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/mempolicy.h> 12 #include <linux/hugetlb.h> 13 14 /* 15 * We can potentially split a vm area into separate 16 * areas, each area with its own behavior. 17 */ 18 static long madvise_behavior(struct vm_area_struct * vma, 19 struct vm_area_struct **prev, 20 unsigned long start, unsigned long end, int behavior) 21 { 22 struct mm_struct * mm = vma->vm_mm; 23 int error = 0; 24 pgoff_t pgoff; 25 int new_flags = vma->vm_flags; 26 27 switch (behavior) { 28 case MADV_NORMAL: 29 new_flags = new_flags & ~VM_RAND_READ & ~VM_SEQ_READ; 30 break; 31 case MADV_SEQUENTIAL: 32 new_flags = (new_flags & ~VM_RAND_READ) | VM_SEQ_READ; 33 break; 34 case MADV_RANDOM: 35 new_flags = (new_flags & ~VM_SEQ_READ) | VM_RAND_READ; 36 break; 37 case MADV_DONTFORK: 38 new_flags |= VM_DONTCOPY; 39 break; 40 case MADV_DOFORK: 41 new_flags &= ~VM_DONTCOPY; 42 break; 43 } 44 45 if (new_flags == vma->vm_flags) { 46 *prev = vma; 47 goto out; 48 } 49 50 pgoff = vma->vm_pgoff + ((start - vma->vm_start) >> PAGE_SHIFT); 51 *prev = vma_merge(mm, *prev, start, end, new_flags, vma->anon_vma, 52 vma->vm_file, pgoff, vma_policy(vma)); 53 if (*prev) { 54 vma = *prev; 55 goto success; 56 } 57 58 *prev = vma; 59 60 if (start != vma->vm_start) { 61 error = split_vma(mm, vma, start, 1); 62 if (error) 63 goto out; 64 } 65 66 if (end != vma->vm_end) { 67 error = split_vma(mm, vma, end, 0); 68 if (error) 69 goto out; 70 } 71 72 success: 73 /* 74 * vm_flags is protected by the mmap_sem held in write mode. 75 */ 76 vma->vm_flags = new_flags; 77 78 out: 79 if (error == -ENOMEM) 80 error = -EAGAIN; 81 return error; 82 } 83 84 /* 85 * Schedule all required I/O operations. Do not wait for completion. 86 */ 87 static long madvise_willneed(struct vm_area_struct * vma, 88 struct vm_area_struct ** prev, 89 unsigned long start, unsigned long end) 90 { 91 struct file *file = vma->vm_file; 92 93 if (!file) 94 return -EBADF; 95 96 if (file->f_mapping->a_ops->get_xip_page) { 97 /* no bad return value, but ignore advice */ 98 return 0; 99 } 100 101 *prev = vma; 102 start = ((start - vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff; 103 if (end > vma->vm_end) 104 end = vma->vm_end; 105 end = ((end - vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff; 106 107 force_page_cache_readahead(file->f_mapping, 108 file, start, max_sane_readahead(end - start)); 109 return 0; 110 } 111 112 /* 113 * Application no longer needs these pages. If the pages are dirty, 114 * it's OK to just throw them away. The app will be more careful about 115 * data it wants to keep. Be sure to free swap resources too. The 116 * zap_page_range call sets things up for refill_inactive to actually free 117 * these pages later if no one else has touched them in the meantime, 118 * although we could add these pages to a global reuse list for 119 * refill_inactive to pick up before reclaiming other pages. 120 * 121 * NB: This interface discards data rather than pushes it out to swap, 122 * as some implementations do. This has performance implications for 123 * applications like large transactional databases which want to discard 124 * pages in anonymous maps after committing to backing store the data 125 * that was kept in them. There is no reason to write this data out to 126 * the swap area if the application is discarding it. 127 * 128 * An interface that causes the system to free clean pages and flush 129 * dirty pages is already available as msync(MS_INVALIDATE). 130 */ 131 static long madvise_dontneed(struct vm_area_struct * vma, 132 struct vm_area_struct ** prev, 133 unsigned long start, unsigned long end) 134 { 135 *prev = vma; 136 if (vma->vm_flags & (VM_LOCKED|VM_HUGETLB|VM_PFNMAP)) 137 return -EINVAL; 138 139 if (unlikely(vma->vm_flags & VM_NONLINEAR)) { 140 struct zap_details details = { 141 .nonlinear_vma = vma, 142 .last_index = ULONG_MAX, 143 }; 144 zap_page_range(vma, start, end - start, &details); 145 } else 146 zap_page_range(vma, start, end - start, NULL); 147 return 0; 148 } 149 150 /* 151 * Application wants to free up the pages and associated backing store. 152 * This is effectively punching a hole into the middle of a file. 153 * 154 * NOTE: Currently, only shmfs/tmpfs is supported for this operation. 155 * Other filesystems return -ENOSYS. 