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qcow2: Move cluster gathering to a non-looping loop 

This patch is mainly to separate the indentation change from the
semantic changes. All that really changes here is that everything moves
into a while loop, all 'goto done' become 'break' and at the end of the
loop a new 'break is inserted.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
This commit is contained in:
Kevin Wolf 2013-03-26 17:50:12 +01:00 committed by Stefan Hajnoczi
parent 88c6588c51
commit 2c3b32d256
1 changed files with 74 additions and 68 deletions
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142
block/qcow2-cluster.c
View File

@ -1147,79 +1147,85 @@ again:
cluster_offset = 0;
*host_offset = 0;
/*
* Now start gathering as many contiguous clusters as possible:
*
* 1. Check for overlaps with in-flight allocations
*
* a) Overlap not in the first cluster -> shorten this request and let
* the caller handle the rest in its next loop iteration.
*
* b) Real overlaps of two requests. Yield and restart the search for
* contiguous clusters (the situation could have changed while we
* were sleeping)
*
* c) TODO: Request starts in the same cluster as the in-flight
* allocation ends. Shorten the COW of the in-fight allocation, set
* cluster_offset to write to the same cluster and set up the right
* synchronisation between the in-flight request and the new one.
*/
cur_bytes = remaining;
ret = handle_dependencies(bs, start, &cur_bytes);
if (ret == -EAGAIN) {
goto again;
} else if (ret < 0) {
return ret;
} else {
/* handle_dependencies() may have decreased cur_bytes (shortened
* the allocations below) so that the next dependency is processed
* correctly during the next loop iteration. */
}
/*
* 2. Count contiguous COPIED clusters.
*/
ret = handle_copied(bs, start, &cluster_offset, &cur_bytes, m);
if (ret < 0) {
return ret;
} else if (ret) {
if (!*host_offset) {
*host_offset = start_of_cluster(s, cluster_offset);
}
start += cur_bytes;
remaining -= cur_bytes;
cluster_offset += cur_bytes;
while (true) {
/*
* Now start gathering as many contiguous clusters as possible:
*
* 1. Check for overlaps with in-flight allocations
*
* a) Overlap not in the first cluster -> shorten this request and
* let the caller handle the rest in its next loop iteration.
*
* b) Real overlaps of two requests. Yield and restart the search
* for contiguous clusters (the situation could have changed
* while we were sleeping)
*
* c) TODO: Request starts in the same cluster as the in-flight
* allocation ends. Shorten the COW of the in-fight allocation,
* set cluster_offset to write to the same cluster and set up
* the right synchronisation between the in-flight request and
* the new one.
*/
cur_bytes = remaining;
} else if (cur_bytes == 0) {
goto done;
}
/* If there is something left to allocate, do that now */
if (remaining == 0) {
goto done;
}
/*
* 3. If the request still hasn't completed, allocate new clusters,
* considering any cluster_offset of steps 1c or 2.
*/
ret = handle_alloc(bs, start, &cluster_offset, &cur_bytes, m);
if (ret < 0) {
return ret;
} else if (ret) {
if (!*host_offset) {
*host_offset = start_of_cluster(s, cluster_offset);
ret = handle_dependencies(bs, start, &cur_bytes);
if (ret == -EAGAIN) {
goto again;
} else if (ret < 0) {
return ret;
} else {
/* handle_dependencies() may have decreased cur_bytes (shortened
* the allocations below) so that the next dependency is processed
* correctly during the next loop iteration. */
}
start += cur_bytes;
remaining -= cur_bytes;
cluster_offset += cur_bytes;
/*
* 2. Count contiguous COPIED clusters.
*/
ret = handle_copied(bs, start, &cluster_offset, &cur_bytes, m);
if (ret < 0) {
return ret;
} else if (ret) {
if (!*host_offset) {
*host_offset = start_of_cluster(s, cluster_offset);
}
start += cur_bytes;
remaining -= cur_bytes;
cluster_offset += cur_bytes;
cur_bytes = remaining;
} else if (cur_bytes == 0) {
break;
}
/* If there is something left to allocate, do that now */
if (remaining == 0) {
break;
}
/*
* 3. If the request still hasn't completed, allocate new clusters,
* considering any cluster_offset of steps 1c or 2.
*/
ret = handle_alloc(bs, start, &cluster_offset, &cur_bytes, m);
if (ret < 0) {
return ret;
} else if (ret) {
if (!*host_offset) {
*host_offset = start_of_cluster(s, cluster_offset);
}
start += cur_bytes;
remaining -= cur_bytes;
cluster_offset += cur_bytes;
break;
} else {
assert(cur_bytes == 0);
break;
}
}
/* Some cleanup work */
done:
*num = (n_end - n_start) - (remaining >> BDRV_SECTOR_BITS);
assert(*num > 0);
assert(*host_offset != 0);