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  */
iomap_swapfile_add_extent(struct iomap_swapfile_info * isi)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 
iomap_swapfile_fail(struct iomap_swapfile_info * isi,const char * str)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  */
iomap_swapfile_iter(const struct iomap_iter * iter,struct iomap * iomap,struct iomap_swapfile_info * isi)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  */
iomap_swapfile_activate(struct swap_info_struct * sis,struct file * swap_file,sector_t * pagespan,const struct iomap_ops * ops)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