qemu

qcow2-bitmap.c (52472B)

---

 /*
  * Bitmaps for the QCOW version 2 format
  *
  * Copyright (c) 2014-2017 Vladimir Sementsov-Ogievskiy
  *
  * This file is derived from qcow2-snapshot.c, original copyright:
  * Copyright (c) 2004-2006 Fabrice Bellard
  *
  * Permission is hereby granted, free of charge, to any person obtaining a copy
  * of this software and associated documentation files (the "Software"), to deal
  * in the Software without restriction, including without limitation the rights
  * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  * copies of the Software, and to permit persons to whom the Software is
  * furnished to do so, subject to the following conditions:
  *
  * The above copyright notice and this permission notice shall be included in
  * all copies or substantial portions of the Software.
  *
  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
  * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
  * THE SOFTWARE.
  */
 
 #include "qemu/osdep.h"
 #include "qapi/error.h"
 #include "qemu/cutils.h"
 
 #include "qcow2.h"
 
 /* NOTICE: BME here means Bitmaps Extension and used as a namespace for
  * _internal_ constants. Please do not use this _internal_ abbreviation for
  * other needs and/or outside of this file. */
 
 /* Bitmap directory entry constraints */
 #define BME_MAX_TABLE_SIZE 0x8000000
 #define BME_MAX_PHYS_SIZE 0x20000000 /* restrict BdrvDirtyBitmap size in RAM */
 #define BME_MAX_GRANULARITY_BITS 31
 #define BME_MIN_GRANULARITY_BITS 9
 #define BME_MAX_NAME_SIZE 1023
 
 /* Size of bitmap table entries */
 #define BME_TABLE_ENTRY_SIZE (sizeof(uint64_t))
 
 QEMU_BUILD_BUG_ON(BME_MAX_NAME_SIZE != BDRV_BITMAP_MAX_NAME_SIZE);
 
 #if BME_MAX_TABLE_SIZE * 8ULL > INT_MAX
 #error In the code bitmap table physical size assumed to fit into int
 #endif
 
 /* Bitmap directory entry flags */
 #define BME_RESERVED_FLAGS 0xfffffffcU
 #define BME_FLAG_IN_USE (1U << 0)
 #define BME_FLAG_AUTO   (1U << 1)
 
 /* bits [1, 8] U [56, 63] are reserved */
 #define BME_TABLE_ENTRY_RESERVED_MASK 0xff000000000001feULL
 #define BME_TABLE_ENTRY_OFFSET_MASK 0x00fffffffffffe00ULL
 #define BME_TABLE_ENTRY_FLAG_ALL_ONES (1ULL << 0)
 
 typedef struct QEMU_PACKED Qcow2BitmapDirEntry {
     /* header is 8 byte aligned */
     uint64_t bitmap_table_offset;
 
     uint32_t bitmap_table_size;
     uint32_t flags;
 
     uint8_t type;
     uint8_t granularity_bits;
     uint16_t name_size;
     uint32_t extra_data_size;
     /* extra data follows  */
     /* name follows  */
 } Qcow2BitmapDirEntry;
 
 typedef struct Qcow2BitmapTable {
     uint64_t offset;
     uint32_t size; /* number of 64bit entries */
     QSIMPLEQ_ENTRY(Qcow2BitmapTable) entry;
 } Qcow2BitmapTable;
 
 typedef struct Qcow2Bitmap {
     Qcow2BitmapTable table;
     uint32_t flags;
     uint8_t granularity_bits;
     char *name;
 
     BdrvDirtyBitmap *dirty_bitmap;
 
     QSIMPLEQ_ENTRY(Qcow2Bitmap) entry;
 } Qcow2Bitmap;
 typedef QSIMPLEQ_HEAD(Qcow2BitmapList, Qcow2Bitmap) Qcow2BitmapList;
 
 typedef enum BitmapType {
     BT_DIRTY_TRACKING_BITMAP = 1
 } BitmapType;
 
 static inline bool can_write(BlockDriverState *bs)
 {
     return !bdrv_is_read_only(bs) && !(bdrv_get_flags(bs) & BDRV_O_INACTIVE);
 }
 
 static int update_header_sync(BlockDriverState *bs)
 {
     int ret;
 
     ret = qcow2_update_header(bs);
     if (ret < 0) {
         return ret;
     }
 
     return bdrv_flush(bs->file->bs);
 }
 
 static inline void bitmap_table_to_be(uint64_t *bitmap_table, size_t size)
 {
     size_t i;
 
     for (i = 0; i < size; ++i) {
         bitmap_table[i] = cpu_to_be64(bitmap_table[i]);
     }
 }
 
 static int check_table_entry(uint64_t entry, int cluster_size)
 {
     uint64_t offset;
 
     if (entry & BME_TABLE_ENTRY_RESERVED_MASK) {
         return -EINVAL;
     }
 
     offset = entry & BME_TABLE_ENTRY_OFFSET_MASK;
     if (offset != 0) {
         /* if offset specified, bit 0 is reserved */
         if (entry & BME_TABLE_ENTRY_FLAG_ALL_ONES) {
             return -EINVAL;
         }
 
         if (offset % cluster_size != 0) {
             return -EINVAL;
         }
     }
 
     return 0;
 }
 
 static int64_t get_bitmap_bytes_needed(int64_t len, uint32_t granularity)
 {
     int64_t num_bits = DIV_ROUND_UP(len, granularity);
 
     return DIV_ROUND_UP(num_bits, 8);
 }
 
 static int check_constraints_on_bitmap(BlockDriverState *bs,
                                        const char *name,
                                        uint32_t granularity,
                                        Error **errp)
 {
     BDRVQcow2State *s = bs->opaque;
     int granularity_bits = ctz32(granularity);
     int64_t len = bdrv_getlength(bs);
     int64_t bitmap_bytes;
 
     assert(granularity > 0);
     assert((granularity & (granularity - 1)) == 0);
 
     if (len < 0) {
         error_setg_errno(errp, -len, "Failed to get size of '%s'",
                          bdrv_get_device_or_node_name(bs));
         return len;
     }
 
     if (granularity_bits > BME_MAX_GRANULARITY_BITS) {
         error_setg(errp, "Granularity exceeds maximum (%llu bytes)",
                    1ULL << BME_MAX_GRANULARITY_BITS);
         return -EINVAL;
     }
     if (granularity_bits < BME_MIN_GRANULARITY_BITS) {
         error_setg(errp, "Granularity is under minimum (%llu bytes)",
                    1ULL << BME_MIN_GRANULARITY_BITS);
         return -EINVAL;
     }
 
     bitmap_bytes = get_bitmap_bytes_needed(len, granularity);
     if ((bitmap_bytes > (uint64_t)BME_MAX_PHYS_SIZE) ||
         (bitmap_bytes > (uint64_t)BME_MAX_TABLE_SIZE * s->cluster_size))
     {
         error_setg(errp, "Too much space will be occupied by the bitmap. "
                    "Use larger granularity");
         return -EINVAL;
     }
 
     if (strlen(name) > BME_MAX_NAME_SIZE) {
         error_setg(errp, "Name length exceeds maximum (%u characters)",
                    BME_MAX_NAME_SIZE);
         return -EINVAL;
     }
 
     return 0;
 }
 
 static void clear_bitmap_table(BlockDriverState *bs, uint64_t *bitmap_table,
                                uint32_t bitmap_table_size)
 {
     BDRVQcow2State *s = bs->opaque;
     int i;
 
     for (i = 0; i < bitmap_table_size; ++i) {
         uint64_t addr = bitmap_table[i] & BME_TABLE_ENTRY_OFFSET_MASK;
         if (!addr) {
             continue;
         }
 
         qcow2_free_clusters(bs, addr, s->cluster_size, QCOW2_DISCARD_ALWAYS);
         bitmap_table[i] = 0;
     }
 }
 
 static int bitmap_table_load(BlockDriverState *bs, Qcow2BitmapTable *tb,
                              uint64_t **bitmap_table)
 {
     int ret;
     BDRVQcow2State *s = bs->opaque;
     uint32_t i;
     uint64_t *table;
 
     assert(tb->size != 0);
     table = g_try_new(uint64_t, tb->size);
     if (table == NULL) {
         return -ENOMEM;
     }
 
     assert(tb->size <= BME_MAX_TABLE_SIZE);
     ret = bdrv_pread(bs->file, tb->offset, tb->size * BME_TABLE_ENTRY_SIZE,
                      table, 0);
     if (ret < 0) {
         goto fail;
     }
 
     for (i = 0; i < tb->size; ++i) {
         table[i] = be64_to_cpu(table[i]);
         ret = check_table_entry(table[i], s->cluster_size);
         if (ret < 0) {
             goto fail;
         }
     }
 
