/* * Block driver for the QCOW version 2 format * * Copyright (c) 2004-2006 Fabrice Bellard * * Permission is hereby granted, free of charge, to any person obtaining a copy * of this software and associated documentation files (the "Software"), to deal * in the Software without restriction, including without limitation the rights * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell * copies of the Software, and to permit persons to whom the Software is * furnished to do so, subject to the following conditions: * * The above copyright notice and this permission notice shall be included in * all copies or substantial portions of the Software. * * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN * THE SOFTWARE. */ #include "qemu/osdep.h" #include <zlib.h> #include "qapi/error.h" #include "qcow2.h" #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) { BDRVQcow2State *s = bs->opaque; int new_l1_size2, ret, i; uint64_t *new_l1_table; int64_t old_l1_table_offset, old_l1_size; int64_t new_l1_table_offset, new_l1_size; uint8_t data[12]; if (min_size <= s->l1_size) return 0; /* Do a sanity check on min_size before trying to calculate new_l1_size * (this prevents overflows during the while loop for the calculation of * new_l1_size) */ if (min_size > INT_MAX / sizeof(uint64_t)) { return -EFBIG; } if (exact_size) { new_l1_size = min_size; } else { /* Bump size up to reduce the number of times we have to grow */ new_l1_size = s->l1_size; if (new_l1_size == 0) { new_l1_size = 1; } while (min_size > new_l1_size) { new_l1_size = DIV_ROUND_UP(new_l1_size * 3, 2); } } QEMU_BUILD_BUG_ON(QCOW_MAX_L1_SIZE > INT_MAX); if (new_l1_size > QCOW_MAX_L1_SIZE / sizeof(uint64_t)) { return -EFBIG; } #ifdef DEBUG_ALLOC2 fprintf(stderr, "grow l1_table from %d to %" PRId64 "\n", s->l1_size, new_l1_size); #endif new_l1_size2 = sizeof(uint64_t) * new_l1_size; new_l1_table = qemu_try_blockalign(bs->file->bs, new_l1_size2); if (new_l1_table == NULL) { return -ENOMEM; } memset(new_l1_table, 0, new_l1_size2); if (s->l1_size) { memcpy(new_l1_table, s->l1_table, s->l1_size * sizeof(uint64_t)); } /* write new table (align to cluster) */ BLKDBG_EVENT(bs->file, BLKDBG_L1_GROW_ALLOC_TABLE); new_l1_table_offset = qcow2_alloc_clusters(bs, new_l1_size2); if (new_l1_table_offset < 0) { qemu_vfree(new_l1_table); return new_l1_table_offset; } ret = qcow2_cache_flush(bs, s->refcount_block_cache); if (ret < 0) { goto fail; } /* the L1 position has not yet been updated, so these clusters must * indeed be completely free */ ret = qcow2_pre_write_overlap_check(bs, 0, new_l1_table_offset, new_l1_size2, false); if (ret < 0) { goto fail; } BLKDBG_EVENT(bs->file, BLKDBG_L1_GROW_WRITE_TABLE); for(i = 0; i < s->l1_size; i++) new_l1_table[i] = cpu_to_be64(new_l1_table[i]); ret = bdrv_pwrite_sync(bs->file, new_l1_table_offset, new_l1_table, new_l1_size2); if (ret < 0) goto fail; for(i = 0; i < s->l1_size; i++) new_l1_table[i] = be64_to_cpu(new_l1_table[i]); /* set new table */ BLKDBG_EVENT(bs->file, BLKDBG_L1_GROW_ACTIVATE_TABLE); stl_be_p(data, new_l1_size); stq_be_p(data + 4, new_l1_table_offset); ret = bdrv_pwrite_sync(bs->file, offsetof(QCowHeader, l1_size), data, sizeof(data)); if (ret < 0) { goto fail; } qemu_vfree(s->l1_table); old_l1_table_offset = s->l1_table_offset; s->l1_table_offset = new_l1_table_offset; s->l1_table = new_l1_table; old_l1_size = s->l1_size; s->l1_size = new_l1_size; qcow2_free_clusters(bs, old_l1_table_offset, old_l1_size * sizeof(uint64_t), QCOW2_DISCARD_OTHER); return 0; fail: qemu_vfree(new_l1_table); qcow2_free_clusters(bs, new_l1_table_offset, new_l1_size2, QCOW2_DISCARD_OTHER); return ret; } /* * l2_load * * @bs: The BlockDriverState * @offset: A guest offset, used to calculate what slice of the L2 * table to load. * @l2_offset: Offset to the L2 table in the image file. * @l2_slice: Location to store the pointer to the L2 slice. * * Loads a L2 slice into memory (L2 slices are the parts of L2 tables * that are loaded by the qcow2 cache). If the slice is in the cache, * the cache is used; otherwise the L2 slice is loaded from the image * file. */ static int l2_load(BlockDriverState *bs, uint64_t offset, uint64_t l2_offset, uint64_t **l2_slice) { BDRVQcow2State *s = bs->opaque; int start_of_slice = sizeof(uint64_t) * (offset_to_l2_index(s, offset) - offset_to_l2_slice_index(s, offset)); return qcow2_cache_get(bs, s->l2_table_cache, l2_offset + start_of_slice, (void **)l2_slice); } /* * Writes an L1 entry to disk (note that depending on the alignment * requirements this function may write more that just one entry in * order to prevent bdrv_pwrite from performing a read-modify-write) */ int qcow2_write_l1_entry(BlockDriverState *bs, int l1_index) { BDRVQcow2State *s = bs->opaque; int l1_start_index; int i, ret; int bufsize = MAX(sizeof(uint64_t), MIN(bs->file->bs->bl.request_alignment, s->cluster_size)); int nentries = bufsize / sizeof(uint64_t); g_autofree uint64_t *buf = g_try_new0(uint64_t, nentries); if (buf == NULL) { return -ENOMEM; } l1_start_index = QEMU_ALIGN_DOWN(l1_index, nentries); for (i = 0; i < MIN(nentries, s->l1_size - l1_start_index); i++) { buf[i] = cpu_to_be64(s->l1_table[l1_start_index + i]); } ret = qcow2_pre_write_overlap_check(bs, QCOW2_OL_ACTIVE_L1, s->l1_table_offset + 8 * l1_start_index, bufsize, false); if (ret < 0) { return ret; } BLKDBG_EVENT(bs->file, BLKDBG_L1_UPDATE); ret = bdrv_pwrite_sync(bs->file, s->l1_table_offset + 8 * l1_start_index, buf, bufsize); if (ret < 0) { return ret; } return 0; } /* * l2_allocate * * Allocate a new l2 entry in the file. If l1_index points to an already * used entry in the L2 table (i.e. we are doing a copy on write for the L2 * table) copy the contents of the old L2 table into the newly allocated one. * Otherwise the new table is initialized with zeros. * */ static int l2_allocate(BlockDriverState *bs, int l1_index) { BDRVQcow2State *s = bs->opaque; uint64_t old_l2_offset; uint64_t *l2_slice = NULL; unsigned slice, slice_size2, n_slices; int64_t l2_offset; int ret; old_l2_offset = s->l1_table[l1_index]; trace_qcow2_l2_allocate(bs, l1_index); /* allocate a new l2 entry */ l2_offset = qcow2_alloc_clusters(bs, s->l2_size * sizeof(uint64_t)); if (l2_offset < 0) { ret = l2_offset; goto fail; } /* The offset must fit in the offset field of the L1 table entry */ assert((l2_offset & L1E_OFFSET_MASK) == l2_offset); /* If we're allocating the table at offset 0 then something is wrong */ if (l2_offset == 0) { qcow2_signal_corruption(bs, true, -1, -1, "Preventing invalid " "allocation of L2 table at offset 0"); ret = -EIO; goto fail; } ret = qcow2_cache_flush(bs, s->refcount_block_cache); if (ret < 0) { goto fail; } /* allocate a new entry in the l2 cache */ slice_size2 = s->l2_slice_size * sizeof(uint64_t); n_slices = s->cluster_size / slice_size2; trace_qcow2_l2_allocate_get_empty(bs, l1_index); for (slice = 0; slice < n_slices; slice++) { ret = qcow2_cache_get_empty(bs, s->l2_table_cache, l2_offset + slice * slice_size2, (void **) &l2_slice); if (ret < 0) { goto fail; } if ((old_l2_offset & L1E_OFFSET_MASK) == 0) { /* if there was no old l2 table, clear the new slice */ memset(l2_slice, 0, slice_size2); } else { uint64_t *old_slice; uint64_t old_l2_slice_offset = (old_l2_offset & L1E_OFFSET_MASK) + slice * slice_size2; /* if there was an old l2 table, read a slice from the disk */ BLKDBG_EVENT(bs->file, BLKDBG_L2_ALLOC_COW_READ); ret = qcow2_cache_get(bs, s->l2_table_cache, old_l2_slice_offset, (void **) &old_slice); if (ret < 0) { goto fail; } memcpy(l2_slice, old_slice, slice_size2); qcow2_cache_put(s->l2_table_cache, (void **) &old_slice); } /* write the l2 slice to the file */ BLKDBG_EVENT(bs->file, BLKDBG_L2_ALLOC_WRITE); trace_qcow2_l2_allocate_write_l2(bs, l1_index); qcow2_cache_entry_mark_dirty(s->l2_table_cache, l2_slice); qcow2_cache_put(s->l2_table_cache, (void **) &l2_slice); } ret = qcow2_cache_flush(bs, s->l2_table_cache); if (ret < 0) { goto fail; } /* update the L1 entry */ trace_qcow2_l2_allocate_write_l1(bs, l1_index); s->l1_table[l1_index] = l2_offset | QCOW_OFLAG_COPIED; ret = qcow2_write_l1_entry(bs, l1_index); if (ret < 0) { goto fail; } trace_qcow2_l2_allocate_done(bs, l1_index, 0); return 0; fail: trace_qcow2_l2_allocate_done(bs, l1_index, ret); if (l2_slice != NULL) { qcow2_cache_put(s->l2_table_cache, (void **) &l2_slice); } s->l1_table[l1_index] = old_l2_offset; if (l2_offset > 0) { qcow2_free_clusters(bs, l2_offset, s->l2_size * sizeof(uint64_t), QCOW2_DISCARD_ALWAYS); } return ret; } /* * Checks how many clusters in a given L2 slice are contiguous in the image * file. As soon as one of the flags in the bitmask stop_flags changes compared * to the first cluster, the search is stopped and the cluster is not counted * as contiguous. (This allows it, for example, to stop at the first compressed * cluster which may require a different handling) */ static int count_contiguous_clusters(BlockDriverState *bs, int nb_clusters, int cluster_size, uint64_t *l2_slice, uint64_t stop_flags) { int i; QCow2ClusterType first_cluster_type; uint64_t mask = stop_flags | L2E_OFFSET_MASK | QCOW_OFLAG_COMPRESSED; uint64_t first_entry = be64_to_cpu(l2_slice[0]); uint64_t offset = first_entry & mask; first_cluster_type = qcow2_get_cluster_type(bs, first_entry); if (first_cluster_type == QCOW2_CLUSTER_UNALLOCATED) { return 0; } /* must be allocated */ assert(first_cluster_type == QCOW2_CLUSTER_NORMAL || first_cluster_type == QCOW2_CLUSTER_ZERO_ALLOC); for (i = 0; i < nb_clusters; i++) { uint64_t l2_entry = be64_to_cpu(l2_slice[i]) & mask; if (offset + (uint64_t) i * cluster_size != l2_entry) { break; } } return i; } /* * Checks how many consecutive unallocated clusters in a given L2 * slice have the same cluster type. */ static int count_contiguous_clusters_unallocated(BlockDriverState *bs, int nb_clusters, uint64_t *l2_slice, QCow2ClusterType wanted_type) { int i; assert(wanted_type == QCOW2_CLUSTER_ZERO_PLAIN || wanted_type == QCOW2_CLUSTER_UNALLOCATED); for (i = 0; i < nb_clusters; i++) { uint64_t entry = be64_to_cpu(l2_slice[i]); QCow2ClusterType type = qcow2_get_cluster_type(bs, entry); if (type != wanted_type) { break; } } return i; } static int coroutine_fn do_perform_cow_read(BlockDriverState *bs, uint64_t src_cluster_offset, unsigned offset_in_cluster, QEMUIOVector *qiov) { int ret; if (qiov->size == 0) { return 0; } BLKDBG_EVENT(bs->file, BLKDBG_COW_READ); if (!bs->drv) { return -ENOMEDIUM; } /* Call .bdrv_co_readv() directly instead of using the public block-layer * interface. This avoids double I/O throttling and request tracking, * which can lead to deadlock when block layer copy-on-read is enabled. */ ret = bs->drv->bdrv_co_preadv_part(bs, src_cluster_offset + offset_in_cluster, qiov->size, qiov, 0, 0); if (ret < 0) { return ret; } return 0; } static int coroutine_fn do_perform_cow_write(BlockDriverState *bs, uint64_t cluster_offset, unsigned offset_in_cluster, QEMUIOVector *qiov) { BDRVQcow2State *s = bs->opaque; int ret; if (qiov->size == 0) { return 0; } ret = qcow2_pre_write_overlap_check(bs, 0, cluster_offset + offset_in_cluster, qiov->size, true); if (ret < 0) { return ret; } BLKDBG_EVENT(bs->file, BLKDBG_COW_WRITE); ret = bdrv_co_pwritev(s->data_file, cluster_offset + offset_in_cluster, qiov->size, qiov, 0); if (ret < 0) { return ret; } return 0; } /* * get_cluster_offset * * For a given offset of the virtual disk, find the cluster type and offset in * the qcow2 file. The offset is stored in *cluster_offset. * * On entry, *bytes is the maximum number of contiguous bytes starting at * offset that we are interested in. * * On exit, *bytes is the number of bytes starting at offset that have the same * cluster type and (if applicable) are stored contiguously in the image file. * Compressed clusters are always returned one by one. * * Returns the cluster type (QCOW2_CLUSTER_*) on success, -errno in error * cases. */ int qcow2_get_cluster_offset(BlockDriverState *bs, uint64_t offset, unsigned int *bytes, uint64_t *cluster_offset) { BDRVQcow2State *s = bs->opaque; unsigned int l2_index; uint64_t l1_index, l2_offset, *l2_slice; int c; unsigned int offset_in_cluster; uint64_t bytes_available, bytes_needed, nb_clusters; QCow2ClusterType type; int ret; offset_in_cluster = offset_into_cluster(s, offset); bytes_needed = (uint64_t) *bytes + offset_in_cluster; /* compute how many bytes there are between the start of the cluster * containing offset and the end of the l2 slice that contains * the entry pointing to it */ bytes_available = ((uint64_t) (s->l2_slice_size - offset_to_l2_slice_index(s, offset))) << s->cluster_bits; if (bytes_needed > bytes_available) { bytes_needed = bytes_available; } *cluster_offset = 0; /* seek to the l2 offset in the l1 table */ l1_index = offset_to_l1_index(s, offset); if (l1_index >= s->l1_size) { type = QCOW2_CLUSTER_UNALLOCATED; goto out; } l2_offset = s->l1_table[l1_index] & L1E_OFFSET_MASK; if (!l2_offset) { type = QCOW2_CLUSTER_UNALLOCATED; goto out; } if (offset_into_cluster(s, l2_offset)) { qcow2_signal_corruption(bs, true, -1, -1, "L2 table offset %#" PRIx64 " unaligned (L1 index: %#" PRIx64 ")", l2_offset, l1_index); return -EIO; } /* load the l2 slice in memory */ ret = l2_load(bs, offset, l2_offset, &l2_slice); if (ret < 0) { return ret; } /* find the cluster offset for the given disk offset */ l2_index = offset_to_l2_slice_index(s, offset); *cluster_offset = be64_to_cpu(l2_slice[l2_index]); nb_clusters = size_to_clusters(s, bytes_needed); /* bytes_needed <= *bytes + offset_in_cluster, both of which are unsigned * integers; the minimum cluster size is 512, so this