swapfile.c (5689B)
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 14struct 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 */ 30static 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 80static 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 */ 97static 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 */ 142int 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} 195EXPORT_SYMBOL_GPL(iomap_swapfile_activate);