     *bitmap_table = table;
     return 0;
 
 fail:
     g_free(table);
 
     return ret;
 }
 
 static int free_bitmap_clusters(BlockDriverState *bs, Qcow2BitmapTable *tb)
 {
     int ret;
     uint64_t *bitmap_table;
 
     ret = bitmap_table_load(bs, tb, &bitmap_table);
     if (ret < 0) {
         return ret;
     }
 
     clear_bitmap_table(bs, bitmap_table, tb->size);
     qcow2_free_clusters(bs, tb->offset, tb->size * BME_TABLE_ENTRY_SIZE,
                         QCOW2_DISCARD_OTHER);
     g_free(bitmap_table);
 
     tb->offset = 0;
     tb->size = 0;
 
     return 0;
 }
 
 /* load_bitmap_data
  * @bitmap_table entries must satisfy specification constraints.
  * @bitmap must be cleared */
 static int load_bitmap_data(BlockDriverState *bs,
                             const uint64_t *bitmap_table,
                             uint32_t bitmap_table_size,
                             BdrvDirtyBitmap *bitmap)
 {
     int ret = 0;
     BDRVQcow2State *s = bs->opaque;
     uint64_t offset, limit;
     uint64_t bm_size = bdrv_dirty_bitmap_size(bitmap);
     uint8_t *buf = NULL;
     uint64_t i, tab_size =
             size_to_clusters(s,
                 bdrv_dirty_bitmap_serialization_size(bitmap, 0, bm_size));
 
     if (tab_size != bitmap_table_size || tab_size > BME_MAX_TABLE_SIZE) {
         return -EINVAL;
     }
 
     buf = g_malloc(s->cluster_size);
     limit = bdrv_dirty_bitmap_serialization_coverage(s->cluster_size, bitmap);
     for (i = 0, offset = 0; i < tab_size; ++i, offset += limit) {
         uint64_t count = MIN(bm_size - offset, limit);
         uint64_t entry = bitmap_table[i];
         uint64_t data_offset = entry & BME_TABLE_ENTRY_OFFSET_MASK;
 
         assert(check_table_entry(entry, s->cluster_size) == 0);
 
         if (data_offset == 0) {
             if (entry & BME_TABLE_ENTRY_FLAG_ALL_ONES) {
                 bdrv_dirty_bitmap_deserialize_ones(bitmap, offset, count,
                                                    false);
             } else {
                 /* No need to deserialize zeros because the dirty bitmap is
                  * already cleared */
             }
         } else {
             ret = bdrv_pread(bs->file, data_offset, s->cluster_size, buf, 0);
             if (ret < 0) {
                 goto finish;
             }
             bdrv_dirty_bitmap_deserialize_part(bitmap, buf, offset, count,
                                                false);
         }
     }
     ret = 0;
 
     bdrv_dirty_bitmap_deserialize_finish(bitmap);
 
 finish:
     g_free(buf);
 
     return ret;
 }
 
 static BdrvDirtyBitmap *load_bitmap(BlockDriverState *bs,
                                     Qcow2Bitmap *bm, Error **errp)
 {
     int ret;
     uint64_t *bitmap_table = NULL;
     uint32_t granularity;
     BdrvDirtyBitmap *bitmap = NULL;
 
     granularity = 1U << bm->granularity_bits;
     bitmap = bdrv_create_dirty_bitmap(bs, granularity, bm->name, errp);
     if (bitmap == NULL) {
         goto fail;
     }
 
     if (bm->flags & BME_FLAG_IN_USE) {
         /* Data is unusable, skip loading it */
         return bitmap;
     }
 
     ret = bitmap_table_load(bs, &bm->table, &bitmap_table);
     if (ret < 0) {
         error_setg_errno(errp, -ret,
                          "Could not read bitmap_table table from image for "
                          "bitmap '%s'", bm->name);
         goto fail;
     }
 
     ret = load_bitmap_data(bs, bitmap_table, bm->table.size, bitmap);
     if (ret < 0) {
         error_setg_errno(errp, -ret, "Could not read bitmap '%s' from image",
                          bm->name);
         goto fail;
     }
 
     g_free(bitmap_table);
     return bitmap;
 
 fail:
     g_free(bitmap_table);
     if (bitmap != NULL) {
         bdrv_release_dirty_bitmap(bitmap);
     }
 
     return NULL;
 }
 
 /*
  * Bitmap List
  */
 
 /*
  * Bitmap List private functions
  * Only Bitmap List knows about bitmap directory structure in Qcow2.
  */
 
 static inline void bitmap_dir_entry_to_cpu(Qcow2BitmapDirEntry *entry)
 {
     entry->bitmap_table_offset = be64_to_cpu(entry->bitmap_table_offset);
     entry->bitmap_table_size = be32_to_cpu(entry->bitmap_table_size);
     entry->flags = be32_to_cpu(entry->flags);
     entry->name_size = be16_to_cpu(entry->name_size);
     entry->extra_data_size = be32_to_cpu(entry->extra_data_size);
 }
 
 static inline void bitmap_dir_entry_to_be(Qcow2BitmapDirEntry *entry)
 {
     entry->bitmap_table_offset = cpu_to_be64(entry->bitmap_table_offset);
     entry->bitmap_table_size = cpu_to_be32(entry->bitmap_table_size);
     entry->flags = cpu_to_be32(entry->flags);
     entry->name_size = cpu_to_be16(entry->name_size);
     entry->extra_data_size = cpu_to_be32(entry->extra_data_size);
 }
 
 static inline int calc_dir_entry_size(size_t name_size, size_t extra_data_size)
 {
     int size = sizeof(Qcow2BitmapDirEntry) + name_size + extra_data_size;
     return ROUND_UP(size, 8);
 }
 
 static inline int dir_entry_size(Qcow2BitmapDirEntry *entry)
 {
     return calc_dir_entry_size(entry->name_size, entry->extra_data_size);
 }
 
 static inline const char *dir_entry_name_field(Qcow2BitmapDirEntry *entry)
 {
     return (const char *)(entry + 1) + entry->extra_data_size;
 }
 
 static inline char *dir_entry_copy_name(Qcow2BitmapDirEntry *entry)
 {
     const char *name_field = dir_entry_name_field(entry);
     return g_strndup(name_field, entry->name_size);
 }
 
 static inline Qcow2BitmapDirEntry *next_dir_entry(Qcow2BitmapDirEntry *entry)
 {
     return (Qcow2BitmapDirEntry *)((uint8_t *)entry + dir_entry_size(entry));
 }
 
