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 SYSCALL_DEFINE4(fadvise64_64, int, fd, loff_t, offset, loff_t, len, int, advice)
  30 {
  31         struct fd f = fdget(fd);
  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         int ret = 0;
  40
  41         if (!f.file)
  42                 return -EBADF;
  43
  44         inode = file_inode(f.file);
  45         if (S_ISFIFO(inode->i_mode)) {
  46                 ret = -ESPIPE;
  47                 goto out;
  48         }
  49
  50         mapping = f.file->f_mapping;
  51         if (!mapping || len < 0) {
  52                 ret = -EINVAL;
  53                 goto out;
  54         }
  55
  56         bdi = inode_to_bdi(mapping->host);
  57
  58         if (IS_DAX(inode) || (bdi == &noop_backing_dev_info)) {
  59                 switch (advice) {
  60                 case POSIX_FADV_NORMAL:
  61                 case POSIX_FADV_RANDOM:
  62                 case POSIX_FADV_SEQUENTIAL:
  63                 case POSIX_FADV_WILLNEED:
  64                 case POSIX_FADV_NOREUSE:
  65                 case POSIX_FADV_DONTNEED:
  66                         /* no bad return value, but ignore advice */
  67                         break;
  68                 default:
  69                         ret = -EINVAL;
  70                 }
  71                 goto out;
  72         }
  73
  74         /* Careful about overflows. Len == 0 means "as much as possible" */
  75         endbyte = offset + len;
  76         if (!len || endbyte < len)
  77                 endbyte = -1;
  78         else
  79                 endbyte--;              /* inclusive */
  80
  81         switch (advice) {
  82         case POSIX_FADV_NORMAL:
  83                 f.file->f_ra.ra_pages = bdi->ra_pages;
  84                 spin_lock(&f.file->f_lock);
  85                 f.file->f_mode &= ~FMODE_RANDOM;
  86                 spin_unlock(&f.file->f_lock);
  87                 break;
  88         case POSIX_FADV_RANDOM:
  89                 spin_lock(&f.file->f_lock);
  90                 f.file->f_mode |= FMODE_RANDOM;
  91                 spin_unlock(&f.file->f_lock);
  92                 break;
  93         case POSIX_FADV_SEQUENTIAL:
  94                 f.file->f_ra.ra_pages = bdi->ra_pages * 2;
  95                 spin_lock(&f.file->f_lock);
  96                 f.file->f_mode &= ~FMODE_RANDOM;
  97                 spin_unlock(&f.file->f_lock);
  98                 break;
  99         case POSIX_FADV_WILLNEED:
 100                 /* First and last PARTIAL page! */
 101                 start_index = offset >> PAGE_SHIFT;
 102                 end_index = endbyte >> PAGE_SHIFT;
 103
 104                 /* Careful about overflow on the "+1" */
 105                 nrpages = end_index - start_index + 1;
 106                 if (!nrpages)
 107                         nrpages = ~0UL;
 108
 109                 /*
 110                  * Ignore return value because fadvise() shall return
 111                  * success even if filesystem can't retrieve a hint,
 112                  */
 113                 force_page_cache_readahead(mapping, f.file, start_index,
 114                                            nrpages);
 115                 break;
 116         case POSIX_FADV_NOREUSE:
 117                 break;
 118         case POSIX_FADV_DONTNEED:
 119                 if (!inode_write_congested(mapping->host))
 120                         __filemap_fdatawrite_range(mapping, offset, endbyte,
 121                                                    WB_SYNC_NONE);
 122
 123                 /*
 124                  * First and last FULL page! Partial pages are deliberately
 125                  * preserved on the expectation that it is better to preserve
 126                  * needed memory than to discard unneeded memory.
 127                  */
 128                 start_index = (offset+(PAGE_SIZE-1)) >> PAGE_SHIFT;
 129                 end_index = (endbyte >> PAGE_SHIFT);
 130                 /*
 131                  * The page at end_index will be inclusively discarded according
 132                  * by invalidate_mapping_pages(), so subtracting 1 from
 133                  * end_index means we will skip the last page.  But if endbyte
 134                  * is page aligned or is at the end of file, we should not skip
 135                  * that page - discarding the last page is safe enough.
 136                  */
 137                 if ((endbyte & ~PAGE_MASK) != ~PAGE_MASK &&
 138                                 endbyte != inode->i_size - 1) {
 139                         /* First page is tricky as 0 - 1 = -1, but pgoff_t
 140                          * is unsigned, so the end_index >= start_index
 141                          * check below would be true and we'll discard the whole
 142                          * file cache which is not what was asked.
 143                          */
 144                         if (end_index == 0)
 145                                 break;
 146
 147                         end_index--;
 148                 }
 149
 150                 if (end_index >= start_index) {
 151                         unsigned long count;
 152
 153                         /*
 154                          * It's common to FADV_DONTNEED right after
 155                          * the read or write that instantiates the
 156                          * pages, in which case there will be some
 157                          * sitting on the local LRU cache. Try to
 158                          * avoid the expensive remote drain and the
 159                          * second cache tree walk below by flushing
 160                          * them out right away.
 161                          */
 162                         lru_add_drain();
 163
 164                         count = invalidate_mapping_pages(mapping,
 165                                                 start_index, end_index);
 166
 167                         /*
 168                          * If fewer pages were invalidated than expected then
 169                          * it is possible that some of the pages were on
 170                          * a per-cpu pagevec for a remote CPU. Drain all
 171                          * pagevecs and try again.
 172                          */
 173                         if (count < (end_index - start_index + 1)) {
 174                                 lru_add_drain_all();
 175                                 invalidate_mapping_pages(mapping, start_index,
 176                                                 end_index);
 177                         }
 178                 }
 179                 break;
 180         default:
 181                 ret = -EINVAL;
 182         }
 183 out:
 184         fdput(f);
 185         return ret;
 186 }
 187
 188 #ifdef __ARCH_WANT_SYS_FADVISE64
 189
 190 SYSCALL_DEFINE4(fadvise64, int, fd, loff_t, offset, size_t, len, int, advice)
 191 {
 192         return sys_fadvise64_64(fd, offset, len, advice);
 193 }
 194
 195 #endif