1// SPDX-License-Identifier: GPL-2.0
2/*
3 * mm/fadvise.c
4 *
5 * Copyright (C) 2002, Linus Torvalds
6 *
7 * 11Jan2003	Andrew Morton
8 *		Initial version.
9 */
10
11#include <linux/kernel.h>
12#include <linux/file.h>
13#include <linux/fs.h>
14#include <linux/mm.h>
15#include <linux/pagemap.h>
16#include <linux/backing-dev.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#include "internal.h"
25
26/*
27 * POSIX_FADV_WILLNEED could set PG_Referenced, and POSIX_FADV_NOREUSE could
28 * deactivate the pages and clear PG_Referenced.
29 */
30
31int generic_fadvise(struct file *file, loff_t offset, loff_t len, int advice)
32{
33	struct inode *inode;
34	struct address_space *mapping;
35	struct backing_dev_info *bdi;
36	loff_t endbyte;			/* inclusive */
37	pgoff_t start_index;
38	pgoff_t end_index;
39	unsigned long nrpages;
40
41	inode = file_inode(file);
42	if (S_ISFIFO(inode->i_mode))
43		return -ESPIPE;
44
45	mapping = file->f_mapping;
46	if (!mapping || len < 0)
47		return -EINVAL;
48
49	bdi = inode_to_bdi(mapping->host);
50
51	if (IS_DAX(inode) || (bdi == &noop_backing_dev_info)) {
52		switch (advice) {
53		case POSIX_FADV_NORMAL:
54		case POSIX_FADV_RANDOM:
55		case POSIX_FADV_SEQUENTIAL:
56		case POSIX_FADV_WILLNEED:
57		case POSIX_FADV_NOREUSE:
58		case POSIX_FADV_DONTNEED:
59			/* no bad return value, but ignore advice */
60			break;
61		default:
62			return -EINVAL;
63		}
64		return 0;
65	}
66
67	/*
68	 * Careful about overflows. Len == 0 means "as much as possible".  Use
69	 * unsigned math because signed overflows are undefined and UBSan
70	 * complains.
71	 */
72	endbyte = (u64)offset + (u64)len;
73	if (!len || endbyte < len)
74		endbyte = LLONG_MAX;
75	else
76		endbyte--;		/* inclusive */
77
78	switch (advice) {
79	case POSIX_FADV_NORMAL:
80		file->f_ra.ra_pages = bdi->ra_pages;
81		spin_lock(&file->f_lock);
82		file->f_mode &= ~(FMODE_RANDOM | FMODE_NOREUSE);
83		spin_unlock(&file->f_lock);
84		break;
85	case POSIX_FADV_RANDOM:
86		spin_lock(&file->f_lock);
87		file->f_mode |= FMODE_RANDOM;
88		spin_unlock(&file->f_lock);
89		break;
90	case POSIX_FADV_SEQUENTIAL:
91		file->f_ra.ra_pages = bdi->ra_pages * 2;
92		spin_lock(&file->f_lock);
93		file->f_mode &= ~FMODE_RANDOM;
94		spin_unlock(&file->f_lock);
95		break;
96	case POSIX_FADV_WILLNEED:
97		/* First and last PARTIAL page! */
98		start_index = offset >> PAGE_SHIFT;
99		end_index = endbyte >> PAGE_SHIFT;
100
101		/* Careful about overflow on the "+1" */
102		nrpages = end_index - start_index + 1;
103		if (!nrpages)
104			nrpages = ~0UL;
105
106		force_page_cache_readahead(mapping, file, start_index, nrpages);
107		break;
108	case POSIX_FADV_NOREUSE:
109		spin_lock(&file->f_lock);
110		file->f_mode |= FMODE_NOREUSE;
111		spin_unlock(&file->f_lock);
112		break;
113	case POSIX_FADV_DONTNEED:
114		__filemap_fdatawrite_range(mapping, offset, endbyte,
115					   WB_SYNC_NONE);
116
117		/*
118		 * First and last FULL page! Partial pages are deliberately
119		 * preserved on the expectation that it is better to preserve
120		 * needed memory than to discard unneeded memory.
