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