Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 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> |
| 11 | #include <linux/hugetlb.h> |
| 12 | |
| 13 | /* |
| 14 | * We can potentially split a vm area into separate |
| 15 | * areas, each area with its own behavior. |
| 16 | */ |
| 17 | static long madvise_behavior(struct vm_area_struct * vma, unsigned long start, |
| 18 | unsigned long end, int behavior) |
| 19 | { |
| 20 | struct mm_struct * mm = vma->vm_mm; |
| 21 | int error = 0; |
Prasanna Meda | e798c6e | 2005-06-21 17:14:36 -0700 | [diff] [blame^] | 22 | int new_flags = vma->vm_flags & ~VM_READHINTMASK; |
| 23 | |
| 24 | switch (behavior) { |
| 25 | case MADV_SEQUENTIAL: |
| 26 | new_flags |= VM_SEQ_READ; |
| 27 | break; |
| 28 | case MADV_RANDOM: |
| 29 | new_flags |= VM_RAND_READ; |
| 30 | break; |
| 31 | default: |
| 32 | break; |
| 33 | } |
| 34 | |
| 35 | if (new_flags == vma->vm_flags) |
| 36 | goto out; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 37 | |
| 38 | if (start != vma->vm_start) { |
| 39 | error = split_vma(mm, vma, start, 1); |
| 40 | if (error) |
| 41 | goto out; |
| 42 | } |
| 43 | |
| 44 | if (end != vma->vm_end) { |
| 45 | error = split_vma(mm, vma, end, 0); |
| 46 | if (error) |
| 47 | goto out; |
| 48 | } |
| 49 | |
| 50 | /* |
| 51 | * vm_flags is protected by the mmap_sem held in write mode. |
| 52 | */ |
| 53 | VM_ClearReadHint(vma); |
Prasanna Meda | e798c6e | 2005-06-21 17:14:36 -0700 | [diff] [blame^] | 54 | vma->vm_flags = new_flags; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 55 | |
| 56 | out: |
| 57 | if (error == -ENOMEM) |
| 58 | error = -EAGAIN; |
| 59 | return error; |
| 60 | } |
| 61 | |
| 62 | /* |
| 63 | * Schedule all required I/O operations. Do not wait for completion. |
| 64 | */ |
| 65 | static long madvise_willneed(struct vm_area_struct * vma, |
| 66 | unsigned long start, unsigned long end) |
| 67 | { |
| 68 | struct file *file = vma->vm_file; |
| 69 | |
| 70 | if (!file) |
| 71 | return -EBADF; |
| 72 | |
| 73 | start = ((start - vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff; |
| 74 | if (end > vma->vm_end) |
| 75 | end = vma->vm_end; |
| 76 | end = ((end - vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff; |
| 77 | |
| 78 | force_page_cache_readahead(file->f_mapping, |
| 79 | file, start, max_sane_readahead(end - start)); |
| 80 | return 0; |
| 81 | } |
| 82 | |
| 83 | /* |
| 84 | * Application no longer needs these pages. If the pages are dirty, |
| 85 | * it's OK to just throw them away. The app will be more careful about |
| 86 | * data it wants to keep. Be sure to free swap resources too. The |
| 87 | * zap_page_range call sets things up for refill_inactive to actually free |
| 88 | * these pages later if no one else has touched them in the meantime, |
| 89 | * although we could add these pages to a global reuse list for |
| 90 | * refill_inactive to pick up before reclaiming other pages. |
| 91 | * |
| 92 | * NB: This interface discards data rather than pushes it out to swap, |
| 93 | * as some implementations do. This has performance implications for |
| 94 | * applications like large transactional databases which want to discard |
| 95 | * pages in anonymous maps after committing to backing store the data |
| 96 | * that was kept in them. There is no reason to write this data out to |
| 97 | * the swap area if the application is discarding it. |
| 98 | * |
| 99 | * An interface that causes the system to free clean pages and flush |
| 100 | * dirty pages is already available as msync(MS_INVALIDATE). |
| 101 | */ |
| 102 | static long madvise_dontneed(struct vm_area_struct * vma, |
| 103 | unsigned long start, unsigned long end) |
| 104 | { |
| 105 | if ((vma->vm_flags & VM_LOCKED) || is_vm_hugetlb_page(vma)) |
| 106 | return -EINVAL; |
| 107 | |
| 108 | if (unlikely(vma->vm_flags & VM_NONLINEAR)) { |
| 109 | struct zap_details details = { |
| 110 | .nonlinear_vma = vma, |
| 111 | .last_index = ULONG_MAX, |
| 112 | }; |
| 113 | zap_page_range(vma, start, end - start, &details); |
| 114 | } else |
| 115 | zap_page_range(vma, start, end - start, NULL); |
| 116 | return 0; |
| 117 | } |
| 118 | |
| 119 | static long madvise_vma(struct vm_area_struct * vma, unsigned long start, |
| 120 | unsigned long end, int behavior) |
| 121 | { |
| 122 | long error = -EBADF; |
| 123 | |
