mm/fadvise.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * mm/fadvise.c
   4  *
   5  * Copyright (C) 2002, Linus Torvalds
   6  *
   7  * 11Jan2003    Andrew Morton
   8  *              Initial version.
   9  */
  10
  11 #include <linux/kernel.h>
  12 #include <linux/file.h>
  13 #include <linux/fs.h>
  14 #include <linux/mm.h>
  15 #include <linux/pagemap.h>
  16 #include <linux/backing-dev.h>
  17 #include <linux/pagevec.h>
  18 #include <linux/fadvise.h>
  19 #include <linux/writeback.h>
  20 #include <linux/syscalls.h>
  21 #include <linux/swap.h>
  22
  23 #include <asm/unistd.h>
  24
  25 #include "internal.h"
  26
  27 /*
  28  * POSIX_FADV_WILLNEED could set PG_Referenced, and POSIX_FADV_NOREUSE could
  29  * deactivate the pages and clear PG_Referenced.
  30  */
  31
  32 int generic_fadvise(struct file *file, loff_t offset, loff_t len, int advice)
  33 {
  34         struct inode *inode;
  35         struct address_space *mapping;
  36         struct backing_dev_info *bdi;
  37         loff_t endbyte;                 /* inclusive */
  38         pgoff_t start_index;
  39         pgoff_t end_index;
  40         unsigned long nrpages;
  41
  42         inode = file_inode(file);
  43         if (S_ISFIFO(inode->i_mode))
  44                 return -ESPIPE;
  45
  46         mapping = file->f_mapping;
  47         if (!mapping || len < 0)
  48                 return -EINVAL;
  49
  50         bdi = inode_to_bdi(mapping->host);
  51
  52         if (IS_DAX(inode) || (bdi == &noop_backing_dev_info)) {
  53                 switch (advice) {
  54                 case POSIX_FADV_NORMAL:
  55                 case POSIX_FADV_RANDOM:
  56                 case POSIX_FADV_SEQUENTIAL:
  57                 case POSIX_FADV_WILLNEED:
  58                 case POSIX_FADV_NOREUSE:
  59                 case POSIX_FADV_DONTNEED:
  60                         /* no bad return value, but ignore advice */
  61                         break;
  62                 default:
  63                         return -EINVAL;
  64                 }
  65                 return 0;
  66         }
  67
  68         /*
  69          * Careful about overflows. Len == 0 means "as much as possible".  Use
  70          * unsigned math because signed overflows are undefined and UBSan
  71          * complains.
  72          */
  73         endbyte = (u64)offset + (u64)len;
  74         if (!len || endbyte < len)
  75                 endbyte = -1;
  76         else
  77                 endbyte--;              /* inclusive */
  78
  79         switch (advice) {
  80         case POSIX_FADV_NORMAL:
  81                 file->f_ra.ra_pages = bdi->ra_pages;
  82                 spin_lock(&file->f_lock);
  83                 file->f_mode &= ~FMODE_RANDOM;
  84                 spin_unlock(&file->f_lock);
  85                 break;
  86         case POSIX_FADV_RANDOM:
  87                 spin_lock(&file->f_lock);
  88                 file->f_mode |= FMODE_RANDOM;
  89                 spin_unlock(&file->f_lock);
  90                 break;
  91         case POSIX_FADV_SEQUENTIAL:
  92                 file->f_ra.ra_pages = bdi->ra_pages * 2;
  93                 spin_lock(&file->f_lock);
  94                 file->f_mode &= ~FMODE_RANDOM;
  95                 spin_unlock(&file->f_lock);
  96                 break;
  97         case POSIX_FADV_WILLNEED:
  98                 /* First and last PARTIAL page! */
  99                 start_index = offset >> PAGE_SHIFT;
 100                 end_index = endbyte >> PAGE_SHIFT;
 101
 102                 /* Careful about overflow on the "+1" */
 103                 nrpages = end_index - start_index + 1;
 104                 if (!nrpages)
 105                         nrpages = ~0UL;
 106
 107                 force_page_cache_readahead(mapping, file, start_index, nrpages);
 108                 break;
 109         case POSIX_FADV_NOREUSE:
 110                 break;
 111         case POSIX_FADV_DONTNEED:
 112                 __filemap_fdatawrite_range(mapping, offset, endbyte,
 113                                            WB_SYNC_NONE);
 114
 115                 /*
 116                  * First and last FULL page! Partial pages are deliberately
 117                  * preserved on the expectation that it is better to preserve
 118                  * needed memory than to discard unneeded memory.
