drivers/md/dm-snap-transient.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * Copyright (C) 2001-2002 Sistina Software (UK) Limited.
   4  * Copyright (C) 2006-2008 Red Hat GmbH
   5  *
   6  * This file is released under the GPL.
   7  */
   8
   9 #include "dm-exception-store.h"
  10
  11 #include <linux/mm.h>
  12 #include <linux/pagemap.h>
  13 #include <linux/vmalloc.h>
  14 #include <linux/export.h>
  15 #include <linux/slab.h>
  16 #include <linux/dm-io.h>
  17
  18 #define DM_MSG_PREFIX "transient snapshot"
  19
  20 /*
  21  *---------------------------------------------------------------
  22  * Implementation of the store for non-persistent snapshots.
  23  *---------------------------------------------------------------
  24  */
  25 struct transient_c {
  26         sector_t next_free;
  27 };
  28
  29 static void transient_dtr(struct dm_exception_store *store)
  30 {
  31         kfree(store->context);
  32 }
  33
  34 static int transient_read_metadata(struct dm_exception_store *store,
  35                                    int (*callback)(void *callback_context,
  36                                                    chunk_t old, chunk_t new),
  37                                    void *callback_context)
  38 {
  39         return 0;
  40 }
  41
  42 static int transient_prepare_exception(struct dm_exception_store *store,
  43                                        struct dm_exception *e)
  44 {
  45         struct transient_c *tc = store->context;
  46         sector_t size = get_dev_size(dm_snap_cow(store->snap)->bdev);
  47
  48         if (size < (tc->next_free + store->chunk_size))
  49                 return -1;
  50
  51         e->new_chunk = sector_to_chunk(store, tc->next_free);
  52         tc->next_free += store->chunk_size;
  53
  54         return 0;
  55 }
  56
  57 static void transient_commit_exception(struct dm_exception_store *store,
  58                                        struct dm_exception *e, int valid,
  59                                        void (*callback)(void *, int success),
  60                                        void *callback_context)
  61 {
  62         /* Just succeed */
  63         callback(callback_context, valid);
  64 }
  65
  66 static void transient_usage(struct dm_exception_store *store,
  67                             sector_t *total_sectors,
  68                             sector_t *sectors_allocated,
  69                             sector_t *metadata_sectors)
  70 {
  71         *sectors_allocated = ((struct transient_c *) store->context)->next_free;
  72         *total_sectors = get_dev_size(dm_snap_cow(store->snap)->bdev);
  73         *metadata_sectors = 0;
  74 }
  75
  76 static int transient_ctr(struct dm_exception_store *store, char *options)
  77 {
  78         struct transient_c *tc;
  79
  80         tc = kmalloc(sizeof(struct transient_c), GFP_KERNEL);
  81         if (!tc)
  82                 return -ENOMEM;
  83
  84         tc->next_free = 0;
  85         store->context = tc;
  86
  87         return 0;
  88 }
  89
  90 static unsigned int transient_status(struct dm_exception_store *store,
  91                                  status_type_t status, char *result,
  92                                  unsigned int maxlen)
  93 {
  94         unsigned int sz = 0;
  95
  96         switch (status) {
  97         case STATUSTYPE_INFO:
  98                 break;
  99         case STATUSTYPE_TABLE:
 100                 DMEMIT(" N %llu", (unsigned long long)store->chunk_size);
 101                 break;
 102         case STATUSTYPE_IMA:
 103                 *result = '\0';
 104                 break;
 105         }
 106
 107         return sz;
 108 }
 109
 110 static struct dm_exception_store_type _transient_type = {
 111         .name = "transient",
 112         .module = THIS_MODULE,
 113         .ctr = transient_ctr,
 114         .dtr = transient_dtr,
 115         .read_metadata = transient_read_metadata,
 116         .prepare_exception = transient_prepare_exception,
 117         .commit_exception = transient_commit_exception,
 118         .usage = transient_usage,
 119         .status = transient_status,
 120 };
 121
 122 static struct dm_exception_store_type _transient_compat_type = {
 123         .name = "N",
 124         .module = THIS_MODULE,
 125         .ctr = transient_ctr,
 126         .dtr = transient_dtr,
 127         .read_metadata = transient_read_metadata,
 128         .prepare_exception = transient_prepare_exception,
 129         .commit_exception = transient_commit_exception,
 130         .usage = transient_usage,
 131         .status = transient_status,
 132 };
 133
 134 int dm_transient_snapshot_init(void)
 135 {
 136         int r;
 137
 138         r = dm_exception_store_type_register(&_transient_type);
 139         if (r) {
 140                 DMWARN("Unable to register transient exception store type");
 141                 return r;
 142         }
 143
 144         r = dm_exception_store_type_register(&_transient_compat_type);
 145         if (r) {
 146                 DMWARN("Unable to register old-style transient exception store type");
 147                 dm_exception_store_type_unregister(&_transient_type);
 148                 return r;
 149         }
 150
 151         return r;
 152 }
 153
 154 void dm_transient_snapshot_exit(void)
 155 {
 156         dm_exception_store_type_unregister(&_transient_type);
 157         dm_exception_store_type_unregister(&_transient_compat_type);
 158 }