From 2c3b32d25620c26e26fd590c198ec6d9cf91da57 Mon Sep 17 00:00:00 2001 From: Kevin Wolf Date: Tue, 26 Mar 2013 17:50:12 +0100 Subject: 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 Signed-off-by: Stefan Hajnoczi --- block/qcow2-cluster.c | 134 ++++++++++++++++++++++++++------------------------ 1 file changed, 70 insertions(+), 64 deletions(-) (limited to 'block') diff --git a/block/qcow2-cluster.c b/block/qcow2-cluster.c index 6dc7f7f36b..960d446417 100644 --- a/block/qcow2-cluster.c +++ b/block/qcow2-cluster.c @@ -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); + 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; + 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); + } - cur_bytes = remaining; - } else if (cur_bytes == 0) { - goto done; - } + start += cur_bytes; + remaining -= cur_bytes; + cluster_offset += cur_bytes; - /* If there is something left to allocate, do that now */ - if (remaining == 0) { - goto done; - } + cur_bytes = remaining; + } else if (cur_bytes == 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); + /* If there is something left to allocate, do that now */ + if (remaining == 0) { + break; } - start += cur_bytes; - remaining -= cur_bytes; - cluster_offset += cur_bytes; + /* + * 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); -- cgit v1.2.1