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![Rasmus Villemoes](/assets/img/avatar_default.png)
In madvise(), there doesn't seem to be any reason for taking the ¤t->mm->mmap_sem before start and len_in have been validated. Incidentally, this removes the need for the out: label. [akpm@linux-foundation.org: s/out_plug/out/, per David] Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk> Acked-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> Acked-by: David Rientjes <rientjes@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
550 lines
14 KiB
C
550 lines
14 KiB
C
/*
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* linux/mm/madvise.c
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*
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* Copyright (C) 1999 Linus Torvalds
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* Copyright (C) 2002 Christoph Hellwig
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*/
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#include <linux/mman.h>
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#include <linux/pagemap.h>
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#include <linux/syscalls.h>
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#include <linux/mempolicy.h>
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#include <linux/page-isolation.h>
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#include <linux/hugetlb.h>
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#include <linux/falloc.h>
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#include <linux/sched.h>
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#include <linux/ksm.h>
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#include <linux/fs.h>
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#include <linux/file.h>
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#include <linux/blkdev.h>
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#include <linux/swap.h>
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#include <linux/swapops.h>
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/*
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* Any behaviour which results in changes to the vma->vm_flags needs to
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* take mmap_sem for writing. Others, which simply traverse vmas, need
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* to only take it for reading.
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*/
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static int madvise_need_mmap_write(int behavior)
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{
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switch (behavior) {
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case MADV_REMOVE:
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case MADV_WILLNEED:
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case MADV_DONTNEED:
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return 0;
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default:
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/* be safe, default to 1. list exceptions explicitly */
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return 1;
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}
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}
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/*
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* We can potentially split a vm area into separate
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* areas, each area with its own behavior.
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*/
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static long madvise_behavior(struct vm_area_struct * vma,
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struct vm_area_struct **prev,
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unsigned long start, unsigned long end, int behavior)
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{
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struct mm_struct * mm = vma->vm_mm;
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int error = 0;
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pgoff_t pgoff;
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unsigned long new_flags = vma->vm_flags;
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switch (behavior) {
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case MADV_NORMAL:
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new_flags = new_flags & ~VM_RAND_READ & ~VM_SEQ_READ;
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break;
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case MADV_SEQUENTIAL:
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new_flags = (new_flags & ~VM_RAND_READ) | VM_SEQ_READ;
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break;
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case MADV_RANDOM:
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new_flags = (new_flags & ~VM_SEQ_READ) | VM_RAND_READ;
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break;
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case MADV_DONTFORK:
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new_flags |= VM_DONTCOPY;
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break;
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case MADV_DOFORK:
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if (vma->vm_flags & VM_IO) {
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error = -EINVAL;
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goto out;
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}
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new_flags &= ~VM_DONTCOPY;
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break;
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case MADV_DONTDUMP:
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new_flags |= VM_DONTDUMP;
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break;
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case MADV_DODUMP:
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if (new_flags & VM_SPECIAL) {
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error = -EINVAL;
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goto out;
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}
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new_flags &= ~VM_DONTDUMP;
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break;
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case MADV_MERGEABLE:
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case MADV_UNMERGEABLE:
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error = ksm_madvise(vma, start, end, behavior, &new_flags);
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if (error)
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goto out;
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break;
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case MADV_HUGEPAGE:
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case MADV_NOHUGEPAGE:
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error = hugepage_madvise(vma, &new_flags, behavior);
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if (error)
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goto out;
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break;
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}
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if (new_flags == vma->vm_flags) {
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*prev = vma;
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goto out;
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}
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pgoff = vma->vm_pgoff + ((start - vma->vm_start) >> PAGE_SHIFT);
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*prev = vma_merge(mm, *prev, start, end, new_flags, vma->anon_vma,
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vma->vm_file, pgoff, vma_policy(vma));
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if (*prev) {
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vma = *prev;
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goto success;
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}
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*prev = vma;
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if (start != vma->vm_start) {
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error = split_vma(mm, vma, start, 1);
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if (error)
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goto out;
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}
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if (end != vma->vm_end) {
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error = split_vma(mm, vma, end, 0);
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if (error)
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goto out;
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}
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success:
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/*
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* vm_flags is protected by the mmap_sem held in write mode.
