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 };
  22
  23 /*
  24  * Collect physical extents for this swap file.  Physical extents reported to
  25  * the swap code must be trimmed to align to a page boundary.  The logical
  26  * offset within the file is irrelevant since the swapfile code maps logical
  27  * page numbers of the swap device to the physical page-aligned extents.
  28  */
  29 static int iomap_swapfile_add_extent(struct iomap_swapfile_info *isi)
  30 {
  31         struct iomap *iomap = &isi->iomap;
  32         unsigned long nr_pages;
  33         uint64_t first_ppage;
  34         uint64_t first_ppage_reported;
  35         uint64_t next_ppage;
  36         int error;
  37
  38         /*
  39          * Round the start up and the end down so that the physical
  40          * extent aligns to a page boundary.
  41          */
  42         first_ppage = ALIGN(iomap->addr, PAGE_SIZE) >> PAGE_SHIFT;
  43         next_ppage = ALIGN_DOWN(iomap->addr + iomap->length, PAGE_SIZE) >>
  44                         PAGE_SHIFT;
  45
  46         /* Skip too-short physical extents. */
  47         if (first_ppage >= next_ppage)
  48                 return 0;
  49         nr_pages = next_ppage - first_ppage;
  50
  51         /*
  52          * Calculate how much swap space we're adding; the first page contains
  53          * the swap header and doesn't count.  The mm still wants that first
  54          * page fed to add_swap_extent, however.
  55          */
  56         first_ppage_reported = first_ppage;
  57         if (iomap->offset == 0)
  58                 first_ppage_reported++;
  59         if (isi->lowest_ppage > first_ppage_reported)
  60                 isi->lowest_ppage = first_ppage_reported;
  61         if (isi->highest_ppage < (next_ppage - 1))
  62                 isi->highest_ppage = next_ppage - 1;
  63
  64         /* Add extent, set up for the next call. */
  65         error = add_swap_extent(isi->sis, isi->nr_pages, nr_pages, first_ppage);
  66         if (error < 0)
  67                 return error;
  68         isi->nr_extents += error;
  69         isi->nr_pages += nr_pages;
  70         return 0;
  71 }
  72
  73 /*
  74  * Accumulate iomaps for this swap file.  We have to accumulate iomaps because
  75  * swap only cares about contiguous page-aligned physical extents and makes no
  76  * distinction between written and unwritten extents.
  77  */
  78 static loff_t iomap_swapfile_activate_actor(struct inode *inode, loff_t pos,
  79                 loff_t count, void *data, struct iomap *iomap,
  80                 struct iomap *srcmap)
  81 {
  82         struct iomap_swapfile_info *isi = data;
  83         int error;
  84
  85         switch (iomap->type) {
  86         case IOMAP_MAPPED:
  87         case IOMAP_UNWRITTEN:
  88                 /* Only real or unwritten extents. */
  89                 break;
  90         case IOMAP_INLINE:
  91                 /* No inline data. */
  92                 pr_err("swapon: file is inline\n");
  93                 return -EINVAL;
  94         default:
  95                 pr_err("swapon: file has unallocated extents\n");
  96                 return -EINVAL;
  97         }
  98
  99         /* No uncommitted metadata or shared blocks. */
 100         if (iomap->flags & IOMAP_F_DIRTY) {
 101                 pr_err("swapon: file is not committed\n");
 102                 return -EINVAL;
 103         }
 104         if (iomap->flags & IOMAP_F_SHARED) {
 105                 pr_err("swapon: file has shared extents\n");
 106                 return -EINVAL;
 107         }
 108
 109         /* Only one bdev per swap file. */
 110         if (iomap->bdev != isi->sis->bdev) {
 111                 pr_err("swapon: file is on multiple devices\n");
 112                 return -EINVAL;
 113         }
 114
 115         if (isi->iomap.length == 0) {
 116                 /* No accumulated extent, so just store it. */
 117                 memcpy(&isi->iomap, iomap, sizeof(isi->iomap));
 118         } else if (isi->iomap.addr + isi->iomap.length == iomap->addr) {
 119                 /* Append this to the accumulated extent. */
 120                 isi->iomap.length += iomap->length;
 121         } else {
 122                 /* Otherwise, add the retained iomap and store this one. */
 123                 error = iomap_swapfile_add_extent(isi);
 124                 if (error)
 125                         return error;
 126                 memcpy(&isi->iomap, iomap, sizeof(isi->iomap));
 127         }
 128         return count;
 129 }
 130
 131 /*
 132  * Iterate a swap file's iomaps to construct physical extents that can be
 133  * passed to the swapfile subsystem.
 134  */
 135 int iomap_swapfile_activate(struct swap_info_struct *sis,
 136                 struct file *swap_file, sector_t *pagespan,
 137                 const struct iomap_ops *ops)
 138 {
 139         struct iomap_swapfile_info isi = {
 140                 .sis = sis,
 141                 .lowest_ppage = (sector_t)-1ULL,
 142         };
 143         struct address_space *mapping = swap_file->f_mapping;
 144         struct inode *inode = mapping->host;
 145         loff_t pos = 0;
 146         loff_t len = ALIGN_DOWN(i_size_read(inode), PAGE_SIZE);
 147         loff_t ret;
 148
 149         /*
 150          * Persist all file mapping metadata so that we won't have any
 151          * IOMAP_F_DIRTY iomaps.
 152          */
 153         ret = vfs_fsync(swap_file, 1);
 154         if (ret)
 155                 return ret;
 156
 157         while (len > 0) {
 158                 ret = iomap_apply(inode, pos, len, IOMAP_REPORT,
 159                                 ops, &isi, iomap_swapfile_activate_actor);
 160                 if (ret <= 0)
 161                         return ret;
 162
 163                 pos += ret;
 164                 len -= ret;
 165         }
 166
 167         if (isi.iomap.length) {
 168                 ret = iomap_swapfile_add_extent(&isi);
 169                 if (ret)
 170                         return ret;
 171         }
 172
 173         *pagespan = 1 + isi.highest_ppage - isi.lowest_ppage;
 174         sis->max = isi.nr_pages;
 175         sis->pages = isi.nr_pages - 1;
 176         sis->highest_bit = isi.nr_pages - 1;
 177         return isi.nr_extents;
 178 }
 179 EXPORT_SYMBOL_GPL(iomap_swapfile_activate);