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