From: Max Reitz <mreitz@redhat.com>
To: qemu-block@nongnu.org
Cc: Peter Maydell <peter.maydell@linaro.org>,
qemu-devel@nongnu.org, Max Reitz <mreitz@redhat.com>
Subject: [PULL 11/22] qcow2: Rewrite the documentation of qcow2_alloc_cluster_offset()
Date: Tue, 15 Sep 2020 12:46:16 +0200 [thread overview]
Message-ID: <20200915104627.699552-12-mreitz@redhat.com> (raw)
In-Reply-To: <20200915104627.699552-1-mreitz@redhat.com>
From: Alberto Garcia <berto@igalia.com>
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>
---
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 f65ccc5840..ce1260e746 100644
--- a/block/qcow2-cluster.c
+++ b/block/qcow2-cluster.c
@@ -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.
--
2.26.2
next prev parent reply other threads:[~2020-09-15 10:56 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-09-15 10:46 [PULL 00/22] Block patches Max Reitz
2020-09-15 10:46 ` [PULL 01/22] qemu-iotests: Fix FilePaths cleanup Max Reitz
2020-09-15 10:46 ` [PULL 02/22] qemu-iotests: Fix FilePaths docstring Max Reitz
2020-09-15 10:46 ` [PULL 03/22] qemu-iotests: Support varargs syntax in FilePaths Max Reitz
2020-09-15 10:46 ` [PULL 04/22] qemu-iotests: Merge FilePaths and FilePath Max Reitz
2020-09-15 10:46 ` [PULL 05/22] qemu-iotests: Simplify FilePath __init__ Max Reitz
2020-09-15 10:46 ` [PULL 06/22] block/quorum.c: stable children names Max Reitz
2020-09-15 10:46 ` [PULL 07/22] qemu-img: avoid unaligned read requests during convert Max Reitz
2020-09-15 10:46 ` [PULL 08/22] qcow2: Use macros for the L1, refcount and bitmap table entry sizes Max Reitz
2020-09-15 10:46 ` [PULL 09/22] qcow2: Fix removal of list members from BDRVQcow2State.cluster_allocs Max Reitz
2020-09-15 10:46 ` [PULL 10/22] qcow2: Don't check nb_clusters when removing l2meta from the list Max Reitz
2020-09-15 10:46 ` Max Reitz [this message]
2020-09-15 10:46 ` [PULL 12/22] qemu-img: Explicit number replaced by a constant Max Reitz
2020-09-15 10:46 ` [PULL 13/22] iotests: Skip test_stream_parallel in test 030 when doing "make check" Max Reitz
2020-09-15 10:46 ` [PULL 14/22] block/vhdx: Support vhdx image only with 512 bytes logical sector size Max Reitz
2020-09-15 10:46 ` [PULL 15/22] qcow2: Handle QCowL2Meta on error in preallocate_co() Max Reitz
2020-09-15 10:46 ` [PULL 16/22] qcow2: Make qcow2_free_any_clusters() free only one cluster Max Reitz
2020-09-15 10:46 ` [PULL 17/22] qcow2: Return the original error code in qcow2_co_pwrite_zeroes() Max Reitz
2020-09-15 10:46 ` [PULL 18/22] block/rbd: remove runtime_opts Max Reitz
2020-09-15 10:46 ` [PULL 19/22] block/qcow: remove runtime opts Max Reitz
2020-09-15 10:46 ` [PULL 20/22] qcow2: Make preallocate_co() resize the image to the correct size Max Reitz
2020-09-15 10:46 ` [PULL 21/22] qcow2: Convert qcow2_alloc_cluster_offset() into qcow2_alloc_host_offset() Max Reitz
2020-09-15 10:46 ` [PULL 22/22] block/rbd: add 'namespace' to qemu_rbd_strong_runtime_opts[] Max Reitz
2020-09-15 12:04 ` [PULL 00/22] Block patches Peter Maydell
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