On 06/21/2018 05:17 AM, Vladimir Sementsov-Ogievskiy wrote:
21.06.2018 06:19, Eric Blake wrote:
From: Vladimir Sementsov-Ogievskiy <vsement...@virtuozzo.com>
Handle a new NBD meta namespace: "qemu", and corresponding queries:
"qemu:dirty-bitmap:<export bitmap name>".
With the new metadata context negotiated, BLOCK_STATUS query will reply
with dirty-bitmap data, converted to extents. The new public function
nbd_export_bitmap selects which bitmap to export. For now, only one
bitmap
may be exported.
+/*
+ * Populate @extents from a dirty bitmap. Unless @dont_fragment, the
+ * final extent may exceed the original @length. Store in @length the
+ * byte length encoded (which may be smaller or larger than the
+ * original), and return the number of extents used.
+ */
+static unsigned int bitmap_to_extents(BdrvDirtyBitmap *bitmap,
uint64_t offset,
+ uint64_t *length, NBDExtent
*extents,
+ unsigned int nb_extents,
+ bool dont_fragment)
+{
+ uint64_t begin = offset, end;
+ uint64_t overall_end = offset + *length;
+ unsigned int i = 0;
+ BdrvDirtyBitmapIter *it;
+ bool dirty;
+
+ bdrv_dirty_bitmap_lock(bitmap);
+
+ it = bdrv_dirty_iter_new(bitmap);
+ dirty = bdrv_get_dirty_locked(NULL, bitmap, offset);
+
+ while (begin < overall_end && i < nb_extents) {
+ if (dirty) {
+ end = bdrv_dirty_bitmap_next_zero(bitmap, begin);
+ } else {
+ bdrv_set_dirty_iter(it, begin);
+ end = bdrv_dirty_iter_next(it);
+ }
after tjos begin may be zero, and end near to the bitmap end,
so end != -1 and end-begin > 4G (and dont_fragment may be false)
Oh, good catch. Such a situation will still need to be clamped to under
4G (it's only possible on the last extent reported to the user, since in
that case, end > overall_end given that overall_end is at most a 32-bit
request beyond the original begin), so...
+ if (end == -1) {
...we just need to tweak this to 'if (end == -1 || end - begin > UINT32_MAX)
+ /* Cap to an aligned value < 4G beyond begin. */
+ end = MIN(bdrv_dirty_bitmap_size(bitmap),
+ begin + 0x100000000ULL -
+ bdrv_dirty_bitmap_granularity(bitmap));
Also, it might be more legible if I spell this as UINT32_MAX + 1 instead
of open-coding the 33-bit constant.
+ }
+ if (dont_fragment && end > overall_end) {
+ end = overall_end;
+ }
--
Eric Blake, Principal Software Engineer
Red Hat, Inc. +1-919-301-3266
Virtualization: qemu.org | libvirt.org
