[linux-2.6-block.git] / mm / madvise.c

/*
 *	linux/mm/madvise.c
 *
 * Copyright (C) 1999  Linus Torvalds
 * Copyright (C) 2002  Christoph Hellwig
 */

#include <linux/mman.h>
#include <linux/pagemap.h>
#include <linux/syscalls.h>
#include <linux/mempolicy.h>
#include <linux/hugetlb.h>
#include <linux/sched.h>
#include <linux/ksm.h>

/*
 * Any behaviour which results in changes to the vma->vm_flags needs to
 * take mmap_sem for writing. Others, which simply traverse vmas, need
 * to only take it for reading.
 */
static int madvise_need_mmap_write(int behavior)
{
	switch (behavior) {
	case MADV_REMOVE:
	case MADV_WILLNEED:
	case MADV_DONTNEED:
		return 0;
	default:
		/* be safe, default to 1. list exceptions explicitly */
		return 1;
	}
}

/*
 * We can potentially split a vm area into separate
 * areas, each area with its own behavior.
 */
static long madvise_behavior(struct vm_area_struct * vma,
		     struct vm_area_struct **prev,
		     unsigned long start, unsigned long end, int behavior)
{
	struct mm_struct * mm = vma->vm_mm;
	int error = 0;
	pgoff_t pgoff;
	unsigned long new_flags = vma->vm_flags;

	switch (behavior) {
	case MADV_NORMAL:
		new_flags = new_flags & ~VM_RAND_READ & ~VM_SEQ_READ;
		break;
	case MADV_SEQUENTIAL:
		new_flags = (new_flags & ~VM_RAND_READ) | VM_SEQ_READ;
		break;
	case MADV_RANDOM:
		new_flags = (new_flags & ~VM_SEQ_READ) | VM_RAND_READ;
		break;
	case MADV_DONTFORK:
		new_flags |= VM_DONTCOPY;
		break;
	case MADV_DOFORK:
		if (vma->vm_flags & VM_IO) {
			error = -EINVAL;
			goto out;
		}
		new_flags &= ~VM_DONTCOPY;
		break;
	case MADV_MERGEABLE:
	case MADV_UNMERGEABLE:
		error = ksm_madvise(vma, start, end, behavior, &new_flags);
		if (error)
			goto out;
		break;
	}

	if (new_flags == vma->vm_flags) {
		*prev = vma;
		goto out;
	}

	pgoff = vma->vm_pgoff + ((start - vma->vm_start) >> PAGE_SHIFT);
	*prev = vma_merge(mm, *prev, start, end, new_flags, vma->anon_vma,
				vma->vm_file, pgoff, vma_policy(vma));
	if (*prev) {
		vma = *prev;
		goto success;
	}

	*prev = vma;

	if (start != vma->vm_start) {
		error = split_vma(mm, vma, start, 1);
		if (error)
			goto out;
	}

	if (end != vma->vm_end) {
		error = split_vma(mm, vma, end, 0);
		if (error)
			goto out;
	}

success:
	/*
	 * vm_flags is protected by the mmap_sem held in write mode.
	 */
	vma->vm_flags = new_flags;

out:
	if (error == -ENOMEM)
		error = -EAGAIN;
	return error;
}

/*
 * Schedule all required I/O operations.  Do not wait for completion.
 */
static long madvise_willneed(struct vm_area_struct * vma,
			     struct vm_area_struct ** prev,
			     unsigned long start, unsigned long end)
{
	struct file *file = vma->vm_file;

	if (!file)
		return -EBADF;

	if (file->f_mapping->a_ops->get_xip_mem) {
		/* no bad return value, but ignore advice */
		return 0;
	}

	*prev = vma;
	start = ((start - vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff;
	if (end > vma->vm_end)
		end = vma->vm_end;
	end = ((end - vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff;

	force_page_cache_readahead(file->f_mapping, file, start, end - start);
	return 0;
}