 static int check_dir_entry(BlockDriverState *bs, Qcow2BitmapDirEntry *entry)
 {
     BDRVQcow2State *s = bs->opaque;
     uint64_t phys_bitmap_bytes;
     int64_t len;
 
     bool fail = (entry->bitmap_table_size == 0) ||
                 (entry->bitmap_table_offset == 0) ||
                 (entry->bitmap_table_offset % s->cluster_size) ||
                 (entry->bitmap_table_size > BME_MAX_TABLE_SIZE) ||
                 (entry->granularity_bits > BME_MAX_GRANULARITY_BITS) ||
                 (entry->granularity_bits < BME_MIN_GRANULARITY_BITS) ||
                 (entry->flags & BME_RESERVED_FLAGS) ||
                 (entry->name_size > BME_MAX_NAME_SIZE) ||
                 (entry->type != BT_DIRTY_TRACKING_BITMAP);
 
     if (fail) {
         return -EINVAL;
     }
 
     phys_bitmap_bytes = (uint64_t)entry->bitmap_table_size * s->cluster_size;
     len = bdrv_getlength(bs);
 
     if (len < 0) {
         return len;
     }
 
     if (phys_bitmap_bytes > BME_MAX_PHYS_SIZE) {
         return -EINVAL;
     }
 
     if (!(entry->flags & BME_FLAG_IN_USE) &&
         (len > ((phys_bitmap_bytes * 8) << entry->granularity_bits)))
     {
         /*
          * We've loaded a valid bitmap (IN_USE not set) or we are going to
          * store a valid bitmap, but the allocated bitmap table size is not
          * enough to store this bitmap.
          *
          * Note, that it's OK to have an invalid bitmap with invalid size due
          * to a bitmap that was not correctly saved after image resize.
          */
         return -EINVAL;
     }
 
     return 0;
 }
 
 static inline void bitmap_directory_to_be(uint8_t *dir, size_t size)
 {
     uint8_t *end = dir + size;
     while (dir < end) {
         Qcow2BitmapDirEntry *e = (Qcow2BitmapDirEntry *)dir;
         dir += dir_entry_size(e);
 
         bitmap_dir_entry_to_be(e);
     }
 }
 
 /*
  * Bitmap List public functions
  */
 
 static void bitmap_free(Qcow2Bitmap *bm)
 {
     if (bm == NULL) {
         return;
     }
 
     g_free(bm->name);
     g_free(bm);
 }
 
 static void bitmap_list_free(Qcow2BitmapList *bm_list)
 {
     Qcow2Bitmap *bm;
 
     if (bm_list == NULL) {
         return;
     }
 
     while ((bm = QSIMPLEQ_FIRST(bm_list)) != NULL) {
         QSIMPLEQ_REMOVE_HEAD(bm_list, entry);
         bitmap_free(bm);
     }
 
     g_free(bm_list);
 }
 
 static Qcow2BitmapList *bitmap_list_new(void)
 {
     Qcow2BitmapList *bm_list = g_new(Qcow2BitmapList, 1);
     QSIMPLEQ_INIT(bm_list);
 
     return bm_list;
 }
 
 static uint32_t bitmap_list_count(Qcow2BitmapList *bm_list)
 {
     Qcow2Bitmap *bm;
     uint32_t nb_bitmaps = 0;
 
     QSIMPLEQ_FOREACH(bm, bm_list, entry) {
         nb_bitmaps++;
     }
 
     return nb_bitmaps;
 }
 
 /* bitmap_list_load
  * Get bitmap list from qcow2 image. Actually reads bitmap directory,
  * checks it and convert to bitmap list.
  */
 static Qcow2BitmapList *bitmap_list_load(BlockDriverState *bs, uint64_t offset,
                                          uint64_t size, Error **errp)
 {
     int ret;
     BDRVQcow2State *s = bs->opaque;
     uint8_t *dir, *dir_end;
     Qcow2BitmapDirEntry *e;
     uint32_t nb_dir_entries = 0;
     Qcow2BitmapList *bm_list = NULL;
 
     if (size == 0) {
         error_setg(errp, "Requested bitmap directory size is zero");
         return NULL;
     }
 
     if (size > QCOW2_MAX_BITMAP_DIRECTORY_SIZE) {
         error_setg(errp, "Requested bitmap directory size is too big");
         return NULL;
     }
 
     dir = g_try_malloc(size);
     if (dir == NULL) {
         error_setg(errp, "Failed to allocate space for bitmap directory");
         return NULL;
     }
     dir_end = dir + size;
 
     ret = bdrv_pread(bs->file, offset, size, dir, 0);
     if (ret < 0) {
         error_setg_errno(errp, -ret, "Failed to read bitmap directory");
         goto fail;
     }
 
     bm_list = bitmap_list_new();
     for (e = (Qcow2BitmapDirEntry *)dir;
          e < (Qcow2BitmapDirEntry *)dir_end;
          e = next_dir_entry(e))
     {
         Qcow2Bitmap *bm;
 
         if ((uint8_t *)(e + 1) > dir_end) {
             goto broken_dir;
         }
 
         if (++nb_dir_entries > s->nb_bitmaps) {
             error_setg(errp, "More bitmaps found than specified in header"
                        " extension");
             goto fail;
         }
         bitmap_dir_entry_to_cpu(e);
 
         if ((uint8_t *)next_dir_entry(e) > dir_end) {
             goto broken_dir;
         }
 
         if (e->extra_data_size != 0) {
             error_setg(errp, "Bitmap extra data is not supported");
             goto fail;
         }
 
         ret = check_dir_entry(bs, e);
         if (ret < 0) {
             error_setg(errp, "Bitmap '%.*s' doesn't satisfy the constraints",
                        e->name_size, dir_entry_name_field(e));
             goto fail;
         }
 
         bm = g_new0(Qcow2Bitmap, 1);
         bm->table.offset = e->bitmap_table_offset;
         bm->table.size = e->bitmap_table_size;
         bm->flags = e->flags;
         bm->granularity_bits = e->granularity_bits;
         bm->name = dir_entry_copy_name(e);
         QSIMPLEQ_INSERT_TAIL(bm_list, bm, entry);
     }
 
     if (nb_dir_entries != s->nb_bitmaps) {
         error_setg(errp, "Less bitmaps found than specified in header"
                          " extension");
         goto fail;
     }
 
     if ((uint8_t *)e != dir_end) {
         goto broken_dir;
     }
 
     g_free(dir);
     return bm_list;
 
 broken_dir:
     error_setg(errp, "Broken bitmap directory");
 
 fail:
     g_free(dir);
     bitmap_list_free(bm_list);
 
     return NULL;
 }
 
 int qcow2_check_bitmaps_refcounts(BlockDriverState *bs, BdrvCheckResult *res,
                                   void **refcount_table,
                                   int64_t *refcount_table_size)
 {
     int ret;
     BDRVQcow2State *s = bs->opaque;
     Qcow2BitmapList *bm_list;
     Qcow2Bitmap *bm;
 
     if (s->nb_bitmaps == 0) {
         return 0;
     }
 
     ret = qcow2_inc_refcounts_imrt(bs, res, refcount_table, refcount_table_size,
                                    s->bitmap_directory_offset,
                                    s->bitmap_directory_size);
     if (ret < 0) {
         return ret;
     }
 
     bm_list = bitmap_list_load(bs, s->bitmap_directory_offset,
                                s->bitmap_directory_size, NULL);
     if (bm_list == NULL) {
         res->corruptions++;
         return -EINVAL;
     }
 
