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block: Resize bitmaps on bdrv_truncate

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Signed-off-by: John Snow <jsnow@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-id: 1429314609-29776-16-git-send-email-jsnow@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
This commit is contained in:
John Snow
2015-04-17 19:50:03 -04:00
committed by Kevin Wolf
parent 20dca81075
commit ce1ffea8cd
3 changed files with 76 additions and 0 deletions
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48
util/hbitmap.c
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@ -400,6 +400,54 @@ HBitmap *hbitmap_alloc(uint64_t size, int granularity)
return hb;
}
void hbitmap_truncate(HBitmap *hb, uint64_t size)
{
bool shrink;
unsigned i;
uint64_t num_elements = size;
uint64_t old;
/* Size comes in as logical elements, adjust for granularity. */
size = (size + (1ULL << hb->granularity) - 1) >> hb->granularity;
assert(size <= ((uint64_t)1 << HBITMAP_LOG_MAX_SIZE));
shrink = size < hb->size;
/* bit sizes are identical; nothing to do. */
if (size == hb->size) {
return;
}
/* If we're losing bits, let's clear those bits before we invalidate all of
* our invariants. This helps keep the bitcount consistent, and will prevent
* us from carrying around garbage bits beyond the end of the map.
*/
if (shrink) {
/* Don't clear partial granularity groups;
* start at the first full one. */
uint64_t start = QEMU_ALIGN_UP(num_elements, 1 << hb->granularity);
uint64_t fix_count = (hb->size << hb->granularity) - start;
assert(fix_count);
hbitmap_reset(hb, start, fix_count);
}
hb->size = size;
for (i = HBITMAP_LEVELS; i-- > 0; ) {
size = MAX(BITS_TO_LONGS(size), 1);
if (hb->sizes[i] == size) {
break;
}
old = hb->sizes[i];
hb->sizes[i] = size;
hb->levels[i] = g_realloc(hb->levels[i], size * sizeof(unsigned long));
if (!shrink) {
memset(&hb->levels[i][old], 0x00,
(size - old) * sizeof(*hb->levels[i]));
}
}
}
/**
* Given HBitmaps A and B, let A := A (BITOR) B.
* Bitmap B will not be modified.