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