[linux.git] / mm / vmacache.c

/*
 * Copyright (C) 2014 Davidlohr Bueso.
 */
#include <linux/sched/signal.h>
#include <linux/sched/task.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;

	count_vm_vmacache_event(VMACACHE_FULL_FLUSHES);

	/*
	 * 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 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 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[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;

	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[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	*/
3f07c014	4	#include <linux/sched/signal.h>
9164bb4a	5	#include <linux/sched/task.h>
615d6e87 DB	6	#include <linux/mm.h>
	7	#include <linux/vmacache.h>
	8
	9	/*
	10	* Flush vma caches for threads that share a given mm.
	11	*
	12	* The operation is safe because the caller holds the mmap_sem
	13	* exclusively and other threads accessing the vma cache will
	14	* have mmap_sem held at least for read, so no extra locking
	15	* is required to maintain the vma cache.
	16	*/
	17	void vmacache_flush_all(struct mm_struct *mm)
	18	{
	19	struct task_struct g, p;
	20
f5f302e2 DB	21	count_vm_vmacache_event(VMACACHE_FULL_FLUSHES);
f5f302e2 DB	22
6b4ebc3a DB	23	/*
	24	* Single threaded tasks need not iterate the entire
	25	* list of process. We can avoid the flushing as well
	26	* since the mm's seqnum was increased and don't have
	27	* to worry about other threads' seqnum. Current's
	28	* flush will occur upon the next lookup.
	29	*/
	30	if (atomic_read(&mm->mm_users) == 1)
	31	return;
	32
615d6e87 DB	33	rcu_read_lock();
	34	for_each_process_thread(g, p) {
	35	/*
	36	* Only flush the vmacache pointers as the
	37	* mm seqnum is already set and curr's will
	38	* be set upon invalidation when the next
	39	* lookup is done.
	40	*/
	41	if (mm == p->mm)
	42	vmacache_flush(p);
	43	}
	44	rcu_read_unlock();
	45	}
	46
	47	/*
	48	* This task may be accessing a foreign mm via (for example)
	49	* get_user_pages()->find_vma(). The vmacache is task-local and this
	50	* task's vmacache pertains to a different mm (ie, its own). There is
	51	* nothing we can do here.
	52	*
	53	* Also handle the case where a kernel thread has adopted this mm via use_mm().
	54	* That kernel thread's vmacache is not applicable to this mm.
	55	*/
a2c1aad3	56	static inline bool vmacache_valid_mm(struct mm_struct *mm)
615d6e87 DB	57	{
	58	return current->mm == mm && !(current->flags & PF_KTHREAD);
	59	}
	60
	61	void vmacache_update(unsigned long addr, struct vm_area_struct *newvma)
	62	{
	63	if (vmacache_valid_mm(newvma->vm_mm))
314ff785	64	current->vmacache.vmas[VMACACHE_HASH(addr)] = newvma;
615d6e87 DB	65	}
	66
	67	static bool vmacache_valid(struct mm_struct *mm)
	68	{
	69	struct task_struct *curr;
	70
	71	if (!vmacache_valid_mm(mm))
	72	return false;
	73
	74	curr = current;
314ff785	75	if (mm->vmacache_seqnum != curr->vmacache.seqnum) {
615d6e87 DB	76	/*
	77	* First attempt will always be invalid, initialize
	78	* the new cache for this task here.
	79	*/
314ff785	80	curr->vmacache.seqnum = mm->vmacache_seqnum;
615d6e87 DB	81	vmacache_flush(curr);
	82	return false;
	83	}
	84	return true;
	85	}
	86
	87	struct vm_area_struct vmacache_find(struct mm_struct mm, unsigned long addr)
	88	{
	89	int i;
	90
131ddc5c AD	91	count_vm_vmacache_event(VMACACHE_FIND_CALLS);
131ddc5c AD	92
615d6e87 DB	93	if (!vmacache_valid(mm))
	94	return NULL;
	95
	96	for (i = 0; i < VMACACHE_SIZE; i++) {
314ff785	97	struct vm_area_struct *vma = current->vmacache.vmas[i];
615d6e87	98
50f5aa8a LT	99	if (!vma)
	100	continue;
	101	if (WARN_ON_ONCE(vma->vm_mm != mm))
	102	break;
4f115147 DB	103	if (vma->vm_start <= addr && vma->vm_end > addr) {
4f115147 DB	104	count_vm_vmacache_event(VMACACHE_FIND_HITS);
615d6e87	105	return vma;
4f115147	106	}
615d6e87 DB	107	}
	108
	109	return NULL;
	110	}
	111
	112	#ifndef CONFIG_MMU
	113	struct vm_area_struct vmacache_find_exact(struct mm_struct mm,
	114	unsigned long start,
	115	unsigned long end)
	116	{
	117	int i;
	118
131ddc5c AD	119	count_vm_vmacache_event(VMACACHE_FIND_CALLS);
131ddc5c AD	120
615d6e87 DB	121	if (!vmacache_valid(mm))
	122	return NULL;
	123
	124	for (i = 0; i < VMACACHE_SIZE; i++) {
314ff785	125	struct vm_area_struct *vma = current->vmacache.vmas[i];
615d6e87	126
4f115147 DB	127	if (vma && vma->vm_start == start && vma->vm_end == end) {
4f115147 DB	128	count_vm_vmacache_event(VMACACHE_FIND_HITS);
615d6e87	129	return vma;
4f115147	130	}
615d6e87 DB	131	}
	132
	133	return NULL;
	134	}
	135	#endif