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*/
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vma->vm_flags = new_flags;
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out:
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if (error == -ENOMEM)
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error = -EAGAIN;
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return error;
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}
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#ifdef CONFIG_SWAP
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static int swapin_walk_pmd_entry(pmd_t *pmd, unsigned long start,
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unsigned long end, struct mm_walk *walk)
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{
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pte_t *orig_pte;
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struct vm_area_struct *vma = walk->private;
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unsigned long index;
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if (pmd_none_or_trans_huge_or_clear_bad(pmd))
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return 0;
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for (index = start; index != end; index += PAGE_SIZE) {
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pte_t pte;
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swp_entry_t entry;
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struct page *page;
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spinlock_t *ptl;
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orig_pte = pte_offset_map_lock(vma->vm_mm, pmd, start, &ptl);
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pte = *(orig_pte + ((index - start) / PAGE_SIZE));
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pte_unmap_unlock(orig_pte, ptl);
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if (pte_present(pte) || pte_none(pte) || pte_file(pte))
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continue;
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entry = pte_to_swp_entry(pte);
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if (unlikely(non_swap_entry(entry)))
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continue;
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page = read_swap_cache_async(entry, GFP_HIGHUSER_MOVABLE,
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vma, index);
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if (page)
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page_cache_release(page);
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}
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return 0;
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}
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static void force_swapin_readahead(struct vm_area_struct *vma,
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unsigned long start, unsigned long end)
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{
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struct mm_walk walk = {
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.mm = vma->vm_mm,
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.pmd_entry = swapin_walk_pmd_entry,
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.private = vma,
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};
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walk_page_range(start, end, &walk);
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lru_add_drain(); /* Push any new pages onto the LRU now */
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}
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static void force_shm_swapin_readahead(struct vm_area_struct *vma,
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unsigned long start, unsigned long end,
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struct address_space *mapping)
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{
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pgoff_t index;
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struct page *page;
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swp_entry_t swap;
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for (; start < end; start += PAGE_SIZE) {
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index = ((start - vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff;
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page = find_get_page(mapping, index);
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if (!radix_tree_exceptional_entry(page)) {
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if (page)
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page_cache_release(page);
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continue;
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}
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swap = radix_to_swp_entry(page);
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page = read_swap_cache_async(swap, GFP_HIGHUSER_MOVABLE,
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NULL, 0);
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if (page)
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page_cache_release(page);
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}
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lru_add_drain(); /* Push any new pages onto the LRU now */
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}
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#endif /* CONFIG_SWAP */
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/*
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* Schedule all required I/O operations. Do not wait for completion.
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*/
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static long madvise_willneed(struct vm_area_struct * vma,
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struct vm_area_struct ** prev,
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unsigned long start, unsigned long end)
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{
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struct file *file = vma->vm_file;
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#ifdef CONFIG_SWAP
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if (!file || mapping_cap_swap_backed(file->f_mapping)) {
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*prev = vma;
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if (!file)
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force_swapin_readahead(vma, start, end);
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else
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force_shm_swapin_readahead(vma, start, end,
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file->f_mapping);
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return 0;
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}
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#endif
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if (!file)
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return -EBADF;
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if (file->f_mapping->a_ops->get_xip_mem) {
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/* no bad return value, but ignore advice */
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return 0;
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}
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*prev = vma;
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start = ((start - vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff;
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if (end > vma->vm_end)
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end = vma->vm_end;
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end = ((end - vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff;
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force_page_cache_readahead(file->f_mapping, file, start, end - start);
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return 0;
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}
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/*
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* Application no longer needs these pages. If the pages are dirty,
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* it's OK to just throw them away. The app will be more careful about
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* data it wants to keep. Be sure to free swap resources too. The
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* zap_page_range call sets things up for shrink_active_list to actually free
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* these pages later if no one else has touched them in the meantime,
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* although we could add these pages to a global reuse list for
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* shrink_active_list to pick up before reclaiming other pages.
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*
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* NB: This interface discards data rather than pushes it out to swap,
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* as some implementations do. This has performance implications for
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* applications like large transactional databases which want to discard
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* pages in anonymous maps after committing to backing store the data
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* that was kept in them. There is no reason to write this data out to
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* the swap area if the application is discarding it.
