area_struct *,
 extern int split_vma(struct mm_struct *, struct vm_area_struct *,
 	unsigned long addr, int new_below);
 extern int insert_vm_struct(struct mm_struct *, struct vm_area_struct *);
-extern void __vma_link_rb(struct mm_struct *, struct vm_area_struct *,
-	struct rb_node **, struct rb_node *);
 extern void unlink_file_vma(struct vm_area_struct *);
 extern struct vm_area_struct *copy_vma(struct vm_area_struct **,
 	unsigned long addr, unsigned long len, pgoff_t pgoff,

include/linux/mm_types.h

@@ -410,19 +410,6 @@ struct vm_area_struct {
 
 	/* linked list of VM areas per task, sorted by address */
 	struct vm_area_struct *vm_next, *vm_prev;
-
-	struct rb_node vm_rb;
-
-	/*
-	 * Largest free memory gap in bytes to the left of this VMA.
-	 * Either between this VMA and vma->vm_prev, or between one of the
-	 * VMAs below us in the VMA rbtree and its ->vm_prev. This helps
-	 * get_unmapped_area find a free area of the right size.
-	 */
-	unsigned long rb_subtree_gap;
-
-	/* Second cache line starts here. */
-
 	struct mm_struct *vm_mm;	/* The address space we belong to. */
 
 	/*
@@ -488,7 +475,6 @@ 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
 		unsigned long (*get_unmapped_area) (struct file *filp,

kernel/fork.c

@@ -586,7 +586,6 @@ static __latent_entropy int dup_mmap(struct mm_struct *mm,
 					struct mm_struct *oldmm)
 {
 	struct vm_area_struct *mpnt, *tmp, *prev, **pprev;
-	struct rb_node **rb_link, *rb_parent;
 	int retval;
 	unsigned long charge = 0;
 	LIST_HEAD(uf);
@@ -613,8 +612,6 @@ static __latent_entropy int dup_mmap(struct mm_struct *mm,
 	mm->exec_vm = oldmm->exec_vm;
 	mm->stack_vm = oldmm->stack_vm;
 
-	rb_link = &mm->mm_rb.rb_node;
-	rb_parent = NULL;
 	pprev = &mm->mmap;
 	retval = ksm_fork(mm, oldmm);
 	if (retval)
@@ -706,10 +703,6 @@ static __latent_entropy int dup_mmap(struct mm_struct *mm,
 		tmp->vm_prev = prev;
 		prev = tmp;
 
-		__vma_link_rb(mm, tmp, rb_link, rb_parent);
-		rb_link = &tmp->vm_rb.rb_right;
-		rb_parent = &tmp->vm_rb;
-
 		/* Link the vma into the MT */
 		mas.index = tmp->vm_start;
 		mas.last = tmp->vm_end - 1;
@@ -1138,7 +1131,6 @@ static struct mm_struct *mm_init(struct mm_struct *mm, struct task_struct *p,
 	struct user_namespace *user_ns)
 {
 	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;

mm/init-mm.c

@@ -1,6 +1,5 @@
 // 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>
@@ -29,7 +28,6 @@
  * and size this cpu_bitmask to NR_CPUS.
  */
 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),