| 124 | switch (behavior) { |
| 125 | case MADV_NORMAL: |
| 126 | case MADV_SEQUENTIAL: |
| 127 | case MADV_RANDOM: |
| 128 | error = madvise_behavior(vma, start, end, behavior); |
| 129 | break; |
| 130 | |
| 131 | case MADV_WILLNEED: |
| 132 | error = madvise_willneed(vma, start, end); |
| 133 | break; |
| 134 | |
| 135 | case MADV_DONTNEED: |
| 136 | error = madvise_dontneed(vma, start, end); |
| 137 | break; |
| 138 | |
| 139 | default: |
| 140 | error = -EINVAL; |
| 141 | break; |
| 142 | } |
| 143 | |
| 144 | return error; |
| 145 | } |
| 146 | |
| 147 | /* |
| 148 | * The madvise(2) system call. |
| 149 | * |
| 150 | * Applications can use madvise() to advise the kernel how it should |
| 151 | * handle paging I/O in this VM area. The idea is to help the kernel |
| 152 | * use appropriate read-ahead and caching techniques. The information |
| 153 | * provided is advisory only, and can be safely disregarded by the |
| 154 | * kernel without affecting the correct operation of the application. |
| 155 | * |
| 156 | * behavior values: |
| 157 | * MADV_NORMAL - the default behavior is to read clusters. This |
| 158 | * results in some read-ahead and read-behind. |
| 159 | * MADV_RANDOM - the system should read the minimum amount of data |
| 160 | * on any access, since it is unlikely that the appli- |
| 161 | * cation will need more than what it asks for. |
| 162 | * MADV_SEQUENTIAL - pages in the given range will probably be accessed |
| 163 | * once, so they can be aggressively read ahead, and |
| 164 | * can be freed soon after they are accessed. |
| 165 | * MADV_WILLNEED - the application is notifying the system to read |
| 166 | * some pages ahead. |
| 167 | * MADV_DONTNEED - the application is finished with the given range, |
| 168 | * so the kernel can free resources associated with it. |
| 169 | * |
| 170 | * return values: |
| 171 | * zero - success |
| 172 | * -EINVAL - start + len < 0, start is not page-aligned, |
| 173 | * "behavior" is not a valid value, or application |
| 174 | * is attempting to release locked or shared pages. |
| 175 | * -ENOMEM - addresses in the specified range are not currently |
| 176 | * mapped, or are outside the AS of the process. |
| 177 | * -EIO - an I/O error occurred while paging in data. |
| 178 | * -EBADF - map exists, but area maps something that isn't a file. |
| 179 | * -EAGAIN - a kernel resource was temporarily unavailable. |
| 180 | */ |
| 181 | asmlinkage long sys_madvise(unsigned long start, size_t len_in, int behavior) |
| 182 | { |
| 183 | unsigned long end; |
| 184 | struct vm_area_struct * vma; |
| 185 | int unmapped_error = 0; |
| 186 | int error = -EINVAL; |
| 187 | size_t len; |
| 188 | |
| 189 | down_write(¤t->mm->mmap_sem); |
| 190 | |
| 191 | if (start & ~PAGE_MASK) |
| 192 | goto out; |
| 193 | len = (len_in + ~PAGE_MASK) & PAGE_MASK; |
| 194 | |
| 195 | /* Check to see whether len was rounded up from small -ve to zero */ |
| 196 | if (len_in && !len) |
| 197 | goto out; |
| 198 | |
| 199 | end = start + len; |
| 200 | if (end < start) |
| 201 | goto out; |
| 202 | |
| 203 | error = 0; |
| 204 | if (end == start) |
| 205 | goto out; |
| 206 | |
| 207 | /* |
| 208 | * If the interval [start,end) covers some unmapped address |
| 209 | * ranges, just ignore them, but return -ENOMEM at the end. |
| 210 | */ |
| 211 | vma = find_vma(current->mm, start); |
| 212 | for (;;) { |
| 213 | /* Still start < end. */ |
| 214 | error = -ENOMEM; |
| 215 | if (!vma) |
| 216 | goto out; |
| 217 | |
| 218 | /* Here start < vma->vm_end. */ |
| 219 | if (start < vma->vm_start) { |
| 220 | unmapped_error = -ENOMEM; |
| 221 | start = vma->vm_start; |
| 222 | } |
| 223 | |
| 224 | /* Here vma->vm_start <= start < vma->vm_end. */ |
| 225 | if (end <= vma->vm_end) { |
| 226 | if (start < end) { |
| 227 | error = madvise_vma(vma, start, end, |
| 228 | behavior); |
| 229 | if (error) |
| 230 | goto out; |
| 231 | } |
| 232 | error = unmapped_error; |
| 233 | goto out; |
| 234 | } |
| 235 | |
| 236 | /* Here vma->vm_start <= start < vma->vm_end < end. */ |
| 237 | error = madvise_vma(vma, start, vma->vm_end, behavior); |
| 238 | if (error) |
| 239 | goto out; |
| 240 | start = vma->vm_end; |
| 241 | vma = vma->vm_next; |
| 242 | } |
| 243 | |
| 244 | out: |
| 245 | up_write(¤t->mm->mmap_sem); |
| 246 | return error; |
| 247 | } |