block/dirty-bitmap.c - qemu - Git at Google

 /*
  * Block Dirty Bitmap
  *
  * Copyright (c) 2016 Red Hat. Inc
  *
  * 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-common.h"
 #include "trace.h"
 #include "block/block_int.h"
 #include "block/blockjob.h"

 /**
  * A BdrvDirtyBitmap can be in three possible states:
  * (1) successor is NULL and disabled is false: full r/w mode
  * (2) successor is NULL and disabled is true: read only mode ("disabled")
  * (3) successor is set: frozen mode.
  *     A frozen bitmap cannot be renamed, deleted, anonymized, cleared, set,
  *     or enabled. A frozen bitmap can only abdicate() or reclaim().
  */
 struct BdrvDirtyBitmap {
     HBitmap *bitmap;            /* Dirty sector bitmap implementation */
     BdrvDirtyBitmap *successor; /* Anonymous child; implies frozen status */
     char *name;                 /* Optional non-empty unique ID */
     int64_t size;               /* Size of the bitmap (Number of sectors) */
     bool disabled;              /* Bitmap is read-only */
     QLIST_ENTRY(BdrvDirtyBitmap) list;
 };

 BdrvDirtyBitmap *bdrv_find_dirty_bitmap(BlockDriverState *bs, const char *name)
 {
     BdrvDirtyBitmap *bm;

     assert(name);
     QLIST_FOREACH(bm, &bs->dirty_bitmaps, list) {
         if (bm->name && !strcmp(name, bm->name)) {
             return bm;
         }
     }
     return NULL;
 }

 void bdrv_dirty_bitmap_make_anon(BdrvDirtyBitmap *bitmap)
 {
     assert(!bdrv_dirty_bitmap_frozen(bitmap));
     g_free(bitmap->name);
     bitmap->name = NULL;
 }

 BdrvDirtyBitmap *bdrv_create_dirty_bitmap(BlockDriverState *bs,
                                           uint32_t granularity,
                                           const char *name,
                                           Error **errp)
 {
     int64_t bitmap_size;
     BdrvDirtyBitmap *bitmap;
     uint32_t sector_granularity;

     assert((granularity & (granularity - 1)) == 0);

     if (name && bdrv_find_dirty_bitmap(bs, name)) {
         error_setg(errp, "Bitmap already exists: %s", name);
         return NULL;
     }
     sector_granularity = granularity >> BDRV_SECTOR_BITS;
     assert(sector_granularity);
     bitmap_size = bdrv_nb_sectors(bs);
     if (bitmap_size < 0) {
         error_setg_errno(errp, -bitmap_size, "could not get length of device");
         errno = -bitmap_size;
         return NULL;
     }
     bitmap = g_new0(BdrvDirtyBitmap, 1);
     bitmap->bitmap = hbitmap_alloc(bitmap_size, ctz32(sector_granularity));
     bitmap->size = bitmap_size;
     bitmap->name = g_strdup(name);
     bitmap->disabled = false;
     QLIST_INSERT_HEAD(&bs->dirty_bitmaps, bitmap, list);
     return bitmap;
 }

 bool bdrv_dirty_bitmap_frozen(BdrvDirtyBitmap *bitmap)
 {
     return bitmap->successor;
 }

 bool bdrv_dirty_bitmap_enabled(BdrvDirtyBitmap *bitmap)
 {
     return !(bitmap->disabled || bitmap->successor);
 }

 DirtyBitmapStatus bdrv_dirty_bitmap_status(BdrvDirtyBitmap *bitmap)
 {
     if (bdrv_dirty_bitmap_frozen(bitmap)) {
         return DIRTY_BITMAP_STATUS_FROZEN;
     } else if (!bdrv_dirty_bitmap_enabled(bitmap)) {
         return DIRTY_BITMAP_STATUS_DISABLED;
     } else {
         return DIRTY_BITMAP_STATUS_ACTIVE;
     }
 }

 /**
  * Create a successor bitmap destined to replace this bitmap after an operation.
  * Requires that the bitmap is not frozen and has no successor.
  */
 int bdrv_dirty_bitmap_create_successor(BlockDriverState *bs,
                                        BdrvDirtyBitmap *bitmap, Error **errp)
 {
     uint64_t granularity;
     BdrvDirtyBitmap *child;

     if (bdrv_dirty_bitmap_frozen(bitmap)) {
         error_setg(errp, "Cannot create a successor for a bitmap that is "
                    "currently frozen");
         return -1;
     }
     assert(!bitmap->successor);

