From: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
To: 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>,
Paolo Bonzini <pbonzini@redhat.com>,
Stefan Hajnoczi <stefanha@redhat.com>,
qemu-devel@nongnu.org
Subject: Re: [PATCH v3 2/5] block-copy: improve comments of BlockCopyTask and BlockCopyState types and functions
Date: Wed, 9 Jun 2021 12:12:04 +0300 [thread overview]
Message-ID: <b466cc82-3905-acba-a2f8-e0b3cbbe2af1@virtuozzo.com> (raw)
In-Reply-To: <20210608073344.53637-3-eesposit@redhat.com>
08.06.2021 10:33, Emanuele Giuseppe Esposito wrote:
> As done in BlockCopyCallState, categorize BlockCopyTask
> and BlockCopyState in IN, State and OUT fields.
> This is just to understand which field has to be protected with a lock.
>
> .sleep_state is handled in the series "coroutine: new sleep/wake API"
> and thus here left as TODO.
>
> Signed-off-by: Emanuele Giuseppe Esposito <eesposit@redhat.com>
> ---
> block/block-copy.c | 47 ++++++++++++++++++++++++++++++----------------
> 1 file changed, 31 insertions(+), 16 deletions(-)
>
> diff --git a/block/block-copy.c b/block/block-copy.c
> index d58051288b..b3533a3003 100644
> --- a/block/block-copy.c
> +++ b/block/block-copy.c
> @@ -56,25 +56,33 @@ typedef struct BlockCopyCallState {
> QLIST_ENTRY(BlockCopyCallState) list;
>
> /* State */
Why previous @list field is not in the state? For sure it's not an IN parameter and should be protected somehow.
> - int ret;
> bool finished;
> - QemuCoSleep sleep;
> - bool cancelled;
> + QemuCoSleep sleep; /* TODO: protect API with a lock */
>
> /* OUT parameters */
> + bool cancelled;
> bool error_is_read;
> + int ret;
> } BlockCopyCallState;
>
> typedef struct BlockCopyTask {
> AioTask task;
>
> + /*
> + * IN parameters. Initialized in block_copy_task_create()
> + * and never changed.
> + */
> BlockCopyState *s;
> BlockCopyCallState *call_state;
> int64_t offset;
> - int64_t bytes;
> - BlockCopyMethod method;
> - QLIST_ENTRY(BlockCopyTask) list;
> + int64_t bytes; /* only re-set in task_shrink, before running the task */
> + BlockCopyMethod method; /* initialized in block_copy_dirty_clusters() */
hmm. to be precise method is initialized in block_copy_task_create.
And after block_copy_task_create finished, task is in the list and can be read by parallel block_copy_dirty_clusters(). So, @bytes is part of State, we must protect it..
method is only read by block_copy_task_entry(), so can be modified without any protection before running the task.
> +
> + /* State */
> CoQueue wait_queue; /* coroutines blocked on this task */
> +
> + /* To reference all call states from BlockCopyState */
That's a misleading comment.. not all sates but all tasks. I don't think we need this new comment, just keep @list in State section.
> + QLIST_ENTRY(BlockCopyTask) list;
> } BlockCopyTask;
>
> static int64_t task_end(BlockCopyTask *task)
> @@ -90,15 +98,25 @@ typedef struct BlockCopyState {
> */
> BdrvChild *source;
> BdrvChild *target;
> - BdrvDirtyBitmap *copy_bitmap;
> +
> + /* State */
> int64_t in_flight_bytes;
> - int64_t cluster_size;
> BlockCopyMethod method;
> - int64_t max_transfer;
> - uint64_t len;
> QLIST_HEAD(, BlockCopyTask) tasks; /* All tasks from all block-copy calls */
> QLIST_HEAD(, BlockCopyCallState) calls;
> + /* State fields that use a thread-safe API */
> + BdrvDirtyBitmap *copy_bitmap;
> + ProgressMeter *progress;
> + SharedResource *mem;
> + RateLimit rate_limit;
>
> + /*
> + * IN parameters. Initialized in block_copy_state_new()
> + * and never changed.
> + */
> + int64_t cluster_size;
> + int64_t max_transfer;
> + uint64_t len;
> BdrvRequestFlags write_flags;
>
> /*
> @@ -114,14 +132,11 @@ typedef struct BlockCopyState {
> * In this case, block_copy() will query the source’s allocation status,
> * skip unallocated regions, clear them in the copy_bitmap, and invoke
> * block_copy_reset_unallocated() every time it does.
> + *
> + * This field is set in backup_run() before coroutines are run,
> + * therefore is an IN.
> */
> bool skip_unallocated;
> -
> - ProgressMeter *progress;
> -
> - SharedResource *mem;
> -
> - RateLimit rate_limit;
> } BlockCopyState;
>
> static BlockCopyTask *find_conflicting_task(BlockCopyState *s,
>
--
Best regards,
Vladimir
next prev parent reply other threads:[~2021-06-09 9:13 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
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 [this message]
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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