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*
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* An interface that causes the system to free clean pages and flush
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* dirty pages is already available as msync(MS_INVALIDATE).
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*/
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static long madvise_dontneed(struct vm_area_struct * vma,
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struct vm_area_struct ** prev,
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unsigned long start, unsigned long end)
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{
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*prev = vma;
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if (vma->vm_flags & (VM_LOCKED|VM_HUGETLB|VM_PFNMAP))
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return -EINVAL;
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if (unlikely(vma->vm_flags & VM_NONLINEAR)) {
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struct zap_details details = {
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.nonlinear_vma = vma,
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.last_index = ULONG_MAX,
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};
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zap_page_range(vma, start, end - start, &details);
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} else
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zap_page_range(vma, start, end - start, NULL);
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return 0;
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}
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/*
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* Application wants to free up the pages and associated backing store.
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* This is effectively punching a hole into the middle of a file.
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*
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* NOTE: Currently, only shmfs/tmpfs is supported for this operation.
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* Other filesystems return -ENOSYS.
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*/
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static long madvise_remove(struct vm_area_struct *vma,
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struct vm_area_struct **prev,
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unsigned long start, unsigned long end)
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{
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loff_t offset;
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int error;
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struct file *f;
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*prev = NULL; /* tell sys_madvise we drop mmap_sem */
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if (vma->vm_flags & (VM_LOCKED|VM_NONLINEAR|VM_HUGETLB))
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return -EINVAL;
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f = vma->vm_file;
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if (!f || !f->f_mapping || !f->f_mapping->host) {
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return -EINVAL;
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}
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if ((vma->vm_flags & (VM_SHARED|VM_WRITE)) != (VM_SHARED|VM_WRITE))
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return -EACCES;
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offset = (loff_t)(start - vma->vm_start)
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+ ((loff_t)vma->vm_pgoff << PAGE_SHIFT);
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/*
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* Filesystem's fallocate may need to take i_mutex. We need to
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* explicitly grab a reference because the vma (and hence the
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* vma's reference to the file) can go away as soon as we drop
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* mmap_sem.
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*/
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get_file(f);
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up_read(¤t->mm->mmap_sem);
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error = do_fallocate(f,
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FALLOC_FL_PUNCH_HOLE | FALLOC_FL_KEEP_SIZE,
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offset, end - start);
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fput(f);
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down_read(¤t->mm->mmap_sem);
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return error;
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}
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#ifdef CONFIG_MEMORY_FAILURE
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/*
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* Error injection support for memory error handling.
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*/
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static int madvise_hwpoison(int bhv, unsigned long start, unsigned long end)
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{
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int ret = 0;
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if (!capable(CAP_SYS_ADMIN))
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return -EPERM;
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for (; start < end; start += PAGE_SIZE) {
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struct page *p;
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int ret = get_user_pages_fast(start, 1, 0, &p);
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if (ret != 1)
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return ret;
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if (bhv == MADV_SOFT_OFFLINE) {
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printk(KERN_INFO "Soft offlining page %lx at %lx\n",
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page_to_pfn(p), start);
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ret = soft_offline_page(p, MF_COUNT_INCREASED);
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if (ret)
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break;
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continue;
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}
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printk(KERN_INFO "Injecting memory failure for page %lx at %lx\n",
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page_to_pfn(p), start);
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/* Ignore return value for now */
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memory_failure(page_to_pfn(p), 0, MF_COUNT_INCREASED);
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}
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return ret;
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}
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#endif
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static long
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madvise_vma(struct vm_area_struct *vma, struct vm_area_struct **prev,
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unsigned long start, unsigned long end, int behavior)
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{
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switch (behavior) {
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case MADV_REMOVE:
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return madvise_remove(vma, prev, start, end);
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case MADV_WILLNEED:
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return madvise_willneed(vma, prev, start, end);
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case MADV_DONTNEED:
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return madvise_dontneed(vma, prev, start, end);
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default:
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return madvise_behavior(vma, prev, start, end, behavior);
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}
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}
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static int
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madvise_behavior_valid(int behavior)
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{
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switch (behavior) {
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case MADV_DOFORK:
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case MADV_DONTFORK:
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case MADV_NORMAL:
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case MADV_SEQUENTIAL:
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case MADV_RANDOM:
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case MADV_REMOVE:
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case MADV_WILLNEED:
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case MADV_DONTNEED:
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#ifdef CONFIG_KSM
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case MADV_MERGEABLE:
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case MADV_UNMERGEABLE:
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#endif
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#ifdef CONFIG_TRANSPARENT_HUGEPAGE
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case MADV_HUGEPAGE:
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case MADV_NOHUGEPAGE:
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#endif
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case MADV_DONTDUMP:
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case MADV_DODUMP:
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return 1;
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default:
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return 0;
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}
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}
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/*
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* The madvise(2) system call.