/*
 * Application no longer needs these pages.  If the pages are dirty,
 * it's OK to just throw them away.  The app will be more careful about
 * data it wants to keep.  Be sure to free swap resources too.  The
 * zap_page_range call sets things up for shrink_active_list to actually free
 * these pages later if no one else has touched them in the meantime,
 * although we could add these pages to a global reuse list for
 * shrink_active_list to pick up before reclaiming other pages.
 *
 * NB: This interface discards data rather than pushes it out to swap,
 * as some implementations do.  This has performance implications for
 * applications like large transactional databases which want to discard
 * pages in anonymous maps after committing to backing store the data
 * that was kept in them.  There is no reason to write this data out to
 * the swap area if the application is discarding it.
 *
 * An interface that causes the system to free clean pages and flush
 * dirty pages is already available as msync(MS_INVALIDATE).
 */
static long madvise_dontneed(struct vm_area_struct * vma,
			     struct vm_area_struct ** prev,
			     unsigned long start, unsigned long end)
{
	*prev = vma;
	if (vma->vm_flags & (VM_LOCKED|VM_HUGETLB|VM_PFNMAP))
		return -EINVAL;

	if (unlikely(vma->vm_flags & VM_NONLINEAR)) {
		struct zap_details details = {
			.nonlinear_vma = vma,
			.last_index = ULONG_MAX,
		};
		zap_page_range(vma, start, end - start, &details);
	} else
		zap_page_range(vma, start, end - start, NULL);
	return 0;
}

/*
 * Application wants to free up the pages and associated backing store.
 * This is effectively punching a hole into the middle of a file.
 *
 * NOTE: Currently, only shmfs/tmpfs is supported for this operation.
 * Other filesystems return -ENOSYS.
 */
static long madvise_remove(struct vm_area_struct *vma,
				struct vm_area_struct **prev,
				unsigned long start, unsigned long end)
{
	struct address_space *mapping;
	loff_t offset, endoff;
	int error;

	*prev = NULL;	/* tell sys_madvise we drop mmap_sem */

	if (vma->vm_flags & (VM_LOCKED|VM_NONLINEAR|VM_HUGETLB))
		return -EINVAL;

	if (!vma->vm_file || !vma->vm_file->f_mapping
		|| !vma->vm_file->f_mapping->host) {
			return -EINVAL;
	}

	if ((vma->vm_flags & (VM_SHARED|VM_WRITE)) != (VM_SHARED|VM_WRITE))
		return -EACCES;

	mapping = vma->vm_file->f_mapping;

	offset = (loff_t)(start - vma->vm_start)
			+ ((loff_t)vma->vm_pgoff << PAGE_SHIFT);
	endoff = (loff_t)(end - vma->vm_start - 1)
			+ ((loff_t)vma->vm_pgoff << PAGE_SHIFT);

	/* vmtruncate_range needs to take i_mutex and i_alloc_sem */
	up_read(&current->mm->mmap_sem);
	error = vmtruncate_range(mapping->host, offset, endoff);
	down_read(&current->mm->mmap_sem);
	return error;
}

#ifdef CONFIG_MEMORY_FAILURE
/*
 * Error injection support for memory error handling.
 */
static int madvise_hwpoison(unsigned long start, unsigned long end)
{
	int ret = 0;

	if (!capable(CAP_SYS_ADMIN))
		return -EPERM;
	for (; start < end; start += PAGE_SIZE) {
		struct page *p;
		int ret = get_user_pages(current, current->mm, start, 1,
						0, 0, &p, NULL);
		if (ret != 1)
			return ret;
		printk(KERN_INFO "Injecting memory failure for page %lx at %lx\n",
		       page_to_pfn(p), start);
		/* Ignore return value for now */
		__memory_failure(page_to_pfn(p), 0, 1);
		put_page(p);
	}
	return ret;
}
#endif

