[linux.git] / mm / vmacache.c

// SPDX-License-Identifier: GPL-2.0
/*
 * Copyright (C) 2014 Davidlohr Bueso.
 */
#include <linux/sched/signal.h>
#include <linux/sched/task.h>
#include <linux/mm.h>
#include <linux/vmacache.h>

/*
 * Hash based on the pmd of addr if configured with MMU, which provides a good
 * hit rate for workloads with spatial locality.  Otherwise, use pages.
 */
#ifdef CONFIG_MMU
#define VMACACHE_SHIFT	PMD_SHIFT
#else
#define VMACACHE_SHIFT	PAGE_SHIFT
#endif
#define VMACACHE_HASH(addr) ((addr >> VMACACHE_SHIFT) & VMACACHE_MASK)

/*
 * This task may be accessing a foreign mm via (for example)
 * get_user_pages()->find_vma().  The vmacache is task-local and this
 * task's vmacache pertains to a different mm (ie, its own).  There is
 * nothing we can do here.
 *
 * Also handle the case where a kernel thread has adopted this mm via
 * kthread_use_mm(). That kernel thread's vmacache is not applicable to this mm.
 */
static inline bool vmacache_valid_mm(struct mm_struct *mm)
{
	return current->mm == mm && !(current->flags & PF_KTHREAD);
}

void vmacache_update(unsigned long addr, struct vm_area_struct *newvma)
{
	if (vmacache_valid_mm(newvma->vm_mm))
		current->vmacache.vmas[VMACACHE_HASH(addr)] = newvma;
}

static bool vmacache_valid(struct mm_struct *mm)
{
	struct task_struct *curr;

	if (!vmacache_valid_mm(mm))
		return false;

	curr = current;
	if (mm->vmacache_seqnum != curr->vmacache.seqnum) {
		/*
		 * First attempt will always be invalid, initialize
		 * the new cache for this task here.
		 */
		curr->vmacache.seqnum = mm->vmacache_seqnum;
		vmacache_flush(curr);
		return false;
	}
	return true;
}

struct vm_area_struct *vmacache_find(struct mm_struct *mm, unsigned long addr)
{
	int idx = VMACACHE_HASH(addr);
	int i;

	count_vm_vmacache_event(VMACACHE_FIND_CALLS);

	if (!vmacache_valid(mm))
		return NULL;

	for (i = 0; i < VMACACHE_SIZE; i++) {
		struct vm_area_struct *vma = current->vmacache.vmas[idx];

		if (vma) {
#ifdef CONFIG_DEBUG_VM_VMACACHE
			if (WARN_ON_ONCE(vma->vm_mm != mm))
				break;
#endif
			if (vma->vm_start <= addr && vma->vm_end > addr) {
				count_vm_vmacache_event(VMACACHE_FIND_HITS);
				return vma;
			}
		}
		if (++idx == VMACACHE_SIZE)
			idx = 0;
	}

	return NULL;
}

#ifndef CONFIG_MMU
struct vm_area_struct *vmacache_find_exact(struct mm_struct *mm,
					   unsigned long start,
					   unsigned long end)
{
	int idx = VMACACHE_HASH(start);
	int i;

	count_vm_vmacache_event(VMACACHE_FIND_CALLS);

	if (!vmacache_valid(mm))
		return NULL;

	for (i = 0; i < VMACACHE_SIZE; i++) {
		struct vm_area_struct *vma = current->vmacache.vmas[idx];

		if (vma && vma->vm_start == start && vma->vm_end == end) {
			count_vm_vmacache_event(VMACACHE_FIND_HITS);
			return vma;
		}
		if (++idx == VMACACHE_SIZE)
			idx = 0;
	}

