/* * 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> /* * 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 & ~VM_READHINTMASK; switch (behavior) { case MADV_SEQUENTIAL: new_flags |= VM_SEQ_READ; break; case MADV_RANDOM: new_flags |= VM_RAND_READ; break; default: 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_page) { /* 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 refill_inactive 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 * refill_inactive 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; } 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_NORMAL: case MADV_SEQUENTIAL: case MADV_RANDOM: error = madvise_behavior(vma, prev, start, end, behavior); 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. * * 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; size_t len; down_write(¤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 (start < prev->vm_end) start = prev->vm_end; error = unmapped_error; if (start >= end) goto out; vma = prev->vm_next; } out: up_write(¤t->mm->mmap_sem); return error; }