Am 12.12.2011 03:03, schrieb Lan Tianyu:
> This patch enables allocating new refcount blocks and so then kvm tools
> could expand qcow2 image much larger.
>
> Signed-off-by: Lan Tianyu <tianyu....@intel.com>
> ---
> tools/kvm/disk/qcow.c | 105 +++++++++++++++++++++++++++++++++++++++++-------
> 1 files changed, 89 insertions(+), 16 deletions(-)
>
> diff --git a/tools/kvm/disk/qcow.c b/tools/kvm/disk/qcow.c
> index e139fa5..929ba69 100644
> --- a/tools/kvm/disk/qcow.c
> +++ b/tools/kvm/disk/qcow.c
> @@ -12,6 +12,7 @@
> #include <string.h>
> #include <unistd.h>
> #include <fcntl.h>
> +#include <errno.h>
> #ifdef CONFIG_HAS_ZLIB
> #include <zlib.h>
> #endif
> @@ -20,6 +21,10 @@
> #include <linux/kernel.h>
> #include <linux/types.h>
>
> +static int update_cluster_refcount(struct qcow *q, u64 clust_idx, u16
> append);
> +static int qcow_write_refcount_table(struct qcow *q);
> +static u64 qcow_alloc_clusters(struct qcow *q, u64 size, int update_ref);
> +static void qcow_free_clusters(struct qcow *q, u64 clust_start, u64 size);
>
> static inline int qcow_pwrite_sync(int fd,
> void *buf, size_t count, off_t offset)
> @@ -657,6 +662,56 @@ static struct qcow_refcount_block
> *refcount_block_search(struct qcow *q, u64 off
> return rfb;
> }
>
> +static struct qcow_refcount_block *qcow_grow_refcount_block(struct qcow *q,
> + u64 clust_idx)
> +{
> + struct qcow_header *header = q->header;
> + struct qcow_refcount_table *rft = &q->refcount_table;
> + struct qcow_refcount_block *rfb;
> + u64 new_block_offset;
> + u64 rft_idx;
> +
> + rft_idx = clust_idx >> (header->cluster_bits -
> + QCOW_REFCOUNT_BLOCK_SHIFT);
> +
> + if (rft_idx >= rft->rf_size) {
> + pr_warning("Don't support grow refcount block table");
> + return NULL;
> + }
> +
> + new_block_offset = qcow_alloc_clusters(q, q->cluster_size, 0);
> + if (new_block_offset < 0)
> + return NULL;
> +
> + rfb = new_refcount_block(q, new_block_offset);
> + if (!rfb)
> + return NULL;
> +
> + memset(rfb->entries, 0x00, q->cluster_size);
> + rfb->dirty = 1;
> +
> + /* write refcount block */
> + if (write_refcount_block(q, rfb) < 0)
> + goto free_rfb;
> +
> + if (cache_refcount_block(q, rfb) < 0)
> + goto free_rfb;
> +
> + rft->rf_table[rft_idx] = cpu_to_be64(new_block_offset);
> + if (qcow_write_refcount_table(q) < 0)
> + goto free_rfb;
> +
> + if (update_cluster_refcount(q, new_block_offset >>
> + header->cluster_bits, 1) < 0)
> + goto free_rfb;
This order is unsafe, you could end up with a refcount block that is
already in use, but still has a refcount of 0.
> +
> + return rfb;
> +
> +free_rfb:
> + free(rfb);
> + return NULL;
> +}
> +
> static struct qcow_refcount_block *qcow_read_refcount_block(struct qcow *q,
> u64 clust_idx)
> {
> struct qcow_header *header = q->header;
> @@ -667,14 +722,11 @@ static struct qcow_refcount_block
> *qcow_read_refcount_block(struct qcow *q, u64
>
> rft_idx = clust_idx >> (header->cluster_bits -
> QCOW_REFCOUNT_BLOCK_SHIFT);
> if (rft_idx >= rft->rf_size)
> - return NULL;
> + return (void *)-ENOSPC;
Is this allowed style in kvm-tool? :-/
Kevin
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