     /* Create an anonymous successor */
     granularity = bdrv_dirty_bitmap_granularity(bitmap);
     child = bdrv_create_dirty_bitmap(bs, granularity, NULL, errp);
     if (!child) {
         return -1;
     }

     /* Successor will be on or off based on our current state. */
     child->disabled = bitmap->disabled;

     /* Install the successor and freeze the parent */
     bitmap->successor = child;
     return 0;
 }

 /**
  * For a bitmap with a successor, yield our name to the successor,
  * delete the old bitmap, and return a handle to the new bitmap.
  */
 BdrvDirtyBitmap *bdrv_dirty_bitmap_abdicate(BlockDriverState *bs,
                                             BdrvDirtyBitmap *bitmap,
                                             Error **errp)
 {
     char *name;
     BdrvDirtyBitmap *successor = bitmap->successor;

     if (successor == NULL) {
         error_setg(errp, "Cannot relinquish control if "
                    "there's no successor present");
         return NULL;
     }

     name = bitmap->name;
     bitmap->name = NULL;
     successor->name = name;
     bitmap->successor = NULL;
     bdrv_release_dirty_bitmap(bs, bitmap);

     return successor;
 }

 /**
  * In cases of failure where we can no longer safely delete the parent,
  * we may wish to re-join the parent and child/successor.
  * The merged parent will be un-frozen, but not explicitly re-enabled.
  */
 BdrvDirtyBitmap *bdrv_reclaim_dirty_bitmap(BlockDriverState *bs,
                                            BdrvDirtyBitmap *parent,
                                            Error **errp)
 {
     BdrvDirtyBitmap *successor = parent->successor;

     if (!successor) {
         error_setg(errp, "Cannot reclaim a successor when none is present");
         return NULL;
     }

     if (!hbitmap_merge(parent->bitmap, successor->bitmap)) {
         error_setg(errp, "Merging of parent and successor bitmap failed");
         return NULL;
     }
     bdrv_release_dirty_bitmap(bs, successor);
     parent->successor = NULL;

     return parent;
 }

 /**
  * Truncates _all_ bitmaps attached to a BDS.
  */
 void bdrv_dirty_bitmap_truncate(BlockDriverState *bs)
 {
     BdrvDirtyBitmap *bitmap;
     uint64_t size = bdrv_nb_sectors(bs);

     QLIST_FOREACH(bitmap, &bs->dirty_bitmaps, list) {
         assert(!bdrv_dirty_bitmap_frozen(bitmap));
         hbitmap_truncate(bitmap->bitmap, size);
         bitmap->size = size;
     }
 }

 static void bdrv_do_release_matching_dirty_bitmap(BlockDriverState *bs,
                                                   BdrvDirtyBitmap *bitmap,
                                                   bool only_named)
 {
     BdrvDirtyBitmap *bm, *next;
     QLIST_FOREACH_SAFE(bm, &bs->dirty_bitmaps, list, next) {
         if ((!bitmap || bm == bitmap) && (!only_named || bm->name)) {
             assert(!bdrv_dirty_bitmap_frozen(bm));
             QLIST_REMOVE(bm, list);
             hbitmap_free(bm->bitmap);
             g_free(bm->name);
             g_free(bm);

             if (bitmap) {
                 return;
             }
         }
     }
 }

 void bdrv_release_dirty_bitmap(BlockDriverState *bs, BdrvDirtyBitmap *bitmap)
 {
     bdrv_do_release_matching_dirty_bitmap(bs, bitmap, false);
 }

 /**
  * Release all named dirty bitmaps attached to a BDS (for use in bdrv_close()).
  * There must not be any frozen bitmaps attached.
  */
 void bdrv_release_named_dirty_bitmaps(BlockDriverState *bs)
 {
     bdrv_do_release_matching_dirty_bitmap(bs, NULL, true);
 }

 void bdrv_disable_dirty_bitmap(BdrvDirtyBitmap *bitmap)
 {
     assert(!bdrv_dirty_bitmap_frozen(bitmap));
     bitmap->disabled = true;
 }

 void bdrv_enable_dirty_bitmap(BdrvDirtyBitmap *bitmap)
 {
     assert(!bdrv_dirty_bitmap_frozen(bitmap));
     bitmap->disabled = false;
 }

