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[PATCH v2 3/3] qcow2: Rewrite the documentation of qcow2_alloc_cluster_o
From: |
Alberto Garcia |
Subject: |
[PATCH v2 3/3] qcow2: Rewrite the documentation of qcow2_alloc_cluster_offset() |
Date: |
Thu, 3 Sep 2020 18:37:49 +0200 |
The current text corresponds to an earlier, simpler version of this
function and it does not explain how it works now.
Signed-off-by: Alberto Garcia <berto@igalia.com>
---
block/qcow2-cluster.c | 24 ++++++++++++++----------
1 file changed, 14 insertions(+), 10 deletions(-)
diff --git a/block/qcow2-cluster.c b/block/qcow2-cluster.c
index 25e38daa78..f1ce6afcf5 100644
--- a/block/qcow2-cluster.c
+++ b/block/qcow2-cluster.c
@@ -1713,18 +1713,22 @@ out:
}
/*
- * alloc_cluster_offset
+ * For a given area on the virtual disk defined by @offset and @bytes,
+ * find the corresponding area on the qcow2 image, allocating new
+ * clusters (or subclusters) if necessary. The result can span a
+ * combination of allocated and previously unallocated clusters.
*
- * For a given offset on the virtual disk, find the cluster offset in qcow2
- * file. If the offset is not found, allocate a new cluster.
+ * On return, @host_offset is set to the beginning of the requested
+ * area. This area is guaranteed to be contiguous on the qcow2 file
+ * but it can be smaller than initially requested. In this case @bytes
+ * is updated with the actual size.
*
- * If the cluster was already allocated, m->nb_clusters is set to 0 and
- * other fields in m are meaningless.
- *
- * If the cluster is newly allocated, m->nb_clusters is set to the number of
- * contiguous clusters that have been allocated. In this case, the other
- * fields of m are valid and contain information about the first allocated
- * cluster.
+ * If any clusters or subclusters were allocated then @m contains a
+ * list with the information of all the affected regions. Note that
+ * this can happen regardless of whether this function succeeds or
+ * not. The caller is responsible for updating the L2 metadata of the
+ * allocated clusters (on success) or freeing them (on failure), and
+ * for clearing the contents of @m afterwards in both cases.
*
* If the request conflicts with another write request in flight, the coroutine
* is queued and will be reentered when the dependency has completed.
--
2.20.1