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qcow2: Factor out handle_alloc()
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Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
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@kevmw @stefanhaRH
kevmw authored and stefanhaRH committed Mar 28, 2013
1 parent 037689d commit 10f0ed8
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Showing 2 changed files with 152 additions and 89 deletions.
240 changes: 151 additions & 89 deletions block/qcow2-cluster.c
View file
Expand Up @@ -858,6 +858,146 @@ static int do_alloc_cluster_offset(BlockDriverState *bs, uint64_t guest_offset,
}
}

/*
* Allocates new clusters for an area that either is yet unallocated or needs a
* copy on write. If *host_offset is non-zero, clusters are only allocated if
* the new allocation can match the specified host offset.
*
* Note that guest_offset may not be cluster aligned.
*
* 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
*
* TODO Get rid of nb_clusters, keep_clusters, n_start, n_end
* TODO Make *bytes actually behave as specified above
*/
static int handle_alloc(BlockDriverState *bs, uint64_t guest_offset,
uint64_t *host_offset, uint64_t *bytes, QCowL2Meta **m,
unsigned int nb_clusters, int keep_clusters, int n_start, int n_end)
{
BDRVQcowState *s = bs->opaque;
int l2_index;
uint64_t *l2_table;
uint64_t entry;
int ret;

uint64_t alloc_offset;
uint64_t alloc_cluster_offset;
uint64_t keep_bytes = keep_clusters * s->cluster_size;

trace_qcow2_handle_alloc(qemu_coroutine_self(), guest_offset, *host_offset,
*bytes);
assert(*bytes > 0);

/* Find L2 entry for the first involved cluster */
ret = get_cluster_table(bs, guest_offset, &l2_table, &l2_index);
if (ret < 0) {
return ret;
}

entry = be64_to_cpu(l2_table[l2_index + keep_clusters]);

/* For the moment, overwrite compressed clusters one by one */
if (entry & QCOW_OFLAG_COMPRESSED) {
nb_clusters = 1;
} else {
nb_clusters = count_cow_clusters(s, nb_clusters, l2_table,
l2_index + keep_clusters);
}

ret = qcow2_cache_put(bs, s->l2_table_cache, (void**) &l2_table);
if (ret < 0) {
return ret;
}

if (nb_clusters == 0) {
*bytes = 0;
return 0;
}

/* Calculate start and size of allocation */
alloc_offset = guest_offset + keep_bytes;

if (keep_clusters == 0) {
alloc_cluster_offset = 0;
} else {
alloc_cluster_offset = *host_offset + keep_bytes;
}

/* Allocate, if necessary at a given offset in the image file */
ret = do_alloc_cluster_offset(bs, alloc_offset, &alloc_cluster_offset,
&nb_clusters);
if (ret < 0) {
goto fail;
}

/* save info needed for meta data update */
if (nb_clusters > 0) {
/*
* requested_sectors: Number of sectors from the start of the first
* newly allocated cluster to the end of the (possibly shortened
* before) write request.
*
* avail_sectors: Number of sectors from the start of the first
* newly allocated to the end of the last newly allocated cluster.
*
* nb_sectors: The number of sectors from the start of the first
* newly allocated cluster to the end of the aread that the write
* request actually writes to (excluding COW at the end)
*/
int requested_sectors = n_end - keep_clusters * s->cluster_sectors;
int avail_sectors = nb_clusters
<< (s->cluster_bits - BDRV_SECTOR_BITS);
int alloc_n_start = keep_clusters == 0 ? n_start : 0;
int nb_sectors = MIN(requested_sectors, avail_sectors);

if (keep_clusters == 0) {
*host_offset = alloc_cluster_offset;
}

*m = g_malloc0(sizeof(**m));

**m = (QCowL2Meta) {
.alloc_offset = alloc_cluster_offset,
.offset = alloc_offset & ~(s->cluster_size - 1),
.nb_clusters = nb_clusters,
.nb_available = nb_sectors,

.cow_start = {
.offset = 0,
.nb_sectors = alloc_n_start,
},
.cow_end = {
.offset = nb_sectors * BDRV_SECTOR_SIZE,
.nb_sectors = avail_sectors - nb_sectors,
},
};
qemu_co_queue_init(&(*m)->dependent_requests);
QLIST_INSERT_HEAD(&s->cluster_allocs, *m, next_in_flight);

*bytes = nb_clusters * s->cluster_size;
} else {
*bytes = 0;
return 0;
}

return 1;

fail:
if (*m && (*m)->nb_clusters > 0) {
QLIST_REMOVE(*m, next_in_flight);
}
return ret;
}

/*
* alloc_cluster_offset
*
Expand Down Expand Up @@ -977,93 +1117,21 @@ int qcow2_alloc_cluster_offset(BlockDriverState *bs, uint64_t offset,
}

