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linux/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 
 19 #include <asm/unistd.h>
 20 
 21 /*
 22  * POSIX_FADV_WILLNEED could set PG_Referenced, and POSIX_FADV_NOREUSE could
 23  * deactivate the pages and clear PG_Referenced.
 24  */
 25 asmlinkage long sys_fadvise64_64(int fd, loff_t offset, loff_t len, int advice)
 26 {
 27         struct file *file = fget(fd);
 28         struct address_space *mapping;
 29         struct backing_dev_info *bdi;
 30         loff_t endbyte;
 31         pgoff_t start_index;
 32         pgoff_t end_index;
 33         unsigned long nrpages;
 34         int ret = 0;
 35 
 36         if (!file)
 37                 return -EBADF;
 38 
 39         mapping = file->f_mapping;
 40         if (!mapping || len < 0) {
 41                 ret = -EINVAL;
 42                 goto out;
 43         }
 44 
 45         /* Careful about overflows. Len == 0 means "as much as possible" */
 46         endbyte = offset + len;
 47         if (!len || endbyte < len)
 48                 endbyte = -1;
 49 
 50         bdi = mapping->backing_dev_info;
 51 
 52         switch (advice) {
 53         case POSIX_FADV_NORMAL:
 54                 file->f_ra.ra_pages = bdi->ra_pages;
 55                 break;
 56         case POSIX_FADV_RANDOM:
 57                 file->f_ra.ra_pages = 0;
 58                 break;
 59         case POSIX_FADV_SEQUENTIAL:
 60                 file->f_ra.ra_pages = bdi->ra_pages * 2;
 61                 break;
 62         case POSIX_FADV_WILLNEED:
 63         case POSIX_FADV_NOREUSE:
 64                 if (!mapping->a_ops->readpage) {
 65                         ret = -EINVAL;
 66                         break;
 67                 }
 68 
 69                 /* First and last PARTIAL page! */
 70                 start_index = offset >> PAGE_CACHE_SHIFT;
 71                 end_index = (endbyte-1) >> PAGE_CACHE_SHIFT;
 72 
 73                 /* Careful about overflow on the "+1" */
 74                 nrpages = end_index - start_index + 1;
 75                 if (!nrpages)
 76                         nrpages = ~0UL;
 77                 
 78                 ret = force_page_cache_readahead(mapping, file,
 79                                 start_index,
 80                                 max_sane_readahead(nrpages));
 81                 if (ret > 0)
 82                         ret = 0;
 83                 break;
 84         case POSIX_FADV_DONTNEED:
 85                 if (!bdi_write_congested(mapping->backing_dev_info))
 86                         filemap_flush(mapping);
 87 
 88                 /* First and last FULL page! */
 89                 start_index = (offset + (PAGE_CACHE_SIZE-1)) >> PAGE_CACHE_SHIFT;
 90                 end_index = (endbyte >> PAGE_CACHE_SHIFT);
 91 
 92                 if (end_index > start_index)
 93                         invalidate_mapping_pages(mapping, start_index, end_index-1);
 94                 break;
 95         default:
 96                 ret = -EINVAL;
 97         }
 98 out:
 99         fput(file);
100         return ret;
101 }
102 
103 #ifdef __ARCH_WANT_SYS_FADVISE64
104 
105 asmlinkage long sys_fadvise64(int fd, loff_t offset, size_t len, int advice)
106 {
107         return sys_fadvise64_64(fd, offset, len, advice);
108 }
109 
110 #endif
111

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