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dirty-bitmap: Track bitmap size by bytes 

We are still using an internal hbitmap that tracks a size in sectors,
with the granularity scaled down accordingly, because it lets us
use a shortcut for our iterators which are currently sector-based.
But there's no reason we can't track the dirty bitmap size in bytes,
since it is (mostly) an internal-only variable (remember, the size
is how many bytes are covered by the bitmap, not how many bytes the
bitmap occupies).  A later cleanup will convert dirty bitmap
internals to be entirely byte-based, eliminating the intermediate
sector rounding added here; and technically, since bdrv_getlength()
already rounds up to sectors, our use of DIV_ROUND_UP is more for
theoretical completeness than for any actual rounding.

Use is_power_of_2() while at it, instead of open-coding that.

Signed-off-by: Eric Blake <eblake@redhat.com>
Reviewed-by: John Snow <jsnow@redhat.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Fam Zheng <famz@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
This commit is contained in:
Eric Blake 2017-09-25 09:55:13 -05:00 committed by Kevin Wolf
parent ebfcd2e75f
commit 993e6525bf
1 changed files with 14 additions and 12 deletions
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26
block/dirty-bitmap.c
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@ -42,7 +42,7 @@ struct BdrvDirtyBitmap {
HBitmap *meta; /* Meta dirty bitmap */
BdrvDirtyBitmap *successor; /* Anonymous child; implies frozen status */
char *name; /* Optional non-empty unique ID */
int64_t size; /* Size of the bitmap (Number of sectors) */
int64_t size; /* Size of the bitmap, in bytes */
bool disabled; /* Bitmap is disabled. It ignores all writes to
the device */
int active_iterators; /* How many iterators are active */
@ -115,17 +115,14 @@ BdrvDirtyBitmap *bdrv_create_dirty_bitmap(BlockDriverState *bs,
{
int64_t bitmap_size;
BdrvDirtyBitmap *bitmap;
uint32_t sector_granularity;
assert((granularity & (granularity - 1)) == 0);
assert(is_power_of_2(granularity) && granularity >= BDRV_SECTOR_SIZE);
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);
bitmap_size = bdrv_getlength(bs);
if (bitmap_size < 0) {
error_setg_errno(errp, -bitmap_size, "could not get length of device");
errno = -bitmap_size;
@ -133,7 +130,12 @@ BdrvDirtyBitmap *bdrv_create_dirty_bitmap(BlockDriverState *bs,
}
bitmap = g_new0(BdrvDirtyBitmap, 1);
bitmap->mutex = &bs->dirty_bitmap_mutex;
bitmap->bitmap = hbitmap_alloc(bitmap_size, ctz32(sector_granularity));
/*
* TODO - let hbitmap track full granularity. For now, it is tracking
* only sector granularity, as a shortcut for our iterators.
*/
bitmap->bitmap = hbitmap_alloc(DIV_ROUND_UP(bitmap_size, BDRV_SECTOR_SIZE),
ctz32(granularity) - BDRV_SECTOR_BITS);
bitmap->size = bitmap_size;
bitmap->name = g_strdup(name);
bitmap->disabled = false;
@ -175,7 +177,7 @@ void bdrv_release_meta_dirty_bitmap(BdrvDirtyBitmap *bitmap)
int64_t bdrv_dirty_bitmap_size(const BdrvDirtyBitmap *bitmap)
{
return bitmap->size * BDRV_SECTOR_SIZE;
return bitmap->size;
}
const char *bdrv_dirty_bitmap_name(const BdrvDirtyBitmap *bitmap)
@ -305,14 +307,13 @@ BdrvDirtyBitmap *bdrv_reclaim_dirty_bitmap(BlockDriverState *bs,
void bdrv_dirty_bitmap_truncate(BlockDriverState *bs, int64_t bytes)
{
BdrvDirtyBitmap *bitmap;
int64_t size = DIV_ROUND_UP(bytes, BDRV_SECTOR_SIZE);
bdrv_dirty_bitmaps_lock(bs);
QLIST_FOREACH(bitmap, &bs->dirty_bitmaps, list) {
assert(!bdrv_dirty_bitmap_frozen(bitmap));
assert(!bitmap->active_iterators);
hbitmap_truncate(bitmap->bitmap, size);
bitmap->size = size;
hbitmap_truncate(bitmap->bitmap, DIV_ROUND_UP(bytes, BDRV_SECTOR_SIZE));
bitmap->size = bytes;
}
bdrv_dirty_bitmaps_unlock(bs);
}
@ -549,7 +550,8 @@ void bdrv_clear_dirty_bitmap(BdrvDirtyBitmap *bitmap, HBitmap **out)
hbitmap_reset_all(bitmap->bitmap);
} else {
HBitmap *backup = bitmap->bitmap;
bitmap->bitmap = hbitmap_alloc(bitmap->size,
bitmap->bitmap = hbitmap_alloc(DIV_ROUND_UP(bitmap->size,
BDRV_SECTOR_SIZE),
hbitmap_granularity(backup));
*out = backup;
}