 119                  */
 120                 start_index = (offset+(PAGE_SIZE-1)) >> PAGE_SHIFT;
 121                 end_index = (endbyte >> PAGE_SHIFT);
 122                 /*
 123                  * The page at end_index will be inclusively discarded according
 124                  * by invalidate_mapping_pages(), so subtracting 1 from
 125                  * end_index means we will skip the last page.  But if endbyte
 126                  * is page aligned or is at the end of file, we should not skip
 127                  * that page - discarding the last page is safe enough.
 128                  */
 129                 if ((endbyte & ~PAGE_MASK) != ~PAGE_MASK &&
 130                                 endbyte != inode->i_size - 1) {
 131                         /* First page is tricky as 0 - 1 = -1, but pgoff_t
 132                          * is unsigned, so the end_index >= start_index
 133                          * check below would be true and we'll discard the whole
 134                          * file cache which is not what was asked.
 135                          */
 136                         if (end_index == 0)
 137                                 break;
 138
 139                         end_index--;
 140                 }
 141
 142                 if (end_index >= start_index) {
 143                         unsigned long nr_pagevec = 0;
 144
 145                         /*
 146                          * It's common to FADV_DONTNEED right after
 147                          * the read or write that instantiates the
 148                          * pages, in which case there will be some
 149                          * sitting on the local LRU cache. Try to
 150                          * avoid the expensive remote drain and the
 151                          * second cache tree walk below by flushing
 152                          * them out right away.
 153                          */
 154                         lru_add_drain();
 155
 156                         invalidate_mapping_pagevec(mapping,
 157                                                 start_index, end_index,
 158                                                 &nr_pagevec);
 159
 160                         /*
 161                          * If fewer pages were invalidated than expected then
 162                          * it is possible that some of the pages were on
 163                          * a per-cpu pagevec for a remote CPU. Drain all
 164                          * pagevecs and try again.
 165                          */
 166                         if (nr_pagevec) {
 167                                 lru_add_drain_all();
 168                                 invalidate_mapping_pages(mapping, start_index,
 169                                                 end_index);
 170                         }
 171                 }
 172                 break;
 173         default:
 174                 return -EINVAL;
 175         }
 176         return 0;
 177 }
 178 EXPORT_SYMBOL(generic_fadvise);
 179
 180 int vfs_fadvise(struct file *file, loff_t offset, loff_t len, int advice)
 181 {
 182         if (file->f_op->fadvise)
 183                 return file->f_op->fadvise(file, offset, len, advice);
 184
 185         return generic_fadvise(file, offset, len, advice);
 186 }
 187 EXPORT_SYMBOL(vfs_fadvise);
 188
 189 #ifdef CONFIG_ADVISE_SYSCALLS
 190
 191 int ksys_fadvise64_64(int fd, loff_t offset, loff_t len, int advice)
 192 {
 193         struct fd f = fdget(fd);
 194         int ret;
 195
 196         if (!f.file)
 197                 return -EBADF;
 198
 199         ret = vfs_fadvise(f.file, offset, len, advice);
 200
 201         fdput(f);
 202         return ret;
 203 }
 204
 205 SYSCALL_DEFINE4(fadvise64_64, int, fd, loff_t, offset, loff_t, len, int, advice)
 206 {
 207         return ksys_fadvise64_64(fd, offset, len, advice);
 208 }
 209
 210 #ifdef __ARCH_WANT_SYS_FADVISE64
 211
 212 SYSCALL_DEFINE4(fadvise64, int, fd, loff_t, offset, size_t, len, int, advice)
 213 {
 214         return ksys_fadvise64_64(fd, offset, len, advice);
 215 }
 216
 217 #endif
 218 #endif