mm/fadvise.c

   1 /*
   2  * mm/fadvise.c
   3  *
   4  * Copyright (C) 2002, Linus Torvalds
   5  *
   6  * 11Jan2003    Andrew Morton
   7  *              Initial version.
   8  */
   9
  10 #include <linux/kernel.h>
  11 #include <linux/file.h>
  12 #include <linux/fs.h>
  13 #include <linux/mm.h>
  14 #include <linux/pagemap.h>
  15 #include <linux/backing-dev.h>
  16 #include <linux/pagevec.h>
  17 #include <linux/fadvise.h>
  18 #include <linux/writeback.h>
  19 #include <linux/syscalls.h>
  20 #include <linux/swap.h>
  21
  22 #include <asm/unistd.h>
  23
  24 /*
  25  * POSIX_FADV_WILLNEED could set PG_Referenced, and POSIX_FADV_NOREUSE could
  26  * deactivate the pages and clear PG_Referenced.
  27  */
  28 SYSCALL_DEFINE4(fadvise64_64, int, fd, loff_t, offset, loff_t, len, int, advice)
  29 {
  30         struct fd f = fdget(fd);
  31         struct inode *inode;
  32         struct address_space *mapping;
  33         struct backing_dev_info *bdi;
  34         loff_t endbyte;                 /* inclusive */
  35         pgoff_t start_index;
  36         pgoff_t end_index;
  37         unsigned long nrpages;
  38         int ret = 0;
  39
  40         if (!f.file)
  41                 return -EBADF;
  42
  43         inode = file_inode(f.file);
  44         if (S_ISFIFO(inode->i_mode)) {
  45                 ret = -ESPIPE;
  46                 goto out;
  47         }
  48
  49         mapping = f.file->f_mapping;
  50         if (!mapping || len < 0) {
  51                 ret = -EINVAL;
  52                 goto out;
  53         }
  54
  55         if (IS_DAX(inode)) {
  56                 switch (advice) {
  57                 case POSIX_FADV_NORMAL:
  58                 case POSIX_FADV_RANDOM:
  59                 case POSIX_FADV_SEQUENTIAL:
  60                 case POSIX_FADV_WILLNEED:
  61                 case POSIX_FADV_NOREUSE:
  62                 case POSIX_FADV_DONTNEED:
  63                         /* no bad return value, but ignore advice */
  64                         break;
  65                 default:
  66                         ret = -EINVAL;
  67                 }
  68                 goto out;
  69         }
  70
  71         /*
  72          * Careful about overflows. Len == 0 means "as much as possible".  Use
  73          * unsigned math because signed overflows are undefined and UBSan
  74          * complains.
  75          */
  76         endbyte = (u64)offset + (u64)len;
  77         if (!len || endbyte < len)
  78                 endbyte = -1;
  79         else
  80                 endbyte--;              /* inclusive */
  81
  82         bdi = inode_to_bdi(mapping->host);
  83
  84         switch (advice) {
  85         case POSIX_FADV_NORMAL:
  86                 f.file->f_ra.ra_pages = bdi->ra_pages;
  87                 spin_lock(&f.file->f_lock);
  88                 f.file->f_mode &= ~FMODE_RANDOM;
  89                 spin_unlock(&f.file->f_lock);
  90                 break;
  91         case POSIX_FADV_RANDOM:
  92                 spin_lock(&f.file->f_lock);
  93                 f.file->f_mode |= FMODE_RANDOM;
  94                 spin_unlock(&f.file->f_lock);
  95                 break;
  96         case POSIX_FADV_SEQUENTIAL:
  97                 f.file->f_ra.ra_pages = bdi->ra_pages * 2;
  98                 spin_lock(&f.file->f_lock);
  99                 f.file->f_mode &= ~FMODE_RANDOM;
 100                 spin_unlock(&f.file->f_lock);
 101                 break;
 102         case POSIX_FADV_WILLNEED:
 103                 /* First and last PARTIAL page! */
 104                 start_index = offset >> PAGE_SHIFT;
 105                 end_index = endbyte >> PAGE_SHIFT;
 106
 107                 /* Careful about overflow on the "+1" */
 108                 nrpages = end_index - start_index + 1;
 109                 if (!nrpages)
 110                         nrpages = ~0UL;
 111
 112                 /*
 113                  * Ignore return value because fadvise() shall return
 114                  * success even if filesystem can't retrieve a hint,
 115                  */
 116                 force_page_cache_readahead(mapping, f.file, start_index,
 117                                            nrpages);
 118                 break;
 119         case POSIX_FADV_NOREUSE:
 120                 break;
 121         case POSIX_FADV_DONTNEED:
 122                 if (!inode_write_congested(mapping->host))
 123                         __filemap_fdatawrite_range(mapping, offset, endbyte,
 124                                                    WB_SYNC_NONE);
 125
 126                 /*
 127                  * First and last FULL page! Partial pages are deliberately
 128                  * preserved on the expectation that it is better to preserve
 129                  * needed memory than to discard unneeded memory.
 130                  */
 131                 start_index = (offset+(PAGE_SIZE-1)) >> PAGE_SHIFT;
 132                 end_index = (endbyte >> PAGE_SHIFT);
 133                 /*
 134                  * The page at end_index will be inclusively discarded according
 135                  * by invalidate_mapping_pages(), so subtracting 1 from
 136                  * end_index means we will skip the last page.  But if endbyte
 137                  * is page aligned or is at the end of file, we should not skip
 138                  * that page - discarding the last page is safe enough.
 139                  */
 140                 if ((endbyte & ~PAGE_MASK) != ~PAGE_MASK &&
 141                                 endbyte != inode->i_size - 1) {
 142                         /* First page is tricky as 0 - 1 = -1, but pgoff_t
 143                          * is unsigned, so the end_index >= start_index
 144                          * check below would be true and we'll discard the whole
 145                          * file cache which is not what was asked.
 146                          */
 147                         if (end_index == 0)
 148                                 break;
 149
 150                         end_index--;
 151                 }
 152
 153                 if (end_index >= start_index) {
 154                         unsigned long count = invalidate_mapping_pages(mapping,
 155                                                 start_index, end_index);
 156
 157                         /*
 158                          * If fewer pages were invalidated than expected then
 159                          * it is possible that some of the pages were on
 160                          * a per-cpu pagevec for a remote CPU. Drain all
 161                          * pagevecs and try again.
 162                          */
 163                         if (count < (end_index - start_index + 1)) {
 164                                 lru_add_drain_all();
 165                                 invalidate_mapping_pages(mapping, start_index,
 166                                                 end_index);
 167                         }
 168                 }
 169                 break;
 170         default:
 171                 ret = -EINVAL;
 172         }
 173 out:
 174         fdput(f);
 175         return ret;
 176 }
 177
 178 #ifdef __ARCH_WANT_SYS_FADVISE64
 179
 180 SYSCALL_DEFINE4(fadvise64, int, fd, loff_t, offset, size_t, len, int, advice)
 181 {
 182         return sys_fadvise64_64(fd, offset, len, advice);
 183 }
 184
 185 #endif