From: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
To: Max Reitz <mreitz@redhat.com>,
qemu-devel@nongnu.org, qemu-block@nongnu.org
Cc: kwolf@redhat.com, den@openvz.org
Subject: Re: [Qemu-devel] [PATCH 3/7] qcow2: split out reading normal clusters from qcow2_co_preadv
Date: Mon, 1 Oct 2018 18:14:35 +0300 [thread overview]
Message-ID: <9e53e78b-a0ef-9486-1036-3737ba8cad11@virtuozzo.com> (raw)
In-Reply-To: <6e19aaeb-8acc-beb9-5ece-9ae6101637a9@redhat.com>
27.09.2018 20:35, Max Reitz wrote:
> On 07.08.18 19:43, Vladimir Sementsov-Ogievskiy wrote:
>> Memory allocation may become less efficient for encrypted case. It's a
>> payment for further asynchronous scheme.
>>
>> Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
>> ---
>> block/qcow2.c | 114 ++++++++++++++++++++++++++++++++--------------------------
>> 1 file changed, 64 insertions(+), 50 deletions(-)
>>
>> diff --git a/block/qcow2.c b/block/qcow2.c
>> index 65e3ca00e2..5e7f2ee318 100644
>> --- a/block/qcow2.c
>> +++ b/block/qcow2.c
>> @@ -1808,6 +1808,67 @@ out:
>> return ret;
>> }
>>
>> +static coroutine_fn int qcow2_co_preadv_normal(BlockDriverState *bs,
>> + uint64_t file_cluster_offset,
>> + uint64_t offset,
>> + uint64_t bytes,
>> + QEMUIOVector *qiov,
>> + uint64_t qiov_offset)
>> +{
>> + int ret;
>> + BDRVQcow2State *s = bs->opaque;
>> + void *crypt_buf = NULL;
>> + QEMUIOVector hd_qiov;
>> + int offset_in_cluster = offset_into_cluster(s, offset);
>> +
>> + if ((file_cluster_offset & 511) != 0) {
>> + return -EIO;
>> + }
>> +
>> + qemu_iovec_init(&hd_qiov, qiov->niov);
> So you're not just re-allocating the bounce buffer for every single
> call, but also this I/O vector. Hm.
>
>> + if (bs->encrypted) {
>> + assert(s->crypto);
>> + assert(bytes <= QCOW_MAX_CRYPT_CLUSTERS * s->cluster_size);
>> +
>> + crypt_buf = qemu_try_blockalign(bs->file->bs, bytes);
> 1. Why did you remove the comment?
>
> 2. The check for whether crypt_buf was successfully allocated is missing.
>
> 3. Do you have any benchmarks for encrypted images? Having to allocate
> the bounce buffer for potentially every single cluster sounds rather bad
> to me.
Hmm, no excuses. 1- Will fix, 2 - will fix, 3 - will fix or at least
test the performance.
>
>> + qemu_iovec_add(&hd_qiov, crypt_buf, bytes);
>> + } else {
>> + qemu_iovec_concat(&hd_qiov, qiov, qiov_offset, bytes);
> qcow2_co_preadv() continues to do this as well. That's superfluous now.
hd_qiov is local here.. or what do you mean?
>
>> + }
>> +
>> + BLKDBG_EVENT(bs->file, BLKDBG_READ_AIO);
>> + ret = bdrv_co_preadv(bs->file,
>> + file_cluster_offset + offset_in_cluster,
>> + bytes, &hd_qiov, 0);
>> + if (ret < 0) {
>> + goto out;
>> + }
>> +
>> + if (bs->encrypted) {
>> + assert(s->crypto);
>> + assert((offset & (BDRV_SECTOR_SIZE - 1)) == 0);
>> + assert((bytes & (BDRV_SECTOR_SIZE - 1)) == 0);
>> + if (qcrypto_block_decrypt(s->crypto,
>> + (s->crypt_physical_offset ?
