On Wed, Apr 19, 2017 at 18:26 Fam Zheng <f...@redhat.com> wrote:
> 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 <ashijeetacha...@gmail.com>
> > ---
> > 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.)
>
Right, I will change it to as you say. I know its big and I didn't like it
either :(
> > /*
> > * 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;
[continuation of why the while loop?]....here. So the bytes may get reduced
if nb_clusters were more than 512 (l2 table margin) . Thus @remaining down
there won't necessarily be zero after first pass. I hope I explained it
correctly!
>
> > + } 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?
I need the while loop in case if I truncate the bytes according to the L2
table margins....[scroll up to handle alloc() __^ ]
Ashijeet