 BlockDirtyInfoList *bdrv_query_dirty_bitmaps(BlockDriverState *bs)
 {
     BdrvDirtyBitmap *bm;
     BlockDirtyInfoList *list = NULL;
     BlockDirtyInfoList **plist = &list;

     QLIST_FOREACH(bm, &bs->dirty_bitmaps, list) {
         BlockDirtyInfo *info = g_new0(BlockDirtyInfo, 1);
         BlockDirtyInfoList *entry = g_new0(BlockDirtyInfoList, 1);
         info->count = bdrv_get_dirty_count(bm);
         info->granularity = bdrv_dirty_bitmap_granularity(bm);
         info->has_name = !!bm->name;
         info->name = g_strdup(bm->name);
         info->status = bdrv_dirty_bitmap_status(bm);
         entry->value = info;
         *plist = entry;
         plist = &entry->next;
     }

     return list;
 }

 int bdrv_get_dirty(BlockDriverState *bs, BdrvDirtyBitmap *bitmap,
                    int64_t sector)
 {
     if (bitmap) {
         return hbitmap_get(bitmap->bitmap, sector);
     } else {
         return 0;
     }
 }

 /**
  * Chooses a default granularity based on the existing cluster size,
  * but clamped between [4K, 64K]. Defaults to 64K in the case that there
  * is no cluster size information available.
  */
 uint32_t bdrv_get_default_bitmap_granularity(BlockDriverState *bs)
 {
     BlockDriverInfo bdi;
     uint32_t granularity;

     if (bdrv_get_info(bs, &bdi) >= 0 && bdi.cluster_size > 0) {
         granularity = MAX(4096, bdi.cluster_size);
         granularity = MIN(65536, granularity);
     } else {
         granularity = 65536;
     }

     return granularity;
 }

 uint32_t bdrv_dirty_bitmap_granularity(BdrvDirtyBitmap *bitmap)
 {
     return BDRV_SECTOR_SIZE << hbitmap_granularity(bitmap->bitmap);
 }

 void bdrv_dirty_iter_init(BdrvDirtyBitmap *bitmap, HBitmapIter *hbi)
 {
     hbitmap_iter_init(hbi, bitmap->bitmap, 0);
 }

 void bdrv_set_dirty_bitmap(BdrvDirtyBitmap *bitmap,
                            int64_t cur_sector, int nr_sectors)
 {
     assert(bdrv_dirty_bitmap_enabled(bitmap));
     hbitmap_set(bitmap->bitmap, cur_sector, nr_sectors);
 }

 void bdrv_reset_dirty_bitmap(BdrvDirtyBitmap *bitmap,
                              int64_t cur_sector, int nr_sectors)
 {
     assert(bdrv_dirty_bitmap_enabled(bitmap));
     hbitmap_reset(bitmap->bitmap, cur_sector, nr_sectors);
 }

 void bdrv_clear_dirty_bitmap(BdrvDirtyBitmap *bitmap, HBitmap **out)
 {
     assert(bdrv_dirty_bitmap_enabled(bitmap));
     if (!out) {
         hbitmap_reset_all(bitmap->bitmap);
     } else {
         HBitmap *backup = bitmap->bitmap;
         bitmap->bitmap = hbitmap_alloc(bitmap->size,
                                        hbitmap_granularity(backup));
         *out = backup;
     }
 }

 void bdrv_undo_clear_dirty_bitmap(BdrvDirtyBitmap *bitmap, HBitmap *in)
 {
     HBitmap *tmp = bitmap->bitmap;
     assert(bdrv_dirty_bitmap_enabled(bitmap));
     bitmap->bitmap = in;
     hbitmap_free(tmp);
 }

 void bdrv_set_dirty(BlockDriverState *bs, int64_t cur_sector,
                     int nr_sectors)
 {
     BdrvDirtyBitmap *bitmap;
     QLIST_FOREACH(bitmap, &bs->dirty_bitmaps, list) {
         if (!bdrv_dirty_bitmap_enabled(bitmap)) {
             continue;
         }
         hbitmap_set(bitmap->bitmap, cur_sector, nr_sectors);
     }
 }

 /**
  * Advance an HBitmapIter to an arbitrary offset.
  */
 void bdrv_set_dirty_iter(HBitmapIter *hbi, int64_t offset)
 {
     assert(hbi->hb);
     hbitmap_iter_init(hbi, hbi->hb, offset);
 }

 int64_t bdrv_get_dirty_count(BdrvDirtyBitmap *bitmap)
 {
     return hbitmap_count(bitmap->bitmap);
 }
	/*
	* Block Dirty Bitmap
	*
	* Copyright (c) 2016 Red Hat. Inc
	*
	* 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-common.h"
	#include "trace.h"
	#include "block/block_int.h"
	#include "block/blockjob.h"

