Am 25.04.2018 um 20:32 hat Eric Blake geschrieben: > We are gradually moving away from sector-based interfaces, towards > byte-based. Make the change for the internal helper function > get_cluster_offset(), by changing n_start and n_end to by byte > offsets rather than sector indices within the cluster being > allocated. > > A later patch will then switch the qcow driver as a whole over > to byte-based operation. > > Signed-off-by: Eric Blake <ebl...@redhat.com> > --- > block/qcow.c | 28 ++++++++++++++-------------- > 1 file changed, 14 insertions(+), 14 deletions(-) > > diff --git a/block/qcow.c b/block/qcow.c > index dd042b8ddbe..32730a8dd91 100644 > --- a/block/qcow.c > +++ b/block/qcow.c > @@ -345,8 +345,8 @@ static int qcow_reopen_prepare(BDRVReopenState *state, > * > * 0 to not allocate. > * > - * 1 to allocate a normal cluster (for sector indexes 'n_start' to > - * 'n_end') > + * 1 to allocate a normal cluster (for byte offsets 'n_start' to > + * 'n_end' within the cluster) > * > * 2 to allocate a compressed cluster of size > * 'compressed_size'. 'compressed_size' must be > 0 and < > @@ -442,7 +442,7 @@ static int get_cluster_offset(BlockDriverState *bs, > BLKDBG_EVENT(bs->file, BLKDBG_CLUSTER_ALLOC); > /* allocate a new cluster */ > if ((cluster_offset & QCOW_OFLAG_COMPRESSED) && > - (n_end - n_start) < s->cluster_sectors) { > + (n_end - n_start) < s->cluster_size) { > /* if the cluster is already compressed, we must > decompress it in the case it is not completely > overwritten */ > @@ -480,16 +480,15 @@ static int get_cluster_offset(BlockDriverState *bs, > /* if encrypted, we must initialize the cluster > content which won't be written */ > if (bs->encrypted && > - (n_end - n_start) < s->cluster_sectors) { > - uint64_t start_sect; > + (n_end - n_start) < s->cluster_size) { > + uint64_t start_offset; > assert(s->crypto); > - start_sect = (offset & ~(s->cluster_size - 1)) >> 9; > - for(i = 0; i < s->cluster_sectors; i++) { > + start_offset = offset & ~(s->cluster_size - 1); > + for (i = 0; i < s->cluster_size; i += BDRV_SECTOR_SIZE) { > if (i < n_start || i >= n_end) { > - memset(s->cluster_data, 0x00, 512); > + memset(s->cluster_data, 0x00, BDRV_SECTOR_SIZE); > if (qcrypto_block_encrypt(s->crypto, > - (start_sect + i) * > - BDRV_SECTOR_SIZE, > + start_offset + i, > s->cluster_data, > BDRV_SECTOR_SIZE, > NULL) < 0) {
This code is still working in blocks of BDRV_SECTOR_SIZE here - which you do need to keep at least partially because that's the block size that qcrypto_block_encrypt() works with. qcrypto_block_qcow_encrypt() even asserts it. However, this means that even though n_start and n_end are byte-based now, the code only works correctly with encrypted images if they are multiples of BDRV_SECTOR_SIZE. This is currently true and we could assert it, but it would kind of defeat the purpose of the patch. I suppose you could make unaligned n_start/n_end work if you round down n_start and round up n_end to the next sector boundary for the comparison with i. For unaligned requests, we would then write a bit more than is actually necessary, but I think that's okay because we're initialising a previously unallocated cluster, so we don't overwrite valid data. Kevin