mirrors/qemu
1
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity

qcow2: Rewrite the documentation of qcow2_alloc_cluster_offset()

Browse Source 
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>
Message-Id: <bb5bd06f07c5a05b0818611de0d06ec5b66c8df3.1599150873.git.berto@igalia.com>
Signed-off-by: Max Reitz <mreitz@redhat.com>
This commit is contained in:
Alberto Garcia 2020-09-03 18:37:49 +02:00 committed by Max Reitz
parent f7bd5bba1b
commit 2b60c5b996
1 changed files with 14 additions and 10 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

24
block/qcow2-cluster.c
View File

@ -1714,18 +1714,22 @@ 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.