assertion is always * true */ assert(nb_clusters <= INT_MAX); type = qcow2_get_cluster_type(bs, *cluster_offset); if (s->qcow_version < 3 && (type == QCOW2_CLUSTER_ZERO_PLAIN || type == QCOW2_CLUSTER_ZERO_ALLOC)) { qcow2_signal_corruption(bs, true, -1, -1, "Zero cluster entry found" " in pre-v3 image (L2 offset: %#" PRIx64 ", L2 index: %#x)", l2_offset, l2_index); ret = -EIO; goto fail; } switch (type) { case QCOW2_CLUSTER_COMPRESSED: if (has_data_file(bs)) { qcow2_signal_corruption(bs, true, -1, -1, "Compressed cluster " "entry found in image with external data " "file (L2 offset: %#" PRIx64 ", L2 index: " "%#x)", l2_offset, l2_index); ret = -EIO; goto fail; } /* Compressed clusters can only be processed one by one */ c = 1; *cluster_offset &= L2E_COMPRESSED_OFFSET_SIZE_MASK; break; case QCOW2_CLUSTER_ZERO_PLAIN: case QCOW2_CLUSTER_UNALLOCATED: /* how many empty clusters ? */ c = count_contiguous_clusters_unallocated(bs, nb_clusters, &l2_slice[l2_index], type); *cluster_offset = 0; break; case QCOW2_CLUSTER_ZERO_ALLOC: case QCOW2_CLUSTER_NORMAL: /* how many allocated clusters ? */ c = count_contiguous_clusters(bs, nb_clusters, s->cluster_size, &l2_slice[l2_index], QCOW_OFLAG_ZERO); *cluster_offset &= L2E_OFFSET_MASK; if (offset_into_cluster(s, *cluster_offset)) { qcow2_signal_corruption(bs, true, -1, -1, "Cluster allocation offset %#" PRIx64 " unaligned (L2 offset: %#" PRIx64 ", L2 index: %#x)", *cluster_offset, l2_offset, l2_index); ret = -EIO; goto fail; } if (has_data_file(bs) && *cluster_offset != offset - offset_in_cluster) { qcow2_signal_corruption(bs, true, -1, -1, "External data file host cluster offset %#" PRIx64 " does not match guest cluster " "offset: %#" PRIx64 ", L2 index: %#x)", *cluster_offset, offset - offset_in_cluster, l2_index); ret = -EIO; goto fail; } break; default: abort(); } qcow2_cache_put(s->l2_table_cache, (void **) &l2_slice); bytes_available = (int64_t)c * s->cluster_size; out: if (bytes_available > bytes_needed) { bytes_available = bytes_needed; } /* bytes_available <= bytes_needed <= *bytes + offset_in_cluster; * subtracting offset_in_cluster will therefore definitely yield something * not exceeding UINT_MAX */ assert(bytes_available - offset_in_cluster <= UINT_MAX); *bytes = bytes_available - offset_in_cluster; return type; fail: qcow2_cache_put(s->l2_table_cache, (void **)&l2_slice); return ret; } /* * get_cluster_table * * for a given disk offset, load (and allocate if needed) * the appropriate slice of its l2 table. * * the cluster index in the l2 slice is given to the caller. * * Returns 0 on success, -errno in failure case */ static int get_cluster_table(BlockDriverState *bs, uint64_t offset, uint64_t **new_l2_slice, int *new_l2_index) { BDRVQcow2State *s = bs->opaque; unsigned int l2_index; uint64_t l1_index, l2_offset; uint64_t *l2_slice = NULL; int ret; /* seek to the l2 offset in the l1 table */ l1_index = offset_to_l1_index(s, offset); if (l1_index >= s->l1_size) { ret = qcow2_grow_l1_table(bs, l1_index + 1, false); if (ret < 0) { return ret; } } assert(l1_index < s->l1_size); l2_offset = s->l1_table[l1_index] & L1E_OFFSET_MASK; if (offset_into_cluster(s, l2_offset)) { qcow2_signal_corruption(bs, true, -1, -1, "L2 table offset %#" PRIx64 " unaligned (L1 index: %#" PRIx64 ")", l2_offset, l1_index); return -EIO; } if (!(s->l1_table[l1_index] & QCOW_OFLAG_COPIED)) { /* First allocate a new L2 table (and do COW if needed) */ ret = l2_allocate(bs, l1_index); if (ret < 0) { return ret; } /* Then decrease the refcount of the old table */ if (l2_offset) { qcow2_free_clusters(bs, l2_offset, s->l2_size * sizeof(uint64_t), QCOW2_DISCARD_OTHER); } /* Get the offset of the newly-allocated l2 table */ l2_offset = s->l1_table[l1_index] & L1E_OFFSET_MASK; assert(offset_into_cluster(s, l2_offset) == 0); } /* load the l2 slice in memory */ ret = l2_load(bs, offset, l2_offset, &l2_slice); if (ret < 0) { return ret; } /* find the cluster offset for the given disk offset */ l2_index = offset_to_l2_slice_index(s, offset); *new_l2_slice = l2_slice; *new_l2_index = l2_index; return 0; } /* * alloc_compressed_cluster_offset * * For a given offset on the virtual disk, allocate a new compressed cluster * and put the host offset of the cluster into *host_offset. If a cluster is * already allocated at the offset, return an error. * * Return 0 on success and -errno in error cases */ int qcow2_alloc_compressed_cluster_offset(BlockDriverState *bs, uint64_t offset, int compressed_size, uint64_t *host_offset) { BDRVQcow2State *s = bs->opaque; int l2_index, ret; uint64_t *l2_slice; int64_t cluster_offset; int nb_csectors; if (has_data_file(bs)) { return 0; } ret = get_cluster_table(bs, offset, &l2_slice, &l2_index); if (ret < 0) { return ret; } /* Compression can't overwrite anything. Fail if the cluster was already * allocated. */ cluster_offset = be64_to_cpu(l2_slice[l2_index]); if (cluster_offset & L2E_OFFSET_MASK) { qcow2_cache_put(s->l2_table_cache, (void **) &l2_slice); return -EIO; } cluster_offset = qcow2_alloc_bytes(bs, compressed_size); if (cluster_offset < 0) { qcow2_cache_put(s->l2_table_cache, (void **) &l2_slice); return cluster_offset; } nb_csectors = (cluster_offset + compressed_size - 1) / QCOW2_COMPRESSED_SECTOR_SIZE - (cluster_offset / QCOW2_COMPRESSED_SECTOR_SIZE); /* The offset and size must fit in their fields of the L2 table entry */ assert((cluster_offset & s->cluster_offset_mask) == cluster_offset); assert((nb_csectors & s->csize_mask) == nb_csectors); cluster_offset |= QCOW_OFLAG_COMPRESSED | ((uint64_t)nb_csectors << s->csize_shift); /* update L2 table */ /* compressed clusters never have the copied flag */ BLKDBG_EVENT(bs->file, BLKDBG_L2_UPDATE_COMPRESSED); qcow2_cache_entry_mark_dirty(s->l2_table_cache, l2_slice); l2_slice[l2_index] = cpu_to_be64(cluster_offset); qcow2_cache_put(s->l2_table_cache, (void **) &l2_slice); *host_offset = cluster_offset & s->cluster_offset_mask; return 0; } static int perform_cow(BlockDriverState *bs, QCowL2Meta *m) { BDRVQcow2State *s = bs->opaque; Qcow2COWRegion *start = &m->cow_start; Qcow2COWRegion *end = &m->cow_end; unsigned buffer_size; unsigned data_bytes = end->offset - (start->offset + start->nb_bytes); bool merge_reads; uint8_t *start_buffer, *end_buffer; QEMUIOVector qiov; int ret; assert(start->nb_bytes <= UINT_MAX - end->nb_bytes); assert(start->nb_bytes + end->nb_bytes <= UINT_MAX - data_bytes); assert(start->offset + start->nb_bytes <= end->offset); if ((start->nb_bytes == 0 && end->nb_bytes == 0) || m->skip_cow) { return 0; } /* If we have to read both the start and end COW regions and the * middle region is not too large then perform just one read * operation */ merge_reads = start->nb_bytes && end->nb_bytes && data_bytes <= 16384; if (merge_reads) { buffer_size = start->nb_bytes + data_bytes + end->nb_bytes; } else { /* If we have to do two reads, add some padding in the middle * if necessary to make sure that the end region is optimally * aligned. */ size_t align = bdrv_opt_mem_align(bs); assert(align > 0 && align <= UINT_MAX); assert(QEMU_ALIGN_UP(start->nb_bytes, align) <= UINT_MAX - end->nb_bytes); buffer_size = QEMU_ALIGN_UP(start->nb_bytes, align) + end->nb_bytes; } /* Reserve a buffer large enough to store all the data that we're * going to read */ start_buffer = qemu_try_blockalign(bs, buffer_size); if (start_buffer == NULL) { return -ENOMEM; } /* The part of the buffer where the end region is located */ end_buffer = start_buffer + buffer_size - end->nb_bytes; qemu_iovec_init(&qiov, 2 + (m->data_qiov ? qemu_iovec_subvec_niov(m->data_qiov, m->data_qiov_offset, data_bytes) : 0)); qemu_co_mutex_unlock(&s->lock); /* First we read the existing data from both COW regions. We * either read the whole region in one go, or the start and end * regions separately. */ if (merge_reads) { qemu_iovec_add(&qiov, start_buffer, buffer_size); ret = do_perform_cow_read(bs, m->offset, start->offset, &qiov); } else { qemu_iovec_add(&qiov, start_buffer, start->nb_bytes); ret = do_perform_cow_read(bs, m->offset, start->offset, &qiov); if (ret < 0) { goto fail; } qemu_iovec_reset(&qiov); qemu_iovec_add(&qiov, end_buffer, end->nb_bytes); ret = do_perform_cow_read(bs, m->offset, end->offset, &qiov); } if (ret < 0) { goto fail; } /* Encrypt the data if necessary before writing it */ if (bs->encrypted) { ret = qcow2_co_encrypt(bs, m->alloc_offset + start->offset, m->offset + start->offset, start_buffer, start->nb_bytes); if (ret < 0) { goto fail; } ret = qcow2_co_encrypt(bs, m->alloc_offset + end->offset, m->offset + end->offset, end_buffer, end->nb_bytes); if (ret < 0) { goto fail; } } /* And now we can write everything. If we have the guest data we * can write everything in one single operation */ if (m->data_qiov) { qemu_iovec_reset(&qiov); if (start->nb_bytes) { qemu_iovec_add(&qiov, start_buffer, start->nb_bytes); } qemu_iovec_concat(&qiov, m->data_qiov, m->data_qiov_offset, data_bytes); if (end->nb_bytes) { qemu_iovec_add(&qiov, end_buffer, end->nb_bytes); } /* NOTE: we have a write_aio blkdebug event here followed by * a cow_write one in do_perform_cow_write(), but there's only * one single I/O operation */ BLKDBG_EVENT(bs->file, BLKDBG_WRITE_AIO); ret = do_perform_cow_write(bs, m->alloc_offset, start->offset, &qiov); } else { /* If there's no guest data then write both COW regions separately */ qemu_iovec_reset(&qiov); qemu_iovec_add(&qiov, start_buffer, start->nb_bytes); ret = do_perform_cow_write(bs, m->alloc_offset, start->offset, &qiov); if (ret < 0) { goto fail; } qemu_iovec_reset(&qiov); qemu_iovec_add(&qiov, end_buffer, end->nb_bytes); ret = do_perform_cow_write(bs, m->alloc_offset, end->offset, &qiov); } fail: qemu_co_mutex_lock(&s->lock); /* * Before we update the L2 table to actually point to the new cluster, we * need to be sure that the refcounts have been increased and COW was * handled. */ if (ret == 0) { qcow2_cache_depends_on_flush(s->l2_table_cache); } qemu_vfree(start_buffer); qemu_iovec_destroy(&qiov); return ret; } int qcow2_alloc_cluster_link_l2(BlockDriverState *bs, QCowL2Meta *m) { BDRVQcow2State *s = bs->opaque; int i, j = 0, l2_index, ret; uint64_t *old_cluster, *l2_slice; uint64_t cluster_offset = m->alloc_offset; trace_qcow2_cluster_link_l2(qemu_coroutine_self(), m->nb_clusters); assert(m->nb_clusters > 0); old_cluster = g_try_new(uint64_t, m->nb_clusters); if (old_cluster == NULL) { ret = -ENOMEM; goto err; } /* copy content of unmodified sectors */ ret = perform_cow(bs, m); if (ret < 0) { goto err; } /* Update L2 table. */ if (s->use_lazy_refcounts) { qcow2_mark_dirty(bs); } if (qcow2_need_accurate_refcounts(s)) { qcow2_cache_set_dependency(bs, s->l2_table_cache, s->refcount_block_cache); } ret = get_cluster_table(bs, m->offset, &l2_slice, &l2_index); if (ret < 0) { goto err; } qcow2_cache_entry_mark_dirty(s->l2_table_cache, l2_slice); assert(l2_index + m->nb_clusters <= s->l2_slice_size); for (i = 0; i < m->nb_clusters; i++) { uint64_t offset = cluster_offset + (i << s->cluster_bits); /* if two concurrent writes happen to the same unallocated cluster * each write allocates separate cluster and writes data concurrently. * The first one to complete updates l2 table with pointer to its * cluster the second one has to do RMW (which is done above by * perform_cow()), update l2 table with its cluster pointer and free * old cluster. This is what this loop does */ if (l2_slice[l2_index + i] != 0) { old_cluster[j++] = l2_slice[l2_index + i]; } /* The offset must fit in the offset field of the L2 table entry */ assert((offset & L2E_OFFSET_MASK) == offset); l2_slice[l2_index + i] = cpu_to_be64(offset | QCOW_OFLAG_COPIED); } qcow2_cache_put(s->l2_table_cache, (void **) &l2_slice); /* * If this was a COW, we need to decrease the refcount of the old cluster. * * Don't discard clusters that reach a refcount of 0 (e.g. compressed * clusters), the next write will reuse them anyway. */ if (!m->keep_old_clusters && j != 0) { for (i = 0; i < j; i++) { qcow2_free_any_clusters(bs, be64_to_cpu(old_cluster[i]), 1, QCOW2_DISCARD_NEVER); } } ret = 0; err: g_free(old_cluster); return ret; } /** * Frees the allocated clusters because the request failed and they won't * actually be linked. */ void qcow2_alloc_cluster_abort(BlockDriverState *bs, QCowL2Meta *m) { BDRVQcow2State *s = bs->opaque; qcow2_free_clusters(bs, m->alloc_offset, m->nb_clusters << s->cluster_bits, QCOW2_DISCARD_NEVER); } /* * Returns the number of contiguous clusters that can be used for an allocating * write, but require COW to be performed (this includes yet unallocated space, * which must copy from the backing file) */ static int count_cow_clusters(BlockDriverState *bs, int nb_clusters, uint64_t *l2_slice, int l2_index) { int i; for (i = 0; i < nb_clusters; i++) { uint64_t l2_entry = be64_to_cpu(l2_slice[l2_index + i]); QCow2ClusterType cluster_type = qcow2_get_cluster_type(bs, l2_entry); switch(cluster_type) { case QCOW2_CLUSTER_NORMAL: if (l2_entry & QCOW_OFLAG_COPIED) { goto out; } break; case QCOW2_CLUSTER_UNALLOCATED: case QCOW2_CLUSTER_COMPRESSED: case QCOW2_CLUSTER_ZERO_PLAIN: case QCOW2_CLUSTER_ZERO_ALLOC: break; default: abort(); } } out: assert(i <= nb_clusters); return i; } /* * Check if there already is an AIO write request in flight which allocates * the same cluster. In this case we need to wait until the previous * request has completed and updated the L2 table accordingly. * * Returns: * 0 if there was no dependency. *cur_bytes indicates the number of * bytes from guest_offset that can be read before the next * dependency must be processed (or the request is complete) * * -EAGAIN if we had to wait