From: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
To: Paolo Bonzini <pbonzini@redhat.com>,
Emanuele Giuseppe Esposito <eesposit@redhat.com>,
qemu-block@nongnu.org
Cc: John Snow <jsnow@redhat.com>, Kevin Wolf <kwolf@redhat.com>,
Max Reitz <mreitz@redhat.com>,
Stefan Hajnoczi <stefanha@redhat.com>,
qemu-devel@nongnu.org
Subject: Re: [PATCH v3 1/5] block-copy: streamline choice of copy_range vs. read/write
Date: Wed, 9 Jun 2021 13:09:49 +0300 [thread overview]
Message-ID: <bfe5e37f-ce7a-d867-cd9a-9de7ccd65966@virtuozzo.com> (raw)
In-Reply-To: <8f49c449-583b-8842-9920-dd0dc1196e1f@redhat.com>
09.06.2021 12:33, Paolo Bonzini wrote:
> On 09/06/21 10:51, Vladimir Sementsov-Ogievskiy wrote:
>>>
>>> + default:
>>> [...]
>>> + bounce_buffer = qemu_blockalign(s->source->bs, nbytes);
>>> + ret = bdrv_co_pread(s->source, offset, nbytes, bounce_buffer, 0);
>>> + if (ret < 0) {
>>> + trace_block_copy_read_fail(s, offset, ret);
>>> + *error_is_read = true;
>>> + goto out;
>>> + }
>>> + ret = bdrv_co_pwrite(s->target, offset, nbytes, bounce_buffer,
>>> + s->write_flags);
>>> + if (ret < 0) {
>>> + trace_block_copy_write_fail(s, offset, ret);
>>> + *error_is_read = false;
>>> + goto out;
>>> + }
>>> +out:
>>> + qemu_vfree(bounce_buffer);
>>
>> label inside switch operator? Rather unusual. Please, let's avoid it and just keep out: after switch operator.
>
> Agreed with all comments except this one, the bounce_buffer doesn't exist in the other cases.
Hmm, as well as "return ret" actually is used only for this "default:" case, other paths returns earlier :) Also, bounce_buffer is defined in outer scope anyway. So I don't think that overall picture becomes better from isolation point of view with this change. Maybe good refactoring is moving default branch to a separate helper function together with bounce_buffer local variable.
Still, I don't care too much, keep it as is if you want, that's works for me.
The thing that comes to my mind not the first time: how to make something similar with g_autofree for qemu_blockalign()?
I can imagine how to implement a macro like ERRP_GUARD, which will work like
void *bounce_buffer = qemu_blockalign(...);
QEMU_AUTO_VFREE(bounce_buffer);
...
>
>>> + ret = block_copy_do_copy(s, t->offset, t->bytes, &method, &error_is_read);
>>> + if (s->method == t->method) {
>>> + s->method = method;
>>
>> you leave another t->s occurrences in the function untouched. It's somehow inconsistent. Could we just use t->s in this patch, and refactor with a follow-up patch (or as preparing patch)?
>
> Maybe as a first patch, yes.
>
> Paolo
>
--
Best regards,
Vladimir
next prev parent reply other threads:[~2021-06-09 10:13 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-06-08 7:33 [PATCH v3 0/5] block-copy: protect block-copy internal structures Emanuele Giuseppe Esposito
2021-06-08 7:33 ` [PATCH v3 1/5] block-copy: streamline choice of copy_range vs. read/write Emanuele Giuseppe Esposito
2021-06-09 8:51 ` Vladimir Sementsov-Ogievskiy
2021-06-09 9:33 ` Paolo Bonzini
2021-06-09 10:09 ` Vladimir Sementsov-Ogievskiy [this message]
2021-06-09 10:54 ` Vladimir Sementsov-Ogievskiy
2021-06-08 7:33 ` [PATCH v3 2/5] block-copy: improve comments of BlockCopyTask and BlockCopyState types and functions Emanuele Giuseppe Esposito
2021-06-09 9:12 ` Vladimir Sementsov-Ogievskiy
2021-06-10 10:14 ` Emanuele Giuseppe Esposito
2021-06-10 10:27 ` Vladimir Sementsov-Ogievskiy
2021-06-10 10:46 ` Emanuele Giuseppe Esposito
2021-06-10 11:12 ` Vladimir Sementsov-Ogievskiy
2021-06-10 14:21 ` Emanuele Giuseppe Esposito
2021-06-10 15:05 ` Vladimir Sementsov-Ogievskiy
2021-06-08 7:33 ` [PATCH v3 3/5] block-copy: move progress_set_remaining in block_copy_task_end Emanuele Giuseppe Esposito
2021-06-08 7:33 ` [PATCH v3 4/5] block-copy: add a CoMutex Emanuele Giuseppe Esposito
2021-06-09 12:25 ` Vladimir Sementsov-Ogievskiy
2021-06-10 14:49 ` Emanuele Giuseppe Esposito
2021-06-08 7:33 ` [PATCH v3 5/5] block-copy: atomic .cancelled and .finished fields in BlockCopyCallState Emanuele Giuseppe Esposito
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