GNU Linux-libre 4.19.211-gnu1
[releases.git] / mm / fadvise.c
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
30 static int generic_fadvise(struct file *file, loff_t offset, loff_t len,
31                            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 = -1;
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;
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                 /*
107                  * Ignore return value because fadvise() shall return
108                  * success even if filesystem can't retrieve a hint,
109                  */
110                 force_page_cache_readahead(mapping, file, start_index, nrpages);
111                 break;
112         case POSIX_FADV_NOREUSE:
113                 break;
114         case POSIX_FADV_DONTNEED:
115                 if (!inode_write_congested(mapping->host))
116                         __filemap_fdatawrite_range(mapping, offset, endbyte,
117                                                    WB_SYNC_NONE);
118
119                 /*
120                  * First and last FULL page! Partial pages are deliberately
121                  * preserved on the expectation that it is better to preserve
122                  * needed memory than to discard unneeded memory.
123                  */
124                 start_index = (offset+(PAGE_SIZE-1)) >> PAGE_SHIFT;
125                 end_index = (endbyte >> PAGE_SHIFT);
126                 /*
127                  * The page at end_index will be inclusively discarded according
128                  * by invalidate_mapping_pages(), so subtracting 1 from
129                  * end_index means we will skip the last page.  But if endbyte
130                  * is page aligned or is at the end of file, we should not skip
131                  * that page - discarding the last page is safe enough.
132                  */
133                 if ((endbyte & ~PAGE_MASK) != ~PAGE_MASK &&
134                                 endbyte != inode->i_size - 1) {
135                         /* First page is tricky as 0 - 1 = -1, but pgoff_t
136                          * is unsigned, so the end_index >= start_index
137                          * check below would be true and we'll discard the whole
138                          * file cache which is not what was asked.
139                          */
140                         if (end_index == 0)
141                                 break;
142
143                         end_index--;
144                 }
145
146                 if (end_index >= start_index) {
147                         unsigned long count;
148
149                         /*
150                          * It's common to FADV_DONTNEED right after
151                          * the read or write that instantiates the
152                          * pages, in which case there will be some
153                          * sitting on the local LRU cache. Try to
154                          * avoid the expensive remote drain and the
155                          * second cache tree walk below by flushing
156                          * them out right away.
157                          */
158                         lru_add_drain();
159
160                         count = invalidate_mapping_pages(mapping,
161                                                 start_index, end_index);
162
163                         /*
164                          * If fewer pages were invalidated than expected then
165                          * it is possible that some of the pages were on
166                          * a per-cpu pagevec for a remote CPU. Drain all
167                          * pagevecs and try again.
168                          */
169                         if (count < (end_index - start_index + 1)) {
170                                 lru_add_drain_all();
171                                 invalidate_mapping_pages(mapping, start_index,
172                                                 end_index);
173                         }
174                 }
175                 break;
176         default:
177                 return -EINVAL;
178         }
179         return 0;
180 }
181
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
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
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
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