Introduce two new helper functions handle_alloc() and
vmdk_alloc_cluster_offset(). handle_alloc() helps to allocate multiple
clusters at once starting from a given offset on disk and performs COW
if necessary for first and last allocated clusters.
vmdk_alloc_cluster_offset() helps to return the offset of the first of
the many newly allocated clusters. Also, provide proper documentation
for both.
Signed-off-by: Ashijeet Acharya <ashijeetacha...@gmail.com>
---
block/vmdk.c | 200 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++---
1 file changed, 190 insertions(+), 10 deletions(-)
diff --git a/block/vmdk.c b/block/vmdk.c
index fe2046b..277db16 100644
--- a/block/vmdk.c
+++ b/block/vmdk.c
@@ -136,6 +136,7 @@ typedef struct VmdkMetaData {
unsigned int l2_offset;
int valid;
uint32_t *l2_cache_entry;
+ uint32_t nb_clusters;
} VmdkMetaData;
typedef struct VmdkGrainMarker {
@@ -1242,6 +1243,182 @@ static int get_cluster_table(VmdkExtent *extent,
uint64_t offset,
return VMDK_OK;
}
+/*
+ * vmdk_handle_alloc
+ *
+ * Allocate new clusters for an area that either is yet unallocated or needs a
+ * copy on write.
+ *
+ * Returns:
+ * VMDK_OK: if new clusters were allocated, *bytes may be decreased if
+ * the new allocation doesn't cover all of the requested area.
+ * *cluster_offset is updated to contain the offset of the
+ * first newly allocated cluster.
+ *
+ * VMDK_UNALLOC: if no clusters could be allocated. *cluster_offset is left
+ * unchanged.
+ *
+ * VMDK_ERROR: in error cases
+ */
+static int vmdk_handle_alloc(BlockDriverState *bs, VmdkExtent *extent,
+ uint64_t offset, uint64_t *cluster_offset,
+ int64_t *bytes, VmdkMetaData *m_data,
+ bool allocate, uint32_t *total_alloc_clusters)
+{
+ int l1_index, l2_offset, l2_index;
+ uint32_t *l2_table;
+ uint32_t cluster_sector;
+ uint32_t nb_clusters;
+ bool zeroed = false;
+ uint64_t skip_start_bytes, skip_end_bytes;
+ int ret;
+
+ ret = get_cluster_table(extent, offset, &l1_index, &l2_offset,
+ &l2_index, &l2_table);
+ if (ret < 0) {
+ return ret;
+ }
+
+ cluster_sector = le32_to_cpu(l2_table[l2_index]);
+
+ skip_start_bytes = vmdk_find_offset_in_cluster(extent, offset);
+ /* Calculate the number of clusters to look for. Here we truncate the last
+ * cluster, i.e. 1 less than the actual value calculated as we may need to
+ * perform COW for the last one. */
+ nb_clusters = DIV_ROUND_UP(skip_start_bytes + *bytes,
+ extent->cluster_sectors << BDRV_SECTOR_BITS) -
1;
+
+ nb_clusters = MIN(nb_clusters, extent->l2_size - l2_index);
+ assert(nb_clusters <= INT_MAX);
+
+ /* update bytes according to final nb_clusters value */
+ if (nb_clusters != 0) {
+ *bytes = ((nb_clusters * extent->cluster_sectors) << BDRV_SECTOR_BITS)
+ - skip_start_bytes;
+ } else {
+ nb_clusters = 1;
+ }
+ *total_alloc_clusters += nb_clusters;
+
+ /* we need to use MIN() for basically 3 cases that arise :
+ * 1. alloc very first cluster : here skip_start_bytes >= 0 and
+ * *bytes <= cluster_size.
+ * 2. alloc middle clusters : here *bytes is a perfect multiple of
+ * cluster_size and skip_start_bytes is 0.
+ * 3. alloc very last cluster : here *bytes <= cluster_size and
+ * skip_start_bytes is 0
+ */
+ skip_end_bytes = skip_start_bytes + MIN(*bytes,
+ extent->cluster_sectors * BDRV_SECTOR_SIZE
+ - skip_start_bytes);
+
+ if (extent->has_zero_grain && cluster_sector == VMDK_GTE_ZEROED) {
+ zeroed = true;
+ }
+
+ if (!cluster_sector || zeroed) {
+ if (!allocate) {
+ return zeroed ? VMDK_ZEROED : VMDK_UNALLOC;
+ }
+
+ cluster_sector = extent->next_cluster_sector;
+ extent->next_cluster_sector += extent->cluster_sectors
+ * nb_clusters;
+
+ ret = vmdk_perform_cow(bs, extent, cluster_sector * BDRV_SECTOR_SIZE,
+ offset, skip_start_bytes,
+ skip_end_bytes);
+ if (ret < 0) {
+ return ret;
+ }
+ if (m_data) {
+ m_data->valid = 1;
+ m_data->l1_index = l1_index;
+ m_data->l2_index = l2_index;
+ m_data->l2_offset = l2_offset;
+ m_data->l2_cache_entry = &l2_table[l2_index];
+ m_data->nb_clusters = nb_clusters;
+ }
+ }
+ *cluster_offset = cluster_sector << BDRV_SECTOR_BITS;
+ return VMDK_OK;
+}
+
+/*
+ * vmdk_alloc_clusters
+ *
+ * For a given offset on the virtual disk, find the cluster offset in vmdk
+ * file. If the offset is not found, allocate a new cluster.