     QSIMPLEQ_FOREACH(bm, bm_list, entry) {
         uint64_t *bitmap_table = NULL;
         int i;
 
         ret = qcow2_inc_refcounts_imrt(bs, res,
                                        refcount_table, refcount_table_size,
                                        bm->table.offset,
                                        bm->table.size * BME_TABLE_ENTRY_SIZE);
         if (ret < 0) {
             goto out;
         }
 
         ret = bitmap_table_load(bs, &bm->table, &bitmap_table);
         if (ret < 0) {
             res->corruptions++;
             goto out;
         }
 
         for (i = 0; i < bm->table.size; ++i) {
             uint64_t entry = bitmap_table[i];
             uint64_t offset = entry & BME_TABLE_ENTRY_OFFSET_MASK;
 
             if (check_table_entry(entry, s->cluster_size) < 0) {
                 res->corruptions++;
                 continue;
             }
 
             if (offset == 0) {
                 continue;
             }
 
             ret = qcow2_inc_refcounts_imrt(bs, res,
                                            refcount_table, refcount_table_size,
                                            offset, s->cluster_size);
             if (ret < 0) {
                 g_free(bitmap_table);
                 goto out;
             }
         }
 
         g_free(bitmap_table);
     }
 
 out:
     bitmap_list_free(bm_list);
 
     return ret;
 }
 
 /* bitmap_list_store
  * Store bitmap list to qcow2 image as a bitmap directory.
  * Everything is checked.
  */
 static int bitmap_list_store(BlockDriverState *bs, Qcow2BitmapList *bm_list,
                              uint64_t *offset, uint64_t *size, bool in_place)
 {
     int ret;
     uint8_t *dir;
     int64_t dir_offset = 0;
     uint64_t dir_size = 0;
     Qcow2Bitmap *bm;
     Qcow2BitmapDirEntry *e;
 
     QSIMPLEQ_FOREACH(bm, bm_list, entry) {
         dir_size += calc_dir_entry_size(strlen(bm->name), 0);
     }
 
     if (dir_size == 0 || dir_size > QCOW2_MAX_BITMAP_DIRECTORY_SIZE) {
         return -EINVAL;
     }
 
     if (in_place) {
         if (*size != dir_size || *offset == 0) {
             return -EINVAL;
         }
 
         dir_offset = *offset;
     }
 
     dir = g_try_malloc0(dir_size);
     if (dir == NULL) {
         return -ENOMEM;
     }
 
     e = (Qcow2BitmapDirEntry *)dir;
     QSIMPLEQ_FOREACH(bm, bm_list, entry) {
         e->bitmap_table_offset = bm->table.offset;
         e->bitmap_table_size = bm->table.size;
         e->flags = bm->flags;
         e->type = BT_DIRTY_TRACKING_BITMAP;
         e->granularity_bits = bm->granularity_bits;
         e->name_size = strlen(bm->name);
         e->extra_data_size = 0;
         memcpy(e + 1, bm->name, e->name_size);
 
         if (check_dir_entry(bs, e) < 0) {
             ret = -EINVAL;
             goto fail;
         }
 
         e = next_dir_entry(e);
     }
 
     bitmap_directory_to_be(dir, dir_size);
 
     if (!in_place) {
         dir_offset = qcow2_alloc_clusters(bs, dir_size);
         if (dir_offset < 0) {
             ret = dir_offset;
             goto fail;
         }
     }
 
     /* Actually, even in the in-place case ignoring QCOW2_OL_BITMAP_DIRECTORY
      * is not necessary, because we drop QCOW2_AUTOCLEAR_BITMAPS when updating
      * bitmap directory in-place (actually, turn-off the extension), which is
      * checked in qcow2_check_metadata_overlap() */
     ret = qcow2_pre_write_overlap_check(
             bs, in_place ? QCOW2_OL_BITMAP_DIRECTORY : 0, dir_offset, dir_size,
             false);
     if (ret < 0) {
         goto fail;
     }
 
     ret = bdrv_pwrite(bs->file, dir_offset, dir_size, dir, 0);
     if (ret < 0) {
         goto fail;
     }
 
     g_free(dir);
 
     if (!in_place) {
         *size = dir_size;
         *offset = dir_offset;
     }
 
     return 0;
 
 fail:
     g_free(dir);
 
     if (!in_place && dir_offset > 0) {
         qcow2_free_clusters(bs, dir_offset, dir_size, QCOW2_DISCARD_OTHER);
     }
 
     return ret;
 }
 
 /*
  * Bitmap List end
  */
 
 static int update_ext_header_and_dir_in_place(BlockDriverState *bs,
                                               Qcow2BitmapList *bm_list)
 {
     BDRVQcow2State *s = bs->opaque;
     int ret;
 
     if (!(s->autoclear_features & QCOW2_AUTOCLEAR_BITMAPS) ||
         bm_list == NULL || QSIMPLEQ_EMPTY(bm_list) ||
         bitmap_list_count(bm_list) != s->nb_bitmaps)
     {
         return -EINVAL;
     }
 
     s->autoclear_features &= ~(uint64_t)QCOW2_AUTOCLEAR_BITMAPS;
     ret = update_header_sync(bs);
     if (ret < 0) {
         /* Two variants are possible here:
          * 1. Autoclear flag is dropped, all bitmaps will be lost.
          * 2. Autoclear flag is not dropped, old state is left.
          */
         return ret;
     }
 
     /* autoclear bit is not set, so we can safely update bitmap directory */
 
     ret = bitmap_list_store(bs, bm_list, &s->bitmap_directory_offset,
                             &s->bitmap_directory_size, true);
     if (ret < 0) {
         /* autoclear bit is cleared, so all leaked clusters would be removed on
          * qemu-img check */
         return ret;
     }
 
     ret = update_header_sync(bs);
     if (ret < 0) {
         /* autoclear bit is cleared, so all leaked clusters would be removed on
          * qemu-img check */
         return ret;
     }
 
     s->autoclear_features |= QCOW2_AUTOCLEAR_BITMAPS;
     return update_header_sync(bs);
     /* If final update_header_sync() fails, two variants are possible:
      * 1. Autoclear flag is not set, all bitmaps will be lost.
      * 2. Autoclear flag is set, header and directory are successfully updated.
      */
 }
 
 static int update_ext_header_and_dir(BlockDriverState *bs,
                                      Qcow2BitmapList *bm_list)
 {
     BDRVQcow2State *s = bs->opaque;
     int ret;
     uint64_t new_offset = 0;
     uint64_t new_size = 0;
     uint32_t new_nb_bitmaps = 0;
     uint64_t old_offset = s->bitmap_directory_offset;
     uint64_t old_size = s->bitmap_directory_size;
     uint32_t old_nb_bitmaps = s->nb_bitmaps;
     uint64_t old_autocl = s->autoclear_features;
 
     if (bm_list != NULL && !QSIMPLEQ_EMPTY(bm_list)) {
         new_nb_bitmaps = bitmap_list_count(bm_list);
 
         if (new_nb_bitmaps > QCOW2_MAX_BITMAPS) {
             return -EINVAL;
         }
 
         ret = bitmap_list_store(bs, bm_list, &new_offset, &new_size, false);
         if (ret < 0) {
             return ret;
         }
 
         ret = qcow2_flush_caches(bs);
         if (ret < 0) {
             goto fail;
         }
 
         s->autoclear_features |= QCOW2_AUTOCLEAR_BITMAPS;
     } else {
         s->autoclear_features &= ~(uint64_t)QCOW2_AUTOCLEAR_BITMAPS;
     }
 
     s->bitmap_directory_offset = new_offset;
     s->bitmap_directory_size = new_size;
     s->nb_bitmaps = new_nb_bitmaps;
 
     ret = update_header_sync(bs);
     if (ret < 0) {
         goto fail;
     }
 
     if (old_size > 0) {
         qcow2_free_clusters(bs, old_offset, old_size, QCOW2_DISCARD_OTHER);
     }
 
     return 0;
 
 fail:
     if (new_offset > 0) {
         qcow2_free_clusters(bs, new_offset, new_size, QCOW2_DISCARD_OTHER);
     }
 
     s->bitmap_directory_offset = old_offset;
     s->bitmap_directory_size = old_size;
     s->nb_bitmaps = old_nb_bitmaps;
     s->autoclear_features = old_autocl;
 
     return ret;
 }
 
 /* for g_slist_foreach for GSList of BdrvDirtyBitmap* elements */
 static void release_dirty_bitmap_helper(gpointer bitmap,
                                         gpointer bs)
 {
     bdrv_release_dirty_bitmap(bitmap);
 }
 