static long
madvise_vma(struct vm_area_struct *vma, struct vm_area_struct **prev,
		unsigned long start, unsigned long end, int behavior)
{
	switch (behavior) {
	case MADV_REMOVE:
		return madvise_remove(vma, prev, start, end);
	case MADV_WILLNEED:
		return madvise_willneed(vma, prev, start, end);
	case MADV_DONTNEED:
		return madvise_dontneed(vma, prev, start, end);
	default:
		return madvise_behavior(vma, prev, start, end, behavior);
	}
}

static int
madvise_behavior_valid(int behavior)
{
	switch (behavior) {
	case MADV_DOFORK:
	case MADV_DONTFORK:
	case MADV_NORMAL:
	case MADV_SEQUENTIAL:
	case MADV_RANDOM:
	case MADV_REMOVE:
	case MADV_WILLNEED:
	case MADV_DONTNEED:
#ifdef CONFIG_KSM
	case MADV_MERGEABLE:
	case MADV_UNMERGEABLE:
#endif
		return 1;

	default:
		return 0;
	}
}

/*
 * The madvise(2) system call.
 *
 * Applications can use madvise() to advise the kernel how it should
 * handle paging I/O in this VM area.  The idea is to help the kernel
 * use appropriate read-ahead and caching techniques.  The information
 * provided is advisory only, and can be safely disregarded by the
 * kernel without affecting the correct operation of the application.
 *
 * behavior values:
 *  MADV_NORMAL - the default behavior is to read clusters.  This
 *		results in some read-ahead and read-behind.
 *  MADV_RANDOM - the system should read the minimum amount of data
 *		on any access, since it is unlikely that the appli-
 *		cation will need more than what it asks for.
 *  MADV_SEQUENTIAL - pages in the given range will probably be accessed
 *		once, so they can be aggressively read ahead, and
 *		can be freed soon after they are accessed.
 *  MADV_WILLNEED - the application is notifying the system to read
 *		some pages ahead.
 *  MADV_DONTNEED - the application is finished with the given range,
 *		so the kernel can free resources associated with it.
 *  MADV_REMOVE - the application wants to free up the given range of
 *		pages and associated backing store.
 *  MADV_DONTFORK - omit this area from child's address space when forking:
 *		typically, to avoid COWing pages pinned by get_user_pages().
 *  MADV_DOFORK - cancel MADV_DONTFORK: no longer omit this area when forking.
 *  MADV_MERGEABLE - the application recommends that KSM try to merge pages in
 *		this area with pages of identical content from other such areas.
 *  MADV_UNMERGEABLE- cancel MADV_MERGEABLE: no longer merge pages with others.
 *
 * return values:
 *  zero    - success
 *  -EINVAL - start + len < 0, start is not page-aligned,
 *		"behavior" is not a valid value, or application
 *		is attempting to release locked or shared pages.
 *  -ENOMEM - addresses in the specified range are not currently
 *		mapped, or are outside the AS of the process.
 *  -EIO    - an I/O error occurred while paging in data.
 *  -EBADF  - map exists, but area maps something that isn't a file.
 *  -EAGAIN - a kernel resource was temporarily unavailable.
 */
SYSCALL_DEFINE3(madvise, unsigned long, start, size_t, len_in, int, behavior)
{
	unsigned long end, tmp;
	struct vm_area_struct * vma, *prev;
	int unmapped_error = 0;
	int error = -EINVAL;
	int write;
	size_t len;

#ifdef CONFIG_MEMORY_FAILURE
	if (behavior == MADV_HWPOISON)
		return madvise_hwpoison(start, start+len_in);
#endif
	if (!madvise_behavior_valid(behavior))
		return error;

	write = madvise_need_mmap_write(behavior);
	if (write)
		down_write(&current->mm->mmap_sem);
	else
		down_read(&current->mm->mmap_sem);

	if (start & ~PAGE_MASK)
		goto out;
	len = (len_in + ~PAGE_MASK) & PAGE_MASK;