+ *
+ * If the cluster is newly allocated, m_data->nb_clusters is set to the number
+ * of contiguous clusters that have been allocated. In this case, the other
+ * fields of m_data are valid and contain information about the first allocated
+ * cluster.
+ *
+ * Returns:
+ *
+ * VMDK_OK: on success and @cluster_offset was set
+ *
+ * VMDK_UNALLOC: if no clusters were allocated and @cluster_offset is
+ * set to zero
+ *
+ * VMDK_ERROR: in error cases
+ */
+static int vmdk_alloc_clusters(BlockDriverState *bs,
+ VmdkExtent *extent,
+ VmdkMetaData *m_data, uint64_t offset,
+ bool allocate, uint64_t *cluster_offset,
+ int64_t bytes,
+ uint32_t *total_alloc_clusters)
+{
+ uint64_t start, remaining;
+ uint64_t new_cluster_offset;
+ int64_t n_bytes;
+ int ret;
+
+ if (extent->flat) {
+ *cluster_offset = extent->flat_start_offset;
+ return VMDK_OK;
+ }
+
+ start = offset;
+ remaining = bytes;
+ new_cluster_offset = 0;
+ *cluster_offset = 0;
+ n_bytes = 0;
+ if (m_data) {
+ m_data->valid = 0;
+ }
+
+ /* due to L2 table margins all bytes may not get allocated at once */
+ while (true) {
+
+ if (!*cluster_offset) {
+ *cluster_offset = new_cluster_offset;
+ }
+
+ start += n_bytes;
+ remaining -= n_bytes;
+ new_cluster_offset += n_bytes;
+
+ if (remaining == 0) {
+ break;
+ }
+
+ n_bytes = remaining;
+
+ ret = vmdk_handle_alloc(bs, extent, start, &new_cluster_offset,
&n_bytes,
+ m_data, allocate, total_alloc_clusters);
+
+ if (ret < 0) {
+ return ret;
+
+ }
+ }
+
+ return VMDK_OK;
+}
+
/**
* vmdk_get_cluster_offset
*
@@ -1625,6 +1802,7 @@ static int vmdk_pwritev(BlockDriverState *bs, uint64_t
offset,
uint64_t bytes_done = 0;
VmdkMetaData m_data;
uint64_t extent_end;
+ uint32_t total_alloc_clusters = 0;
if (DIV_ROUND_UP(offset, BDRV_SECTOR_SIZE) > bs->total_sectors) {
error_report("Wrong offset: offset=0x%" PRIx64
@@ -1650,10 +1828,10 @@ static int vmdk_pwritev(BlockDriverState *bs, uint64_t
offset,
n_bytes = MIN(bytes, extent_end - offset);
}
- ret = vmdk_get_cluster_offset(bs, extent, &m_data, offset,
- !(extent->compressed || zeroed),
- &cluster_offset, offset_in_cluster,
- offset_in_cluster + n_bytes);
+ ret = vmdk_alloc_clusters(bs, extent, &m_data, offset,
+ !(extent->compressed || zeroed),
+ &cluster_offset, n_bytes,
+ &total_alloc_clusters);
if (extent->compressed) {
if (ret == VMDK_OK) {
/* Refuse write to allocated cluster for streamOptimized */
@@ -1662,8 +1840,9 @@ static int vmdk_pwritev(BlockDriverState *bs, uint64_t
offset,
return -EIO;
} else {
/* allocate */
- ret = vmdk_get_cluster_offset(bs, extent, &m_data, offset,
- true, &cluster_offset, 0, 0);
+ ret = vmdk_alloc_clusters(bs, extent, &m_data, offset,
+ true, &cluster_offset, n_bytes,
+ &total_alloc_clusters);
}
}
if (ret == VMDK_ERROR) {
@@ -1671,10 +1850,11 @@ static int vmdk_pwritev(BlockDriverState *bs, uint64_t
offset,
}
if (zeroed) {
/* Do zeroed write, buf is ignored */
- if (extent->has_zero_grain &&
- offset_in_cluster == 0 &&
- n_bytes >= extent->cluster_sectors * BDRV_SECTOR_SIZE) {
- n_bytes = extent->cluster_sectors * BDRV_SECTOR_SIZE;
+ if (extent->has_zero_grain && offset_in_cluster == 0 &&
+ n_bytes >= extent->cluster_sectors * BDRV_SECTOR_SIZE *
+ total_alloc_clusters) {
+ n_bytes = extent->cluster_sectors * BDRV_SECTOR_SIZE *
+ total_alloc_clusters;
if (!zero_dry_run) {
/* update L2 tables */
if (vmdk_L2update(extent, &m_data, VMDK_GTE_ZEROED)
--
2.6.2
