fadvise.c revision 8f72e4028a1ff968000cec4a034f45619fbd7ec4 
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 */
27asmlinkage long sys_fadvise64_64(int fd, loff_t offset, loff_t len, int advice)
28{
29	struct file *file = fget(fd);
30	struct address_space *mapping;
31	struct backing_dev_info *bdi;
32	loff_t endbyte;			/* inclusive */
33	pgoff_t start_index;
34	pgoff_t end_index;
35	unsigned long nrpages;
36	int ret = 0;
37
38	if (!file)
39		return -EBADF;
40
41	if (S_ISFIFO(file->f_dentry->d_inode->i_mode)) {
42		ret = -ESPIPE;
43		goto out;
44	}
45
46	mapping = file->f_mapping;
47	if (!mapping || len < 0) {
48		ret = -EINVAL;
49		goto out;
50	}
51
52	if (mapping->a_ops->get_xip_page)
53		/* no bad return value, but ignore advice */
54		goto out;
55
56	/* Careful about overflows. Len == 0 means "as much as possible" */
57	endbyte = offset + len;
58	if (!len || endbyte < len)
59		endbyte = -1;
60	else
61		endbyte--;		/* inclusive */
62
63	bdi = mapping->backing_dev_info;
64
65	switch (advice) {
66	case POSIX_FADV_NORMAL:
67		file->f_ra.ra_pages = bdi->ra_pages;
68		break;
69	case POSIX_FADV_RANDOM:
70		file->f_ra.ra_pages = 0;
71		break;
72	case POSIX_FADV_SEQUENTIAL:
73		file->f_ra.ra_pages = bdi->ra_pages * 2;
74		break;
75	case POSIX_FADV_WILLNEED:
76	case POSIX_FADV_NOREUSE:
77		if (!mapping->a_ops->readpage) {
78			ret = -EINVAL;
79			break;
80		}
81
82		/* First and last PARTIAL page! */
83		start_index = offset >> PAGE_CACHE_SHIFT;
84		end_index = endbyte >> PAGE_CACHE_SHIFT;
85
86		/* Careful about overflow on the "+1" */
87		nrpages = end_index - start_index + 1;
88		if (!nrpages)
89			nrpages = ~0UL;
90
91		ret = force_page_cache_readahead(mapping, file,
92				start_index,
93				max_sane_readahead(nrpages));
94		if (ret > 0)
95			ret = 0;
96		break;
97	case POSIX_FADV_DONTNEED:
98		if (!bdi_write_congested(mapping->backing_dev_info))
99			filemap_flush(mapping);
100
101		/* First and last FULL page! */
102		start_index = (offset+(PAGE_CACHE_SIZE-1)) >> PAGE_CACHE_SHIFT;
103		end_index = (endbyte >> PAGE_CACHE_SHIFT);
104
105		if (end_index >= start_index)
106			invalidate_mapping_pages(mapping, start_index,
107						end_index);
108		break;
109	default:
110		ret = -EINVAL;
111	}
112out:
113	fput(file);
114	return ret;
115}
116
117#ifdef __ARCH_WANT_SYS_FADVISE64
118
119asmlinkage long sys_fadvise64(int fd, loff_t offset, size_t len, int advice)
120{
121	return sys_fadvise64_64(fd, offset, len, advice);
122}
123
124#endif
125