for another request, previously gathered * information on cluster allocation may be invalid now. The caller * must start over anyway, so consider *cur_bytes undefined. */ static int handle_dependencies(BlockDriverState *bs, uint64_t guest_offset, uint64_t *cur_bytes, QCowL2Meta **m) { BDRVQcow2State *s = bs->opaque; QCowL2Meta *old_alloc; uint64_t bytes = *cur_bytes; QLIST_FOREACH(old_alloc, &s->cluster_allocs, next_in_flight) { uint64_t start = guest_offset; uint64_t end = start + bytes; uint64_t old_start = l2meta_cow_start(old_alloc); uint64_t old_end = l2meta_cow_end(old_alloc); if (end <= old_start || start >= old_end) { /* No intersection */ } else { if (start < old_start) { /* Stop at the start of a running allocation */ bytes = old_start - start; } else { bytes = 0; } /* Stop if already an l2meta exists. After yielding, it wouldn't * be valid any more, so we'd have to clean up the old L2Metas * and deal with requests depending on them before starting to * gather new ones. Not worth the trouble. */ if (bytes == 0 && *m) { *cur_bytes = 0; return 0; } if (bytes == 0) { /* Wait for the dependency to complete. We need to recheck * the free/allocated clusters when we continue. */ qemu_co_queue_wait(&old_alloc->dependent_requests, &s->lock); return -EAGAIN; } } } /* Make sure that existing clusters and new allocations are only used up to * the next dependency if we shortened the request above */ *cur_bytes = bytes; return 0; } /* * Checks how many already allocated clusters that don't require a copy on * write there are at the given guest_offset (up to *bytes). If *host_offset is * not INV_OFFSET, only physically contiguous clusters beginning at this host * offset are counted. * * Note that guest_offset may not be cluster aligned. In this case, the * returned *host_offset points to exact byte referenced by guest_offset and * therefore isn't cluster aligned as well. * * Returns: * 0: if no allocated clusters are available at the given offset. * *bytes is normally unchanged. It is set to 0 if the cluster * is allocated and doesn't need COW, but doesn't have the right * physical offset. * * 1: if allocated clusters that don't require a COW are available at * the requested offset. *bytes may have decreased and describes * the length of the area that can be written to. * * -errno: in error cases */ static int handle_copied(BlockDriverState *bs, uint64_t guest_offset, uint64_t *host_offset, uint64_t *bytes, QCowL2Meta **m) { BDRVQcow2State *s = bs->opaque; int l2_index; uint64_t cluster_offset; uint64_t *l2_slice; uint64_t nb_clusters; unsigned int keep_clusters; int ret; trace_qcow2_handle_copied(qemu_coroutine_self(), guest_offset, *host_offset, *bytes); assert(*host_offset == INV_OFFSET || offset_into_cluster(s, guest_offset) == offset_into_cluster(s, *host_offset)); /* * Calculate the number of clusters to look for. We stop at L2 slice * boundaries to keep things simple. */ nb_clusters = size_to_clusters(s, offset_into_cluster(s, guest_offset) + *bytes); l2_index = offset_to_l2_slice_index(s, guest_offset); nb_clusters = MIN(nb_clusters, s->l2_slice_size - l2_index); assert(nb_clusters <= INT_MAX); /* Find L2 entry for the first involved cluster */ ret = get_cluster_table(bs, guest_offset, &l2_slice, &l2_index); if (ret < 0) { return ret; } cluster_offset = be64_to_cpu(l2_slice[l2_index]); /* Check how many clusters are already allocated and don't need COW */ if (qcow2_get_cluster_type(bs, cluster_offset) == QCOW2_CLUSTER_NORMAL && (cluster_offset & QCOW_OFLAG_COPIED)) { /* If a specific host_offset is required, check it */ bool offset_matches = (cluster_offset & L2E_OFFSET_MASK) == *host_offset; if (offset_into_cluster(s, cluster_offset & L2E_OFFSET_MASK)) { qcow2_signal_corruption(bs, true, -1, -1, "Data cluster offset " "%#llx unaligned (guest offset: %#" PRIx64 ")", cluster_offset & L2E_OFFSET_MASK, guest_offset); ret = -EIO; goto out; } if (*host_offset != INV_OFFSET && !offset_matches) { *bytes = 0; ret = 0; goto out; } /* We keep all QCOW_OFLAG_COPIED clusters */ keep_clusters = count_contiguous_clusters(bs, nb_clusters, s->cluster_size, &l2_slice[l2_index], QCOW_OFLAG_COPIED | QCOW_OFLAG_ZERO); assert(keep_clusters <= nb_clusters); *bytes = MIN(*bytes, keep_clusters * s->cluster_size - offset_into_cluster(s, guest_offset)); ret = 1; } else { ret = 0; } /* Cleanup */ out: qcow2_cache_put(s->l2_table_cache, (void **) &l2_slice); /* Only return a host offset if we actually made progress. Otherwise we * would make requirements for handle_alloc() that it can't fulfill */ if (ret > 0) { *host_offset = (cluster_offset & L2E_OFFSET_MASK) + offset_into_cluster(s, guest_offset); } return ret; } /* * Allocates new clusters for the given guest_offset. * * At most *nb_clusters are allocated, and on return *nb_clusters is updated to * contain the number of clusters that have been allocated and are contiguous * in the image file. * * If *host_offset is not INV_OFFSET, it specifies the offset in the image file * at which the new clusters must start. *nb_clusters can be 0 on return in * this case if the cluster at host_offset is already in use. If *host_offset * is INV_OFFSET, the clusters can be allocated anywhere in the image file. * * *host_offset is updated to contain the offset into the image file at which * the first allocated cluster starts. * * Return 0 on success and -errno in error cases. -EAGAIN means that the * function has been waiting for another request and the allocation must be * restarted, but the whole request should not be failed. */ static int do_alloc_cluster_offset(BlockDriverState *bs, uint64_t guest_offset, uint64_t *host_offset, uint64_t *nb_clusters) { BDRVQcow2State *s = bs->opaque; trace_qcow2_do_alloc_clusters_offset(qemu_coroutine_self(), guest_offset, *host_offset, *nb_clusters); if (has_data_file(bs)) { assert(*host_offset == INV_OFFSET || *host_offset == start_of_cluster(s, guest_offset)); *host_offset = start_of_cluster(s, guest_offset); return 0; } /* Allocate new clusters */ trace_qcow2_cluster_alloc_phys(qemu_coroutine_self()); if (*host_offset == INV_OFFSET) { int64_t cluster_offset = qcow2_alloc_clusters(bs, *nb_clusters * s->cluster_size); if (cluster_offset < 0) { return cluster_offset; } *host_offset = cluster_offset; return 0; } else { int64_t ret = qcow2_alloc_clusters_at(bs, *host_offset, *nb_clusters); if (ret < 0) { return ret; } *nb_clusters = ret; return 0; } } /* * Allocates new clusters for an area that either is yet unallocated or needs a * copy on write. If *host_offset is not INV_OFFSET, clusters are only * allocated if the new allocation can match the specified host offset. * * Note that guest_offset may not be cluster aligned. In this case, the * returned *host_offset points to exact byte referenced by guest_offset and * therefore