>> + file_cluster_offset + offset_in_cluster :
>> + offset),
>> + crypt_buf,
>> + bytes,
>> + NULL) < 0) {
> What's the reason against decrypting this in-place in qiov so we could
> save the bounce buffer? We allow offsets in clusters, so why can't we
> just call this function once per involved I/O vector entry?
Isn't it unsafe to do decryption in guest buffers?
>
> Max
>
>> + ret = -EIO;
>> + goto out;
>> + }
>> + qemu_iovec_from_buf(qiov, qiov_offset, crypt_buf, bytes);
>> + }
>> +
>> +out:
>> + qemu_vfree(crypt_buf);
>> + qemu_iovec_destroy(&hd_qiov);
>> +
>> + return ret;
>> +}
>> +
>> static coroutine_fn int qcow2_co_preadv(BlockDriverState *bs, uint64_t offset,
>> uint64_t bytes, QEMUIOVector *qiov,
>> int flags)
>> @@ -1819,7 +1880,6 @@ static coroutine_fn int qcow2_co_preadv(BlockDriverState *bs, uint64_t offset,
>> uint64_t cluster_offset = 0;
>> uint64_t bytes_done = 0;
>> QEMUIOVector hd_qiov;
>> - uint8_t *cluster_data = NULL;
>>
>> qemu_iovec_init(&hd_qiov, qiov->niov);
>>
>> @@ -1882,57 +1942,12 @@ static coroutine_fn int qcow2_co_preadv(BlockDriverState *bs, uint64_t offset,
>> case QCOW2_CLUSTER_NORMAL:
>> qemu_co_mutex_unlock(&s->lock);
>>
>> - if ((cluster_offset & 511) != 0) {
>> - ret = -EIO;
>> - goto fail_nolock;
>> - }
>> -
>> - if (bs->encrypted) {
>> - assert(s->crypto);
>> -
>> - /*
>> - * For encrypted images, read everything into a temporary
>> - * contiguous buffer on which the AES functions can work.
>> - */
>> - if (!cluster_data) {
>> - cluster_data =
>> - qemu_try_blockalign(bs->file->bs,
>> - QCOW_MAX_CRYPT_CLUSTERS
>> - * s->cluster_size);
>> - if (cluster_data == NULL) {
>> - ret = -ENOMEM;
>> - goto fail_nolock;
>> - }
>> - }
>> -
>> - assert(cur_bytes <= QCOW_MAX_CRYPT_CLUSTERS * s->cluster_size);
>> - qemu_iovec_reset(&hd_qiov);
>> - qemu_iovec_add(&hd_qiov, cluster_data, cur_bytes);
>> - }
>> -
>> - BLKDBG_EVENT(bs->file, BLKDBG_READ_AIO);
>> - ret = bdrv_co_preadv(bs->file,
>> - cluster_offset + offset_in_cluster,
>> - cur_bytes, &hd_qiov, 0);
>> + ret = qcow2_co_preadv_normal(bs, cluster_offset,
>> + offset, cur_bytes, qiov, bytes_done);
>> if (ret < 0) {
>> goto fail_nolock;
>> }
>> - if (bs->encrypted) {
>> - assert(s->crypto);
>> - assert((offset & (BDRV_SECTOR_SIZE - 1)) == 0);
>> - assert((cur_bytes & (BDRV_SECTOR_SIZE - 1)) == 0);
>> - if (qcrypto_block_decrypt(s->crypto,
>> - (s->crypt_physical_offset ?
