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/pagevec.h>
18 #include <linux/fadvise.h>
19 #include <linux/writeback.h>
20 #include <linux/syscalls.h>
21 #include <linux/swap.h>
22
23 #include <asm/unistd.h>
24
25 /*
26 * POSIX_FADV_WILLNEED could set PG_Referenced, and POSIX_FADV_NOREUSE could
27 * deactivate the pages and clear PG_Referenced.
28 */
29
generic_fadvise(struct file * file,loff_t offset,loff_t len,int advice)30 int generic_fadvise(struct file *file, loff_t offset, loff_t len, int advice)
31 {
32 struct inode *inode;
33 struct address_space *mapping;
34 struct backing_dev_info *bdi;
35 loff_t endbyte; /* inclusive */
36 pgoff_t start_index;
37 pgoff_t end_index;
38 unsigned long nrpages;
39
40 inode = file_inode(file);
41 if (S_ISFIFO(inode->i_mode))
42 return -ESPIPE;
43
44 mapping = file->f_mapping;
45 if (!mapping || len < 0)
46 return -EINVAL;
47
48 bdi = inode_to_bdi(mapping->host);
49
50 if (IS_DAX(inode) || (bdi == &noop_backing_dev_info)) {
51 switch (advice) {
52 case POSIX_FADV_NORMAL:
53 case POSIX_FADV_RANDOM:
54 case POSIX_FADV_SEQUENTIAL:
55 case POSIX_FADV_WILLNEED:
56 case POSIX_FADV_NOREUSE:
57 case POSIX_FADV_DONTNEED:
58 /* no bad return value, but ignore advice */
59 break;
60 default:
61 return -EINVAL;
62 }
63 return 0;
64 }
65
66 /*
67 * Careful about overflows. Len == 0 means "as much as possible". Use
68 * unsigned math because signed overflows are undefined and UBSan
69 * complains.
70 */
71 endbyte = (u64)offset + (u64)len;
72 if (!len || endbyte < len)
73 endbyte = -1;
74 else
75 endbyte--; /* inclusive */
76
77 switch (advice) {
78 case POSIX_FADV_NORMAL:
79 file->f_ra.ra_pages = bdi->ra_pages;
80 spin_lock(&file->f_lock);
81 file->f_mode &= ~FMODE_RANDOM;
82 spin_unlock(&file->f_lock);
83 break;
84 case POSIX_FADV_RANDOM:
85 spin_lock(&file->f_lock);
86 file->f_mode |= FMODE_RANDOM;
87 spin_unlock(&file->f_lock);
88 break;
89 case POSIX_FADV_SEQUENTIAL:
90 file->f_ra.ra_pages = bdi->ra_pages * 2;
91 spin_lock(&file->f_lock);
92 file->f_mode &= ~FMODE_RANDOM;
93 spin_unlock(&file->f_lock);
94 break;
95 case POSIX_FADV_WILLNEED:
96 /* First and last PARTIAL page! */
97 start_index = offset >> PAGE_SHIFT;
98 end_index = endbyte >> PAGE_SHIFT;
99
100 /* Careful about overflow on the "+1" */
101 nrpages = end_index - start_index + 1;
102 if (!nrpages)
103 nrpages = ~0UL;
104
105 /*
106 * Ignore return value because fadvise() shall return
107 * success even if filesystem can't retrieve a hint,
108 */
109 force_page_cache_readahead(mapping, file, start_index, nrpages);
110 break;
111 case POSIX_FADV_NOREUSE:
112 break;
113 case POSIX_FADV_DONTNEED:
114 if (!inode_write_congested(mapping->host))
115 __filemap_fdatawrite_range(mapping, offset, endbyte,
116 WB_SYNC_NONE);
117
118 /*
119 * First and last FULL page! Partial pages are deliberately
120 * preserved on the expectation that it is better to preserve
121 * needed memory than to discard unneeded memory.
122 */
123 start_index = (offset+(PAGE_SIZE-1)) >> PAGE_SHIFT;
124 end_index = (endbyte >> PAGE_SHIFT);
125 /*
126 * The page at end_index will be inclusively discarded according
127 * by invalidate_mapping_pages(), so subtracting 1 from
128 * end_index means we will skip the last page. But if endbyte
129 * is page aligned or is at the end of file, we should not skip
130 * that page - discarding the last page is safe enough.
131 */
132 if ((endbyte & ~PAGE_MASK) != ~PAGE_MASK &&
133 endbyte != inode->i_size - 1) {
134 /* First page is tricky as 0 - 1 = -1, but pgoff_t
135 * is unsigned, so the end_index >= start_index
136 * check below would be true and we'll discard the whole
137 * file cache which is not what was asked.
138 */
139 if (end_index == 0)
140 break;
141
142 end_index--;
143 }
144
145 if (end_index >= start_index) {
146 unsigned long count;
147
148 /*
149 * It's common to FADV_DONTNEED right after
150 * the read or write that instantiates the
151 * pages, in which case there will be some
152 * sitting on the local LRU cache. Try to
153 * avoid the expensive remote drain and the
154 * second cache tree walk below by flushing
155 * them out right away.
156 */
157 lru_add_drain();
158
159 count = invalidate_mapping_pages(mapping,
160 start_index, end_index);
161
162 /*
163 * If fewer pages were invalidated than expected then
164 * it is possible that some of the pages were on
165 * a per-cpu pagevec for a remote CPU. Drain all
166 * pagevecs and try again.
167 */
168 if (count < (end_index - start_index + 1)) {
169 lru_add_drain_all();
170 invalidate_mapping_pages(mapping, start_index,
171 end_index);
172 }
173 }
174 break;
175 default:
176 return -EINVAL;
177 }
178 return 0;
179 }
180 EXPORT_SYMBOL(generic_fadvise);
181
vfs_fadvise(struct file * file,loff_t offset,loff_t len,int advice)182 int vfs_fadvise(struct file *file, loff_t offset, loff_t len, int advice)
183 {
184 if (file->f_op->fadvise)
185 return file->f_op->fadvise(file, offset, len, advice);
186
187 return generic_fadvise(file, offset, len, advice);
188 }
189 EXPORT_SYMBOL(vfs_fadvise);
190
191 #ifdef CONFIG_ADVISE_SYSCALLS
192
ksys_fadvise64_64(int fd,loff_t offset,loff_t len,int advice)193 int ksys_fadvise64_64(int fd, loff_t offset, loff_t len, int advice)
194 {
195 struct fd f = fdget(fd);
196 int ret;
197
198 if (!f.file)
199 return -EBADF;
200
201 ret = vfs_fadvise(f.file, offset, len, advice);
202
203 fdput(f);
204 return ret;
205 }
206
SYSCALL_DEFINE4(fadvise64_64,int,fd,loff_t,offset,loff_t,len,int,advice)207 SYSCALL_DEFINE4(fadvise64_64, int, fd, loff_t, offset, loff_t, len, int, advice)
208 {
209 return ksys_fadvise64_64(fd, offset, len, advice);
210 }
211
212 #ifdef __ARCH_WANT_SYS_FADVISE64
213
SYSCALL_DEFINE4(fadvise64,int,fd,loff_t,offset,size_t,len,int,advice)214 SYSCALL_DEFINE4(fadvise64, int, fd, loff_t, offset, size_t, len, int, advice)
215 {
216 return ksys_fadvise64_64(fd, offset, len, advice);
217 }
218
219 #endif
220 #endif
221