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 out; 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 success: 66 /* 67 * vm_flags is protected by the mmap_sem held in write mode. 68 */ 69 vma->vm_flags = new_flags; 70 71 out: 72 if (error == -ENOMEM) 73 error = -EAGAIN; 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->f_mapping->a_ops->get_xip_page) { 87 /* no bad return value, but ignore advice */ 88 return 0; 89 } 90 91 *prev = vma; 92 start = ((start - vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff; 93 if (end > vma->vm_end) 94 end = vma->vm_end; 95 end = ((end - vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff; 96 97 force_page_cache_readahead(file->f_mapping, 98 file, start, max_sane_readahead(end - start)); 99 return 0; 100 } 101 102 /* 103 * Application no longer needs these pages. If the pages are dirty, 104 * it's OK to just throw them away. The app will be more careful about 105 * data it wants to keep. Be sure to free swap resources too. The 106 * zap_page_range call sets things up for refill_inactive to actually free 107 * these pages later if no one else has touched them in the meantime, 108 * although we could add these pages to a global reuse list for 109 * refill_inactive to pick up before reclaiming other pages. 110 * 111 * NB: This interface discards data rather than pushes it out to swap, 112 * as some implementations do. This has performance implications for 113 * applications like large transactional databases which want to discard 114 * pages in anonymous maps after committing to backing store the data 115 * that was kept in them. There is no reason to write this data out to 116 * the swap area if the application is discarding it. 117 * 118 * An interface that causes the system to free clean pages and flush 119 * dirty pages is already available as msync(MS_INVALIDATE). 120 */ 121 static long madvise_dontneed(struct vm_area_struct * vma, 122 struct vm_area_struct ** prev, 123 unsigned long start, unsigned long end) 124 { 125 *prev = vma; 126 if ((vma->vm_flags & VM_LOCKED) || is_vm_hugetlb_page(vma)) 127 return -EINVAL; 128 129 if (unlikely(vma->vm_flags & VM_NONLINEAR)) { 130 struct zap_details details = { 131 .nonlinear_vma = vma, 132 .last_index = ULONG_MAX, 133 }; 134 zap_page_range(vma, start, end - start, &details); 135 } else 136 zap_page_range(vma, start, end - start, NULL); 137 return 0; 138 } 139 140 static long 141 madvise_vma(struct vm_area_struct *vma, struct vm_area_struct **prev, 142 unsigned long start, unsigned long end, int behavior) 143 { 144 struct file *filp = vma->vm_file; 145 long error = -EBADF; 146 147 if (!filp) 148 goto out; 149 150 switch (behavior) { 151 case MADV_NORMAL: 152 case MADV_SEQUENTIAL: 153 case MADV_RANDOM: 154 error = madvise_behavior(vma, prev, start, end, behavior); 155 break; 156 157 case MADV_WILLNEED: 158 error = madvise_willneed(vma, prev, start, end); 159 break; 160 161 case MADV_DONTNEED: 162 error = madvise_dontneed(vma, prev, start, end); 163 break; 164 165 default: 166 error = -EINVAL; 167 break; 168 } 169 170 out: 171 return error; 172 } 173 174 /* 175 * The madvise(2) system call. 176 * 177 * Applications can use madvise() to advise the kernel how it should 178 * handle paging I/O in this VM area. The idea is to help the kernel 179 * use appropriate read-ahead and caching techniques. The information 180 * provided is advisory only, and can be safely disregarded by the 181 * kernel without affecting the correct operation of the application. 182 * 183 * behavior values: 184 * MADV_NORMAL - the default behavior is to read clusters. This 185 * results in some read-ahead and read-behind. 186 * MADV_RANDOM - the system should read the minimum amount of data 187 * on any access, since it is unlikely that the appli- 188 * cation will need more than what it asks for. 189 * MADV_SEQUENTIAL - pages in the given range will probably be accessed 190 * once, so they can be aggressively read ahead, and 191 * can be freed soon after they are accessed. 192 * MADV_WILLNEED - the application is notifying the system to read 193 * some pages ahead. 194 * MADV_DONTNEED - the application is finished with the given range, 195 * so the kernel can free resources associated with it. 196 * 197 * return values: 198 * zero - success 199 * -EINVAL - start + len < 0, start is not page-aligned, 200 * "behavior" is not a valid value, or application 201 * is attempting to release locked or shared pages. 202 * -ENOMEM - addresses in the specified range are not currently 203 * mapped, or are outside the AS of the process. 204 * -EIO - an I/O error occurred while paging in data. 205 * -EBADF - map exists, but area maps something that isn't a file. 206 * -EAGAIN - a kernel resource was temporarily unavailable. 207 */ 208 asmlinkage long sys_madvise(unsigned long start, size_t len_in, int behavior) 209 { 210 unsigned long end, tmp; 211 struct vm_area_struct * vma, *prev; 212 int unmapped_error = 0; 213 int error = -EINVAL; 214 size_t len; 215 216 down_write(¤t->mm->mmap_sem); 217 218 if (start & ~PAGE_MASK) 219 goto out; 220 len = (len_in + ~PAGE_MASK) & PAGE_MASK; 221 222 /* Check to see whether len was rounded up from small -ve to zero */ 223 if (len_in && !len) 224 goto out; 225 226 end = start + len; 227 if (end < start) 228 goto out; 229 230 error = 0; 231 if (end == start) 232 goto out; 233 234 /* 235 * If the interval [start,end) covers some unmapped address 236 * ranges, just ignore them, but return -ENOMEM at the end. 237 * - different from the way of handling in mlock etc. 238 */ 239 vma = find_vma_prev(current->mm, start, &prev); 240 if (vma && start > vma->vm_start) 241 prev = vma; 242 243 for (;;) { 244 /* Still start < end. */ 245 error = -ENOMEM; 246 if (!vma) 247 goto out; 248 249 /* Here start < (end|vma->vm_end). */ 250 if (start < vma->vm_start) { 251 unmapped_error = -ENOMEM; 252 start = vma->vm_start; 253 if (start >= end) 254 goto out; 255 } 256 257 /* Here vma->vm_start <= start < (end|vma->vm_end) */ 258 tmp = vma->vm_end; 259 if (end < tmp) 260 tmp = end; 261 262 /* Here vma->vm_start <= start < tmp <= (end|vma->vm_end). */ 263 error = madvise_vma(vma, &prev, start, tmp, behavior); 264 if (error) 265 goto out; 266 start = tmp; 267 if (start < prev->vm_end) 268 start = prev->vm_end; 269 error = unmapped_error; 270 if (start >= end) 271 goto out; 272 vma = prev->vm_next; 273 } 274 out: 275 up_write(¤t->mm->mmap_sem); 276 return error; 277 } 278