	/* Check to see whether len was rounded up from small -ve to zero */
	if (len_in && !len)
		goto out;

	end = start + len;
	if (end < start)
		goto out;

	error = 0;
	if (end == start)
		goto out;

	/*
	 * If the interval [start,end) covers some unmapped address
	 * ranges, just ignore them, but return -ENOMEM at the end.
	 * - different from the way of handling in mlock etc.
	 */
	vma = find_vma_prev(current->mm, start, &prev);
	if (vma && start > vma->vm_start)
		prev = vma;

	for (;;) {
		/* Still start < end. */
		error = -ENOMEM;
		if (!vma)
			goto out;

		/* Here start < (end|vma->vm_end). */
		if (start < vma->vm_start) {
			unmapped_error = -ENOMEM;
			start = vma->vm_start;
			if (start >= end)
				goto out;
		}

		/* Here vma->vm_start <= start < (end|vma->vm_end) */
		tmp = vma->vm_end;
		if (end < tmp)
			tmp = end;

		/* Here vma->vm_start <= start < tmp <= (end|vma->vm_end). */
		error = madvise_vma(vma, &prev, start, tmp, behavior);
		if (error)
			goto out;
		start = tmp;
		if (prev && start < prev->vm_end)
			start = prev->vm_end;
		error = unmapped_error;
		if (start >= end)
			goto out;
		if (prev)
			vma = prev->vm_next;
		else	/* madvise_remove dropped mmap_sem */
			vma = find_vma(current->mm, start);
	}
out:
	if (write)
		up_write(&current->mm->mmap_sem);
	else
		up_read(&current->mm->mmap_sem);