	/**
	* A BdrvDirtyBitmap can be in three possible states:
	* (1) successor is NULL and disabled is false: full r/w mode
	* (2) successor is NULL and disabled is true: read only mode ("disabled")
	* (3) successor is set: frozen mode.
	* A frozen bitmap cannot be renamed, deleted, anonymized, cleared, set,
	* or enabled. A frozen bitmap can only abdicate() or reclaim().
	*/
	struct BdrvDirtyBitmap {
	HBitmap bitmap; / Dirty sector bitmap implementation */
	BdrvDirtyBitmap successor; / Anonymous child; implies frozen status */
	char name; / Optional non-empty unique ID */
	int64_t size; /* Size of the bitmap (Number of sectors) */
	bool disabled; /* Bitmap is read-only */
	QLIST_ENTRY(BdrvDirtyBitmap) list;
	};

	BdrvDirtyBitmap bdrv_find_dirty_bitmap(BlockDriverState bs, const char *name)
	{
	BdrvDirtyBitmap *bm;

	assert(name);
	QLIST_FOREACH(bm, &bs->dirty_bitmaps, list) {
	if (bm->name && !strcmp(name, bm->name)) {
	return bm;
	}
	}
	return NULL;
	}

	void bdrv_dirty_bitmap_make_anon(BdrvDirtyBitmap *bitmap)
	{
	assert(!bdrv_dirty_bitmap_frozen(bitmap));
	g_free(bitmap->name);
	bitmap->name = NULL;
	}

	BdrvDirtyBitmap bdrv_create_dirty_bitmap(BlockDriverState bs,
	uint32_t granularity,
	const char *name,
	Error **errp)
	{
	int64_t bitmap_size;
	BdrvDirtyBitmap *bitmap;
	uint32_t sector_granularity;

	assert((granularity & (granularity - 1)) == 0);

	if (name && bdrv_find_dirty_bitmap(bs, name)) {
	error_setg(errp, "Bitmap already exists: %s", name);
	return NULL;
	}
	sector_granularity = granularity >> BDRV_SECTOR_BITS;
	assert(sector_granularity);
	bitmap_size = bdrv_nb_sectors(bs);
	if (bitmap_size < 0) {
	error_setg_errno(errp, -bitmap_size, "could not get length of device");
	errno = -bitmap_size;
	return NULL;
	}
	bitmap = g_new0(BdrvDirtyBitmap, 1);
	bitmap->bitmap = hbitmap_alloc(bitmap_size, ctz32(sector_granularity));
	bitmap->size = bitmap_size;
	bitmap->name = g_strdup(name);
	bitmap->disabled = false;
	QLIST_INSERT_HEAD(&bs->dirty_bitmaps, bitmap, list);
	return bitmap;
	}

	bool bdrv_dirty_bitmap_frozen(BdrvDirtyBitmap *bitmap)
	{
	return bitmap->successor;
	}

	bool bdrv_dirty_bitmap_enabled(BdrvDirtyBitmap *bitmap)
	{
	return !(bitmap->disabled \|\| bitmap->successor);
	}

	DirtyBitmapStatus bdrv_dirty_bitmap_status(BdrvDirtyBitmap *bitmap)
	{
	if (bdrv_dirty_bitmap_frozen(bitmap)) {
	return DIRTY_BITMAP_STATUS_FROZEN;
	} else if (!bdrv_dirty_bitmap_enabled(bitmap)) {
	return DIRTY_BITMAP_STATUS_DISABLED;
	} else {
	return DIRTY_BITMAP_STATUS_ACTIVE;
	}
	}

	/**
	* Create a successor bitmap destined to replace this bitmap after an operation.
	* Requires that the bitmap is not frozen and has no successor.
	*/
	int bdrv_dirty_bitmap_create_successor(BlockDriverState *bs,
	BdrvDirtyBitmap bitmap, Error *errp)
	{
	uint64_t granularity;
	BdrvDirtyBitmap *child;

	if (bdrv_dirty_bitmap_frozen(bitmap)) {
	error_setg(errp, "Cannot create a successor for a bitmap that is "
	"currently frozen");
	return -1;
	}
	assert(!bitmap->successor);

