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Re: [Qemu-block] [PATCH v3 3/6] vmdk: New functions to assist allocating
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From: |
Fam Zheng |
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Subject: |
Re: [Qemu-block] [PATCH v3 3/6] vmdk: New functions to assist allocating multiple clusters |
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Date: |
Wed, 19 Apr 2017 20:56:14 +0800 |
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User-agent: |
Mutt/1.8.0 (2017-02-23) |
On Sat, 04/01 20:14, Ashijeet Acharya wrote:
> Move the cluster tables loading code out of the existing
> get_cluster_offset() function to avoid code duplication and implement it
> in separate get_cluster_table() and vmdk_L2load() functions.
>
> 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 <address@hidden>
> ---
> block/vmdk.c | 337
> ++++++++++++++++++++++++++++++++++++++++++++++++++++++-----
> 1 file changed, 308 insertions(+), 29 deletions(-)
>
> diff --git a/block/vmdk.c b/block/vmdk.c
> index 73ae786..e5a289d 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 {
> @@ -254,6 +255,14 @@ static inline uint64_t
> vmdk_find_offset_in_cluster(VmdkExtent *extent,
> return extent_relative_offset % cluster_size;
> }
>
> +static inline uint64_t size_to_clusters(VmdkExtent *extent, uint64_t size)
> +{
> + uint64_t cluster_size, round_off_size;
> + cluster_size = extent->cluster_sectors * BDRV_SECTOR_SIZE;
> + round_off_size = cluster_size - (size % cluster_size);
> + return DIV_ROUND_UP(size + round_off_size, BDRV_SECTOR_SIZE * 128) - 1;
What is (BDRV_SECTOR_SIZE * 128)? Do you mean extent->cluster_size? And the
function doesn't make sense up to me.
Just un-inline this to
DIV_ROUND_UP(size,
extent->cluster_sectors << BDRV_SECTOR_BITS) - 1
in the calling site and be done with it.
> +}
> +
> static uint32_t vmdk_read_cid(BlockDriverState *bs, int parent)
> {
> char *desc;
> @@ -1028,6 +1037,133 @@ static void vmdk_refresh_limits(BlockDriverState *bs,
> Error **errp)
> }
> }
>
> +static int vmdk_L2update(VmdkExtent *extent, VmdkMetaData *m_data,
> + uint32_t offset)
> +{
> + offset = cpu_to_le32(offset);
> + /* update L2 table */
> + if (bdrv_pwrite_sync(extent->file,
> + ((int64_t)m_data->l2_offset * 512)
> + + (m_data->l2_index * sizeof(offset)),
> + &offset, sizeof(offset)) < 0) {
> + return VMDK_ERROR;
> + }
> + /* update backup L2 table */
> + if (extent->l1_backup_table_offset != 0) {
> + m_data->l2_offset = extent->l1_backup_table[m_data->l1_index];
> + if (bdrv_pwrite_sync(extent->file,
> + ((int64_t)m_data->l2_offset * 512)
> + + (m_data->l2_index * sizeof(offset)),
> + &offset, sizeof(offset)) < 0) {
> + return VMDK_ERROR;
> + }
> + }
> + if (m_data->l2_cache_entry) {
> + *m_data->l2_cache_entry = offset;
> + }
> +
> + return VMDK_OK;
> +}
> +
> +/*
> + * vmdk_l2load
> + *
> + * Loads a new L2 table into memory. If the table is in the cache, the cache
Not a native speaker, but s/Loads/Load/ feels more nature and consistent with
other comments.
> + * is used; otherwise the L2 table is loaded from the image file.
