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