 /* for g_slist_foreach for GSList of BdrvDirtyBitmap* elements */
 static void set_readonly_helper(gpointer bitmap, gpointer value)
 {
     bdrv_dirty_bitmap_set_readonly(bitmap, (bool)value);
 }
 
 /*
  * Return true on success, false on failure.
  * If header_updated is not NULL then it is set appropriately regardless of
  * the return value.
  */
 bool coroutine_fn qcow2_load_dirty_bitmaps(BlockDriverState *bs,
                                            bool *header_updated, Error **errp)
 {
     BDRVQcow2State *s = bs->opaque;
     Qcow2BitmapList *bm_list;
     Qcow2Bitmap *bm;
     GSList *created_dirty_bitmaps = NULL;
     bool needs_update = false;
 
     if (header_updated) {
         *header_updated = false;
     }
 
     if (s->nb_bitmaps == 0) {
         /* No bitmaps - nothing to do */
         return true;
     }
 
     bm_list = bitmap_list_load(bs, s->bitmap_directory_offset,
                                s->bitmap_directory_size, errp);
     if (bm_list == NULL) {
         return false;
     }
 
     QSIMPLEQ_FOREACH(bm, bm_list, entry) {
         BdrvDirtyBitmap *bitmap;
 
         if ((bm->flags & BME_FLAG_IN_USE) &&
             bdrv_find_dirty_bitmap(bs, bm->name))
         {
             /*
              * We already have corresponding BdrvDirtyBitmap, and bitmap in the
              * image is marked IN_USE. Firstly, this state is valid, no reason
              * to consider existing BdrvDirtyBitmap to be bad. Secondly it's
              * absolutely possible, when we do migration with shared storage
              * with dirty-bitmaps capability enabled: if the bitmap was loaded
              * from this storage before migration start, the storage will
              * of-course contain IN_USE outdated version of the bitmap, and we
              * should not load it on migration target, as we already have this
              * bitmap, being migrated.
              */
             continue;
         }
 
         bitmap = load_bitmap(bs, bm, errp);
         if (bitmap == NULL) {
             goto fail;
         }
 
         bdrv_dirty_bitmap_set_persistence(bitmap, true);
         if (bm->flags & BME_FLAG_IN_USE) {
             bdrv_dirty_bitmap_set_inconsistent(bitmap);
         } else {
             /* NB: updated flags only get written if can_write(bs) is true. */
             bm->flags |= BME_FLAG_IN_USE;
             needs_update = true;
         }
         if (!(bm->flags & BME_FLAG_AUTO)) {
             bdrv_disable_dirty_bitmap(bitmap);
         }
         created_dirty_bitmaps =
             g_slist_append(created_dirty_bitmaps, bitmap);
     }
 
     if (needs_update && can_write(bs)) {
         /* in_use flags must be updated */
         int ret = update_ext_header_and_dir_in_place(bs, bm_list);
         if (ret < 0) {
             error_setg_errno(errp, -ret, "Can't update bitmap directory");
             goto fail;
         }
         if (header_updated) {
             *header_updated = true;
         }
     }
 
     if (!can_write(bs)) {
         g_slist_foreach(created_dirty_bitmaps, set_readonly_helper,
                         (gpointer)true);
     }
 
     g_slist_free(created_dirty_bitmaps);
     bitmap_list_free(bm_list);
 
     return true;
 
 fail:
     g_slist_foreach(created_dirty_bitmaps, release_dirty_bitmap_helper, bs);
     g_slist_free(created_dirty_bitmaps);
     bitmap_list_free(bm_list);
 
     return false;
 }
 
 
 static Qcow2BitmapInfoFlagsList *get_bitmap_info_flags(uint32_t flags)
 {
     Qcow2BitmapInfoFlagsList *list = NULL;
     Qcow2BitmapInfoFlagsList **tail = &list;
     int i;
 
     static const struct {
         int bme;  /* Bitmap directory entry flags */
         int info; /* The flags to report to the user */
     } map[] = {
         { BME_FLAG_IN_USE, QCOW2_BITMAP_INFO_FLAGS_IN_USE },
         { BME_FLAG_AUTO,   QCOW2_BITMAP_INFO_FLAGS_AUTO },
     };
 
     int map_size = ARRAY_SIZE(map);
 
     for (i = 0; i < map_size; ++i) {
         if (flags & map[i].bme) {
             QAPI_LIST_APPEND(tail, map[i].info);
             flags &= ~map[i].bme;
         }
     }
     /* Check if the BME_* mapping above is complete */
     assert(!flags);
 
     return list;
 }
 
 /*
  * qcow2_get_bitmap_info_list()
  * Returns a list of QCOW2 bitmap details.
  * On success return true with info_list set (note, that if there are no
  * bitmaps, info_list is set to NULL).
  * On failure return false with errp set.
  */
 bool qcow2_get_bitmap_info_list(BlockDriverState *bs,
                                 Qcow2BitmapInfoList **info_list, Error **errp)
 {
     BDRVQcow2State *s = bs->opaque;
     Qcow2BitmapList *bm_list;
     Qcow2Bitmap *bm;
     Qcow2BitmapInfoList **tail;
 
     if (s->nb_bitmaps == 0) {
         *info_list = NULL;
         return true;
     }
 
     bm_list = bitmap_list_load(bs, s->bitmap_directory_offset,
                                s->bitmap_directory_size, errp);
     if (!bm_list) {
         return false;
     }
 
     *info_list = NULL;
     tail = info_list;
 
     QSIMPLEQ_FOREACH(bm, bm_list, entry) {
         Qcow2BitmapInfo *info = g_new0(Qcow2BitmapInfo, 1);
         info->granularity = 1U << bm->granularity_bits;
         info->name = g_strdup(bm->name);
         info->flags = get_bitmap_info_flags(bm->flags & ~BME_RESERVED_FLAGS);
         QAPI_LIST_APPEND(tail, info);
     }
 
     bitmap_list_free(bm_list);
 
     return true;
 }
 
 int qcow2_reopen_bitmaps_rw(BlockDriverState *bs, Error **errp)
 {
     BDRVQcow2State *s = bs->opaque;
     Qcow2BitmapList *bm_list;
     Qcow2Bitmap *bm;
     GSList *ro_dirty_bitmaps = NULL;
     int ret = -EINVAL;
     bool need_header_update = false;
 
     if (s->nb_bitmaps == 0) {
         /* No bitmaps - nothing to do */
         return 0;
     }
 
     bm_list = bitmap_list_load(bs, s->bitmap_directory_offset,
                                s->bitmap_directory_size, errp);
     if (bm_list == NULL) {
         return -EINVAL;
     }
 
