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         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);