	return error;
}
Commit	Line	Data
1da177e4 LT	1	/*
	2	* linux/mm/madvise.c
	3	*
	4	* Copyright (C) 1999 Linus Torvalds
	5	* Copyright (C) 2002 Christoph Hellwig
	6	*/
	7
	8	#include <linux/mman.h>
	9	#include <linux/pagemap.h>
	10	#include <linux/syscalls.h>
05b74384	11	#include <linux/mempolicy.h>
1da177e4	12	#include <linux/hugetlb.h>
e8edc6e0	13	#include <linux/sched.h>
f8af4da3	14	#include <linux/ksm.h>
1da177e4	15
0a27a14a NP	16	/*
	17	* Any behaviour which results in changes to the vma->vm_flags needs to
	18	* take mmap_sem for writing. Others, which simply traverse vmas, need
	19	* to only take it for reading.
	20	*/
	21	static int madvise_need_mmap_write(int behavior)
	22	{
	23	switch (behavior) {
	24	case MADV_REMOVE:
	25	case MADV_WILLNEED:
	26	case MADV_DONTNEED:
	27	return 0;
	28	default:
	29	/* be safe, default to 1. list exceptions explicitly */
	30	return 1;
	31	}
	32	}
	33
1da177e4 LT	34	/*
	35	* We can potentially split a vm area into separate
	36	* areas, each area with its own behavior.
	37	*/
05b74384 PM	38	static long madvise_behavior(struct vm_area_struct * vma,
	39	struct vm_area_struct **prev,
	40	unsigned long start, unsigned long end, int behavior)
1da177e4 LT	41	{
	42	struct mm_struct * mm = vma->vm_mm;
	43	int error = 0;
05b74384	44	pgoff_t pgoff;
3866ea90	45	unsigned long new_flags = vma->vm_flags;
e798c6e8 PM	46
e798c6e8 PM	47	switch (behavior) {
f8225661 MT	48	case MADV_NORMAL:
	49	new_flags = new_flags & ~VM_RAND_READ & ~VM_SEQ_READ;
	50	break;
e798c6e8	51	case MADV_SEQUENTIAL:
f8225661	52	new_flags = (new_flags & ~VM_RAND_READ) \| VM_SEQ_READ;
e798c6e8 PM	53	break;
e798c6e8 PM	54	case MADV_RANDOM:
f8225661	55	new_flags = (new_flags & ~VM_SEQ_READ) \| VM_RAND_READ;
e798c6e8	56	break;
f8225661 MT	57	case MADV_DONTFORK:
	58	new_flags \|= VM_DONTCOPY;
	59	break;
	60	case MADV_DOFORK:
3866ea90 HD	61	if (vma->vm_flags & VM_IO) {
	62	error = -EINVAL;
	63	goto out;
	64	}
f8225661	65	new_flags &= ~VM_DONTCOPY;
e798c6e8	66	break;
f8af4da3 HD	67	case MADV_MERGEABLE:
	68	case MADV_UNMERGEABLE:
	69	error = ksm_madvise(vma, start, end, behavior, &new_flags);
	70	if (error)
	71	goto out;
	72	break;
e798c6e8 PM	73	}
e798c6e8 PM	74
05b74384 PM	75	if (new_flags == vma->vm_flags) {
05b74384 PM	76	*prev = vma;
836d5ffd	77	goto out;
05b74384 PM	78	}
	79
	80	pgoff = vma->vm_pgoff + ((start - vma->vm_start) >> PAGE_SHIFT);
	81	prev = vma_merge(mm, prev, start, end, new_flags, vma->anon_vma,
	82	vma->vm_file, pgoff, vma_policy(vma));
	83	if (*prev) {
	84	vma = *prev;
	85	goto success;
	86	}
	87
	88	*prev = vma;
1da177e4 LT	89
	90	if (start != vma->vm_start) {
	91	error = split_vma(mm, vma, start, 1);
	92	if (error)
	93	goto out;
	94	}
	95
	96	if (end != vma->vm_end) {
	97	error = split_vma(mm, vma, end, 0);
	98	if (error)
	99	goto out;
	100	}
	101
836d5ffd	102	success:
1da177e4 LT	103	/*
	104	* vm_flags is protected by the mmap_sem held in write mode.
	105	*/
e798c6e8	106	vma->vm_flags = new_flags;
1da177e4 LT	107
	108	out:
	109	if (error == -ENOMEM)
	110	error = -EAGAIN;
	111	return error;
	112	}
	113
	114	/*
	115	* Schedule all required I/O operations. Do not wait for completion.
	116	*/
	117	static long madvise_willneed(struct vm_area_struct * vma,
05b74384	118	struct vm_area_struct ** prev,
1da177e4 LT	119	unsigned long start, unsigned long end)
	120	{
	121	struct file *file = vma->vm_file;
	122
1bef4003 S	123	if (!file)
	124	return -EBADF;
	125
70688e4d	126	if (file->f_mapping->a_ops->get_xip_mem) {
fe77ba6f CO	127	/* no bad return value, but ignore advice */
