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