[linux.git] / mm / vmacache.c

/*
 * Copyright (C) 2014 Davidlohr Bueso.
 */
#include <linux/sched.h>
#include <linux/mm.h>
#include <linux/vmacache.h>

/*
 * Flush vma caches for threads that share a given mm.
 *
 * The operation is safe because the caller holds the mmap_sem
 * exclusively and other threads accessing the vma cache will
 * have mmap_sem held at least for read, so no extra locking
 * is required to maintain the vma cache.
 */
void vmacache_flush_all(struct mm_struct *mm)
{
	struct task_struct *g, *p;

	/*
	 * Single threaded tasks need not iterate the entire
	 * list of process. We can avoid the flushing as well
	 * since the mm's seqnum was increased and don't have
	 * to worry about other threads' seqnum. Current's
	 * flush will occur upon the next lookup.
	 */
	if (atomic_read(&mm->mm_users) == 1)
		return;

	rcu_read_lock();
	for_each_process_thread(g, p) {
		/*
		 * Only flush the vmacache pointers as the
		 * mm seqnum is already set and curr's will
		 * be set upon invalidation when the next
		 * lookup is done.
		 */
		if (mm == p->mm)
			vmacache_flush(p);
	}
	rcu_read_unlock();
}

/*
 * 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 use_mm().
 * That kernel thread's vmacache is not applicable to this mm.
 */
static 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[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 i;

	if (!vmacache_valid(mm))
		return NULL;

	count_vm_vmacache_event(VMACACHE_FIND_CALLS);

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

		if (!vma)
			continue;
		if (WARN_ON_ONCE(vma->vm_mm != mm))
			break;
		if (vma->vm_start <= addr && vma->vm_end > addr) {
			count_vm_vmacache_event(VMACACHE_FIND_HITS);
			return vma;
		}
	}

	return NULL;
}

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

	if (!vmacache_valid(mm))
		return NULL;

	count_vm_vmacache_event(VMACACHE_FIND_CALLS);

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

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

	return NULL;
}
#endif
Commit	Line	Data
615d6e87 DB	1	/*
	2	* Copyright (C) 2014 Davidlohr Bueso.
	3	*/
	4	#include <linux/sched.h>
	5	#include <linux/mm.h>
	6	#include <linux/vmacache.h>
	7
	8	/*
	9	* Flush vma caches for threads that share a given mm.
	10	*
	11	* The operation is safe because the caller holds the mmap_sem
	12	* exclusively and other threads accessing the vma cache will
	13	* have mmap_sem held at least for read, so no extra locking
	14	* is required to maintain the vma cache.
	15	*/
	16	void vmacache_flush_all(struct mm_struct *mm)
	17	{
	18	struct task_struct g, p;
	19
6b4ebc3a DB	20	/*
	21	* Single threaded tasks need not iterate the entire
	22	* list of process. We can avoid the flushing as well
	23	* since the mm's seqnum was increased and don't have
	24	* to worry about other threads' seqnum. Current's
	25	* flush will occur upon the next lookup.
	26	*/
	27	if (atomic_read(&mm->mm_users) == 1)
	28	return;
	29
615d6e87 DB	30	rcu_read_lock();
	31	for_each_process_thread(g, p) {
	32	/*
	33	* Only flush the vmacache pointers as the
	34	* mm seqnum is already set and curr's will
	35	* be set upon invalidation when the next
	36	* lookup is done.
	37	*/
	38	if (mm == p->mm)
	39	vmacache_flush(p);
	40	}
	41	rcu_read_unlock();
	42	}
	43
	44	/*
	45	* This task may be accessing a foreign mm via (for example)
	46	* get_user_pages()->find_vma(). The vmacache is task-local and this
	47	* task's vmacache pertains to a different mm (ie, its own). There is
	48	* nothing we can do here.
	49	*
	50	* Also handle the case where a kernel thread has adopted this mm via use_mm().
	51	* That kernel thread's vmacache is not applicable to this mm.
	52	*/
	53	static bool vmacache_valid_mm(struct mm_struct *mm)
	54	{
	55	return current->mm == mm && !(current->flags & PF_KTHREAD);
	56	}
	57
	58	void vmacache_update(unsigned long addr, struct vm_area_struct *newvma)
	59	{
	60	if (vmacache_valid_mm(newvma->vm_mm))
	61	current->vmacache[VMACACHE_HASH(addr)] = newvma;
	62	}
	63
	64	static bool vmacache_valid(struct mm_struct *mm)
	65	{
	66	struct task_struct *curr;
	67
	68	if (!vmacache_valid_mm(mm))
	69	return false;
	70
	71	curr = current;
	72	if (mm->vmacache_seqnum != curr->vmacache_seqnum) {
	73	/*
	74	* First attempt will always be invalid, initialize
	75	* the new cache for this task here.
	76	*/
	77	curr->vmacache_seqnum = mm->vmacache_seqnum;
	78	vmacache_flush(curr);
	79	return false;
	80	}
	81	return true;
	82	}
	83
	84	struct vm_area_struct vmacache_find(struct mm_struct mm, unsigned long addr)
	85	{
	86	int i;
	87
	88	if (!vmacache_valid(mm))
	89	return NULL;
	90
4f115147 DB	91	count_vm_vmacache_event(VMACACHE_FIND_CALLS);
4f115147 DB	92
615d6e87 DB	93	for (i = 0; i < VMACACHE_SIZE; i++) {
	94	struct vm_area_struct *vma = current->vmacache[i];
	95
50f5aa8a LT	96	if (!vma)
	97	continue;
	98	if (WARN_ON_ONCE(vma->vm_mm != mm))
	99	break;
4f115147 DB	100	if (vma->vm_start <= addr && vma->vm_end > addr) {
4f115147 DB	101	count_vm_vmacache_event(VMACACHE_FIND_HITS);
615d6e87	102	return vma;
4f115147	103	}
615d6e87 DB	104	}
	105
	106	return NULL;
	107	}
	108
	109	#ifndef CONFIG_MMU
	110	struct vm_area_struct vmacache_find_exact(struct mm_struct mm,
	111	unsigned long start,
	112	unsigned long end)
	113	{
	114	int i;
	115
	116	if (!vmacache_valid(mm))
	117	return NULL;
	118
4f115147 DB	119	count_vm_vmacache_event(VMACACHE_FIND_CALLS);
4f115147 DB	120
615d6e87 DB	121	for (i = 0; i < VMACACHE_SIZE; i++) {
	122	struct vm_area_struct *vma = current->vmacache[i];
	123
4f115147 DB	124	if (vma && vma->vm_start == start && vma->vm_end == end) {
4f115147 DB	125	count_vm_vmacache_event(VMACACHE_FIND_HITS);
615d6e87	126	return vma;
4f115147	127	}
615d6e87 DB	128	}
	129
	130	return NULL;
	131	}
	132	#endif