> + *
> + * Returns:
> + * VMDK_OK: on success
> + * VMDK_ERROR: in error cases
> + */
> +static int vmdk_l2load(VmdkExtent *extent, uint64_t offset, int l2_offset,
> + uint32_t **new_l2_table, int *new_l2_index)
> +{
> + int min_index, i, j;
> + uint32_t *l2_table;
> + uint32_t min_count;
> +
> + for (i = 0; i < L2_CACHE_SIZE; i++) {
> + if (l2_offset == extent->l2_cache_offsets[i]) {
> + /* increment the hit count */
> + if (++extent->l2_cache_counts[i] == UINT32_MAX) {
> + for (j = 0; j < L2_CACHE_SIZE; j++) {
> + extent->l2_cache_counts[j] >>= 1;
> + }
> + }
> + l2_table = extent->l2_cache + (i * extent->l2_size);
> + goto found;
> + }
> + }
> + /* not found: load a new entry in the least used one */
> + min_index = 0;
> + min_count = UINT32_MAX;
> + for (i = 0; i < L2_CACHE_SIZE; i++) {
> + if (extent->l2_cache_counts[i] < min_count) {
> + min_count = extent->l2_cache_counts[i];
> + min_index = i;
> + }
> + }
> + l2_table = extent->l2_cache + (min_index * extent->l2_size);
> + if (bdrv_pread(extent->file,
> + (int64_t)l2_offset * 512,
> + l2_table,
> + extent->l2_size * sizeof(uint32_t)
> + ) != extent->l2_size * sizeof(uint32_t)) {
> + return VMDK_ERROR;
> + }
> +
> + extent->l2_cache_offsets[min_index] = l2_offset;
> + extent->l2_cache_counts[min_index] = 1;
> +found:
> + *new_l2_index = ((offset >> 9) / extent->cluster_sectors) %
> extent->l2_size;
> + *new_l2_table = l2_table;
> +
> + return VMDK_OK;
> +}
> +
> +/*
> + * get_cluster_table
> + *
> + * for a given offset, load (and allocate if needed) the l2 table.
> + *
> + * Returns:
> + * VMDK_OK: on success
> + *
> + * VMDK_UNALLOC: if cluster is not mapped
> + *
> + * VMDK_ERROR: in error cases
> + */
> +static int get_cluster_table(VmdkExtent *extent, uint64_t offset,
> + int *new_l1_index, int *new_l2_offset,
> + int *new_l2_index, uint32_t **new_l2_table)
> +{
> + int l1_index, l2_offset, l2_index;
> + uint32_t *l2_table;
> + int ret;
> +
> + offset -= (extent->end_sector - extent->sectors) * SECTOR_SIZE;
> + l1_index = (offset >> 9) / extent->l1_entry_sectors;
> + if (l1_index >= extent->l1_size) {
> + return VMDK_ERROR;
> + }
> + l2_offset = extent->l1_table[l1_index];
> + if (!l2_offset) {
> + return VMDK_UNALLOC;
> + }
> +
> + ret = vmdk_l2load(extent, offset, l2_offset, &l2_table, &l2_index);
> + if (ret < 0) {
> + return ret;
> + }
> +
> + *new_l1_index = l1_index;
> + *new_l2_offset = l2_offset;
> + *new_l2_index = l2_index;
> + *new_l2_table = l2_table;
> +
> + return VMDK_OK;
> +}
> +
Can you move this hunk into patch 4 and put it before this patch? It will make
reviewing a bit easier. (Yes, this patch is already big.)
> /*
> * vmdk_perform_cow
> *
> @@ -1115,29 +1251,168 @@ exit:
> return ret;
> }
>
> -static int vmdk_L2update(VmdkExtent *extent, VmdkMetaData *m_data,
> - uint32_t offset)
> +/*
> + * handle_alloc
> + *
> + * Allocates new clusters for an area that either is yet unallocated or
> needs a
Similar to vmdk_l2load, s/Allocates/Allocate/
> + * copy on write. If *cluster_offset is non_zero, clusters are only
> allocated if
> + * the new allocation can match the specified host offset.
