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/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_flush_range(mapping, offset, endbyte);
115
116		/*
117		 * First and last FULL page! Partial pages are deliberately
118		 * preserved on the expectation that it is better to preserve
119		 * needed memory than to discard unneeded memory.
120		 */
121		start_index = (offset+(PAGE_SIZE-1)) >> PAGE_SHIFT;
122		end_index = (endbyte >> PAGE_SHIFT);
123		/*
124		 * The page at end_index will be inclusively discarded according
125		 * by invalidate_mapping_pages(), so subtracting 1 from
126		 * end_index means we will skip the last page.  But if endbyte
127		 * is page aligned or is at the end of file, we should not skip
128		 * that page - discarding the last page is safe enough.
129		 */
130		if ((endbyte & ~PAGE_MASK) != ~PAGE_MASK &&
131				endbyte != inode->i_size - 1) {
132			/* First page is tricky as 0 - 1 = -1, but pgoff_t
133			 * is unsigned, so the end_index >= start_index
134			 * check below would be true and we'll discard the whole
135			 * file cache which is not what was asked.
136			 */
137			if (end_index == 0)
138				break;
139
140			end_index--;
141		}
142
143		if (end_index >= start_index) {
144			unsigned long nr_failed = 0;
145
146			/*
147			 * It's common to FADV_DONTNEED right after
148			 * the read or write that instantiates the
149			 * pages, in which case there will be some
150			 * sitting on the local LRU cache. Try to
151			 * avoid the expensive remote drain and the
152			 * second cache tree walk below by flushing
153			 * them out right away.
154			 */
155			lru_add_drain();
156
157			mapping_try_invalidate(mapping, start_index, end_index,
158					&nr_failed);
159
160			/*
161			 * The failures may be due to the folio being
162			 * in the LRU cache of a remote CPU. Drain all
163			 * caches and try again.
164			 */
165			if (nr_failed) {
166				lru_add_drain_all();
167				invalidate_mapping_pages(mapping, start_index,
168						end_index);
169			}
170		}
171		break;
172	default:
173		return -EINVAL;
174	}
175	return 0;
176}
177EXPORT_SYMBOL(generic_fadvise);
178
179int vfs_fadvise(struct file *file, loff_t offset, loff_t len, int advice)
180{
181	if (file->f_op->fadvise)
182		return file->f_op->fadvise(file, offset, len, advice);
183
184	return generic_fadvise(file, offset, len, advice);
185}
186EXPORT_SYMBOL(vfs_fadvise);
187
188#ifdef CONFIG_ADVISE_SYSCALLS
189
190int ksys_fadvise64_64(int fd, loff_t offset, loff_t len, int advice)
191{
192	CLASS(fd, f)(fd);
193
194	if (fd_empty(f))
195		return -EBADF;
196
197	return vfs_fadvise(fd_file(f), offset, len, advice);
198}
199
200SYSCALL_DEFINE4(fadvise64_64, int, fd, loff_t, offset, loff_t, len, int, advice)
201{
202	return ksys_fadvise64_64(fd, offset, len, advice);
203}
204
205#ifdef __ARCH_WANT_SYS_FADVISE64
206
207SYSCALL_DEFINE4(fadvise64, int, fd, loff_t, offset, size_t, len, int, advice)
208{
209	return ksys_fadvise64_64(fd, offset, len, advice);
210}
211
212#endif
213
214#if defined(CONFIG_COMPAT) && defined(__ARCH_WANT_COMPAT_FADVISE64_64)
215
216COMPAT_SYSCALL_DEFINE6(fadvise64_64, int, fd, compat_arg_u64_dual(offset),
217		       compat_arg_u64_dual(len), int, advice)
218{
219	return ksys_fadvise64_64(fd, compat_arg_u64_glue(offset),
220				 compat_arg_u64_glue(len), advice);
221}
222
223#endif
224#endif