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DEFINITIONS
This source file includes following definitions.
- madvise_need_mmap_write
- madvise_behavior
- madvise_willneed
- madvise_dontneed
- madvise_remove
- madvise_vma
- sys_madvise
/*
* 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>
/*
* 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;
int 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:
new_flags &= ~VM_DONTCOPY;
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, max_sane_readahead(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(¤t->mm->mmap_sem);
error = vmtruncate_range(mapping->host, offset, endoff);
down_read(¤t->mm->mmap_sem);
return error;
}
static long
madvise_vma(struct vm_area_struct *vma, struct vm_area_struct **prev,
unsigned long start, unsigned long end, int behavior)
{
long error;
switch (behavior) {
case MADV_DOFORK:
if (vma->vm_flags & VM_IO) {
error = -EINVAL;
break;
}
case MADV_DONTFORK:
case MADV_NORMAL:
case MADV_SEQUENTIAL:
case MADV_RANDOM:
error = madvise_behavior(vma, prev, start, end, behavior);
break;
case MADV_REMOVE:
error = madvise_remove(vma, prev, start, end);
break;
case MADV_WILLNEED:
error = madvise_willneed(vma, prev, start, end);
break;
case MADV_DONTNEED:
error = madvise_dontneed(vma, prev, start, end);
break;
default:
error = -EINVAL;
break;
}
return error;
}
/*
* 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.
*
* 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.
*/
asmlinkage long sys_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;
write = madvise_need_mmap_write(behavior);
if (write)
down_write(¤t->mm->mmap_sem);
else
down_read(¤t->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(¤t->mm->mmap_sem);
else
up_read(¤t->mm->mmap_sem);
return error;
}