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Re: [Qemu-devel] [PATCH v2 3/7] vmdk: Factor out metadata loading code o
From: |
Fam Zheng |
Subject: |
Re: [Qemu-devel] [PATCH v2 3/7] vmdk: Factor out metadata loading code out of get_cluster_offset() |
Date: |
Fri, 31 Mar 2017 14:03:11 +0800 |
User-agent: |
Mutt/1.8.0 (2017-02-23) |
On Sat, 03/25 16:48, Ashijeet Acharya wrote:
> Move the cluster tables loading code out of the existing
> get_cluster_offset() function and implement it in separate
Now it's renamed to vmdk_perform_cow() in previous patch, the commit message
following it should be updated.
> get_cluster_table() and vmdk_L2load() functions. This patch will help
> us avoid code duplication in future patches of this series.
>
> Signed-off-by: Ashijeet Acharya <address@hidden>
> ---
> block/vmdk.c | 99
> ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
> 1 file changed, 99 insertions(+)
>
> diff --git a/block/vmdk.c b/block/vmdk.c
> index f5fda2c..a42322e 100644
> --- a/block/vmdk.c
> +++ b/block/vmdk.c
> @@ -1037,6 +1037,105 @@ static void vmdk_refresh_limits(BlockDriverState *bs,
> Error **errp)
> }
>
> /*
> + * vmdk_L2load
Personally, I think vmdk_l2load is good enough, the upper case doesn't add
readability but makes it slightly harder to type.
> + *
> + * Loads a new L2 table into memory. If the table is in the cache, the cache
> + * 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] == 0xffffffff) {
Please use 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 = 0xffffffff;
Please use 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)
Again, a static function must be introduced with the code change where it is
used, at least for once. It keeps the compiler happy (-Wunused-function) and
makes reviewing easy.
> +{
> + 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;
> +}
> +
> +/*
> * vmdk_perform_cow
> *
> * Copy backing file's cluster that covers @sector_num, otherwise write zero,
> --
> 2.6.2
>
>
Fam
- [Qemu-devel] [PATCH v2 0/7] Optiomize VMDK I/O by allocating multiple clusters, Ashijeet Acharya, 2017/03/25
- [Qemu-devel] [PATCH v2 1/7] vmdk: Refactor and introduce new helper functions, Ashijeet Acharya, 2017/03/25
- [Qemu-devel] [PATCH v2 2/7] vmdk: Rename get_whole_cluster() to vmdk_perform_cow(), Ashijeet Acharya, 2017/03/25
- [Qemu-devel] [PATCH v2 3/7] vmdk: Factor out metadata loading code out of get_cluster_offset(), Ashijeet Acharya, 2017/03/25
- Re: [Qemu-devel] [PATCH v2 3/7] vmdk: Factor out metadata loading code out of get_cluster_offset(),
Fam Zheng <=
- [Qemu-devel] [PATCH v2 4/7] vmdk: New functions to allocate multiple clusters and cluster offset, Ashijeet Acharya, 2017/03/25
- [Qemu-devel] [PATCH v2 5/7] vmdk: Rename get_cluster_offset() to vmdk_get_cluster_offset(), Ashijeet Acharya, 2017/03/25
- [Qemu-devel] [PATCH v2 6/7] vmdk: Allocate multiple clusters at once, Ashijeet Acharya, 2017/03/25
- [Qemu-devel] [PATCH v2 7/7] vmdk: Update metadata for multiple clusters, Ashijeet Acharya, 2017/03/25