isn't cluster aligned as well. * * Returns: * 0: if no clusters could be allocated. *bytes is set to 0, * *host_offset is left unchanged. * * 1: if new clusters were allocated. *bytes may be decreased if the * new allocation doesn't cover all of the requested area. * *host_offset is updated to contain the host offset of the first * newly allocated cluster. * * -errno: in error cases */ static int handle_alloc(BlockDriverState *bs, uint64_t guest_offset, uint64_t *host_offset, uint64_t *bytes, QCowL2Meta **m) { BDRVQcow2State *s = bs->opaque; int l2_index; uint64_t *l2_slice; uint64_t entry; uint64_t nb_clusters; int ret; bool keep_old_clusters = false; uint64_t alloc_cluster_offset = INV_OFFSET; trace_qcow2_handle_alloc(qemu_coroutine_self(), guest_offset, *host_offset, *bytes); assert(*bytes > 0); /* * Calculate the number of clusters to look for. We stop at L2 slice * boundaries to keep things simple. */ nb_clusters = size_to_clusters(s, offset_into_cluster(s, guest_offset) + *bytes); l2_index = offset_to_l2_slice_index(s, guest_offset); nb_clusters = MIN(nb_clusters, s->l2_slice_size - l2_index); assert(nb_clusters <= INT_MAX); /* Limit total allocation byte count to INT_MAX */ nb_clusters = MIN(nb_clusters, INT_MAX >> s->cluster_bits); /* Find L2 entry for the first involved cluster */ ret = get_cluster_table(bs, guest_offset, &l2_slice, &l2_index); if (ret < 0) { return ret; } entry = be64_to_cpu(l2_slice[l2_index]); nb_clusters = count_cow_clusters(bs, nb_clusters, l2_slice, l2_index); /* This function is only called when there were no non-COW clusters, so if * we can't find any unallocated or COW clusters either, something is * wrong with our code. */ assert(nb_clusters > 0); if (qcow2_get_cluster_type(bs, entry) == QCOW2_CLUSTER_ZERO_ALLOC && (entry & QCOW_OFLAG_COPIED) && (*host_offset == INV_OFFSET || start_of_cluster(s, *host_offset) == (entry & L2E_OFFSET_MASK))) { int preallocated_nb_clusters; if (offset_into_cluster(s, entry & L2E_OFFSET_MASK)) { qcow2_signal_corruption(bs, true, -1, -1, "Preallocated zero " "cluster offset %#llx unaligned (guest " "offset: %#" PRIx64 ")", entry & L2E_OFFSET_MASK, guest_offset); ret = -EIO; goto fail; } /* Try to reuse preallocated zero clusters; contiguous normal clusters * would be fine, too, but count_cow_clusters() above has limited * nb_clusters already to a range of COW clusters */ preallocated_nb_clusters = count_contiguous_clusters(bs, nb_clusters, s->cluster_size, &l2_slice[l2_index], QCOW_OFLAG_COPIED); assert(preallocated_nb_clusters > 0); nb_clusters = preallocated_nb_clusters; alloc_cluster_offset = entry & L2E_OFFSET_MASK; /* We want to reuse these clusters, so qcow2_alloc_cluster_link_l2() * should not free them. */ keep_old_clusters = true; } qcow2_cache_put(s->l2_table_cache, (void **) &l2_slice); if (alloc_cluster_offset == INV_OFFSET) { /* Allocate, if necessary at a given offset in the image file */ alloc_cluster_offset = *host_offset == INV_OFFSET ? INV_OFFSET : start_of_cluster(s, *host_offset); ret = do_alloc_cluster_offset(bs, guest_offset, &alloc_cluster_offset, &nb_clusters); if (ret < 0) { goto fail; } /* Can't extend contiguous allocation */ if (nb_clusters == 0) { *bytes = 0; return 0; } assert(alloc_cluster_offset != INV_OFFSET); } /* * Save info needed for meta data update. * * requested_bytes: Number of bytes from the start of the first * newly allocated cluster to the end of the (possibly shortened * before) write request. * * avail_bytes: Number of bytes from the start of the first * newly allocated to the end of the last newly allocated cluster. * * nb_bytes: The number of bytes from the start of the first * newly allocated cluster to the end of the area that the write * request actually writes to (excluding COW at the end) */ uint64_t requested_bytes = *bytes + offset_into_cluster(s, guest_offset); int avail_bytes = nb_clusters << s->cluster_bits; int nb_bytes = MIN(requested_bytes, avail_bytes); QCowL2Meta *old_m = *m; *m = g_malloc0(sizeof(**m)); **m = (QCowL2Meta) { .next = old_m, .alloc_offset = alloc_cluster_offset, .offset = start_of_cluster(s, guest_offset), .nb_clusters = nb_clusters, .keep_old_clusters = keep_old_clusters, .cow_start = { .offset = 0, .nb_bytes = offset_into_cluster(s, guest_offset), }, .cow_end = { .offset = nb_bytes, .nb_bytes = avail_bytes - nb_bytes, }, }; qemu_co_queue_init(&(*m)->dependent_requests); QLIST_INSERT_HEAD(&s->cluster_allocs, *m, next_in_flight); *host_offset = alloc_cluster_offset + offset_into_cluster(s, guest_offset); *bytes = MIN(*bytes, nb_bytes - offset_into_cluster(s, guest_offset)); assert(*bytes != 0); return 1; fail: if (*m && (*m)->nb_clusters > 0) { QLIST_REMOVE(*m, next_in_flight); } return ret; } /* * alloc_cluster_offset * * For a given offset on the virtual disk, find the cluster offset in qcow2 * file. If the offset is not found, allocate a new cluster. * * If the cluster was already allocated, m->nb_clusters is set to 0 and * other fields in m are meaningless. * * If the cluster is newly allocated, m->nb_clusters is set to the number of * contiguous clusters that have been allocated. In this case, the other * fields of m are valid and contain information about the first allocated * cluster. * * If the request conflicts with another write request in flight, the coroutine * is queued and will be reentered when the dependency has completed. * * Return 0 on success and -errno in error cases */ int qcow2_alloc_cluster_offset(BlockDriverState *bs, uint64_t offset, unsigned int *bytes, uint64_t *host_offset, QCowL2Meta **m) { BDRVQcow2State *s = bs->opaque; uint64_t start, remaining; uint64_t cluster_offset; uint64_t cur_bytes; int ret; trace_qcow2_alloc_clusters_offset(qemu_coroutine_self(), offset, *bytes); again: start = offset; remaining = *bytes; cluster_offset = INV_OFFSET; *host_offset = INV_OFFSET; cur_bytes = 0; *m = NULL; while (true) { if (*host_offset == INV_OFFSET && cluster_offset != INV_OFFSET) { *host_offset = start_of_cluster(s, cluster_offset); } assert(remaining >= cur_bytes); start += cur_bytes; remaining -= cur_bytes; if (cluster_offset != INV_OFFSET) { cluster_offset += cur_bytes; } if (remaining == 0) { break; } cur_bytes = remaining; /* * Now start gathering as many contiguous clusters as possible: * * 1. Check for overlaps with in-flight allocations * * a) Overlap not in the first cluster -> shorten this request and * let the caller handle the rest in its next loop iteration. * * b) Real overlaps of two requests. Yield and restart the search * for contiguous clusters (the situation could have changed * while we were sleeping) * * c) TODO: Request starts in the same cluster as the in-flight * allocation ends. Shorten the COW of the in-fight allocation, * set cluster_offset to write to the same cluster and set up * the right