     QSIMPLEQ_FOREACH(bm, bm_list, entry) {
         BdrvDirtyBitmap *bitmap = bdrv_find_dirty_bitmap(bs, bm->name);
 
         if (!bitmap) {
             error_setg(errp, "Unexpected bitmap '%s' in image '%s'",
                        bm->name, bs->filename);
             goto out;
         }
 
         if (!(bm->flags & BME_FLAG_IN_USE)) {
             if (!bdrv_dirty_bitmap_readonly(bitmap)) {
                 error_setg(errp, "Corruption: bitmap '%s' is not marked IN_USE "
                            "in the image '%s' and not marked readonly in RAM",
                            bm->name, bs->filename);
                 goto out;
             }
             if (bdrv_dirty_bitmap_inconsistent(bitmap)) {
                 error_setg(errp, "Corruption: bitmap '%s' is inconsistent but "
                            "is not marked IN_USE in the image '%s'", bm->name,
                            bs->filename);
                 goto out;
             }
 
             bm->flags |= BME_FLAG_IN_USE;
             need_header_update = true;
         } else {
             /*
              * What if flags already has BME_FLAG_IN_USE ?
              *
              * 1. if we are reopening RW -> RW it's OK, of course.
              * 2. if we are reopening RO -> RW:
              *   2.1 if @bitmap is inconsistent, it's OK. It means that it was
              *       inconsistent (IN_USE) when we loaded it
              *   2.2 if @bitmap is not inconsistent. This seems to be impossible
              *       and implies third party interaction. Let's error-out for
              *       safety.
              */
             if (bdrv_dirty_bitmap_readonly(bitmap) &&
                 !bdrv_dirty_bitmap_inconsistent(bitmap))
             {
                 error_setg(errp, "Corruption: bitmap '%s' is marked IN_USE "
                            "in the image '%s' but it is readonly and "
                            "consistent in RAM",
                            bm->name, bs->filename);
                 goto out;
             }
         }
 
         if (bdrv_dirty_bitmap_readonly(bitmap)) {
             ro_dirty_bitmaps = g_slist_append(ro_dirty_bitmaps, bitmap);
         }
     }
 
     if (need_header_update) {
         if (!can_write(bs->file->bs) || !(bs->file->perm & BLK_PERM_WRITE)) {
             error_setg(errp, "Failed to reopen bitmaps rw: no write access "
                        "the protocol file");
             goto out;
         }
 
         /* in_use flags must be updated */
         ret = update_ext_header_and_dir_in_place(bs, bm_list);
         if (ret < 0) {
             error_setg_errno(errp, -ret, "Cannot update bitmap directory");
             goto out;
         }
     }
 
     g_slist_foreach(ro_dirty_bitmaps, set_readonly_helper, (gpointer)false);
     ret = 0;
 
 out:
     g_slist_free(ro_dirty_bitmaps);
     bitmap_list_free(bm_list);
 
     return ret;
 }
 
 /* Checks to see if it's safe to resize bitmaps */
 int qcow2_truncate_bitmaps_check(BlockDriverState *bs, Error **errp)
 {
     BDRVQcow2State *s = bs->opaque;
     Qcow2BitmapList *bm_list;
     Qcow2Bitmap *bm;
     int ret = 0;
 
     if (s->nb_bitmaps == 0) {
         return 0;
     }
 
     bm_list = bitmap_list_load(bs, s->bitmap_directory_offset,
                                s->bitmap_directory_size, errp);
     if (bm_list == NULL) {
         return -EINVAL;
     }
 
     QSIMPLEQ_FOREACH(bm, bm_list, entry) {
         BdrvDirtyBitmap *bitmap = bdrv_find_dirty_bitmap(bs, bm->name);
         if (bitmap == NULL) {
             /*
              * We rely on all bitmaps being in-memory to be able to resize them,
              * Otherwise, we'd need to resize them on disk explicitly
              */
             error_setg(errp, "Cannot resize qcow2 with persistent bitmaps that "
                        "were not loaded into memory");
             ret = -ENOTSUP;
             goto out;
         }
 
         /*
          * The checks against readonly and busy are redundant, but certainly
          * do no harm. checks against inconsistent are crucial:
          */
         if (bdrv_dirty_bitmap_check(bitmap, BDRV_BITMAP_DEFAULT, errp)) {
             ret = -ENOTSUP;
             goto out;
         }
     }
 
 out:
     bitmap_list_free(bm_list);
     return ret;
 }
 
 /* store_bitmap_data()
  * Store bitmap to image, filling bitmap table accordingly.
  */
 static uint64_t *store_bitmap_data(BlockDriverState *bs,
                                    BdrvDirtyBitmap *bitmap,
                                    uint32_t *bitmap_table_size, Error **errp)
 {
     int ret;
     BDRVQcow2State *s = bs->opaque;
     int64_t offset;
     uint64_t limit;
     uint64_t bm_size = bdrv_dirty_bitmap_size(bitmap);
     const char *bm_name = bdrv_dirty_bitmap_name(bitmap);
     uint8_t *buf = NULL;
     uint64_t *tb;
     uint64_t tb_size =
             size_to_clusters(s,
                 bdrv_dirty_bitmap_serialization_size(bitmap, 0, bm_size));
 
     if (tb_size > BME_MAX_TABLE_SIZE ||
         tb_size * s->cluster_size > BME_MAX_PHYS_SIZE)
     {
         error_setg(errp, "Bitmap '%s' is too big", bm_name);
         return NULL;
     }
 
     tb = g_try_new0(uint64_t, tb_size);
     if (tb == NULL) {
         error_setg(errp, "No memory");
         return NULL;
     }
 
     buf = g_malloc(s->cluster_size);
     limit = bdrv_dirty_bitmap_serialization_coverage(s->cluster_size, bitmap);
     assert(DIV_ROUND_UP(bm_size, limit) == tb_size);
 
     offset = 0;
     while ((offset = bdrv_dirty_bitmap_next_dirty(bitmap, offset, INT64_MAX))
            >= 0)
     {
         uint64_t cluster = offset / limit;
         uint64_t end, write_size;
         int64_t off;
 
         /*
          * We found the first dirty offset, but want to write out the
          * entire cluster of the bitmap that includes that offset,
          * including any leading zero bits.
          */
         offset = QEMU_ALIGN_DOWN(offset, limit);
         end = MIN(bm_size, offset + limit);
         write_size = bdrv_dirty_bitmap_serialization_size(bitmap, offset,
                                                           end - offset);
         assert(write_size <= s->cluster_size);
 
         off = qcow2_alloc_clusters(bs, s->cluster_size);
         if (off < 0) {
             error_setg_errno(errp, -off,
                              "Failed to allocate clusters for bitmap '%s'",
                              bm_name);
             goto fail;
         }
         tb[cluster] = off;
 
         bdrv_dirty_bitmap_serialize_part(bitmap, buf, offset, end - offset);
         if (write_size < s->cluster_size) {
             memset(buf + write_size, 0, s->cluster_size - write_size);
         }
 
         ret = qcow2_pre_write_overlap_check(bs, 0, off, s->cluster_size, false);
         if (ret < 0) {
             error_setg_errno(errp, -ret, "Qcow2 overlap check failed");
             goto fail;
         }
 
         ret = bdrv_pwrite(bs->file, off, s->cluster_size, buf, 0);
         if (ret < 0) {
             error_setg_errno(errp, -ret, "Failed to write bitmap '%s' to file",
                              bm_name);
             goto fail;
         }
 
         offset = end;
     }
 
     *bitmap_table_size = tb_size;
     g_free(buf);
 
     return tb;
 
 fail:
     clear_bitmap_table(bs, tb, tb_size);
     g_free(buf);
     g_free(tb);
 
