mm/fadvise.c

   1 /*
   2  * mm/fadvise.c
   3  *
   4  * Copyright (C) 2002, Linus Torvalds
   5  *
   6  * 11Jan2003    akpm@digeo.com
   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
  21 #include <asm/unistd.h>
  22
  23 /*
  24  * POSIX_FADV_WILLNEED could set PG_Referenced, and POSIX_FADV_NOREUSE could
  25  * deactivate the pages and clear PG_Referenced.
  26  *
  27  * LINUX_FADV_ASYNC_WRITE: start async writeout of any dirty pages between file
  28  * offsets `offset' and `offset+len' inclusive.  Any pages which are currently
  29  * under writeout are skipped, whether or not they are dirty.
  30  *
  31  * LINUX_FADV_WRITE_WAIT: wait upon writeout of any dirty pages between file
  32  * offsets `offset' and `offset+len'.
  33  *
  34  * By combining these two operations the application may do several things:
  35  *
  36  * LINUX_FADV_ASYNC_WRITE: push some or all of the dirty pages at the disk.
  37  *
  38  * LINUX_FADV_WRITE_WAIT, LINUX_FADV_ASYNC_WRITE: push all of the currently
  39  * dirty pages at the disk.
  40  *
  41  * LINUX_FADV_WRITE_WAIT, LINUX_FADV_ASYNC_WRITE, LINUX_FADV_WRITE_WAIT: push
  42  * all of the currently dirty pages at the disk, wait until they have been
  43  * written.
  44  *
  45  * It should be noted that none of these operations write out the file's
  46  * metadata.  So unless the application is strictly performing overwrites of
  47  * already-instantiated disk blocks, there are no guarantees here that the data
  48  * will be available after a crash.
  49  */
  50 asmlinkage long sys_fadvise64_64(int fd, loff_t offset, loff_t len, int advice)
  51 {
  52         struct file *file = fget(fd);
  53         struct address_space *mapping;
  54         struct backing_dev_info *bdi;
  55         loff_t endbyte;                 /* inclusive */
  56         pgoff_t start_index;
  57         pgoff_t end_index;
  58         unsigned long nrpages;
  59         int ret = 0;
  60
  61         if (!file)
  62                 return -EBADF;
  63
  64         if (S_ISFIFO(file->f_dentry->d_inode->i_mode)) {
  65                 ret = -ESPIPE;
  66                 goto out;
  67         }
  68
  69         mapping = file->f_mapping;
  70         if (!mapping || len < 0) {
  71                 ret = -EINVAL;
  72                 goto out;
  73         }
  74
  75         if (mapping->a_ops->get_xip_page)
  76                 /* no bad return value, but ignore advice */
  77                 goto out;
  78
  79         /* Careful about overflows. Len == 0 means "as much as possible" */
  80         endbyte = offset + len;
  81         if (!len || endbyte < len)
  82                 endbyte = -1;
  83         else
  84                 endbyte--;              /* inclusive */
  85
  86         bdi = mapping->backing_dev_info;
  87
  88         switch (advice) {
  89         case POSIX_FADV_NORMAL:
  90                 file->f_ra.ra_pages = bdi->ra_pages;
  91                 break;
  92         case POSIX_FADV_RANDOM:
  93                 file->f_ra.ra_pages = 0;
  94                 break;
  95         case POSIX_FADV_SEQUENTIAL:
  96                 file->f_ra.ra_pages = bdi->ra_pages * 2;
  97                 break;
  98         case POSIX_FADV_WILLNEED:
  99         case POSIX_FADV_NOREUSE:
 100                 if (!mapping->a_ops->readpage) {
 101                         ret = -EINVAL;
 102                         break;
 103                 }
 104
 105                 /* First and last PARTIAL page! */
 106                 start_index = offset >> PAGE_CACHE_SHIFT;
 107                 end_index = endbyte >> PAGE_CACHE_SHIFT;
 108
 109                 /* Careful about overflow on the "+1" */
 110                 nrpages = end_index - start_index + 1;
 111                 if (!nrpages)
 112                         nrpages = ~0UL;
 113
 114                 ret = force_page_cache_readahead(mapping, file,
 115                                 start_index,
 116                                 max_sane_readahead(nrpages));
 117                 if (ret > 0)
 118                         ret = 0;
 119                 break;
 120         case POSIX_FADV_DONTNEED:
 121                 if (!bdi_write_congested(mapping->backing_dev_info))
 122                         filemap_flush(mapping);
 123
 124                 /* First and last FULL page! */
 125                 start_index = (offset+(PAGE_CACHE_SIZE-1)) >> PAGE_CACHE_SHIFT;
 126                 end_index = (endbyte >> PAGE_CACHE_SHIFT);
 127
 128                 if (end_index >= start_index)
 129                         invalidate_mapping_pages(mapping, start_index,
 130                                                 end_index);
 131                 break;
 132         case LINUX_FADV_ASYNC_WRITE:
 133                 ret = __filemap_fdatawrite_range(mapping, offset, endbyte,
 134                                                 WB_SYNC_NONE);
 135                 break;
 136         case LINUX_FADV_WRITE_WAIT:
 137                 ret = wait_on_page_writeback_range(mapping,
 138                                         offset >> PAGE_CACHE_SHIFT,
 139                                         endbyte >> PAGE_CACHE_SHIFT);
 140                 break;
 141         default:
 142                 ret = -EINVAL;
 143         }
 144 out:
 145         fput(file);
 146         return ret;
 147 }
 148
 149 #ifdef __ARCH_WANT_SYS_FADVISE64
 150
 151 asmlinkage long sys_fadvise64(int fd, loff_t offset, size_t len, int advice)
 152 {
 153         return sys_fadvise64_64(fd, offset, len, advice);
 154 }
 155
 156 #endif