synchronisation between the in-flight request and * the new one. */ ret = handle_dependencies(bs, start, &cur_bytes, m); if (ret == -EAGAIN) { /* Currently handle_dependencies() doesn't yield if we already had * an allocation. If it did, we would have to clean up the L2Meta * structs before starting over. */ assert(*m == NULL); goto again; } else if (ret < 0) { return ret; } else if (cur_bytes == 0) { break; } else { /* handle_dependencies() may have decreased cur_bytes (shortened * the allocations below) so that the next dependency is processed * correctly during the next loop iteration. */ } /* * 2. Count contiguous COPIED clusters. */ ret = handle_copied(bs, start, &cluster_offset, &cur_bytes, m); if (ret < 0) { return ret; } else if (ret) { continue; } else if (cur_bytes == 0) { break; } /* * 3. If the request still hasn't completed, allocate new clusters, * considering any cluster_offset of steps 1c or 2. */ ret = handle_alloc(bs, start, &cluster_offset, &cur_bytes, m); if (ret < 0) { return ret; } else if (ret) { continue; } else { assert(cur_bytes == 0); break; } } *bytes -= remaining; assert(*bytes > 0); assert(*host_offset != INV_OFFSET); return 0; } /* * This discards as many clusters of nb_clusters as possible at once (i.e. * all clusters in the same L2 slice) and returns the number of discarded * clusters. */ static int discard_in_l2_slice(BlockDriverState *bs, uint64_t offset, uint64_t nb_clusters, enum qcow2_discard_type type, bool full_discard) { BDRVQcow2State *s = bs->opaque; uint64_t *l2_slice; int l2_index; int ret; int i; ret = get_cluster_table(bs, offset, &l2_slice, &l2_index); if (ret < 0) { return ret; } /* Limit nb_clusters to one L2 slice */ nb_clusters = MIN(nb_clusters, s->l2_slice_size - l2_index); assert(nb_clusters <= INT_MAX); for (i = 0; i < nb_clusters; i++) { uint64_t old_l2_entry; old_l2_entry = be64_to_cpu(l2_slice[l2_index + i]); /* * If full_discard is false, make sure that a discarded area reads back * as zeroes for v3 images (we cannot do it for v2 without actually * writing a zero-filled buffer). We can skip the operation if the * cluster is already marked as zero, or if it's unallocated and we * don't have a backing file. * * TODO We might want to use bdrv_block_status(bs) here, but we're * holding s->lock, so that doesn't work today. * * If full_discard is true, the sector should not read back as zeroes, * but rather fall through to the backing file. */ switch (qcow2_get_cluster_type(bs, old_l2_entry)) { case QCOW2_CLUSTER_UNALLOCATED: if (full_discard || !bs->backing) { continue; } break; case QCOW2_CLUSTER_ZERO_PLAIN: if (!full_discard) { continue; } break; case QCOW2_CLUSTER_ZERO_ALLOC: case QCOW2_CLUSTER_NORMAL: case QCOW2_CLUSTER_COMPRESSED: break; default: abort(); } /* First remove L2 entries */ qcow2_cache_entry_mark_dirty(s->l2_table_cache, l2_slice); if (!full_discard && s->qcow_version >= 3) { l2_slice[l2_index + i] = cpu_to_be64(QCOW_OFLAG_ZERO); } else { l2_slice[l2_index + i] = cpu_to_be64(0); } /* Then decrease the refcount */ qcow2_free_any_clusters(bs, old_l2_entry, 1, type); } qcow2_cache_put(s->l2_table_cache, (void **) &l2_slice); return nb_clusters; } int qcow2_cluster_discard(BlockDriverState *bs, uint64_t offset, uint64_t bytes, enum qcow2_discard_type type, bool full_discard) { BDRVQcow2State *s = bs->opaque; uint64_t end_offset = offset + bytes; uint64_t nb_clusters; int64_t cleared; int ret; /* Caller must pass aligned values, except at image end */ assert(QEMU_IS_ALIGNED(offset, s->cluster_size)); assert(QEMU_IS_ALIGNED(end_offset, s->cluster_size) || end_offset == bs->total_sectors << BDRV_SECTOR_BITS); nb_clusters = size_to_clusters(s, bytes); s->cache_discards = true; /* Each L2 slice is handled by its own loop iteration */ while (nb_clusters > 0) { cleared = discard_in_l2_slice(bs, offset, nb_clusters, type, full_discard); if (cleared < 0) { ret = cleared; goto fail; } nb_clusters -= cleared; offset += (cleared * s->cluster_size); } ret = 0; fail: s->cache_discards = false; qcow2_process_discards(bs, ret); return ret; } /* * This zeroes as many clusters of nb_clusters as possible at once (i.e. * all clusters in the same L2 slice) and returns the number of zeroed * clusters. */ static int zero_in_l2_slice(BlockDriverState *bs, uint64_t offset, uint64_t nb_clusters, int flags) { BDRVQcow2State *s = bs->opaque; uint64_t *l2_slice; int l2_index; int ret; int i; bool unmap = !!(flags & BDRV_REQ_MAY_UNMAP); ret = get_cluster_table(bs, offset, &l2_slice, &l2_index); if (ret < 0) { return ret; } /* Limit nb_clusters to one L2 slice */ nb_clusters = MIN(nb_clusters, s->l2_slice_size - l2_index); assert(nb_clusters <= INT_MAX); for (i = 0; i < nb_clusters; i++) { uint64_t old_offset; QCow2ClusterType cluster_type; old_offset = be64_to_cpu(l2_slice[l2_index + i]); /* * Minimize L2 changes if the cluster already reads back as * zeroes with correct allocation. */ cluster_type = qcow2_get_cluster_type(bs, old_offset); if (cluster_type == QCOW2_CLUSTER_ZERO_PLAIN || (cluster_type == QCOW2_CLUSTER_ZERO_ALLOC && !unmap)) { continue; } qcow2_cache_entry_mark_dirty(s->l2_table_cache, l2_slice); if (cluster_type == QCOW2_CLUSTER_COMPRESSED || unmap) { l2_slice[l2_index + i] = cpu_to_be64(QCOW_OFLAG_ZERO); qcow2_free_any_clusters(bs, old_offset, 1, QCOW2_DISCARD_REQUEST); } else { l2_slice[l2_index + i] |= cpu_to_be64(QCOW_OFLAG_ZERO); } } qcow2_cache_put(s->l2_table_cache, (void **) &l2_slice); return nb_clusters; } int qcow2_cluster_zeroize(BlockDriverState *bs, uint64_t offset, uint64_t bytes, int flags) { BDRVQcow2State *s = bs->opaque; uint64_t end_offset = offset + bytes; uint64_t nb_clusters; int64_t cleared; int ret; /* If we have to stay in sync with an external data file, zero out * s->data_file first. */ if (data_file_is_raw(bs)) { assert(has_data_file(bs)); ret = bdrv_co_pwrite_zeroes(s->data_file, offset, bytes, flags); if (ret < 0) { return ret; } } /* Caller must pass aligned values, except at image end */ assert(QEMU_IS_ALIGNED(offset, s->cluster_size)); assert(QEMU_IS_ALIGNED(end_offset, s->cluster_size) || end_offset == bs->total_sectors << BDRV_SECTOR_BITS); /* The zero flag is only supported by version 3 and newer */ if (s->qcow_version < 3) { return -ENOTSUP; } /* Each L2 slice is handled by its own loop iteration */ nb_clusters = size_to_clusters(s, bytes); s->cache_discards = true; while (nb_clusters > 0) { cleared = zero_in_l2_slice(bs, offset, nb_clusters, flags); if (cleared < 0) { ret = cleared; goto fail; } nb_clusters -= cleared; offset += (cleared * s->cluster_size); } ret = 0; fail: s->cache_discards = false; qcow2_process_discards(bs, ret); return ret; } /* * Expands all zero clusters in a specific L1 table (or deallocates them, for * non-backed non-pre-allocated zero clusters). * * l1_entries