1 // SPDX-License-Identifier: GPL-2.0
2 /*
3 * Copyright (C) 2018 Oracle. All Rights Reserved.
4 * Author: Darrick J. Wong <darrick.wong@oracle.com>
5 */
6 #include <linux/module.h>
7 #include <linux/compiler.h>
8 #include <linux/fs.h>
9 #include <linux/iomap.h>
10 #include <linux/swap.h>
11
12 /* Swapfile activation */
13
14 struct iomap_swapfile_info {
15 struct iomap iomap; /* accumulated iomap */
16 struct swap_info_struct *sis;
17 uint64_t lowest_ppage; /* lowest physical addr seen (pages) */
18 uint64_t highest_ppage; /* highest physical addr seen (pages) */
19 unsigned long nr_pages; /* number of pages collected */
20 int nr_extents; /* extent count */
21 struct file *file;
22 };
23
24 /*
25 * Collect physical extents for this swap file. Physical extents reported to
26 * the swap code must be trimmed to align to a page boundary. The logical
27 * offset within the file is irrelevant since the swapfile code maps logical
28 * page numbers of the swap device to the physical page-aligned extents.
29 */
30 static int iomap_swapfile_add_extent(struct iomap_swapfile_info *isi)
31 {
32 struct iomap *iomap = &isi->iomap;
33 unsigned long nr_pages;
34 unsigned long max_pages;
35 uint64_t first_ppage;
36 uint64_t first_ppage_reported;
37 uint64_t next_ppage;
38 int error;
39
40 if (unlikely(isi->nr_pages >= isi->sis->max))
41 return 0;
42 max_pages = isi->sis->max - isi->nr_pages;
43
44 /*
45 * Round the start up and the end down so that the physical
46 * extent aligns to a page boundary.
47 */
48 first_ppage = ALIGN(iomap->addr, PAGE_SIZE) >> PAGE_SHIFT;
49 next_ppage = ALIGN_DOWN(iomap->addr + iomap->length, PAGE_SIZE) >>
50 PAGE_SHIFT;
51
52 /* Skip too-short physical extents. */
53 if (first_ppage >= next_ppage)
54 return 0;
55 nr_pages = next_ppage - first_ppage;
56 nr_pages = min(nr_pages, max_pages);
57
58 /*
59 * Calculate how much swap space we're adding; the first page contains
60 * the swap header and doesn't count. The mm still wants that first
61 * page fed to add_swap_extent, however.
62 */
63 first_ppage_reported = first_ppage;
64 if (iomap->offset == 0)
65 first_ppage_reported++;
66 if (isi->lowest_ppage > first_ppage_reported)
67 isi->lowest_ppage = first_ppage_reported;
68 if (isi->highest_ppage < (next_ppage - 1))
69 isi->highest_ppage = next_ppage - 1;
70
71 /* Add extent, set up for the next call. */
72 error = add_swap_extent(isi->sis, isi->nr_pages, nr_pages, first_ppage);
73 if (error < 0)
74 return error;
75 isi->nr_extents += error;
76 isi->nr_pages += nr_pages;
77 return 0;
78 }
79
80 static int iomap_swapfile_fail(struct iomap_swapfile_info *isi, const char *str)
81 {
82 char *buf, *p = ERR_PTR(-ENOMEM);
83
84 buf = kmalloc(PATH_MAX, GFP_KERNEL);
85 if (buf)
86 p = file_path(isi->file, buf, PATH_MAX);
87 pr_err("swapon: file %s %s\n", IS_ERR(p) ? "<unknown>" : p, str);
88 kfree(buf);
89 return -EINVAL;
90 }
91
92 /*
93 * Accumulate iomaps for this swap file. We have to accumulate iomaps because
94 * swap only cares about contiguous page-aligned physical extents and makes no
95 * distinction between written and unwritten extents.
96 */
97 static loff_t iomap_swapfile_iter(const struct iomap_iter *iter,
98 struct iomap *iomap, struct iomap_swapfile_info *isi)
99 {
100 switch (iomap->type) {
101 case IOMAP_MAPPED:
102 case IOMAP_UNWRITTEN:
103 /* Only real or unwritten extents. */
104 break;
105 case IOMAP_INLINE:
106 /* No inline data. */
107 return iomap_swapfile_fail(isi, "is inline");
108 default:
109 return iomap_swapfile_fail(isi, "has unallocated extents");
110 }
111
112 /* No uncommitted metadata or shared blocks. */
113 if (iomap->flags & IOMAP_F_DIRTY)
114 return iomap_swapfile_fail(isi, "is not committed");
115 if (iomap->flags & IOMAP_F_SHARED)
116 return iomap_swapfile_fail(isi, "has shared extents");
117
118 /* Only one bdev per swap file. */
119 if (iomap->bdev != isi->sis->bdev)
120 return iomap_swapfile_fail(isi, "outside the main device");
121
122 if (isi->iomap.length == 0) {
123 /* No accumulated extent, so just store it. */
124 memcpy(&isi->iomap, iomap, sizeof(isi->iomap));
125 } else if (isi->iomap.addr + isi->iomap.length == iomap->addr) {
126 /* Append this to the accumulated extent. */
127 isi->iomap.length += iomap->length;
128 } else {
129 /* Otherwise, add the retained iomap and store this one. */
130 int error = iomap_swapfile_add_extent(isi);
131 if (error)
132 return error;
133 memcpy(&isi->iomap, iomap, sizeof(isi->iomap));
134 }
135 return iomap_length(iter);
136 }
137
138 /*
139 * Iterate a swap file's iomaps to construct physical extents that can be
140 * passed to the swapfile subsystem.
141 */
142 int iomap_swapfile_activate(struct swap_info_struct *sis,
143 struct file *swap_file, sector_t *pagespan,
144 const struct iomap_ops *ops)
145 {
146 struct inode *inode = swap_file->f_mapping->host;
147 struct iomap_iter iter = {
148 .inode = inode,
149 .pos = 0,
150 .len = ALIGN_DOWN(i_size_read(inode), PAGE_SIZE),
151 .flags = IOMAP_REPORT,
152 };
153 struct iomap_swapfile_info isi = {
154 .sis = sis,
155 .lowest_ppage = (sector_t)-1ULL,
156 .file = swap_file,
157 };
158 int ret;
159
160 /*
161 * Persist all file mapping metadata so that we won't have any
162 * IOMAP_F_DIRTY iomaps.
163 */
164 ret = vfs_fsync(swap_file, 1);
165 if (ret)
166 return ret;
167
168 while ((ret = iomap_iter(&iter, ops)) > 0)
169 iter.processed = iomap_swapfile_iter(&iter, &iter.iomap, &isi);
170 if (ret < 0)
171 return ret;
172
173 if (isi.iomap.length) {
174 ret = iomap_swapfile_add_extent(&isi);
175 if (ret)
176 return ret;
177 }
178
179 /*
180 * If this swapfile doesn't contain even a single page-aligned
181 * contiguous range of blocks, reject this useless swapfile to
182 * prevent confusion later on.
183 */
184 if (isi.nr_pages == 0) {
185 pr_warn("swapon: Cannot find a single usable page in file.\n");
186 return -EINVAL;
187 }
188
189 *pagespan = 1 + isi.highest_ppage - isi.lowest_ppage;
190 sis->max = isi.nr_pages;
191 sis->pages = isi.nr_pages - 1;
192 sis->highest_bit = isi.nr_pages - 1;
193 return isi.nr_extents;
194 }
195 EXPORT_SYMBOL_GPL(iomap_swapfile_activate);
196
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