	/* Create an anonymous successor */
	granularity = bdrv_dirty_bitmap_granularity(bitmap);
	child = bdrv_create_dirty_bitmap(bs, granularity, NULL, errp);
	if (!child) {
	return -1;
	}

	/* Successor will be on or off based on our current state. */
	child->disabled = bitmap->disabled;

	/* Install the successor and freeze the parent */
	bitmap->successor = child;
	return 0;
	}

	/**
	* For a bitmap with a successor, yield our name to the successor,
	* delete the old bitmap, and return a handle to the new bitmap.
	*/
	BdrvDirtyBitmap bdrv_dirty_bitmap_abdicate(BlockDriverState bs,
	BdrvDirtyBitmap *bitmap,
	Error **errp)
	{
	char *name;
	BdrvDirtyBitmap *successor = bitmap->successor;

	if (successor == NULL) {
	error_setg(errp, "Cannot relinquish control if "
	"there's no successor present");
	return NULL;
	}

	name = bitmap->name;
	bitmap->name = NULL;
	successor->name = name;
	bitmap->successor = NULL;
	bdrv_release_dirty_bitmap(bs, bitmap);

	return successor;
	}

	/**
	* In cases of failure where we can no longer safely delete the parent,
	* we may wish to re-join the parent and child/successor.
	* The merged parent will be un-frozen, but not explicitly re-enabled.
	*/
	BdrvDirtyBitmap bdrv_reclaim_dirty_bitmap(BlockDriverState bs,
	BdrvDirtyBitmap *parent,
	Error **errp)
	{
	BdrvDirtyBitmap *successor = parent->successor;

	if (!successor) {
	error_setg(errp, "Cannot reclaim a successor when none is present");
	return NULL;
	}

	if (!hbitmap_merge(parent->bitmap, successor->bitmap)) {
	error_setg(errp, "Merging of parent and successor bitmap failed");
	return NULL;
	}
	bdrv_release_dirty_bitmap(bs, successor);
	parent->successor = NULL;

	return parent;
	}

	/**
	* Truncates _all_ bitmaps attached to a BDS.
	*/
	void bdrv_dirty_bitmap_truncate(BlockDriverState *bs)
	{
	BdrvDirtyBitmap *bitmap;
	uint64_t size = bdrv_nb_sectors(bs);

	QLIST_FOREACH(bitmap, &bs->dirty_bitmaps, list) {
	assert(!bdrv_dirty_bitmap_frozen(bitmap));
	hbitmap_truncate(bitmap->bitmap, size);
	bitmap->size = size;
	}
	}

	static void bdrv_do_release_matching_dirty_bitmap(BlockDriverState *bs,
	BdrvDirtyBitmap *bitmap,
	bool only_named)
	{
	BdrvDirtyBitmap bm, next;
	QLIST_FOREACH_SAFE(bm, &bs->dirty_bitmaps, list, next) {
	if ((!bitmap \|\| bm == bitmap) && (!only_named \|\| bm->name)) {
	assert(!bdrv_dirty_bitmap_frozen(bm));
	QLIST_REMOVE(bm, list);
	hbitmap_free(bm->bitmap);
	g_free(bm->name);
	g_free(bm);

	if (bitmap) {
	return;
	}
	}
	}
	}

	void bdrv_release_dirty_bitmap(BlockDriverState bs, BdrvDirtyBitmap bitmap)
	{
	bdrv_do_release_matching_dirty_bitmap(bs, bitmap, false);
	}

	/**
	* Release all named dirty bitmaps attached to a BDS (for use in bdrv_close()).
	* There must not be any frozen bitmaps attached.
	*/
	void bdrv_release_named_dirty_bitmaps(BlockDriverState *bs)
	{
	bdrv_do_release_matching_dirty_bitmap(bs, NULL, true);
	}

	void bdrv_disable_dirty_bitmap(BdrvDirtyBitmap *bitmap)
	{
	assert(!bdrv_dirty_bitmap_frozen(bitmap));
	bitmap->disabled = true;
	}

	void bdrv_enable_dirty_bitmap(BdrvDirtyBitmap *bitmap)
	{
	assert(!bdrv_dirty_bitmap_frozen(bitmap));
	bitmap->disabled = false;
	}