     return NULL;
 }
 
 /* store_bitmap()
  * Store bm->dirty_bitmap to qcow2.
  * Set bm->table_offset and bm->table_size accordingly.
  */
 static int store_bitmap(BlockDriverState *bs, Qcow2Bitmap *bm, Error **errp)
 {
     int ret;
     uint64_t *tb;
     int64_t tb_offset;
     uint32_t tb_size;
     BdrvDirtyBitmap *bitmap = bm->dirty_bitmap;
     const char *bm_name;
 
     assert(bitmap != NULL);
 
     bm_name = bdrv_dirty_bitmap_name(bitmap);
 
     tb = store_bitmap_data(bs, bitmap, &tb_size, errp);
     if (tb == NULL) {
         return -EINVAL;
     }
 
     assert(tb_size <= BME_MAX_TABLE_SIZE);
     tb_offset = qcow2_alloc_clusters(bs, tb_size * sizeof(tb[0]));
     if (tb_offset < 0) {
         error_setg_errno(errp, -tb_offset,
                          "Failed to allocate clusters for bitmap '%s'",
                          bm_name);
         ret = tb_offset;
         goto fail;
     }
 
     ret = qcow2_pre_write_overlap_check(bs, 0, tb_offset,
                                         tb_size * sizeof(tb[0]), false);
     if (ret < 0) {
         error_setg_errno(errp, -ret, "Qcow2 overlap check failed");
         goto fail;
     }
 
     bitmap_table_to_be(tb, tb_size);
     ret = bdrv_pwrite(bs->file, tb_offset, tb_size * sizeof(tb[0]), tb, 0);
     if (ret < 0) {
         error_setg_errno(errp, -ret, "Failed to write bitmap '%s' to file",
                          bm_name);
         goto fail;
     }
 
     g_free(tb);
 
     bm->table.offset = tb_offset;
     bm->table.size = tb_size;
 
     return 0;
 
 fail:
     clear_bitmap_table(bs, tb, tb_size);
 
     if (tb_offset > 0) {
         qcow2_free_clusters(bs, tb_offset, tb_size * sizeof(tb[0]),
                             QCOW2_DISCARD_OTHER);
     }
 
     g_free(tb);
 
     return ret;
 }
 
 static Qcow2Bitmap *find_bitmap_by_name(Qcow2BitmapList *bm_list,
                                         const char *name)
 {
     Qcow2Bitmap *bm;
 
     QSIMPLEQ_FOREACH(bm, bm_list, entry) {
         if (strcmp(name, bm->name) == 0) {
             return bm;
         }
     }
 
     return NULL;
 }
 
 int coroutine_fn qcow2_co_remove_persistent_dirty_bitmap(BlockDriverState *bs,
                                                          const char *name,
                                                          Error **errp)
 {
     int ret;
     BDRVQcow2State *s = bs->opaque;
     Qcow2Bitmap *bm = NULL;
     Qcow2BitmapList *bm_list;
 
     if (s->nb_bitmaps == 0) {
         /*
          * Absence of the bitmap is not an error: see explanation above
          * bdrv_co_remove_persistent_dirty_bitmap() definition.
          */
         return 0;
     }
 
     qemu_co_mutex_lock(&s->lock);
 
     bm_list = bitmap_list_load(bs, s->bitmap_directory_offset,
                                s->bitmap_directory_size, errp);
     if (bm_list == NULL) {
         ret = -EIO;
         goto out;
     }
 
     bm = find_bitmap_by_name(bm_list, name);
     if (bm == NULL) {
         /* Absence of the bitmap is not an error, see above. */
         ret = 0;
         goto out;
     }
 
     QSIMPLEQ_REMOVE(bm_list, bm, Qcow2Bitmap, entry);
 
     ret = update_ext_header_and_dir(bs, bm_list);
     if (ret < 0) {
         error_setg_errno(errp, -ret, "Failed to update bitmap extension");
         goto out;
     }
 
     free_bitmap_clusters(bs, &bm->table);
 
 out:
     qemu_co_mutex_unlock(&s->lock);
 
     bitmap_free(bm);
     bitmap_list_free(bm_list);
 
     return ret;
 }
 
 /*
  * qcow2_store_persistent_dirty_bitmaps
  *
  * Stores persistent BdrvDirtyBitmap objects.
  *
  * @release_stored: if true, release BdrvDirtyBitmap's after storing to the
  * image. This is used in two cases, both via qcow2_inactivate:
  * 1. bdrv_close: It's correct to remove bitmaps on close.
  * 2. migration: If bitmaps are migrated through migration channel via
  *    'dirty-bitmaps' migration capability they are not handled by this code.
  *    Otherwise, it's OK to drop BdrvDirtyBitmap's and reload them on
  *    invalidation.
  *
  * Anyway, it's correct to remove BdrvDirtyBitmap's on inactivation, as
  * inactivation means that we lose control on disk, and therefore on bitmaps,
  * we should sync them and do not touch more.
  *
  * Contrariwise, we don't want to release any bitmaps on just reopen-to-ro,
  * when we need to store them, as image is still under our control, and it's
  * good to keep all the bitmaps in read-only mode. Moreover, keeping them
  * read-only is correct because this is what would happen if we opened the node
  * readonly to begin with, and whether we opened directly or reopened to that
  * state shouldn't matter for the state we get afterward.
  */
 bool qcow2_store_persistent_dirty_bitmaps(BlockDriverState *bs,
                                           bool release_stored, Error **errp)
 {
     ERRP_GUARD();
     BdrvDirtyBitmap *bitmap;
     BDRVQcow2State *s = bs->opaque;
     uint32_t new_nb_bitmaps = s->nb_bitmaps;
     uint64_t new_dir_size = s->bitmap_directory_size;
     int ret;
     Qcow2BitmapList *bm_list;
     Qcow2Bitmap *bm;
     QSIMPLEQ_HEAD(, Qcow2BitmapTable) drop_tables;
     Qcow2BitmapTable *tb, *tb_next;
     bool need_write = false;
 
     QSIMPLEQ_INIT(&drop_tables);
 
     if (s->nb_bitmaps == 0) {
         bm_list = bitmap_list_new();
     } else {
         bm_list = bitmap_list_load(bs, s->bitmap_directory_offset,
                                    s->bitmap_directory_size, errp);
         if (bm_list == NULL) {
             return false;
         }
     }
 
     /* check constraints and names */
     FOR_EACH_DIRTY_BITMAP(bs, bitmap) {
         const char *name = bdrv_dirty_bitmap_name(bitmap);
         uint32_t granularity = bdrv_dirty_bitmap_granularity(bitmap);
         Qcow2Bitmap *bm;
 
         if (!bdrv_dirty_bitmap_get_persistence(bitmap) ||
             bdrv_dirty_bitmap_inconsistent(bitmap)) {
             continue;
         }
 
         if (bdrv_dirty_bitmap_readonly(bitmap)) {
             /*
              * Store the bitmap in the associated Qcow2Bitmap so it
              * can be released later
              */
             bm = find_bitmap_by_name(bm_list, name);
             if (bm) {
                 bm->dirty_bitmap = bitmap;
             }
             continue;
         }
 
         need_write = true;
 
         if (check_constraints_on_bitmap(bs, name, granularity, errp) < 0) {
             error_prepend(errp, "Bitmap '%s' doesn't satisfy the constraints: ",
                           name);
             goto fail;
         }
 
         bm = find_bitmap_by_name(bm_list, name);
         if (bm == NULL) {
             if (++new_nb_bitmaps > QCOW2_MAX_BITMAPS) {
                 error_setg(errp, "Too many persistent bitmaps");
                 goto fail;
             }
 