	return NULL;
}
#endif
Commit	Line	Data
b2441318	1	// SPDX-License-Identifier: GPL-2.0
615d6e87 DB	2	/*
	3	* Copyright (C) 2014 Davidlohr Bueso.
	4	*/
3f07c014	5	#include <linux/sched/signal.h>
9164bb4a	6	#include <linux/sched/task.h>
615d6e87 DB	7	#include <linux/mm.h>
615d6e87 DB	8	#include <linux/vmacache.h>
ddbf369c DR	9
	10	/*
	11	* Hash based on the pmd of addr if configured with MMU, which provides a good
	12	* hit rate for workloads with spatial locality. Otherwise, use pages.
	13	*/
	14	#ifdef CONFIG_MMU
	15	#define VMACACHE_SHIFT PMD_SHIFT
	16	#else
	17	#define VMACACHE_SHIFT PAGE_SHIFT
	18	#endif
	19	#define VMACACHE_HASH(addr) ((addr >> VMACACHE_SHIFT) & VMACACHE_MASK)
615d6e87	20
615d6e87 DB	21	/*
	22	* This task may be accessing a foreign mm via (for example)
	23	* get_user_pages()->find_vma(). The vmacache is task-local and this
	24	* task's vmacache pertains to a different mm (ie, its own). There is
	25	* nothing we can do here.
	26	*
f5678e7f CH	27	* Also handle the case where a kernel thread has adopted this mm via
f5678e7f CH	28	* kthread_use_mm(). That kernel thread's vmacache is not applicable to this mm.
615d6e87	29	*/
a2c1aad3	30	static inline bool vmacache_valid_mm(struct mm_struct *mm)
615d6e87 DB	31	{
	32	return current->mm == mm && !(current->flags & PF_KTHREAD);
	33	}
	34
	35	void vmacache_update(unsigned long addr, struct vm_area_struct *newvma)
	36	{
	37	if (vmacache_valid_mm(newvma->vm_mm))
314ff785	38	current->vmacache.vmas[VMACACHE_HASH(addr)] = newvma;
615d6e87 DB	39	}
	40
	41	static bool vmacache_valid(struct mm_struct *mm)
	42	{
	43	struct task_struct *curr;
	44
	45	if (!vmacache_valid_mm(mm))
	46	return false;
	47
	48	curr = current;
314ff785	49	if (mm->vmacache_seqnum != curr->vmacache.seqnum) {
615d6e87 DB	50	/*
	51	* First attempt will always be invalid, initialize
	52	* the new cache for this task here.
	53	*/
314ff785	54	curr->vmacache.seqnum = mm->vmacache_seqnum;
615d6e87 DB	55	vmacache_flush(curr);
	56	return false;
	57	}
	58	return true;
	59	}
	60
	61	struct vm_area_struct vmacache_find(struct mm_struct mm, unsigned long addr)
	62	{
ddbf369c	63	int idx = VMACACHE_HASH(addr);
615d6e87 DB	64	int i;
615d6e87 DB	65
131ddc5c AD	66	count_vm_vmacache_event(VMACACHE_FIND_CALLS);
131ddc5c AD	67
615d6e87 DB	68	if (!vmacache_valid(mm))
	69	return NULL;
	70
	71	for (i = 0; i < VMACACHE_SIZE; i++) {
ddbf369c	72	struct vm_area_struct *vma = current->vmacache.vmas[idx];
615d6e87	73
ddbf369c DR	74	if (vma) {
	75	#ifdef CONFIG_DEBUG_VM_VMACACHE
	76	if (WARN_ON_ONCE(vma->vm_mm != mm))
	77	break;
	78	#endif
	79	if (vma->vm_start <= addr && vma->vm_end > addr) {
	80	count_vm_vmacache_event(VMACACHE_FIND_HITS);
	81	return vma;
	82	}
4f115147	83	}
ddbf369c DR	84	if (++idx == VMACACHE_SIZE)
ddbf369c DR	85	idx = 0;
615d6e87 DB	86	}
	87
	88	return NULL;
	89	}
	90
	91	#ifndef CONFIG_MMU
	92	struct vm_area_struct vmacache_find_exact(struct mm_struct mm,
	93	unsigned long start,
	94	unsigned long end)
	95	{
ddbf369c	96	int idx = VMACACHE_HASH(start);
615d6e87 DB	97	int i;
615d6e87 DB	98
131ddc5c AD	99	count_vm_vmacache_event(VMACACHE_FIND_CALLS);
131ddc5c AD	100
615d6e87 DB	101	if (!vmacache_valid(mm))
	102	return NULL;
	103
	104	for (i = 0; i < VMACACHE_SIZE; i++) {
ddbf369c	105	struct vm_area_struct *vma = current->vmacache.vmas[idx];
615d6e87	106
4f115147 DB	107	if (vma && vma->vm_start == start && vma->vm_end == end) {
4f115147 DB	108	count_vm_vmacache_event(VMACACHE_FIND_HITS);
615d6e87	109	return vma;
4f115147	110	}
ddbf369c DR	111	if (++idx == VMACACHE_SIZE)
ddbf369c DR	112	idx = 0;
615d6e87 DB	113	}
	114
	115	return NULL;
	116	}
	117	#endif