| Message ID | 1492838021-10538-7-git-send-email-ashijeetacharya@gmail.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Sat, 04/22 10:43, Ashijeet Acharya wrote: > 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 <ashijeetacharya@gmail.com> > --- > block/vmdk.c | 192 +++++++++++++++++++++++++++++++++++++++++++++++++++++++---- > 1 file changed, 182 insertions(+), 10 deletions(-) > > diff --git a/block/vmdk.c b/block/vmdk.c > index 7862791..8d34cd9 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 +1243,174 @@ static int get_cluster_table(VmdkExtent *extent, uint64_t offset, > return VMDK_OK; > } > > +/* > + * handle_alloc > + * > + * Allocate new clusters for an area that either is yet unallocated or needs a > + * 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) Not super important but personally I always prefer to stick to a "vmdk_" prefix when naming local identifiers, so that ctags and git grep can take it easy. > +{ > + 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; Alignment could be improved: here ^ > + > + 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) Better use BDRV_SECTOR_BITS instead of 9. > + - skip_start_bytes; > + } else { > + nb_clusters = 1; > + } > + *total_alloc_clusters += nb_clusters; It is weird that you increment *total_alloc_clusters instead of simply assigning to it, because it's not clear why before reading the caller code. It's better if you just return nb_clusters from this function (either as a return value, or assign to *total_alloc_clusters), then do the accumulation in vmdk_pwritev by adding m_data->nb_clusters, which is simpler. > + 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 = 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 +1794,7 @@ 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 +1820,10 @@ 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 +1832,9 @@ 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 +1842,11 @@ 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 > > Fam
On Thu, Jun 1, 2017 at 7:27 PM, Fam Zheng <famz@redhat.com> wrote: > On Sat, 04/22 10:43, Ashijeet Acharya wrote: >> 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 <ashijeetacharya@gmail.com> >> --- >> block/vmdk.c | 192 +++++++++++++++++++++++++++++++++++++++++++++++++++++++---- >> 1 file changed, 182 insertions(+), 10 deletions(-) >> >> diff --git a/block/vmdk.c b/block/vmdk.c >> index 7862791..8d34cd9 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 +1243,174 @@ static int get_cluster_table(VmdkExtent *extent, uint64_t offset, >> return VMDK_OK; >> } >> >> +/* >> + * handle_alloc >> + * >> + * Allocate new clusters for an area that either is yet unallocated or needs a >> + * 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) > > Not super important but personally I always prefer to stick to a "vmdk_" prefix > when naming local identifiers, so that ctags and git grep can take it easy. Done. > >> +{ >> + 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; > > Alignment could be improved: here ^ Done. > >> + >> + 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) > > Better use BDRV_SECTOR_BITS instead of 9. Done. > >> + - skip_start_bytes; >> + } else { >> + nb_clusters = 1; >> + } >> + *total_alloc_clusters += nb_clusters; > > It is weird that you increment *total_alloc_clusters instead of simply assigning > to it, because it's not clear why before reading the caller code. > I am incrementing it because we allocate clusters in every iteration and *total_alloc_clusters contains number of clusters allocated in total and not just in one iteration. So basically it is a sum of all the m_data->nb_clusters present in every element of the linked list I prepare. > It's better if you just return nb_clusters from this function (either as a > return value, or assign to *total_alloc_clusters), then do the accumulation in > vmdk_pwritev by adding m_data->nb_clusters, which is simpler. If I understood it correctly, you mean to say that I should add all the m_data->nb_clusters present in my linked list inside vmdk_pwritev() using a loop? If yes, I think that's what I have been doing earlier by incrementing *total_alloc_clusters there itself and is better, no? Also, please correct me if I am wrong :-) Ashijeet
diff --git a/block/vmdk.c b/block/vmdk.c index 7862791..8d34cd9 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 +1243,174 @@ static int get_cluster_table(VmdkExtent *extent, uint64_t offset, return VMDK_OK; } +/* + * handle_alloc + * + * Allocate new clusters for an area that either is yet unallocated or needs a + * 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) +{ + 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) << 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; + } + } + *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 = 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 +1794,7 @@ 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 +1820,10 @@ 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 +1832,9 @@ 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 +1842,11 @@ 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)
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 <ashijeetacharya@gmail.com> --- block/vmdk.c | 192 +++++++++++++++++++++++++++++++++++++++++++++++++++++++---- 1 file changed, 182 insertions(+), 10 deletions(-)