             new_dir_size += calc_dir_entry_size(strlen(name), 0);
             if (new_dir_size > QCOW2_MAX_BITMAP_DIRECTORY_SIZE) {
                 error_setg(errp, "Bitmap directory is too large");
                 goto fail;
             }
 
             bm = g_new0(Qcow2Bitmap, 1);
             bm->name = g_strdup(name);
             QSIMPLEQ_INSERT_TAIL(bm_list, bm, entry);
         } else {
             if (!(bm->flags & BME_FLAG_IN_USE)) {
                 error_setg(errp, "Bitmap '%s' already exists in the image",
                            name);
                 goto fail;
             }
             tb = g_memdup(&bm->table, sizeof(bm->table));
             bm->table.offset = 0;
             bm->table.size = 0;
             QSIMPLEQ_INSERT_TAIL(&drop_tables, tb, entry);
         }
         bm->flags = bdrv_dirty_bitmap_enabled(bitmap) ? BME_FLAG_AUTO : 0;
         bm->granularity_bits = ctz32(bdrv_dirty_bitmap_granularity(bitmap));
         bm->dirty_bitmap = bitmap;
     }
 
     if (!need_write) {
         goto success;
     }
 
     if (!can_write(bs)) {
         error_setg(errp, "No write access");
         goto fail;
     }
 
     /* allocate clusters and store bitmaps */
     QSIMPLEQ_FOREACH(bm, bm_list, entry) {
         BdrvDirtyBitmap *bitmap = bm->dirty_bitmap;
 
         if (bitmap == NULL || bdrv_dirty_bitmap_readonly(bitmap)) {
             continue;
         }
 
         ret = store_bitmap(bs, bm, errp);
         if (ret < 0) {
             goto fail;
         }
     }
 
     ret = update_ext_header_and_dir(bs, bm_list);
     if (ret < 0) {
         error_setg_errno(errp, -ret, "Failed to update bitmap extension");
         goto fail;
     }
 
     /* Bitmap directory was successfully updated, so, old data can be dropped.
      * TODO it is better to reuse these clusters */
     QSIMPLEQ_FOREACH_SAFE(tb, &drop_tables, entry, tb_next) {
         free_bitmap_clusters(bs, tb);
         g_free(tb);
     }
 
 success:
     if (release_stored) {
         QSIMPLEQ_FOREACH(bm, bm_list, entry) {
             if (bm->dirty_bitmap == NULL) {
                 continue;
             }
 
             bdrv_release_dirty_bitmap(bm->dirty_bitmap);
         }
     }
 
     bitmap_list_free(bm_list);
     return true;
 
 fail:
     QSIMPLEQ_FOREACH(bm, bm_list, entry) {
         if (bm->dirty_bitmap == NULL || bm->table.offset == 0 ||
             bdrv_dirty_bitmap_readonly(bm->dirty_bitmap))
         {
             continue;
         }
 
         free_bitmap_clusters(bs, &bm->table);
     }
 
     QSIMPLEQ_FOREACH_SAFE(tb, &drop_tables, entry, tb_next) {
         g_free(tb);
     }
 
     bitmap_list_free(bm_list);
     return false;
 }
 
 int qcow2_reopen_bitmaps_ro(BlockDriverState *bs, Error **errp)
 {
     BdrvDirtyBitmap *bitmap;
 
     if (!qcow2_store_persistent_dirty_bitmaps(bs, false, errp)) {
         return -EINVAL;
     }
 
     FOR_EACH_DIRTY_BITMAP(bs, bitmap) {
         if (bdrv_dirty_bitmap_get_persistence(bitmap)) {
             bdrv_dirty_bitmap_set_readonly(bitmap, true);
         }
     }
 
     return 0;
 }
 
 bool coroutine_fn qcow2_co_can_store_new_dirty_bitmap(BlockDriverState *bs,
                                                       const char *name,
                                                       uint32_t granularity,
                                                       Error **errp)
 {
     BDRVQcow2State *s = bs->opaque;
     BdrvDirtyBitmap *bitmap;
     uint64_t bitmap_directory_size = 0;
     uint32_t nb_bitmaps = 0;
 
     if (bdrv_find_dirty_bitmap(bs, name)) {
         error_setg(errp, "Bitmap already exists: %s", name);
         return false;
     }
 
     if (s->qcow_version < 3) {
         /* Without autoclear_features, we would always have to assume
          * that a program without persistent dirty bitmap support has
          * accessed this qcow2 file when opening it, and would thus
          * have to drop all dirty bitmaps (defeating their purpose).
          */
         error_setg(errp, "Cannot store dirty bitmaps in qcow2 v2 files");
         goto fail;
     }
 
     if (check_constraints_on_bitmap(bs, name, granularity, errp) != 0) {
         goto fail;
     }
 
     FOR_EACH_DIRTY_BITMAP(bs, bitmap) {
         if (bdrv_dirty_bitmap_get_persistence(bitmap)) {
             nb_bitmaps++;
             bitmap_directory_size +=
                 calc_dir_entry_size(strlen(bdrv_dirty_bitmap_name(bitmap)), 0);
         }
     }
     nb_bitmaps++;
     bitmap_directory_size += calc_dir_entry_size(strlen(name), 0);
 
     if (nb_bitmaps > QCOW2_MAX_BITMAPS) {
         error_setg(errp,
                    "Maximum number of persistent bitmaps is already reached");
         goto fail;
     }
 
     if (bitmap_directory_size > QCOW2_MAX_BITMAP_DIRECTORY_SIZE) {
         error_setg(errp, "Not enough space in the bitmap directory");
         goto fail;
     }
 
     return true;
 
 fail:
     error_prepend(errp, "Can't make bitmap '%s' persistent in '%s': ",
                   name, bdrv_get_device_or_node_name(bs));
     return false;
 }
 
 bool qcow2_supports_persistent_dirty_bitmap(BlockDriverState *bs)
 {
     BDRVQcow2State *s = bs->opaque;
 
     return s->qcow_version >= 3;
 }
 
 /*
  * Compute the space required to copy bitmaps from @in_bs.
  *
  * The computation is based as if copying to a new image with the
  * given @cluster_size, which may differ from the cluster size in
  * @in_bs; in fact, @in_bs might be something other than qcow2.
  */
 uint64_t qcow2_get_persistent_dirty_bitmap_size(BlockDriverState *in_bs,
                                                 uint32_t cluster_size)
 {
     uint64_t bitmaps_size = 0;
     BdrvDirtyBitmap *bm;
     size_t bitmap_dir_size = 0;
 
     FOR_EACH_DIRTY_BITMAP(in_bs, bm) {
         if (bdrv_dirty_bitmap_get_persistence(bm)) {
             const char *name = bdrv_dirty_bitmap_name(bm);
             uint32_t granularity = bdrv_dirty_bitmap_granularity(bm);
             uint64_t bmbytes =
                 get_bitmap_bytes_needed(bdrv_dirty_bitmap_size(bm),
                                         granularity);
             uint64_t bmclusters = DIV_ROUND_UP(bmbytes, cluster_size);
 
             /* Assume the entire bitmap is allocated */
             bitmaps_size += bmclusters * cluster_size;
             /* Also reserve space for the bitmap table entries */
             bitmaps_size += ROUND_UP(bmclusters * BME_TABLE_ENTRY_SIZE,
                                      cluster_size);
             /* And space for contribution to bitmap directory size */
             bitmap_dir_size += calc_dir_entry_size(strlen(name), 0);
         }
     }
     bitmaps_size += ROUND_UP(bitmap_dir_size, cluster_size);
 
     return bitmaps_size;
 }