	128	return 0;
	129	}
	130
05b74384	131	*prev = vma;
1da177e4 LT	132	start = ((start - vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff;
	133	if (end > vma->vm_end)
	134	end = vma->vm_end;
	135	end = ((end - vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff;
	136
f7e839dd	137	force_page_cache_readahead(file->f_mapping, file, start, end - start);
1da177e4 LT	138	return 0;
	139	}
	140
	141	/*
	142	* Application no longer needs these pages. If the pages are dirty,
	143	* it's OK to just throw them away. The app will be more careful about
	144	* data it wants to keep. Be sure to free swap resources too. The
7e6cbea3	145	* zap_page_range call sets things up for shrink_active_list to actually free
1da177e4 LT	146	* these pages later if no one else has touched them in the meantime,
1da177e4 LT	147	* although we could add these pages to a global reuse list for
7e6cbea3	148	* shrink_active_list to pick up before reclaiming other pages.
1da177e4 LT	149	*
	150	* NB: This interface discards data rather than pushes it out to swap,
	151	* as some implementations do. This has performance implications for
	152	* applications like large transactional databases which want to discard
	153	* pages in anonymous maps after committing to backing store the data
	154	* that was kept in them. There is no reason to write this data out to
	155	* the swap area if the application is discarding it.
	156	*
	157	* An interface that causes the system to free clean pages and flush
	158	* dirty pages is already available as msync(MS_INVALIDATE).
	159	*/
	160	static long madvise_dontneed(struct vm_area_struct * vma,
05b74384	161	struct vm_area_struct ** prev,
1da177e4 LT	162	unsigned long start, unsigned long end)
1da177e4 LT	163	{
05b74384	164	*prev = vma;
6aab341e	165	if (vma->vm_flags & (VM_LOCKED\|VM_HUGETLB\|VM_PFNMAP))
1da177e4 LT	166	return -EINVAL;
	167
	168	if (unlikely(vma->vm_flags & VM_NONLINEAR)) {
	169	struct zap_details details = {
	170	.nonlinear_vma = vma,
	171	.last_index = ULONG_MAX,
	172	};
	173	zap_page_range(vma, start, end - start, &details);
	174	} else
	175	zap_page_range(vma, start, end - start, NULL);
	176	return 0;
	177	}
	178
f6b3ec23 BP	179	/*
	180	* Application wants to free up the pages and associated backing store.
	181	* This is effectively punching a hole into the middle of a file.
	182	*
	183	* NOTE: Currently, only shmfs/tmpfs is supported for this operation.
	184	* Other filesystems return -ENOSYS.
	185	*/
	186	static long madvise_remove(struct vm_area_struct *vma,
00e9fa2d	187	struct vm_area_struct **prev,
f6b3ec23 BP	188	unsigned long start, unsigned long end)
	189	{
	190	struct address_space *mapping;
90ed52eb HD	191	loff_t offset, endoff;
90ed52eb HD	192	int error;
f6b3ec23	193
90ed52eb	194	prev = NULL; / tell sys_madvise we drop mmap_sem */
00e9fa2d	195
f6b3ec23 BP	196	if (vma->vm_flags & (VM_LOCKED\|VM_NONLINEAR\|VM_HUGETLB))
	197	return -EINVAL;
	198
	199	if (!vma->vm_file \|\| !vma->vm_file->f_mapping
	200	\|\| !vma->vm_file->f_mapping->host) {
	201	return -EINVAL;
	202	}
	203
69cf0fac HD	204	if ((vma->vm_flags & (VM_SHARED\|VM_WRITE)) != (VM_SHARED\|VM_WRITE))
	205	return -EACCES;
	206
f6b3ec23 BP	207	mapping = vma->vm_file->f_mapping;
	208
	209	offset = (loff_t)(start - vma->vm_start)
	210	+ ((loff_t)vma->vm_pgoff << PAGE_SHIFT);
	211	endoff = (loff_t)(end - vma->vm_start - 1)
	212	+ ((loff_t)vma->vm_pgoff << PAGE_SHIFT);
90ed52eb HD	213
90ed52eb HD	214	/* vmtruncate_range needs to take i_mutex and i_alloc_sem */
0a27a14a	215	up_read(&current->mm->mmap_sem);
