diff options
| -rw-r--r-- | block/qcow2-cluster.c | 50 | ||||
| -rw-r--r-- | block/qcow2-refcount.c | 120 | ||||
| -rw-r--r-- | block/qcow2.c | 43 | ||||
| -rw-r--r-- | block/qcow2.h | 14 | ||||
| -rw-r--r-- | qapi/block-core.json | 8 |
5 files changed, 225 insertions, 10 deletions
diff --git a/block/qcow2-cluster.c b/block/qcow2-cluster.c index 0d48249..d2518d1 100644 --- a/block/qcow2-cluster.c +++ b/block/qcow2-cluster.c @@ -32,6 +32,56 @@ #include "qemu/bswap.h" #include "trace.h" +int qcow2_shrink_l1_table(BlockDriverState *bs, uint64_t exact_size) +{ + BDRVQcow2State *s = bs->opaque; + int new_l1_size, i, ret; + + if (exact_size >= s->l1_size) { + return 0; + } + + new_l1_size = exact_size; + +#ifdef DEBUG_ALLOC2 + fprintf(stderr, "shrink l1_table from %d to %d\n", s->l1_size, new_l1_size); +#endif + + BLKDBG_EVENT(bs->file, BLKDBG_L1_SHRINK_WRITE_TABLE); + ret = bdrv_pwrite_zeroes(bs->file, s->l1_table_offset + + new_l1_size * sizeof(uint64_t), + (s->l1_size - new_l1_size) * sizeof(uint64_t), 0); + if (ret < 0) { + goto fail; + } + + ret = bdrv_flush(bs->file->bs); + if (ret < 0) { + goto fail; + } + + BLKDBG_EVENT(bs->file, BLKDBG_L1_SHRINK_FREE_L2_CLUSTERS); + for (i = s->l1_size - 1; i > new_l1_size - 1; i--) { + if ((s->l1_table[i] & L1E_OFFSET_MASK) == 0) { + continue; + } + qcow2_free_clusters(bs, s->l1_table[i] & L1E_OFFSET_MASK, + s->cluster_size, QCOW2_DISCARD_ALWAYS); + s->l1_table[i] = 0; + } + return 0; + +fail: + /* + * If the write in the l1_table failed the image may contain a partially + * overwritten l1_table. In this case it would be better to clear the + * l1_table in memory to avoid possible image corruption. + */ + memset(s->l1_table + new_l1_size, 0, + (s->l1_size - new_l1_size) * sizeof(uint64_t)); + return ret; +} + int qcow2_grow_l1_table(BlockDriverState *bs, uint64_t min_size, bool exact_size) { diff --git a/block/qcow2-refcount.c b/block/qcow2-refcount.c index 8c17c0e..88d5a3f 100644 --- a/block/qcow2-refcount.c +++ b/block/qcow2-refcount.c @@ -29,6 +29,7 @@ #include "block/qcow2.h" #include "qemu/range.h" #include "qemu/bswap.h" +#include "qemu/cutils.h" static int64_t alloc_clusters_noref(BlockDriverState *bs, uint64_t size); static int QEMU_WARN_UNUSED_RESULT update_refcount(BlockDriverState *bs, @@ -3061,3 +3062,122 @@ done: qemu_vfree(new_refblock); return ret; } + +static int qcow2_discard_refcount_block(BlockDriverState *bs, + uint64_t discard_block_offs) +{ + BDRVQcow2State *s = bs->opaque; + uint64_t refblock_offs = get_refblock_offset(s, discard_block_offs); + uint64_t cluster_index = discard_block_offs >> s->cluster_bits; + uint32_t block_index = cluster_index & (s->refcount_block_size - 1); + void *refblock; + int ret; + + assert(discard_block_offs != 0); + + ret = qcow2_cache_get(bs, s->refcount_block_cache, refblock_offs, + &refblock); + if (ret < 0) { + return ret; + } + + if (s->get_refcount(refblock, block_index) != 1) { + qcow2_signal_corruption(bs, true, -1, -1, "Invalid refcount:" + " refblock offset %#" PRIx64 + ", reftable index %u" + ", block offset %#" PRIx64 + ", refcount %#" PRIx64, + refblock_offs, + offset_to_reftable_index(s, discard_block_offs), + discard_block_offs, + s->get_refcount(refblock, block_index)); + qcow2_cache_put(bs, s->refcount_block_cache, &refblock); + return -EINVAL; + } + s->set_refcount(refblock, block_index, 0); + + qcow2_cache_entry_mark_dirty(bs, s->refcount_block_cache, refblock); + + qcow2_cache_put(bs, s->refcount_block_cache, &refblock); + + if (cluster_index < s->free_cluster_index) { + s->free_cluster_index = cluster_index; + } + + refblock = qcow2_cache_is_table_offset(bs, s->refcount_block_cache, + discard_block_offs); + if (refblock) { + /* discard refblock from the cache if refblock is cached */ + qcow2_cache_discard(bs, s->refcount_block_cache, refblock); + } + update_refcount_discard(bs, discard_block_offs, s->cluster_size); + + return 0; +} + +int qcow2_shrink_reftable(BlockDriverState *bs) +{ + BDRVQcow2State *s = bs->opaque; + uint64_t *reftable_tmp = + g_malloc(s->refcount_table_size * sizeof(uint64_t)); + int i, ret; + + for (i = 0; i < s->refcount_table_size; i++) { + int64_t refblock_offs = s->refcount_table[i] & REFT_OFFSET_MASK; + void *refblock; + bool unused_block; + + if (refblock_offs == 0) { + reftable_tmp[i] = 0; + continue; + } + ret = qcow2_cache_get(bs, s->refcount_block_cache, refblock_offs, + &refblock); + if (ret < 0) { + goto out; + } + + /* the refblock has own reference */ + if (i == offset_to_reftable_index(s, refblock_offs)) { + uint64_t block_index = (refblock_offs >> s->cluster_bits) & + (s->refcount_block_size - 1); + uint64_t refcount = s->get_refcount(refblock, block_index); + + s->set_refcount(refblock, block_index, 0); + + unused_block = buffer_is_zero(refblock, s->cluster_size); + + s->set_refcount(refblock, block_index, refcount); + } else { + unused_block = buffer_is_zero(refblock, s->cluster_size); + } + qcow2_cache_put(bs, s->refcount_block_cache, &refblock); + + reftable_tmp[i] = unused_block ? 0 : cpu_to_be64(s->refcount_table[i]); + } + + ret = bdrv_pwrite_sync(bs->file, s->refcount_table_offset, reftable_tmp, + s->refcount_table_size * sizeof(uint64_t)); + /* + * If the write in the reftable failed the image may contain a partially + * overwritten reftable. In this case it would be better to clear the + * reftable in memory to avoid possible image corruption. + */ + for (i = 0; i < s->refcount_table_size; i++) { + if (s->refcount_table[i] && !reftable_tmp[i]) { + if (ret == 0) { + ret = qcow2_discard_refcount_block(bs, s->refcount_table[i] & + REFT_OFFSET_MASK); + } + s->refcount_table[i] = 0; + } + } + + if (!s->cache_discards) { + qcow2_process_discards(bs, ret); + } + +out: + g_free(reftable_tmp); + return ret; +} diff --git a/block/qcow2.c b/block/qcow2.c index d33fb3e..970006f 100644 --- a/block/qcow2.c +++ b/block/qcow2.c @@ -3104,18 +3104,43 @@ static int qcow2_truncate(BlockDriverState *bs, int64_t offset, } old_length = bs->total_sectors * 512; + new_l1_size = size_to_l1(s, offset); - /* shrinking is currently not supported */ if (offset < old_length) { - error_setg(errp, "qcow2 doesn't support shrinking images yet"); - return -ENOTSUP; - } + if (prealloc != PREALLOC_MODE_OFF) { + error_setg(errp, + "Preallocation can't be used for shrinking an image"); + return -EINVAL; + } - new_l1_size = size_to_l1(s, offset); - ret = qcow2_grow_l1_table(bs, new_l1_size, true); - if (ret < 0) { - error_setg_errno(errp, -ret, "Failed to grow the L1 table"); - return ret; + ret = qcow2_cluster_discard(bs, ROUND_UP(offset, s->cluster_size), + old_length - ROUND_UP(offset, + s->cluster_size), + QCOW2_DISCARD_ALWAYS, true); + if (ret < 0) { + error_setg_errno(errp, -ret, "Failed to discard cropped clusters"); + return ret; + } + + ret = qcow2_shrink_l1_table(bs, new_l1_size); + if (ret < 0) { + error_setg_errno(errp, -ret, + "Failed to reduce the number of L2 tables"); + return ret; + } + + ret = qcow2_shrink_reftable(bs); + if (ret < 0) { + error_setg_errno(errp, -ret, + "Failed to discard unused refblocks"); + return ret; + } + } else { + ret = qcow2_grow_l1_table(bs, new_l1_size, true); + if (ret < 0) { + error_setg_errno(errp, -ret, "Failed to grow the L1 table"); + return ret; + } } switch (prealloc) { diff --git a/block/qcow2.h b/block/qcow2.h index 52c374e..5a289a8 100644 --- a/block/qcow2.h +++ b/block/qcow2.h @@ -521,6 +521,18 @@ static inline uint64_t refcount_diff(uint64_t r1, uint64_t r2) return r1 > r2 ? r1 - r2 : r2 - r1; } +static inline +uint32_t offset_to_reftable_index(BDRVQcow2State *s, uint64_t offset) +{ + return offset >> (s->refcount_block_bits + s->cluster_bits); +} + +static inline uint64_t get_refblock_offset(BDRVQcow2State *s, uint64_t offset) +{ + uint32_t index = offset_to_reftable_index(s, offset); + return s->refcount_table[index] & REFT_OFFSET_MASK; +} + /* qcow2.c functions */ int qcow2_backing_read1(BlockDriverState *bs, QEMUIOVector *qiov, int64_t sector_num, int nb_sectors); @@ -584,10 +596,12 @@ int qcow2_inc_refcounts_imrt(BlockDriverState *bs, BdrvCheckResult *res, int qcow2_change_refcount_order(BlockDriverState *bs, int refcount_order, BlockDriverAmendStatusCB *status_cb, void *cb_opaque, Error **errp); +int qcow2_shrink_reftable(BlockDriverState *bs); /* qcow2-cluster.c functions */ int qcow2_grow_l1_table(BlockDriverState *bs, uint64_t min_size, bool exact_size); +int qcow2_shrink_l1_table(BlockDriverState *bs, uint64_t max_size); int qcow2_write_l1_entry(BlockDriverState *bs, int l1_index); int qcow2_decompress_cluster(BlockDriverState *bs, uint64_t cluster_offset); int qcow2_encrypt_sectors(BDRVQcow2State *s, int64_t sector_num, diff --git a/qapi/block-core.json b/qapi/block-core.json index c69a395..750bb0c 100644 --- a/qapi/block-core.json +++ b/qapi/block-core.json @@ -2533,6 +2533,11 @@ # # Trigger events supported by blkdebug. # +# @l1_shrink_write_table: write zeros to the l1 table to shrink image. +# (since 2.11) +# +# @l1_shrink_free_l2_clusters: discard the l2 tables. (since 2.11) +# # Since: 2.9 ## { 'enum': 'BlkdebugEvent', 'prefix': 'BLKDBG', @@ -2549,7 +2554,8 @@ 'cluster_alloc_bytes', 'cluster_free', 'flush_to_os', 'flush_to_disk', 'pwritev_rmw_head', 'pwritev_rmw_after_head', 'pwritev_rmw_tail', 'pwritev_rmw_after_tail', 'pwritev', - 'pwritev_zero', 'pwritev_done', 'empty_image_prepare' ] } + 'pwritev_zero', 'pwritev_done', 'empty_image_prepare', + 'l1_shrink_write_table', 'l1_shrink_free_l2_clusters' ] } ## # @BlkdebugInjectErrorOptions: |