1 // SPDX-License-Identifier: GPL-2.0
5 * Copyright (C) 2002, Linus Torvalds
7 * 11Jan2003 Andrew Morton
11 #include <linux/kernel.h>
12 #include <linux/file.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>
23 #include <asm/unistd.h>
26 * POSIX_FADV_WILLNEED could set PG_Referenced, and POSIX_FADV_NOREUSE could
27 * deactivate the pages and clear PG_Referenced.
29 SYSCALL_DEFINE4(fadvise64_64, int, fd, loff_t, offset, loff_t, len, int, advice)
31 struct fd f = fdget(fd);
33 struct address_space *mapping;
34 struct backing_dev_info *bdi;
35 loff_t endbyte; /* inclusive */
38 unsigned long nrpages;
44 inode = file_inode(f.file);
45 if (S_ISFIFO(inode->i_mode)) {
50 mapping = f.file->f_mapping;
51 if (!mapping || len < 0) {
56 bdi = inode_to_bdi(mapping->host);
58 if (IS_DAX(inode) || (bdi == &noop_backing_dev_info)) {
60 case POSIX_FADV_NORMAL:
61 case POSIX_FADV_RANDOM:
62 case POSIX_FADV_SEQUENTIAL:
63 case POSIX_FADV_WILLNEED:
64 case POSIX_FADV_NOREUSE:
65 case POSIX_FADV_DONTNEED:
66 /* no bad return value, but ignore advice */
75 * Careful about overflows. Len == 0 means "as much as possible". Use
76 * unsigned math because signed overflows are undefined and UBSan
79 endbyte = (u64)offset + (u64)len;
80 if (!len || endbyte < len)
83 endbyte--; /* inclusive */
86 case POSIX_FADV_NORMAL:
87 f.file->f_ra.ra_pages = bdi->ra_pages;
88 spin_lock(&f.file->f_lock);
89 f.file->f_mode &= ~FMODE_RANDOM;
90 spin_unlock(&f.file->f_lock);
92 case POSIX_FADV_RANDOM:
93 spin_lock(&f.file->f_lock);
94 f.file->f_mode |= FMODE_RANDOM;
95 spin_unlock(&f.file->f_lock);
97 case POSIX_FADV_SEQUENTIAL:
98 f.file->f_ra.ra_pages = bdi->ra_pages * 2;
99 spin_lock(&f.file->f_lock);
100 f.file->f_mode &= ~FMODE_RANDOM;
101 spin_unlock(&f.file->f_lock);
103 case POSIX_FADV_WILLNEED:
104 /* First and last PARTIAL page! */
105 start_index = offset >> PAGE_SHIFT;
106 end_index = endbyte >> PAGE_SHIFT;
108 /* Careful about overflow on the "+1" */
109 nrpages = end_index - start_index + 1;
114 * Ignore return value because fadvise() shall return
115 * success even if filesystem can't retrieve a hint,
117 force_page_cache_readahead(mapping, f.file, start_index,
120 case POSIX_FADV_NOREUSE:
122 case POSIX_FADV_DONTNEED:
123 if (!inode_write_congested(mapping->host))
124 __filemap_fdatawrite_range(mapping, offset, endbyte,
128 * First and last FULL page! Partial pages are deliberately
129 * preserved on the expectation that it is better to preserve
130 * needed memory than to discard unneeded memory.
132 start_index = (offset+(PAGE_SIZE-1)) >> PAGE_SHIFT;
133 end_index = (endbyte >> PAGE_SHIFT);
135 * The page at end_index will be inclusively discarded according
136 * by invalidate_mapping_pages(), so subtracting 1 from
137 * end_index means we will skip the last page. But if endbyte
138 * is page aligned or is at the end of file, we should not skip
139 * that page - discarding the last page is safe enough.
141 if ((endbyte & ~PAGE_MASK) != ~PAGE_MASK &&
142 endbyte != inode->i_size - 1) {
143 /* First page is tricky as 0 - 1 = -1, but pgoff_t
144 * is unsigned, so the end_index >= start_index
145 * check below would be true and we'll discard the whole
146 * file cache which is not what was asked.
154 if (end_index >= start_index) {
158 * It's common to FADV_DONTNEED right after
159 * the read or write that instantiates the
160 * pages, in which case there will be some
161 * sitting on the local LRU cache. Try to
162 * avoid the expensive remote drain and the
163 * second cache tree walk below by flushing
164 * them out right away.
168 count = invalidate_mapping_pages(mapping,
169 start_index, end_index);
172 * If fewer pages were invalidated than expected then
173 * it is possible that some of the pages were on
174 * a per-cpu pagevec for a remote CPU. Drain all
175 * pagevecs and try again.
177 if (count < (end_index - start_index + 1)) {
179 invalidate_mapping_pages(mapping, start_index,
192 #ifdef __ARCH_WANT_SYS_FADVISE64
194 SYSCALL_DEFINE4(fadvise64, int, fd, loff_t, offset, size_t, len, int, advice)
196 return sys_fadvise64_64(fd, offset, len, advice);