On Thu, May 13, 2021 at 13:23:05 +0200, Pavel Hrdina wrote:
From QEMU docs/interop/qcow2.txt :
Byte 20 - 23: cluster_bits Number of bits that are used for addressing an offset within a cluster (1 << cluster_bits is the cluster size).
With this patch libvirt will be able to report the current cluster_size for all existing storage volumes managed by storage driver.
Signed-off-by: Pavel Hrdina <phrdina@redhat.com> --- src/storage/storage_util.c | 3 ++ src/storage_file/storage_file_probe.c | 55 +++++++++++++++++++-------- 2 files changed, 42 insertions(+), 16 deletions(-)
[...]
diff --git a/src/storage_file/storage_file_probe.c b/src/storage_file/storage_file_probe.c index afe64da02e..423597049f 100644 --- a/src/storage_file/storage_file_probe.c +++ b/src/storage_file/storage_file_probe.c @@ -94,6 +94,9 @@ struct FileTypeInfo { /* Store a COW base image path (possibly relative), * or NULL if there is no COW base image, to RES; * return BACKING_STORE_* */ + int clusterBitsOffset; /* Byte offset from start of file where we find + * number of cluster bits, -1 to skip. */ + int clusterBitsSize; /* Number of bytes for cluster bits. */
This isn't actually used [1].
const struct FileEncryptionInfo *cryptInfo; /* Encryption info */ int (*getBackingStore)(char **res, int *format, const char *buf, size_t buf_size);
Given how the value is stored in the header it seems that it won't really be usable for any other format. I think we should parse it via a callback rather than the generic offset/size parser. Specifically since the cluster size is stored as number of bits.
@@ -116,7 +119,8 @@ qedGetBackingStore(char **, int *, const char *, size_t); #define QCOWX_HDR_VERSION (4) #define QCOWX_HDR_BACKING_FILE_OFFSET (QCOWX_HDR_VERSION+4) #define QCOWX_HDR_BACKING_FILE_SIZE (QCOWX_HDR_BACKING_FILE_OFFSET+8) -#define QCOWX_HDR_IMAGE_SIZE (QCOWX_HDR_BACKING_FILE_SIZE+4+4) +#define QCOWX_HDR_CLUSTER_BITS_OFFSET (QCOWX_HDR_BACKING_FILE_SIZE+4) +#define QCOWX_HDR_IMAGE_SIZE (QCOWX_HDR_CLUSTER_BITS_OFFSET+4)
#define QCOW1_HDR_CRYPT (QCOWX_HDR_IMAGE_SIZE+8+1+1+2) #define QCOW2_HDR_CRYPT (QCOWX_HDR_IMAGE_SIZE+8)
G_STATIC_ASSERT(G_N_ELEMENTS(fileTypeInfo) == VIR_STORAGE_FILE_LAST); @@ -890,6 +896,23 @@ virStorageFileProbeGetMetadata(virStorageSource *meta, meta->capacity *= fileTypeInfo[meta->format].sizeMultiplier; }
+ if (fileTypeInfo[meta->format].clusterBitsOffset != -1) { + int clusterBits = 0; + + if ((fileTypeInfo[meta->format].clusterBitsOffset + 4) > len)
[1] ... you hardcode the value.
+ return 0; + + if (fileTypeInfo[meta->format].endian == LV_LITTLE_ENDIAN) + clusterBits = virReadBufInt32LE(buf + + fileTypeInfo[meta->format].clusterBitsOffset); + else + clusterBits = virReadBufInt32BE(buf + + fileTypeInfo[meta->format].clusterBitsOffset); + + if (clusterBits > 0) + meta->clusterSize = 1 << clusterBits; + } + VIR_FREE(meta->backingStoreRaw); if (fileTypeInfo[meta->format].getBackingStore != NULL) { int store = fileTypeInfo[meta->format].getBackingStore(&meta->backingStoreRaw, -- 2.31.1