/* If there is something left to allocate, do that now */
if (nb_clusters > 0) {
uint64_t alloc_offset;
uint64_t alloc_cluster_offset;
uint64_t keep_bytes = keep_clusters * s->cluster_size;

ret = get_cluster_table(bs, offset, &l2_table, &l2_index);
if (ret < 0) {
return ret;
}

/* For the moment, overwrite compressed clusters one by one */
uint64_t entry = be64_to_cpu(l2_table[l2_index + keep_clusters]);
if (entry & QCOW_OFLAG_COMPRESSED) {
nb_clusters = 1;
} else {
nb_clusters = count_cow_clusters(s, nb_clusters, l2_table,
l2_index + keep_clusters);
}

ret = qcow2_cache_put(bs, s->l2_table_cache, (void**) &l2_table);
if (ret < 0) {
return ret;
}

/* Calculate start and size of allocation */
alloc_offset = offset + keep_bytes;

if (keep_clusters == 0) {
alloc_cluster_offset = 0;
} else {
alloc_cluster_offset = cluster_offset + keep_bytes;
}

/* Allocate, if necessary at a given offset in the image file */
ret = do_alloc_cluster_offset(bs, alloc_offset, &alloc_cluster_offset,
&nb_clusters);
if (ret < 0) {
goto fail;
}

/* save info needed for meta data update */
if (nb_clusters > 0) {
/*
* requested_sectors: Number of sectors from the start of the first
* newly allocated cluster to the end of the (possibly shortened
* before) write request.
*
* avail_sectors: Number of sectors from the start of the first
* newly allocated to the end of the last newly allocated cluster.
*
* nb_sectors: The number of sectors from the start of the first
* newly allocated cluster to the end of the aread that the write
* request actually writes to (excluding COW at the end)
*/
int requested_sectors = n_end - keep_clusters * s->cluster_sectors;
int avail_sectors = nb_clusters
<< (s->cluster_bits - BDRV_SECTOR_BITS);
int alloc_n_start = keep_clusters == 0 ? n_start : 0;
int nb_sectors = MIN(requested_sectors, avail_sectors);

if (keep_clusters == 0) {
cluster_offset = alloc_cluster_offset;
}
if (nb_clusters == 0) {
goto done;
}

*m = g_malloc0(sizeof(**m));

**m = (QCowL2Meta) {
.alloc_offset = alloc_cluster_offset,
.offset = alloc_offset & ~(s->cluster_size - 1),
.nb_clusters = nb_clusters,
.nb_available = nb_sectors,

.cow_start = {
.offset = 0,
.nb_sectors = alloc_n_start,
},
.cow_end = {
.offset = nb_sectors * BDRV_SECTOR_SIZE,
.nb_sectors = avail_sectors - nb_sectors,
},
};
qemu_co_queue_init(&(*m)->dependent_requests);
QLIST_INSERT_HEAD(&s->cluster_allocs, *m, next_in_flight);
}
cur_bytes = nb_clusters * s->cluster_size;
ret = handle_alloc(bs, offset, &cluster_offset, &cur_bytes, m,
nb_clusters, keep_clusters, n_start, n_end);
if (ret < 0) {
return ret;
}

nb_clusters = size_to_clusters(s, cur_bytes);

/* Some cleanup work */
done:
sectors = (keep_clusters + nb_clusters) << (s->cluster_bits - 9);
if (sectors > n_end) {
sectors = n_end;
Expand All @@ -1074,12 +1142,6 @@ int qcow2_alloc_cluster_offset(BlockDriverState *bs, uint64_t offset,
*host_offset = cluster_offset;

return 0;

fail:
if (*m && (*m)->nb_clusters > 0) {
QLIST_REMOVE(*m, next_in_flight);
}
return ret;
}

static int decompress_buffer(uint8_t *out_buf, int out_buf_size,
Expand Down
1 change: 1 addition & 0 deletions trace-events
View file
Expand Up @@ -483,6 +483,7 @@ qcow2_writev_done_part(void *co, int cur_nr_sectors) "co %p cur_nr_sectors %d"
qcow2_writev_data(void *co, uint64_t offset) "co %p offset %" PRIx64

qcow2_alloc_clusters_offset(void *co, uint64_t offset, int n_start, int n_end) "co %p offet %" PRIx64 " n_start %d n_end %d"
qcow2_handle_alloc(void *co, uint64_t guest_offset, uint64_t host_offset, uint64_t bytes) "co %p guest_offet %" PRIx64 " host_offset %" PRIx64 " bytes %" PRIx64
qcow2_do_alloc_clusters_offset(void *co, uint64_t guest_offset, uint64_t host_offset, int nb_clusters) "co %p guest_offet %" PRIx64 " host_offset %" PRIx64 " nb_clusters %d"
qcow2_cluster_alloc_phys(void *co) "co %p"
qcow2_cluster_link_l2(void *co, int nb_clusters) "co %p nb_clusters %d"
Expand Down

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