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authorKevin Wolf <kwolf@redhat.com>2013-03-26 17:50:05 +0100
committerStefan Hajnoczi <stefanha@redhat.com>2013-03-28 11:52:43 +0100
commit0af729ec007ea4d103a2e3f3fc5db522610a2290 (patch)
treeaed97e83973786b68f0536f6da6ac07a5696216e /block
parent83baa9a4719b42bc28d525fa28af643523cc2bf3 (diff)
qcow2: Factor out handle_copied()
Signed-off-by: Kevin Wolf <kwolf@redhat.com> Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Diffstat (limited to 'block')
-rw-r--r--block/qcow2-cluster.c134
1 files changed, 94 insertions, 40 deletions
diff --git a/block/qcow2-cluster.c b/block/qcow2-cluster.c
index 11414830ec..9036bd8fae 100644
--- a/block/qcow2-cluster.c
+++ b/block/qcow2-cluster.c
@@ -812,6 +812,84 @@ static int handle_dependencies(BlockDriverState *bs, uint64_t guest_offset,
}
/*
+ * Checks how many already allocated clusters that don't require a copy on
+ * write there are at the given guest_offset (up to *bytes). If
+ * *host_offset is not zero, only physically contiguous clusters beginning at
+ * this host offset are counted.
+ *
+ * Note that guest_offset may not be cluster aligned.
+ *
+ * Returns:
+ * 0: if no allocated clusters are available at the given offset.
+ * *bytes is normally unchanged. It is set to 0 if the cluster
+ * is allocated and doesn't need COW, but doesn't have the right
+ * physical offset.
+ *
+ * 1: if allocated clusters that don't require a COW are available at
+ * the requested offset. *bytes may have decreased and describes
+ * the length of the area that can be written to.
+ *
+ * -errno: in error cases
+ *
+ * TODO Get rid of keep_clusters, nb_clusters parameters
+ * TODO Make bytes behave like described above
+ * TODO Make non-zero host_offset behave like describe above
+ */
+static int handle_copied(BlockDriverState *bs, uint64_t guest_offset,
+ uint64_t *host_offset, uint64_t *bytes, QCowL2Meta **m,
+ unsigned int *keep_clusters, unsigned int *nb_clusters)
+{
+ BDRVQcowState *s = bs->opaque;
+ int l2_index;
+ uint64_t cluster_offset;
+ uint64_t *l2_table;
+ int ret, pret;
+
+ trace_qcow2_handle_copied(qemu_coroutine_self(), guest_offset, *host_offset,
+ *bytes);
+ assert(*host_offset == 0);
+
+ /* Find L2 entry for the first involved cluster */
+ ret = get_cluster_table(bs, guest_offset, &l2_table, &l2_index);
+ if (ret < 0) {
+ return ret;
+ }
+
+ cluster_offset = be64_to_cpu(l2_table[l2_index]);
+
+ /* Check how many clusters are already allocated and don't need COW */
+ if (qcow2_get_cluster_type(cluster_offset) == QCOW2_CLUSTER_NORMAL
+ && (cluster_offset & QCOW_OFLAG_COPIED))
+ {
+ /* We keep all QCOW_OFLAG_COPIED clusters */
+ *keep_clusters =
+ count_contiguous_clusters(*nb_clusters, s->cluster_size,
+ &l2_table[l2_index], 0,
+ QCOW_OFLAG_COPIED | QCOW_OFLAG_ZERO);
+ assert(*keep_clusters <= *nb_clusters);
+ *nb_clusters -= *keep_clusters;
+
+ ret = 1;
+ } else {
+ *keep_clusters = 0;
+ cluster_offset = 0;
+
+ ret = 0;
+ }
+
+ cluster_offset &= L2E_OFFSET_MASK;
+ *host_offset = cluster_offset;
+
+ /* Cleanup */
+ pret = qcow2_cache_put(bs, s->l2_table_cache, (void**) &l2_table);
+ if (pret < 0) {
+ return pret;
+ }
+
+ return ret;
+}
+
+/*
* Allocates new clusters for the given guest_offset.
*
* At most *nb_clusters are allocated, and on return *nb_clusters is updated to
@@ -1023,7 +1101,6 @@ int qcow2_alloc_cluster_offset(BlockDriverState *bs, uint64_t offset,
{
BDRVQcowState *s = bs->opaque;
int l2_index, ret, sectors;
- uint64_t *l2_table;
unsigned int nb_clusters, keep_clusters;
uint64_t cluster_offset;
uint64_t cur_bytes;
@@ -1032,6 +1109,9 @@ int qcow2_alloc_cluster_offset(BlockDriverState *bs, uint64_t offset,
n_start, n_end);
again:
+ cluster_offset = 0;
+ *host_offset = 0;
+
/*
* Calculate the number of clusters to look for. We stop at L2 table
* boundaries to keep things simple.
@@ -1057,12 +1137,6 @@ again:
* 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.
- *
- * 2. Count contiguous COPIED clusters.
- * TODO: Consider cluster_offset if set in step 1c.
- *
- * 3. If the request still hasn't completed, allocate new clusters,
- * considering any cluster_offset of steps 1c or 2.
*/
cur_bytes = (n_end - n_start) * BDRV_SECTOR_SIZE;
ret = handle_dependencies(bs, offset, &cur_bytes);
@@ -1079,43 +1153,19 @@ again:
nb_clusters = size_to_clusters(s, offset + cur_bytes)
- (offset >> s->cluster_bits);
- /* Find L2 entry for the first involved cluster */
- ret = get_cluster_table(bs, offset, &l2_table, &l2_index);
- if (ret < 0) {
- return ret;
- }
-
- cluster_offset = be64_to_cpu(l2_table[l2_index]);
-
- /* Check how many clusters are already allocated and don't need COW */
- if (qcow2_get_cluster_type(cluster_offset) == QCOW2_CLUSTER_NORMAL
- && (cluster_offset & QCOW_OFLAG_COPIED))
- {
- /* We keep all QCOW_OFLAG_COPIED clusters */
- keep_clusters =
- count_contiguous_clusters(nb_clusters, s->cluster_size,
- &l2_table[l2_index], 0,
- QCOW_OFLAG_COPIED | QCOW_OFLAG_ZERO);
- assert(keep_clusters <= nb_clusters);
- nb_clusters -= keep_clusters;
- } else {
- keep_clusters = 0;
- cluster_offset = 0;
- }
-
- cluster_offset &= L2E_OFFSET_MASK;
- *host_offset = cluster_offset;
-
/*
- * The L2 table isn't used any more after this. As long as the cache works
- * synchronously, it's important to release it before calling
- * do_alloc_cluster_offset, which may yield if we need to wait for another
- * request to complete. If we still had the reference, we could use up the
- * whole cache with sleeping requests.
+ * 2. Count contiguous COPIED clusters.
+ * TODO: Consider cluster_offset if set in step 1c.
*/
- ret = qcow2_cache_put(bs, s->l2_table_cache, (void**) &l2_table);
+ uint64_t tmp_bytes = cur_bytes;
+ ret = handle_copied(bs, offset, &cluster_offset, &tmp_bytes, m,
+ &keep_clusters, &nb_clusters);
if (ret < 0) {
return ret;
+ } else if (ret) {
+ if (!*host_offset) {
+ *host_offset = cluster_offset;
+ }
}
/* If there is something left to allocate, do that now */
@@ -1123,6 +1173,10 @@ again:
goto done;
}
+ /*
+ * 3. If the request still hasn't completed, allocate new clusters,
+ * considering any cluster_offset of steps 1c or 2.
+ */
int alloc_n_start;
int alloc_n_end;