90ed52eb	216	error = vmtruncate_range(mapping->host, offset, endoff);
0a27a14a	217	down_read(&current->mm->mmap_sem);
90ed52eb	218	return error;
f6b3ec23 BP	219	}
f6b3ec23 BP	220
9893e49d AK	221	#ifdef CONFIG_MEMORY_FAILURE
	222	/*
	223	* Error injection support for memory error handling.
	224	*/
	225	static int madvise_hwpoison(unsigned long start, unsigned long end)
	226	{
	227	int ret = 0;
	228
	229	if (!capable(CAP_SYS_ADMIN))
	230	return -EPERM;
	231	for (; start < end; start += PAGE_SIZE) {
	232	struct page *p;
	233	int ret = get_user_pages(current, current->mm, start, 1,
	234	0, 0, &p, NULL);
	235	if (ret != 1)
	236	return ret;
	237	printk(KERN_INFO "Injecting memory failure for page %lx at %lx\n",
	238	page_to_pfn(p), start);
	239	/* Ignore return value for now */
	240	__memory_failure(page_to_pfn(p), 0, 1);
	241	put_page(p);
	242	}
	243	return ret;
	244	}
	245	#endif
	246
165cd402	247	static long
	248	madvise_vma(struct vm_area_struct vma, struct vm_area_struct *prev,
	249	unsigned long start, unsigned long end, int behavior)
1da177e4	250	{
1da177e4	251	switch (behavior) {
f6b3ec23	252	case MADV_REMOVE:
3866ea90	253	return madvise_remove(vma, prev, start, end);
1da177e4	254	case MADV_WILLNEED:
3866ea90	255	return madvise_willneed(vma, prev, start, end);
1da177e4	256	case MADV_DONTNEED:
3866ea90	257	return madvise_dontneed(vma, prev, start, end);
1da177e4	258	default:
3866ea90	259	return madvise_behavior(vma, prev, start, end, behavior);
1da177e4	260	}
1da177e4 LT	261	}
1da177e4 LT	262
75927af8 NP	263	static int
	264	madvise_behavior_valid(int behavior)
	265	{
	266	switch (behavior) {
	267	case MADV_DOFORK:
	268	case MADV_DONTFORK:
	269	case MADV_NORMAL:
	270	case MADV_SEQUENTIAL:
	271	case MADV_RANDOM:
	272	case MADV_REMOVE:
	273	case MADV_WILLNEED:
	274	case MADV_DONTNEED:
f8af4da3 HD	275	#ifdef CONFIG_KSM
	276	case MADV_MERGEABLE:
	277	case MADV_UNMERGEABLE:
	278	#endif
75927af8 NP	279	return 1;
	280
	281	default:
	282	return 0;
	283	}
	284	}
3866ea90	285
1da177e4 LT	286	/*
	287	* The madvise(2) system call.
	288	*
	289	* Applications can use madvise() to advise the kernel how it should
	290	* handle paging I/O in this VM area. The idea is to help the kernel
	291	* use appropriate read-ahead and caching techniques. The information
	292	* provided is advisory only, and can be safely disregarded by the
	293	* kernel without affecting the correct operation of the application.
	294	*
	295	* behavior values:
	296	* MADV_NORMAL - the default behavior is to read clusters. This
	297	* results in some read-ahead and read-behind.
	298	* MADV_RANDOM - the system should read the minimum amount of data
	299	* on any access, since it is unlikely that the appli-
	300	* cation will need more than what it asks for.
	301	* MADV_SEQUENTIAL - pages in the given range will probably be accessed
	302	* once, so they can be aggressively read ahead, and
	303	* can be freed soon after they are accessed.
	304	* MADV_WILLNEED - the application is notifying the system to read
	305	* some pages ahead.
	306	* MADV_DONTNEED - the application is finished with the given range,
	307	* so the kernel can free resources associated with it.
f6b3ec23 BP	308	* MADV_REMOVE - the application wants to free up the given range of
f6b3ec23 BP	309	* pages and associated backing store.
3866ea90 HD	310	* MADV_DONTFORK - omit this area from child's address space when forking:
	311	* typically, to avoid COWing pages pinned by get_user_pages().
	312	* MADV_DOFORK - cancel MADV_DONTFORK: no longer omit this area when forking.