156 */ 157 static long madvise_remove(struct vm_area_struct *vma, 158 unsigned long start, unsigned long end) 159 { 160 struct address_space *mapping; 161 loff_t offset, endoff; 162 163 if (vma->vm_flags & (VM_LOCKED|VM_NONLINEAR|VM_HUGETLB)) 164 return -EINVAL; 165 166 if (!vma->vm_file || !vma->vm_file->f_mapping 167 || !vma->vm_file->f_mapping->host) { 168 return -EINVAL; 169 } 170 171 if ((vma->vm_flags & (VM_SHARED|VM_WRITE)) != (VM_SHARED|VM_WRITE)) 172 return -EACCES; 173 174 mapping = vma->vm_file->f_mapping; 175 176 offset = (loff_t)(start - vma->vm_start) 177 + ((loff_t)vma->vm_pgoff << PAGE_SHIFT); 178 endoff = (loff_t)(end - vma->vm_start - 1) 179 + ((loff_t)vma->vm_pgoff << PAGE_SHIFT); 180 return vmtruncate_range(mapping->host, offset, endoff); 181 } 182 183 static long 184 madvise_vma(struct vm_area_struct *vma, struct vm_area_struct **prev, 185 unsigned long start, unsigned long end, int behavior) 186 { 187 long error; 188 189 switch (behavior) { 190 case MADV_DOFORK: 191 if (vma->vm_flags & VM_IO) { 192 error = -EINVAL; 193 break; 194 } 195 case MADV_DONTFORK: 196 case MADV_NORMAL: 197 case MADV_SEQUENTIAL: 198 case MADV_RANDOM: 199 error = madvise_behavior(vma, prev, start, end, behavior); 200 break; 201 case MADV_REMOVE: 202 error = madvise_remove(vma, start, end); 203 break; 204 205 case MADV_WILLNEED: 206 error = madvise_willneed(vma, prev, start, end); 207 break; 208 209 case MADV_DONTNEED: 210 error = madvise_dontneed(vma, prev, start, end); 211 break; 212 213 default: 214 error = -EINVAL; 215 break; 216 } 217 return error; 218 } 219 220 /* 221 * The madvise(2) system call. 222 * 223 * Applications can use madvise() to advise the kernel how it should 224 * handle paging I/O in this VM area. The idea is to help the kernel 225 * use appropriate read-ahead and caching techniques. The information 226 * provided is advisory only, and can be safely disregarded by the 227 * kernel without affecting the correct operation of the application. 228 * 229 * behavior values: 230 * MADV_NORMAL - the default behavior is to read clusters. This 231 * results in some read-ahead and read-behind. 232 * MADV_RANDOM - the system should read the minimum amount of data 233 * on any access, since it is unlikely that the appli- 234 * cation will need more than what it asks for. 235 * MADV_SEQUENTIAL - pages in the given range will probably be accessed 236 * once, so they can be aggressively read ahead, and 237 * can be freed soon after they are accessed. 238 * MADV_WILLNEED - the application is notifying the system to read 239 * some pages ahead. 240 * MADV_DONTNEED - the application is finished with the given range, 241 * so the kernel can free resources associated with it. 242 * MADV_REMOVE - the application wants to free up the given range of 243 * pages and associated backing store. 244 * 245 * return values: 246 * zero - success 247 * -EINVAL - start + len < 0, start is not page-aligned, 248 * "behavior" is not a valid value, or application 249 * is attempting to release locked or shared pages. 250 * -ENOMEM - addresses in the specified range are not currently 251 * mapped, or are outside the AS of the process. 252 * -EIO - an I/O error occurred while paging in data. 253 * -EBADF - map exists, but area maps something that isn't a file. 254 * -EAGAIN - a kernel resource was temporarily unavailable. 255 */ 256 asmlinkage long sys_madvise(unsigned long start, size_t len_in, int behavior) 257 { 258 unsigned long end, tmp; 259 struct vm_area_struct * vma, *prev; 260 int unmapped_error = 0; 261 int error = -EINVAL; 262 size_t len; 263 264 down_write(¤t->mm->mmap_sem); 265 266 if (start & ~PAGE_MASK) 267 goto out; 268 len = (len_in + ~PAGE_MASK) & PAGE_MASK; 269 270 /* Check to see whether len was rounded up from small -ve to zero */ 271 if (len_in && !len) 272 goto out; 273 274 end = start + len; 275 if (end < start) 276 goto out; 277 278 error = 0; 279 if (end == start) 280 goto out; 281 282 /* 283 * If the interval [start,end) covers some unmapped address 284 * ranges, just ignore them, but return -ENOMEM at the end. 285 * - different from the way of handling in mlock etc. 286 */ 287 vma = find_vma_prev(current->mm, start, &prev); 288 if (vma && start > vma->vm_start) 289 prev = vma; 290 291 for (;;) { 292 /* Still start < end. */ 293 error = -ENOMEM; 294 if (!vma) 295 goto out; 296 297 /* Here start < (end|vma->vm_end). */ 298 if (start < vma->vm_start) { 299 unmapped_error = -ENOMEM; 300 start = vma->vm_start; 301 if (start >= end) 302 goto out; 303 } 304 305 /* Here vma->vm_start <= start < (end|vma->vm_end) */ 306 tmp = vma->vm_end; 307 if (end < tmp) 308 tmp = end; 309 310 /* Here vma->vm_start <= start < tmp <= (end|vma->vm_end). */ 311 error = madvise_vma(vma, &prev, start, tmp, behavior); 312 if (error) 313 goto out; 314 start = tmp; 315 if (start < prev->vm_end) 316 start = prev->vm_end; 317 error = unmapped_error; 318 if (start >= end) 319 goto out; 320 vma = prev->vm_next; 321 } 322 out: 323 up_write(¤t->mm->mmap_sem); 324 return error; 325 } 326