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*
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* Applications can use madvise() to advise the kernel how it should
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* handle paging I/O in this VM area. The idea is to help the kernel
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* use appropriate read-ahead and caching techniques. The information
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* provided is advisory only, and can be safely disregarded by the
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* kernel without affecting the correct operation of the application.
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*
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* behavior values:
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* MADV_NORMAL - the default behavior is to read clusters. This
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* results in some read-ahead and read-behind.
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* MADV_RANDOM - the system should read the minimum amount of data
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* on any access, since it is unlikely that the appli-
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* cation will need more than what it asks for.
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* MADV_SEQUENTIAL - pages in the given range will probably be accessed
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* once, so they can be aggressively read ahead, and
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* can be freed soon after they are accessed.
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* MADV_WILLNEED - the application is notifying the system to read
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* some pages ahead.
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* MADV_DONTNEED - the application is finished with the given range,
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* so the kernel can free resources associated with it.
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* MADV_REMOVE - the application wants to free up the given range of
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* pages and associated backing store.
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* MADV_DONTFORK - omit this area from child's address space when forking:
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* typically, to avoid COWing pages pinned by get_user_pages().
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* MADV_DOFORK - cancel MADV_DONTFORK: no longer omit this area when forking.
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* MADV_MERGEABLE - the application recommends that KSM try to merge pages in
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* this area with pages of identical content from other such areas.
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* MADV_UNMERGEABLE- cancel MADV_MERGEABLE: no longer merge pages with others.
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*
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* return values:
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* zero - success
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* -EINVAL - start + len < 0, start is not page-aligned,
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* "behavior" is not a valid value, or application
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* is attempting to release locked or shared pages.
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* -ENOMEM - addresses in the specified range are not currently
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* mapped, or are outside the AS of the process.
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* -EIO - an I/O error occurred while paging in data.
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* -EBADF - map exists, but area maps something that isn't a file.
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* -EAGAIN - a kernel resource was temporarily unavailable.
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*/
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SYSCALL_DEFINE3(madvise, unsigned long, start, size_t, len_in, int, behavior)
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{
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unsigned long end, tmp;
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struct vm_area_struct * vma, *prev;
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int unmapped_error = 0;
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int error = -EINVAL;
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int write;
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size_t len;
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struct blk_plug plug;
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#ifdef CONFIG_MEMORY_FAILURE
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if (behavior == MADV_HWPOISON || behavior == MADV_SOFT_OFFLINE)
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return madvise_hwpoison(behavior, start, start+len_in);
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#endif
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if (!madvise_behavior_valid(behavior))
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return error;
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if (start & ~PAGE_MASK)
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return error;
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len = (len_in + ~PAGE_MASK) & PAGE_MASK;
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/* Check to see whether len was rounded up from small -ve to zero */
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if (len_in && !len)
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return error;
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end = start + len;
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if (end < start)
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return error;
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error = 0;
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if (end == start)
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return error;
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write = madvise_need_mmap_write(behavior);
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if (write)
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down_write(¤t->mm->mmap_sem);
|
|
else
|
|
down_read(¤t->mm->mmap_sem);
|
|
|
|
/*
|
|
* 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;
|
|
|
|
blk_start_plug(&plug);
|
|
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:
|
|
blk_finish_plug(&plug);
|
|
if (write)
|
|
up_write(¤t->mm->mmap_sem);
|
|
else
|
|
up_read(¤t->mm->mmap_sem);
|
|
|
|
return error;
|
|
}
|