fs/iomap/swapfile.c

   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         uint64_t first_ppage;
  35         uint64_t first_ppage_reported;
  36         uint64_t next_ppage;
  37         int error;
  38
  39         /*
  40          * Round the start up and the end down so that the physical
  41          * extent aligns to a page boundary.
  42          */
  43         first_ppage = ALIGN(iomap->addr, PAGE_SIZE) >> PAGE_SHIFT;
  44         next_ppage = ALIGN_DOWN(iomap->addr + iomap->length, PAGE_SIZE) >>
  45                         PAGE_SHIFT;
  46
  47         /* Skip too-short physical extents. */
  48         if (first_ppage >= next_ppage)
  49                 return 0;
  50         nr_pages = next_ppage - first_ppage;
  51
  52         /*
  53          * Calculate how much swap space we're adding; the first page contains
  54          * the swap header and doesn't count.  The mm still wants that first
  55          * page fed to add_swap_extent, however.
  56          */
  57         first_ppage_reported = first_ppage;
  58         if (iomap->offset == 0)
  59                 first_ppage_reported++;
  60         if (isi->lowest_ppage > first_ppage_reported)
  61                 isi->lowest_ppage = first_ppage_reported;
  62         if (isi->highest_ppage < (next_ppage - 1))
  63                 isi->highest_ppage = next_ppage - 1;
  64
  65         /* Add extent, set up for the next call. */
  66         error = add_swap_extent(isi->sis, isi->nr_pages, nr_pages, first_ppage);
  67         if (error < 0)
  68                 return error;
  69         isi->nr_extents += error;
  70         isi->nr_pages += nr_pages;
  71         return 0;
  72 }
  73
  74 static int iomap_swapfile_fail(struct iomap_swapfile_info *isi, const char *str)
  75 {
  76         char *buf, *p = ERR_PTR(-ENOMEM);
  77
  78         buf = kmalloc(PATH_MAX, GFP_KERNEL);
  79         if (buf)
  80                 p = file_path(isi->file, buf, PATH_MAX);
  81         pr_err("swapon: file %s %s\n", IS_ERR(p) ? "<unknown>" : p, str);
  82         kfree(buf);
  83         return -EINVAL;
  84 }
  85
  86 /*
  87  * Accumulate iomaps for this swap file.  We have to accumulate iomaps because
  88  * swap only cares about contiguous page-aligned physical extents and makes no
  89  * distinction between written and unwritten extents.
  90  */
  91 static loff_t iomap_swapfile_activate_actor(struct inode *inode, loff_t pos,
  92                 loff_t count, void *data, struct iomap *iomap,
  93                 struct iomap *srcmap)
  94 {
  95         struct iomap_swapfile_info *isi = data;
  96         int error;
  97
  98         switch (iomap->type) {
  99         case IOMAP_MAPPED:
 100         case IOMAP_UNWRITTEN:
 101                 /* Only real or unwritten extents. */
 102                 break;
 103         case IOMAP_INLINE:
 104                 /* No inline data. */
 105                 return iomap_swapfile_fail(isi, "is inline");
 106         default:
 107                 return iomap_swapfile_fail(isi, "has unallocated extents");
 108         }
 109
 110         /* No uncommitted metadata or shared blocks. */
 111         if (iomap->flags & IOMAP_F_DIRTY)
 112                 return iomap_swapfile_fail(isi, "is not committed");
 113         if (iomap->flags & IOMAP_F_SHARED)
 114                 return iomap_swapfile_fail(isi, "has shared extents");
 115
 116         /* Only one bdev per swap file. */
 117         if (iomap->bdev != isi->sis->bdev)
 118                 return iomap_swapfile_fail(isi, "outside the main device");
 119
 120         if (isi->iomap.length == 0) {
 121                 /* No accumulated extent, so just store it. */
 122                 memcpy(&isi->iomap, iomap, sizeof(isi->iomap));
 123         } else if (isi->iomap.addr + isi->iomap.length == iomap->addr) {
 124                 /* Append this to the accumulated extent. */
 125                 isi->iomap.length += iomap->length;
 126         } else {
 127                 /* Otherwise, add the retained iomap and store this one. */
 128                 error = iomap_swapfile_add_extent(isi);
 129                 if (error)
 130                         return error;
 131                 memcpy(&isi->iomap, iomap, sizeof(isi->iomap));
 132         }
 133         return count;
 134 }
 135
 136 /*
 137  * Iterate a swap file's iomaps to construct physical extents that can be
 138  * passed to the swapfile subsystem.
 139  */
 140 int iomap_swapfile_activate(struct swap_info_struct *sis,
 141                 struct file *swap_file, sector_t *pagespan,
 142                 const struct iomap_ops *ops)
 143 {
 144         struct iomap_swapfile_info isi = {
 145                 .sis = sis,
 146                 .lowest_ppage = (sector_t)-1ULL,
 147                 .file = swap_file,
 148         };
 149         struct address_space *mapping = swap_file->f_mapping;
 150         struct inode *inode = mapping->host;
 151         loff_t pos = 0;
 152         loff_t len = ALIGN_DOWN(i_size_read(inode), PAGE_SIZE);
 153         loff_t ret;
 154
 155         /*
 156          * Persist all file mapping metadata so that we won't have any
 157          * IOMAP_F_DIRTY iomaps.
 158          */
 159         ret = vfs_fsync(swap_file, 1);
 160         if (ret)
 161                 return ret;
 162
 163         while (len > 0) {
 164                 ret = iomap_apply(inode, pos, len, IOMAP_REPORT,
 165                                 ops, &isi, iomap_swapfile_activate_actor);
 166                 if (ret <= 0)
 167                         return ret;
 168
 169                 pos += ret;
 170                 len -= ret;
 171         }
 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);