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         /* Careful about overflows. Len == 0 means "as much as possible" */
  72         endbyte = offset + len;
  73         if (!len || endbyte < len)
  74                 endbyte = -1;
  75         else
  76                 endbyte--;              /* inclusive */
  77
  78         bdi = inode_to_bdi(mapping->host);
  79
  80         switch (advice) {
  81         case POSIX_FADV_NORMAL:
  82                 f.file->f_ra.ra_pages = bdi->ra_pages;
  83                 spin_lock(&f.file->f_lock);
  84                 f.file->f_mode &= ~FMODE_RANDOM;
  85                 spin_unlock(&f.file->f_lock);
  86                 break;
  87         case POSIX_FADV_RANDOM:
  88                 spin_lock(&f.file->f_lock);
  89                 f.file->f_mode |= FMODE_RANDOM;
  90                 spin_unlock(&f.file->f_lock);
  91                 break;
  92         case POSIX_FADV_SEQUENTIAL:
  93                 f.file->f_ra.ra_pages = bdi->ra_pages * 2;
  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_WILLNEED:
  99                 /* First and last PARTIAL page! */
 100                 start_index = offset >> PAGE_SHIFT;
 101                 end_index = endbyte >> PAGE_SHIFT;
 102
 103                 /* Careful about overflow on the "+1" */
 104                 nrpages = end_index - start_index + 1;
 105                 if (!nrpages)
 106                         nrpages = ~0UL;
 107
 108                 /*
 109                  * Ignore return value because fadvise() shall return
 110                  * success even if filesystem can't retrieve a hint,
 111                  */
 112                 force_page_cache_readahead(mapping, f.file, start_index,
 113                                            nrpages);
 114                 break;
 115         case POSIX_FADV_NOREUSE:
 116                 break;
 117         case POSIX_FADV_DONTNEED:
 118                 if (!inode_write_congested(mapping->host))
 119                         __filemap_fdatawrite_range(mapping, offset, endbyte,
 120                                                    WB_SYNC_NONE);
 121
 122                 /*
 123                  * First and last FULL page! Partial pages are deliberately
 124                  * preserved on the expectation that it is better to preserve
 125                  * needed memory than to discard unneeded memory.
 126                  */
 127                 start_index = (offset+(PAGE_SIZE-1)) >> PAGE_SHIFT;
 128                 end_index = (endbyte >> PAGE_SHIFT);
 129                 /*
 130                  * The page at end_index will be inclusively discarded according
 131                  * by invalidate_mapping_pages(), so subtracting 1 from
 132                  * end_index means we will skip the last page.  But if endbyte
 133                  * is page aligned or is at the end of file, we should not skip
 134                  * that page - discarding the last page is safe enough.
 135                  */
 136                 if ((endbyte & ~PAGE_MASK) != ~PAGE_MASK &&
 137                                 endbyte != inode->i_size - 1) {
 138                         /* First page is tricky as 0 - 1 = -1, but pgoff_t
 139                          * is unsigned, so the end_index >= start_index
 140                          * check below would be true and we'll discard the whole
 141                          * file cache which is not what was asked.
 142                          */
 143                         if (end_index == 0)
 144                                 break;
 145
 146                         end_index--;
 147                 }
 148
 149                 if (end_index >= start_index) {
 150                         unsigned long count = invalidate_mapping_pages(mapping,
 151                                                 start_index, end_index);
 152
 153                         /*
 154                          * If fewer pages were invalidated than expected then
 155                          * it is possible that some of the pages were on
 156                          * a per-cpu pagevec for a remote CPU. Drain all
 157                          * pagevecs and try again.
 158                          */
 159                         if (count < (end_index - start_index + 1)) {
 160                                 lru_add_drain_all();
 161                                 invalidate_mapping_pages(mapping, start_index,
 162                                                 end_index);
 163                         }
 164                 }
 165                 break;
 166         default:
 167                 ret = -EINVAL;
 168         }
 169 out:
 170         fdput(f);
 171         return ret;
 172 }
 173
 174 #ifdef __ARCH_WANT_SYS_FADVISE64
 175
 176 SYSCALL_DEFINE4(fadvise64, int, fd, loff_t, offset, size_t, len, int, advice)
 177 {
 178         return sys_fadvise64_64(fd, offset, len, advice);
 179 }
 180
 181 #endif