[linux-2.6-block.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>

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