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Re: [Qemu-block] [PATCH 5/7] qcow2: use byte-based read in qcow2_decompr
From: |
Vladimir Sementsov-Ogievskiy |
Subject: |
Re: [Qemu-block] [PATCH 5/7] qcow2: use byte-based read in qcow2_decompress_cluster |
Date: |
Tue, 6 Nov 2018 15:18:08 +0000 |
06.11.2018 16:53, Alberto Garcia wrote:
> On Thu 01 Nov 2018 07:27:36 PM CET, Vladimir Sementsov-Ogievskiy wrote:
>
>> diff --git a/block/qcow2.c b/block/qcow2.c
>> index e9d24b801e..950b9f7ec6 100644
>> --- a/block/qcow2.c
>> +++ b/block/qcow2.c
>> @@ -3956,14 +3956,15 @@ fail:
>> int qcow2_decompress_cluster(BlockDriverState *bs, uint64_t cluster_offset)
>> {
>> BDRVQcow2State *s = bs->opaque;
>> - int ret, csize, nb_csectors, sector_offset;
>> + int ret, csize, nb_csectors;
>> uint64_t coffset;
>> + struct iovec iov;
>> + QEMUIOVector local_qiov;
>>
>> coffset = cluster_offset & s->cluster_offset_mask;
>> if (s->cluster_cache_offset != coffset) {
>> nb_csectors = ((cluster_offset >> s->csize_shift) & s->csize_mask)
>> + 1;
>> - sector_offset = coffset & 511;
>> - csize = nb_csectors * 512 - sector_offset;
>> + csize = nb_csectors * 512 - (coffset & 511);
>>
>> /* Allocate buffers on first decompress operation, most images are
>> * uncompressed and the memory overhead can be avoided. The
>> buffers
>> @@ -3981,14 +3982,17 @@ int qcow2_decompress_cluster(BlockDriverState *bs,
>> uint64_t cluster_offset)
>> s->cluster_cache = g_malloc(s->cluster_size);
>> }
>>
>> + iov.iov_base = s->cluster_data;
>> + iov.iov_len = csize;
>> + qemu_iovec_init_external(&local_qiov, &iov, 1);
>> +
>> BLKDBG_EVENT(bs->file, BLKDBG_READ_COMPRESSED);
>> - ret = bdrv_read(bs->file, coffset >> 9, s->cluster_data,
>> - nb_csectors);
>> + ret = bdrv_co_preadv(bs->file, coffset, csize, &local_qiov,
>> 0);
> I think you should annotate the function with coroutine_fn or use
> bdrv_pread() instead.
>
> Berto
it is called only from qcow2_co_preadv, so it's ok to move to
already-in-coroutine behaviour. I'll add coroutine_fn if new version is
needed, or it can be added inflight.
--
Best regards,
Vladimir
- [Qemu-block] [PATCH 0/7] qcow2 decompress in threads, Vladimir Sementsov-Ogievskiy, 2018/11/01
- [Qemu-block] [PATCH 5/7] qcow2: use byte-based read in qcow2_decompress_cluster, Vladimir Sementsov-Ogievskiy, 2018/11/01
- [Qemu-block] [PATCH 7/7] qcow2: do decompression in threads, Vladimir Sementsov-Ogievskiy, 2018/11/01
- [Qemu-block] [PATCH 2/7] qcow2: make more generic interface for qcow2_compress, Vladimir Sementsov-Ogievskiy, 2018/11/01
- [Qemu-block] [PATCH 4/7] qcow2: refactor decompress_buffer, Vladimir Sementsov-Ogievskiy, 2018/11/01
- [Qemu-block] [PATCH 3/7] qcow2: move decompression from qcow2-cluster.c to qcow2.c, Vladimir Sementsov-Ogievskiy, 2018/11/01
- [Qemu-block] [PATCH 1/7] qcow2: use Z_OK instead of 0 for deflateInit2 return code check, Vladimir Sementsov-Ogievskiy, 2018/11/01