121		 */
122		start_index = (offset+(PAGE_SIZE-1)) >> PAGE_SHIFT;
123		end_index = (endbyte >> PAGE_SHIFT);
124		/*
125		 * The page at end_index will be inclusively discarded according
126		 * by invalidate_mapping_pages(), so subtracting 1 from
127		 * end_index means we will skip the last page.  But if endbyte
128		 * is page aligned or is at the end of file, we should not skip
129		 * that page - discarding the last page is safe enough.
130		 */
131		if ((endbyte & ~PAGE_MASK) != ~PAGE_MASK &&
132				endbyte != inode->i_size - 1) {
133			/* First page is tricky as 0 - 1 = -1, but pgoff_t
134			 * is unsigned, so the end_index >= start_index
135			 * check below would be true and we'll discard the whole
136			 * file cache which is not what was asked.
137			 */
138			if (end_index == 0)
139				break;
140
141			end_index--;
142		}
143
144		if (end_index >= start_index) {
145			unsigned long nr_failed = 0;
146
147			/*
148			 * It's common to FADV_DONTNEED right after
149			 * the read or write that instantiates the
150			 * pages, in which case there will be some
151			 * sitting on the local LRU cache. Try to
152			 * avoid the expensive remote drain and the
153			 * second cache tree walk below by flushing
154			 * them out right away.
155			 */
156			lru_add_drain();
157
158			mapping_try_invalidate(mapping, start_index, end_index,
159					&nr_failed);
160
161			/*
162			 * The failures may be due to the folio being
163			 * in the LRU cache of a remote CPU. Drain all
164			 * caches and try again.
165			 */
166			if (nr_failed) {
167				lru_add_drain_all();
168				invalidate_mapping_pages(mapping, start_index,
169						end_index);
170			}
171		}
172		break;
173	default:
174		return -EINVAL;
175	}
176	return 0;
177}
178EXPORT_SYMBOL(generic_fadvise);
179
180int vfs_fadvise(struct file *file, loff_t offset, loff_t len, int advice)
181{
182	if (file->f_op->fadvise)
183		return file->f_op->fadvise(file, offset, len, advice);
184
185	return generic_fadvise(file, offset, len, advice);
186}
187EXPORT_SYMBOL(vfs_fadvise);
188
189#ifdef CONFIG_ADVISE_SYSCALLS
190
191int ksys_fadvise64_64(int fd, loff_t offset, loff_t len, int advice)
192{
193	struct fd f = fdget(fd);
194	int ret;
195
196	if (!f.file)
197		return -EBADF;
198
199	ret = vfs_fadvise(f.file, offset, len, advice);
200
201	fdput(f);
202	return ret;
203}
204
205SYSCALL_DEFINE4(fadvise64_64, int, fd, loff_t, offset, loff_t, len, int, advice)
206{
207	return ksys_fadvise64_64(fd, offset, len, advice);
208}
209
210#ifdef __ARCH_WANT_SYS_FADVISE64
211
212SYSCALL_DEFINE4(fadvise64, int, fd, loff_t, offset, size_t, len, int, advice)
213{
214	return ksys_fadvise64_64(fd, offset, len, advice);
215}
216
217#endif
218
219#if defined(CONFIG_COMPAT) && defined(__ARCH_WANT_COMPAT_FADVISE64_64)
220
221COMPAT_SYSCALL_DEFINE6(fadvise64_64, int, fd, compat_arg_u64_dual(offset),
222		       compat_arg_u64_dual(len), int, advice)
223{
224	return ksys_fadvise64_64(fd, compat_arg_u64_glue(offset),
225				 compat_arg_u64_glue(len), advice);
226}
227
228#endif
229#endif
230