	BlockDirtyInfoList bdrv_query_dirty_bitmaps(BlockDriverState bs)
	{
	BdrvDirtyBitmap *bm;
	BlockDirtyInfoList *list = NULL;
	BlockDirtyInfoList **plist = &list;

	QLIST_FOREACH(bm, &bs->dirty_bitmaps, list) {
	BlockDirtyInfo *info = g_new0(BlockDirtyInfo, 1);
	BlockDirtyInfoList *entry = g_new0(BlockDirtyInfoList, 1);
	info->count = bdrv_get_dirty_count(bm);
	info->granularity = bdrv_dirty_bitmap_granularity(bm);
	info->has_name = !!bm->name;
	info->name = g_strdup(bm->name);
	info->status = bdrv_dirty_bitmap_status(bm);
	entry->value = info;
	*plist = entry;
	plist = &entry->next;
	}

	return list;
	}

	int bdrv_get_dirty(BlockDriverState bs, BdrvDirtyBitmap bitmap,
	int64_t sector)
	{
	if (bitmap) {
	return hbitmap_get(bitmap->bitmap, sector);
	} else {
	return 0;
	}
	}

	/**
	* Chooses a default granularity based on the existing cluster size,
	* but clamped between [4K, 64K]. Defaults to 64K in the case that there
	* is no cluster size information available.
	*/
	uint32_t bdrv_get_default_bitmap_granularity(BlockDriverState *bs)
	{
	BlockDriverInfo bdi;
	uint32_t granularity;

	if (bdrv_get_info(bs, &bdi) >= 0 && bdi.cluster_size > 0) {
	granularity = MAX(4096, bdi.cluster_size);
	granularity = MIN(65536, granularity);
	} else {
	granularity = 65536;
	}

	return granularity;
	}

	uint32_t bdrv_dirty_bitmap_granularity(BdrvDirtyBitmap *bitmap)
	{
	return BDRV_SECTOR_SIZE << hbitmap_granularity(bitmap->bitmap);
	}

	void bdrv_dirty_iter_init(BdrvDirtyBitmap bitmap, HBitmapIter hbi)
	{
	hbitmap_iter_init(hbi, bitmap->bitmap, 0);
	}

	void bdrv_set_dirty_bitmap(BdrvDirtyBitmap *bitmap,
	int64_t cur_sector, int nr_sectors)
	{
	assert(bdrv_dirty_bitmap_enabled(bitmap));
	hbitmap_set(bitmap->bitmap, cur_sector, nr_sectors);
	}

	void bdrv_reset_dirty_bitmap(BdrvDirtyBitmap *bitmap,
	int64_t cur_sector, int nr_sectors)
	{
	assert(bdrv_dirty_bitmap_enabled(bitmap));
	hbitmap_reset(bitmap->bitmap, cur_sector, nr_sectors);
	}

	void bdrv_clear_dirty_bitmap(BdrvDirtyBitmap bitmap, HBitmap *out)
	{
	assert(bdrv_dirty_bitmap_enabled(bitmap));
	if (!out) {
	hbitmap_reset_all(bitmap->bitmap);
	} else {
	HBitmap *backup = bitmap->bitmap;
	bitmap->bitmap = hbitmap_alloc(bitmap->size,
	hbitmap_granularity(backup));
	*out = backup;
	}
	}

	void bdrv_undo_clear_dirty_bitmap(BdrvDirtyBitmap bitmap, HBitmap in)
	{
	HBitmap *tmp = bitmap->bitmap;
	assert(bdrv_dirty_bitmap_enabled(bitmap));
	bitmap->bitmap = in;
	hbitmap_free(tmp);
	}

	void bdrv_set_dirty(BlockDriverState *bs, int64_t cur_sector,
	int nr_sectors)
	{
	BdrvDirtyBitmap *bitmap;
	QLIST_FOREACH(bitmap, &bs->dirty_bitmaps, list) {
	if (!bdrv_dirty_bitmap_enabled(bitmap)) {
	continue;
	}
	hbitmap_set(bitmap->bitmap, cur_sector, nr_sectors);
	}
	}

	/**
	* Advance an HBitmapIter to an arbitrary offset.
	*/
	void bdrv_set_dirty_iter(HBitmapIter *hbi, int64_t offset)
	{
	assert(hbi->hb);
	hbitmap_iter_init(hbi, hbi->hb, offset);
	}

	int64_t bdrv_get_dirty_count(BdrvDirtyBitmap *bitmap)
	{
	return hbitmap_count(bitmap->bitmap);
	}