xref: /openbmc/linux/mm/fadvise.c (revision d5cb9783536a41df9f9cba5b0a1d78047ed787f7)
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/syscalls.h>
19 
20 #include <asm/unistd.h>
21 
22 /*
23  * POSIX_FADV_WILLNEED could set PG_Referenced, and POSIX_FADV_NOREUSE could
24  * deactivate the pages and clear PG_Referenced.
25  */
26 asmlinkage long sys_fadvise64_64(int fd, loff_t offset, loff_t len, int advice)
27 {
28 	struct file *file = fget(fd);
29 	struct address_space *mapping;
30 	struct backing_dev_info *bdi;
31 	loff_t endbyte;
32 	pgoff_t start_index;
33 	pgoff_t end_index;
34 	unsigned long nrpages;
35 	int ret = 0;
36 
37 	if (!file)
38 		return -EBADF;
39 
40 	mapping = file->f_mapping;
41 	if (!mapping || len < 0) {
42 		ret = -EINVAL;
43 		goto out;
44 	}
45 
46 	if (mapping->a_ops->get_xip_page)
47 		/* no bad return value, but ignore advice */
48 		goto out;
49 
50 	/* Careful about overflows. Len == 0 means "as much as possible" */
51 	endbyte = offset + len;
52 	if (!len || endbyte < len)
53 		endbyte = -1;
54 
55 	bdi = mapping->backing_dev_info;
56 
57 	switch (advice) {
58 	case POSIX_FADV_NORMAL:
59 		file->f_ra.ra_pages = bdi->ra_pages;
60 		break;
61 	case POSIX_FADV_RANDOM:
62 		file->f_ra.ra_pages = 0;
63 		break;
64 	case POSIX_FADV_SEQUENTIAL:
65 		file->f_ra.ra_pages = bdi->ra_pages * 2;
66 		break;
67 	case POSIX_FADV_WILLNEED:
68 	case POSIX_FADV_NOREUSE:
69 		if (!mapping->a_ops->readpage) {
70 			ret = -EINVAL;
71 			break;
72 		}
73 
74 		/* First and last PARTIAL page! */
75 		start_index = offset >> PAGE_CACHE_SHIFT;
76 		end_index = (endbyte-1) >> PAGE_CACHE_SHIFT;
77 
78 		/* Careful about overflow on the "+1" */
79 		nrpages = end_index - start_index + 1;
80 		if (!nrpages)
81 			nrpages = ~0UL;
82 
83 		ret = force_page_cache_readahead(mapping, file,
84 				start_index,
85 				max_sane_readahead(nrpages));
86 		if (ret > 0)
87 			ret = 0;
88 		break;
89 	case POSIX_FADV_DONTNEED:
90 		if (!bdi_write_congested(mapping->backing_dev_info))
91 			filemap_flush(mapping);
92 
93 		/* First and last FULL page! */
94 		start_index = (offset + (PAGE_CACHE_SIZE-1)) >> PAGE_CACHE_SHIFT;
95 		end_index = (endbyte >> PAGE_CACHE_SHIFT);
96 
97 		if (end_index > start_index)
98 			invalidate_mapping_pages(mapping, start_index, end_index-1);
99 		break;
100 	default:
101 		ret = -EINVAL;
102 	}
103 out:
104 	fput(file);
105 	return ret;
106 }
107 
108 #ifdef __ARCH_WANT_SYS_FADVISE64
109 
110 asmlinkage long sys_fadvise64(int fd, loff_t offset, size_t len, int advice)
111 {
112 	return sys_fadvise64_64(fd, offset, len, advice);
113 }
114 
115 #endif
116