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         /*
  76          * Careful about overflows. Len == 0 means "as much as possible".  Use
  77          * unsigned math because signed overflows are undefined and UBSan
  78          * complains.
  79          */
  80         endbyte = (u64)offset + (u64)len;
  81         if (!len || endbyte < len)
  82                 endbyte = -1;
  83         else
  84                 endbyte--;              /* inclusive */
  85
  86         switch (advice) {
  87         case POSIX_FADV_NORMAL:
  88                 f.file->f_ra.ra_pages = bdi->ra_pages;
  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_RANDOM:
  94                 spin_lock(&f.file->f_lock);
  95                 f.file->f_mode |= FMODE_RANDOM;
  96                 spin_unlock(&f.file->f_lock);
  97                 break;
  98         case POSIX_FADV_SEQUENTIAL:
  99                 f.file->f_ra.ra_pages = bdi->ra_pages * 2;
 100                 spin_lock(&f.file->f_lock);
 101                 f.file->f_mode &= ~FMODE_RANDOM;
 102                 spin_unlock(&f.file->f_lock);
 103                 break;
 104         case POSIX_FADV_WILLNEED:
 105                 /* First and last PARTIAL page! */
 106                 start_index = offset >> PAGE_SHIFT;
 107                 end_index = endbyte >> PAGE_SHIFT;
 108
 109                 /* Careful about overflow on the "+1" */
 110                 nrpages = end_index - start_index + 1;
 111                 if (!nrpages)
 112                         nrpages = ~0UL;
 113
 114                 /*
 115                  * Ignore return value because fadvise() shall return
 116                  * success even if filesystem can't retrieve a hint,
 117                  */
 118                 force_page_cache_readahead(mapping, f.file, start_index,
 119                                            nrpages);
 120                 break;
 121         case POSIX_FADV_NOREUSE:
 122                 break;
 123         case POSIX_FADV_DONTNEED:
 124                 if (!inode_write_congested(mapping->host))
 125                         __filemap_fdatawrite_range(mapping, offset, endbyte,
 126                                                    WB_SYNC_NONE);
 127
 128                 /*
 129                  * First and last FULL page! Partial pages are deliberately
 130                  * preserved on the expectation that it is better to preserve
 131                  * needed memory than to discard unneeded memory.
 132                  */
 133                 start_index = (offset+(PAGE_SIZE-1)) >> PAGE_SHIFT;
 134                 end_index = (endbyte >> PAGE_SHIFT);
 135                 /*
 136                  * The page at end_index will be inclusively discarded according
 137                  * by invalidate_mapping_pages(), so subtracting 1 from
 138                  * end_index means we will skip the last page.  But if endbyte
 139                  * is page aligned or is at the end of file, we should not skip
 140                  * that page - discarding the last page is safe enough.
 141                  */
 142                 if ((endbyte & ~PAGE_MASK) != ~PAGE_MASK &&
 143                                 endbyte != inode->i_size - 1) {
 144                         /* First page is tricky as 0 - 1 = -1, but pgoff_t
 145                          * is unsigned, so the end_index >= start_index
 146                          * check below would be true and we'll discard the whole
 147                          * file cache which is not what was asked.
 148                          */
 149                         if (end_index == 0)
 150                                 break;
 151
 152                         end_index--;
 153                 }
 154
 155                 if (end_index >= start_index) {
 156                         unsigned long count;
 157
 158                         /*
 159                          * It's common to FADV_DONTNEED right after
 160                          * the read or write that instantiates the
 161                          * pages, in which case there will be some
 162                          * sitting on the local LRU cache. Try to
 163                          * avoid the expensive remote drain and the
 164                          * second cache tree walk below by flushing
 165                          * them out right away.
 166                          */
 167                         lru_add_drain();
 168
 169                         count = invalidate_mapping_pages(mapping,
 170                                                 start_index, end_index);
 171
 172                         /*
 173                          * If fewer pages were invalidated than expected then
 174                          * it is possible that some of the pages were on
 175                          * a per-cpu pagevec for a remote CPU. Drain all
 176                          * pagevecs and try again.
 177                          */
 178                         if (count < (end_index - start_index + 1)) {
 179                                 lru_add_drain_all();
 180                                 invalidate_mapping_pages(mapping, start_index,
 181                                                 end_index);
 182                         }
 183                 }
 184                 break;
 185         default:
 186                 ret = -EINVAL;
 187         }
 188 out:
 189         fdput(f);
 190         return ret;
 191 }
 192
 193 SYSCALL_DEFINE4(fadvise64_64, int, fd, loff_t, offset, loff_t, len, int, advice)
 194 {
 195         return ksys_fadvise64_64(fd, offset, len, advice);
 196 }
 197
 198 #ifdef __ARCH_WANT_SYS_FADVISE64
 199
 200 SYSCALL_DEFINE4(fadvise64, int, fd, loff_t, offset, size_t, len, int, advice)
 201 {
 202         return ksys_fadvise64_64(fd, offset, len, advice);
 203 }
 204
 205 #endif