f8af4da3 HD	313	* MADV_MERGEABLE - the application recommends that KSM try to merge pages in
	314	* this area with pages of identical content from other such areas.
	315	* MADV_UNMERGEABLE- cancel MADV_MERGEABLE: no longer merge pages with others.
1da177e4 LT	316	*
	317	* return values:
	318	* zero - success
	319	* -EINVAL - start + len < 0, start is not page-aligned,
	320	* "behavior" is not a valid value, or application
	321	* is attempting to release locked or shared pages.
	322	* -ENOMEM - addresses in the specified range are not currently
	323	* mapped, or are outside the AS of the process.
	324	* -EIO - an I/O error occurred while paging in data.
	325	* -EBADF - map exists, but area maps something that isn't a file.
	326	* -EAGAIN - a kernel resource was temporarily unavailable.
	327	*/
3480b257	328	SYSCALL_DEFINE3(madvise, unsigned long, start, size_t, len_in, int, behavior)
1da177e4	329	{
05b74384 PM	330	unsigned long end, tmp;
05b74384 PM	331	struct vm_area_struct * vma, *prev;
1da177e4 LT	332	int unmapped_error = 0;
1da177e4 LT	333	int error = -EINVAL;
f7977793	334	int write;
1da177e4 LT	335	size_t len;
1da177e4 LT	336
9893e49d AK	337	#ifdef CONFIG_MEMORY_FAILURE
	338	if (behavior == MADV_HWPOISON)
	339	return madvise_hwpoison(start, start+len_in);
	340	#endif
75927af8 NP	341	if (!madvise_behavior_valid(behavior))
	342	return error;
	343
f7977793 JB	344	write = madvise_need_mmap_write(behavior);
f7977793 JB	345	if (write)
0a27a14a NP	346	down_write(&current->mm->mmap_sem);
	347	else
	348	down_read(&current->mm->mmap_sem);
1da177e4 LT	349
	350	if (start & ~PAGE_MASK)
	351	goto out;
	352	len = (len_in + ~PAGE_MASK) & PAGE_MASK;
	353
	354	/* Check to see whether len was rounded up from small -ve to zero */
	355	if (len_in && !len)
	356	goto out;
	357
	358	end = start + len;
	359	if (end < start)
	360	goto out;
	361
	362	error = 0;
	363	if (end == start)
	364	goto out;
	365
	366	/*
	367	* If the interval [start,end) covers some unmapped address
	368	* ranges, just ignore them, but return -ENOMEM at the end.
05b74384	369	* - different from the way of handling in mlock etc.
1da177e4	370	*/
05b74384	371	vma = find_vma_prev(current->mm, start, &prev);
836d5ffd HD	372	if (vma && start > vma->vm_start)
	373	prev = vma;
	374
1da177e4 LT	375	for (;;) {
	376	/* Still start < end. */
	377	error = -ENOMEM;
	378	if (!vma)
	379	goto out;
	380
05b74384	381	/* Here start < (end\|vma->vm_end). */
1da177e4 LT	382	if (start < vma->vm_start) {
	383	unmapped_error = -ENOMEM;
	384	start = vma->vm_start;
05b74384 PM	385	if (start >= end)
05b74384 PM	386	goto out;
1da177e4 LT	387	}
1da177e4 LT	388
05b74384 PM	389	/* Here vma->vm_start <= start < (end\|vma->vm_end) */
	390	tmp = vma->vm_end;
	391	if (end < tmp)
	392	tmp = end;
1da177e4	393
05b74384 PM	394	/* Here vma->vm_start <= start < tmp <= (end\|vma->vm_end). */
05b74384 PM	395	error = madvise_vma(vma, &prev, start, tmp, behavior);
1da177e4 LT	396	if (error)
1da177e4 LT	397	goto out;
05b74384	398	start = tmp;
90ed52eb	399	if (prev && start < prev->vm_end)
05b74384 PM	400	start = prev->vm_end;
	401	error = unmapped_error;
	402	if (start >= end)
	403	goto out;
90ed52eb HD	404	if (prev)
	405	vma = prev->vm_next;
	406	else /* madvise_remove dropped mmap_sem */
	407	vma = find_vma(current->mm, start);
1da177e4	408	}
1da177e4	409	out:
f7977793	410	if (write)
0a27a14a NP	411	up_write(&current->mm->mmap_sem);
	412	else
	413	up_read(&current->mm->mmap_sem);
	414
1da177e4 LT	415	return error;
1da177e4 LT	416	}