>> - cluster_offset + offset_in_cluster :
>> - offset),
>> - cluster_data,
>> - cur_bytes,
>> - NULL) < 0) {
>> - ret = -EIO;
>> - goto fail_nolock;
>> - }
>> - qemu_iovec_from_buf(qiov, bytes_done, cluster_data, cur_bytes);
>> - }
>> +
>> qemu_co_mutex_lock(&s->lock);
>> break;
>>
>> @@ -1953,7 +1968,6 @@ fail:
>>
>> fail_nolock:
>> qemu_iovec_destroy(&hd_qiov);
>> - qemu_vfree(cluster_data);
>>
>> return ret;
>> }
>>
>
--
Best regards,
Vladimir
next prev parent reply other threads:[~2018-10-01 15:14 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-08-07 17:43 [Qemu-devel] [PATCH 0/7] qcow2: async handling of fragmented io Vladimir Sementsov-Ogievskiy
2018-08-07 17:43 ` [Qemu-devel] [PATCH 1/7] qcow2: move qemu_co_mutex_lock below decryption procedure Vladimir Sementsov-Ogievskiy
[not found] ` <8e1cc18c-307f-99b1-5892-713ebd17a15f@redhat.com>
[not found] ` <43277786-b6b9-e18c-b0ca-064ff7c9c0c9@redhat.com>
2018-10-01 15:56 ` Vladimir Sementsov-Ogievskiy
2018-08-07 17:43 ` [Qemu-devel] [PATCH 2/7] qcow2: bdrv_co_pwritev: move encryption code out of lock Vladimir Sementsov-Ogievskiy
2018-08-07 17:43 ` [Qemu-devel] [PATCH 3/7] qcow2: split out reading normal clusters from qcow2_co_preadv Vladimir Sementsov-Ogievskiy
[not found] ` <6e19aaeb-8acc-beb9-5ece-9ae6101637a9@redhat.com>
2018-10-01 15:14 ` Vladimir Sementsov-Ogievskiy [this message]
2018-10-01 15:39 ` Max Reitz
2018-10-01 16:00 ` Vladimir Sementsov-Ogievskiy
2018-11-01 12:17 ` Vladimir Sementsov-Ogievskiy
2018-11-07 13:51 ` Max Reitz
2018-11-07 18:16 ` Kevin Wolf
2018-11-08 10:02 ` Vladimir Sementsov-Ogievskiy
2018-11-08 10:33 ` Kevin Wolf
2018-11-08 12:36 ` Vladimir Sementsov-Ogievskiy
2018-08-07 17:43 ` [Qemu-devel] [PATCH 4/7] qcow2: async scheme for qcow2_co_preadv Vladimir Sementsov-Ogievskiy
[not found] ` <08a610aa-9c78-1c83-5e48-b93080aac87b@redhat.com>
2018-10-01 15:33 ` Vladimir Sementsov-Ogievskiy
2018-10-01 15:49 ` Max Reitz
2018-10-01 16:17 ` Vladimir Sementsov-Ogievskiy
2018-08-07 17:43 ` [Qemu-devel] [PATCH 5/7] qcow2: refactor qcow2_co_pwritev: split out qcow2_co_do_pwritev Vladimir Sementsov-Ogievskiy
[not found] ` <5c871ce7-2cab-f897-0b06-cbc05b9ffe97@redhat.com>
2018-10-01 15:43 ` Vladimir Sementsov-Ogievskiy
2018-10-01 15:50 ` Max Reitz
2018-08-07 17:43 ` [Qemu-devel] [PATCH 6/7] qcow2: refactor qcow2_co_pwritev locals scope Vladimir Sementsov-Ogievskiy
2018-08-07 17:43 ` [Qemu-devel] [PATCH 7/7] qcow2: async scheme for qcow2_co_pwritev Vladimir Sementsov-Ogievskiy
[not found] ` <1c8299bf-0b31-82a7-c7c4-5069581f2d94@redhat.com>
2018-10-01 15:46 ` Vladimir Sementsov-Ogievskiy
2018-08-16 0:51 ` [Qemu-devel] [PATCH 0/7] qcow2: async handling of fragmented io Max Reitz
2018-08-16 13:58 ` Vladimir Sementsov-Ogievskiy
2018-08-17 19:34 ` Max Reitz
2018-08-17 19:43 ` Denis V. Lunev
2018-08-20 16:33 ` Vladimir Sementsov-Ogievskiy
2018-08-20 16:39 ` Max Reitz
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