and *visited_l1_entries are used to keep track of progress for * status_cb(). l1_entries contains the total number of L1 entries and * *visited_l1_entries counts all visited L1 entries. */ static int expand_zero_clusters_in_l1(BlockDriverState *bs, uint64_t *l1_table, int l1_size, int64_t *visited_l1_entries, int64_t l1_entries, BlockDriverAmendStatusCB *status_cb, void *cb_opaque) { BDRVQcow2State *s = bs->opaque; bool is_active_l1 = (l1_table == s->l1_table); uint64_t *l2_slice = NULL; unsigned slice, slice_size2, n_slices; int ret; int i, j; slice_size2 = s->l2_slice_size * sizeof(uint64_t); n_slices = s->cluster_size / slice_size2; if (!is_active_l1) { /* inactive L2 tables require a buffer to be stored in when loading * them from disk */ l2_slice = qemu_try_blockalign(bs->file->bs, slice_size2); if (l2_slice == NULL) { return -ENOMEM; } } for (i = 0; i < l1_size; i++) { uint64_t l2_offset = l1_table[i] & L1E_OFFSET_MASK; uint64_t l2_refcount; if (!l2_offset) { /* unallocated */ (*visited_l1_entries)++; if (status_cb) { status_cb(bs, *visited_l1_entries, l1_entries, cb_opaque); } continue; } if (offset_into_cluster(s, l2_offset)) { qcow2_signal_corruption(bs, true, -1, -1, "L2 table offset %#" PRIx64 " unaligned (L1 index: %#x)", l2_offset, i); ret = -EIO; goto fail; } ret = qcow2_get_refcount(bs, l2_offset >> s->cluster_bits, &l2_refcount); if (ret < 0) { goto fail; } for (slice = 0; slice < n_slices; slice++) { uint64_t slice_offset = l2_offset + slice * slice_size2; bool l2_dirty = false; if (is_active_l1) { /* get active L2 tables from cache */ ret = qcow2_cache_get(bs, s->l2_table_cache, slice_offset, (void **)&l2_slice); } else { /* load inactive L2 tables from disk */ ret = bdrv_pread(bs->file, slice_offset, l2_slice, slice_size2); } if (ret < 0) { goto fail; } for (j = 0; j < s->l2_slice_size; j++) { uint64_t l2_entry = be64_to_cpu(l2_slice[j]); int64_t offset = l2_entry & L2E_OFFSET_MASK; QCow2ClusterType cluster_type = qcow2_get_cluster_type(bs, l2_entry); if (cluster_type != QCOW2_CLUSTER_ZERO_PLAIN && cluster_type != QCOW2_CLUSTER_ZERO_ALLOC) { continue; } if (cluster_type == QCOW2_CLUSTER_ZERO_PLAIN) { if (!bs->backing) { /* not backed; therefore we can simply deallocate the * cluster */ l2_slice[j] = 0; l2_dirty = true; continue; } offset = qcow2_alloc_clusters(bs, s->cluster_size); if (offset < 0) { ret = offset; goto fail; } /* The offset must fit in the offset field */ assert((offset & L2E_OFFSET_MASK) == offset); if (l2_refcount > 1) { /* For shared L2 tables, set the refcount accordingly * (it is already 1 and needs to be l2_refcount) */ ret = qcow2_update_cluster_refcount( bs, offset >> s->cluster_bits, refcount_diff(1, l2_refcount), false, QCOW2_DISCARD_OTHER); if (ret < 0) { qcow2_free_clusters(bs, offset, s->cluster_size, QCOW2_DISCARD_OTHER); goto fail; } } } if (offset_into_cluster(s, offset)) { int l2_index = slice * s->l2_slice_size + j; qcow2_signal_corruption( bs, true, -1, -1, "Cluster allocation offset " "%#" PRIx64 " unaligned (L2 offset: %#" PRIx64 ", L2 index: %#x)", offset, l2_offset, l2_index); if (cluster_type == QCOW2_CLUSTER_ZERO_PLAIN) { qcow2_free_clusters(bs, offset, s->cluster_size, QCOW2_DISCARD_ALWAYS); } ret = -EIO; goto fail; } ret = qcow2_pre_write_overlap_check(bs, 0, offset, s->cluster_size, true); if (ret < 0) { if (cluster_type == QCOW2_CLUSTER_ZERO_PLAIN) { qcow2_free_clusters(bs, offset, s->cluster_size, QCOW2_DISCARD_ALWAYS); } goto fail; } ret = bdrv_pwrite_zeroes(s->data_file, offset, s->cluster_size, 0); if (ret < 0) { if (cluster_type == QCOW2_CLUSTER_ZERO_PLAIN) { qcow2_free_clusters(bs, offset, s->cluster_size, QCOW2_DISCARD_ALWAYS); } goto fail; } if (l2_refcount == 1) { l2_slice[j] = cpu_to_be64(offset | QCOW_OFLAG_COPIED); } else { l2_slice[j] = cpu_to_be64(offset); } l2_dirty = true; } if (is_active_l1) { if (l2_dirty) { qcow2_cache_entry_mark_dirty(s->l2_table_cache, l2_slice); qcow2_cache_depends_on_flush(s->l2_table_cache); } qcow2_cache_put(s->l2_table_cache, (void **) &l2_slice); } else { if (l2_dirty) { ret = qcow2_pre_write_overlap_check( bs, QCOW2_OL_INACTIVE_L2 | QCOW2_OL_ACTIVE_L2, slice_offset, slice_size2, false); if (ret < 0) { goto fail; } ret = bdrv_pwrite(bs->file, slice_offset, l2_slice, slice_size2); if (ret < 0) { goto fail; } } } } (*visited_l1_entries)++; if (status_cb) { status_cb(bs, *visited_l1_entries, l1_entries, cb_opaque); } } ret = 0; fail: if (l2_slice) { if (!is_active_l1) { qemu_vfree(l2_slice); } else { qcow2_cache_put(s->l2_table_cache, (void **) &l2_slice); } } return ret; } /* * For backed images, expands all zero clusters on the image. For non-backed * images, deallocates all non-pre-allocated zero clusters (and claims the * allocation for pre-allocated ones). This is important for downgrading to a * qcow2 version which doesn't yet support metadata zero clusters. */ int qcow2_expand_zero_clusters(BlockDriverState *bs, BlockDriverAmendStatusCB *status_cb, void *cb_opaque) { BDRVQcow2State *s = bs->opaque; uint64_t *l1_table = NULL; int64_t l1_entries = 0, visited_l1_entries = 0; int ret; int i, j; if (status_cb) { l1_entries = s->l1_size; for (i = 0; i < s->nb_snapshots; i++) { l1_entries += s->snapshots[i].l1_size; } } ret = expand_zero_clusters_in_l1(bs, s->l1_table, s->l1_size, &visited_l1_entries, l1_entries, status_cb, cb_opaque); if (ret < 0) { goto fail; } /* Inactive L1 tables may point to active L2 tables - therefore it is * necessary to flush the L2 table cache before trying to access the L2 * tables pointed to by inactive L1 entries (else we might try to expand * zero clusters that have already been expanded); furthermore, it is also * necessary to empty the L2 table cache, since it may contain tables which * are now going to be modified directly on disk, bypassing the cache. * qcow2_cache_empty() does both for us. */ ret = qcow2_cache_empty(bs, s->l2_table_cache); if (ret < 0) { goto fail; } for (i = 0; i < s->nb_snapshots; i++) { int l1_size2; uint64_t *new_l1_table; Error *local_err = NULL; ret = qcow2_validate_table(bs, s->snapshots[i].l1_table_offset, s->snapshots[i].l1_size, sizeof(uint64_t), QCOW_MAX_L1_SIZE, "Snapshot L1 table", &local_err); if (ret < 0) { error_report_err(local_err); goto fail; } l1_size2 = s->snapshots[i].l1_size * sizeof(uint64_t); new_l1_table = g_try_realloc(l1_table, l1_size2); if (!new_l1_table) { ret = -ENOMEM; goto fail; } l1_table = new_l1_table; ret = bdrv_pread(bs->file, s->snapshots[i].l1_table_offset, l1_table, l1_size2); if (ret < 0) { goto fail; } for (j = 0; j < s->snapshots[i].l1_size; j++) { be64_to_cpus(&l1_table[j]); } ret = expand_zero_clusters_in_l1(bs, l1_table, s->snapshots[i].l1_size, &visited_l1_entries, l1_entries, status_cb, cb_opaque); if (ret < 0) { goto fail; } } ret = 0; fail: g_free(l1_table); return ret; }