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block/backup: add backup_is_cluster_allocated 

Modify bdrv_is_unallocated_range to utilize the pnum return from
bdrv_is_allocated, and in the process change the semantics from
"is unallocated" to "is allocated."

Optionally returns a full number of clusters that share the same
allocation status.

This will be used to carefully toggle bits in the bitmap for sync=top
initialization in the following commits.

Signed-off-by: John Snow <jsnow@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Message-id: 20190716000117.25219-9-jsnow@redhat.com
Signed-off-by: John Snow <jsnow@redhat.com>
This commit is contained in:
John Snow 2019-07-29 16:35:55 -04:00
parent 141cdcdf84
commit dba8700f16
1 changed files with 44 additions and 18 deletions
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62
block/backup.c
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@ -185,6 +185,48 @@ static int coroutine_fn backup_cow_with_offload(BackupBlockJob *job,
return nbytes;
}
/*
* Check if the cluster starting at offset is allocated or not.
* return via pnum the number of contiguous clusters sharing this allocation.
*/
static int backup_is_cluster_allocated(BackupBlockJob *s, int64_t offset,
int64_t *pnum)
{
BlockDriverState *bs = blk_bs(s->common.blk);
int64_t count, total_count = 0;
int64_t bytes = s->len - offset;
int ret;
assert(QEMU_IS_ALIGNED(offset, s->cluster_size));
while (true) {
ret = bdrv_is_allocated(bs, offset, bytes, &count);
if (ret < 0) {
return ret;
}
total_count += count;
if (ret || count == 0) {
/*
* ret: partial segment(s) are considered allocated.
* otherwise: unallocated tail is treated as an entire segment.
*/
*pnum = DIV_ROUND_UP(total_count, s->cluster_size);
return ret;
}
/* Unallocated segment(s) with uncertain following segment(s) */
if (total_count >= s->cluster_size) {
*pnum = total_count / s->cluster_size;
return 0;
}
offset += count;
bytes -= count;
}
}
static int coroutine_fn backup_do_cow(BackupBlockJob *job,
int64_t offset, uint64_t bytes,
bool *error_is_read,
@ -398,34 +440,18 @@ static bool coroutine_fn yield_and_check(BackupBlockJob *job)
return false;
}
static bool bdrv_is_unallocated_range(BlockDriverState *bs,
int64_t offset, int64_t bytes)
{
int64_t end = offset + bytes;
while (offset < end && !bdrv_is_allocated(bs, offset, bytes, &bytes)) {
if (bytes == 0) {
return true;
}
offset += bytes;
bytes = end - offset;
}
return offset >= end;
}
static int coroutine_fn backup_loop(BackupBlockJob *job)
{
bool error_is_read;
int64_t offset;
BdrvDirtyBitmapIter *bdbi;
BlockDriverState *bs = blk_bs(job->common.blk);
int ret = 0;
int64_t dummy;
bdbi = bdrv_dirty_iter_new(job->copy_bitmap);
while ((offset = bdrv_dirty_iter_next(bdbi)) != -1) {
if (job->sync_mode == MIRROR_SYNC_MODE_TOP &&
bdrv_is_unallocated_range(bs, offset, job->cluster_size))
!backup_is_cluster_allocated(job, offset, &dummy))
{
bdrv_reset_dirty_bitmap(job->copy_bitmap, offset,
job->cluster_size);