> + *
> + * 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 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)
> {
> - offset = cpu_to_le32(offset);
> - /* update L2 table */
> - if (bdrv_pwrite_sync(extent->file,
> - ((int64_t)m_data->l2_offset * 512)
> - + (m_data->l2_index * sizeof(offset)),
> - &offset, sizeof(offset)) < 0) {
> - return VMDK_ERROR;
> + 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;
> }
> - /* update backup L2 table */
> - if (extent->l1_backup_table_offset != 0) {
> - m_data->l2_offset = extent->l1_backup_table[m_data->l1_index];
> - if (bdrv_pwrite_sync(extent->file,
> - ((int64_t)m_data->l2_offset * 512)
> - + (m_data->l2_index * sizeof(offset)),
> - &offset, sizeof(offset)) < 0) {
> - return VMDK_ERROR;
> +
> + 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 it will return one
> + * cluster less than the actual value calculated as we may need to
> perfrom
> + * COW for the last one. */
> + nb_clusters = size_to_clusters(extent, skip_start_bytes + *bytes);
> +
> + 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) << 9)
> + - skip_start_bytes;
> + } else {
> + nb_clusters = 1;
> + }
> + *total_alloc_clusters += nb_clusters;
> + 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;
> }
> }
> - if (m_data->l2_cache_entry) {
> - *m_data->l2_cache_entry = offset;
> + *cluster_offset = cluster_sector << BDRV_SECTOR_BITS;
> + return VMDK_OK;
> +}
> +
> +/*
> + * vmdk_alloc_cluster_offset
Maybe just name it "vmdk_alloc_clusters", which sounds better to me? Because the
clusters are what we allocate here, it's rather
"vmdk_alloc_clusters_and_get_offset" but we probably don't want it that long.
> + *
> + * 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
Thank you for adding the function documentations!
> + */
> +static int vmdk_alloc_cluster_offset(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;
Here, in the first iteration, remaining == bytes and n_bytes == 0.
> + new_cluster_offset += n_bytes;
> +
> + if (remaining == 0) {
> + break;
> + }
> +
> + n_bytes = remaining;
Then n_bytes becomes bytes;
In the second iteration, remaining is always 0 because of "remaining -=
n_bytes". What's the point of the while loop?
> +
> + ret = handle_alloc(bs, extent, start, &new_cluster_offset, &n_bytes,
> + m_data, allocate, total_alloc_clusters);
> +
> + if (ret < 0) {
> + return ret;
> +
> + }
> }
>
> return VMDK_OK;
> @@ -1567,6 +1842,7 @@ static int vmdk_pwritev(BlockDriverState *bs, uint64_t
> offset,
> uint64_t cluster_offset;
> uint64_t bytes_done = 0;
> VmdkMetaData m_data;
> + uint32_t total_alloc_clusters = 0;
>
> if (DIV_ROUND_UP(offset, BDRV_SECTOR_SIZE) > bs->total_sectors) {
> error_report("Wrong offset: offset=0x%" PRIx64
> @@ -1584,10 +1860,10 @@ static int vmdk_pwritev(BlockDriverState *bs,
> uint64_t offset,
> n_bytes = MIN(bytes, extent->cluster_sectors * BDRV_SECTOR_SIZE
> - offset_in_cluster);
>
> - ret = get_cluster_offset(bs, extent, &m_data, offset,
> - !(extent->compressed || zeroed),
> - &cluster_offset, offset_in_cluster,
> - offset_in_cluster + n_bytes);
> + ret = vmdk_alloc_cluster_offset(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 */
> @@ -1596,19 +1872,22 @@ static int vmdk_pwritev(BlockDriverState *bs,
> uint64_t offset,
> return -EIO;
> } else {
> /* allocate */
> - ret = get_cluster_offset(bs, extent, &m_data, offset,
> - true, &cluster_offset, 0, 0);
> + ret = vmdk_alloc_cluster_offset(bs, extent, &m_data, offset,
> + true, &cluster_offset, n_bytes,
> + &total_alloc_clusters);
Parameter list is no longer aligned now.
> }
> }
> if (ret == VMDK_ERROR) {
> return -EINVAL;
> }
> +
> 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
>
[Qemu-block] [PATCH v3 5/6] vmdk: Set maximum bytes allocated in one cycle, Ashijeet Acharya, 2017/04/01