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Re: [Qemu-block] [PATCH 1/7] qcow2: move qemu_co_mutex_lock below decryp
From: |
Max Reitz |
Subject: |
Re: [Qemu-block] [PATCH 1/7] qcow2: move qemu_co_mutex_lock below decryption procedure |
Date: |
Thu, 27 Sep 2018 18:58:47 +0200 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.0 |
On 07.08.18 19:43, Vladimir Sementsov-Ogievskiy wrote:
> From: "Denis V. Lunev" <address@hidden>
>
> We are not working with a shared state data in the decruption code and
> thus this operation is safe. On the other hand this significantly
> reduces the scope of the lock.
Sure, but does it have any effect? This is a coroutine lock and I don't
see any yield points besides the bdrv_co_preadv() that was executed
outside of the lock anyway.
Max
> Signed-off-by: Denis V. Lunev <address@hidden>
> ---
> block/qcow2.c | 14 ++++++++------
> 1 file changed, 8 insertions(+), 6 deletions(-)
>
> diff --git a/block/qcow2.c b/block/qcow2.c
> index ec9e6238a0..41def07c67 100644
> --- a/block/qcow2.c
> +++ b/block/qcow2.c
> @@ -1880,9 +1880,11 @@ static coroutine_fn int
> qcow2_co_preadv(BlockDriverState *bs, uint64_t offset,
> break;
>
> case QCOW2_CLUSTER_NORMAL:
> + qemu_co_mutex_unlock(&s->lock);
> +
> if ((cluster_offset & 511) != 0) {
> ret = -EIO;
> - goto fail;
> + goto fail_nolock;
> }
>
> if (bs->encrypted) {
> @@ -1899,7 +1901,7 @@ static coroutine_fn int
> qcow2_co_preadv(BlockDriverState *bs, uint64_t offset,
> * s->cluster_size);
> if (cluster_data == NULL) {
> ret = -ENOMEM;
> - goto fail;
> + goto fail_nolock;
> }
> }
>
> @@ -1909,13 +1911,11 @@ static coroutine_fn int
> qcow2_co_preadv(BlockDriverState *bs, uint64_t offset,
> }
>
> BLKDBG_EVENT(bs->file, BLKDBG_READ_AIO);
> - qemu_co_mutex_unlock(&s->lock);
> ret = bdrv_co_preadv(bs->file,
> cluster_offset + offset_in_cluster,
> cur_bytes, &hd_qiov, 0);
> - qemu_co_mutex_lock(&s->lock);
> if (ret < 0) {
> - goto fail;
> + goto fail_nolock;
> }
> if (bs->encrypted) {
> assert(s->crypto);
> @@ -1929,10 +1929,11 @@ static coroutine_fn int
> qcow2_co_preadv(BlockDriverState *bs, uint64_t offset,
> cur_bytes,
> NULL) < 0) {
> ret = -EIO;
> - goto fail;
> + goto fail_nolock;
> }
> qemu_iovec_from_buf(qiov, bytes_done, cluster_data,
> cur_bytes);
> }
> + qemu_co_mutex_lock(&s->lock);
> break;
>
> default:
> @@ -1950,6 +1951,7 @@ static coroutine_fn int
> qcow2_co_preadv(BlockDriverState *bs, uint64_t offset,
> fail:
> qemu_co_mutex_unlock(&s->lock);
>
> +fail_nolock:
> qemu_iovec_destroy(&hd_qiov);
> qemu_vfree(cluster_data);
>
>
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- Re: [Qemu-block] [PATCH 1/7] qcow2: move qemu_co_mutex_lock below decryption procedure,
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