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From: Kevin Wolf <kwolf@redhat.com>
To: Max Reitz <mreitz@redhat.com>
Cc: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>,
	qemu-devel@nongnu.org, qemu-block@nongnu.org
Subject: Re: [PATCH v3 09/21] quorum: Add QuorumChild.to_be_replaced
Date: Wed, 5 Feb 2020 16:38:59 +0100	[thread overview]
Message-ID: <20200205153859.GE5768@dhcp-200-226.str.redhat.com> (raw)
In-Reply-To: <20200130214431.333510-10-mreitz@redhat.com>

Am 30.01.2020 um 22:44 hat Max Reitz geschrieben:
> We will need this to verify that Quorum can let one of its children be
> replaced without breaking anything else.
> 
> Signed-off-by: Max Reitz <mreitz@redhat.com>
> ---
>  block/quorum.c | 25 +++++++++++++++++++++++++
>  1 file changed, 25 insertions(+)
> 
> diff --git a/block/quorum.c b/block/quorum.c
> index 59cd524502..6a7224c9e4 100644
> --- a/block/quorum.c
> +++ b/block/quorum.c
> @@ -67,6 +67,13 @@ typedef struct QuorumVotes {
>  
>  typedef struct QuorumChild {
>      BdrvChild *child;
> +
> +    /*
> +     * If set, check whether this node can be replaced without any
> +     * other parent noticing: Unshare CONSISTENT_READ, and take the
> +     * WRITE permission.
> +     */
> +    bool to_be_replaced;

I don't understand these permission changes. How does (preparing for)
detaching a node from quorum make its content invalid? And why do we
suddenly need WRITE permissions even if the quorum node is only used
read-only?

The comment is a bit unclear, too. "check whether" implies that both
outcomes could be true, but it doesn't say what happens in either case.
Is this really "make sure that"?

Kevin



  parent reply	other threads:[~2020-02-05 15:39 UTC|newest]

Thread overview: 41+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-01-30 21:44 [PATCH v3 00/21] block: Fix check_to_replace_node() Max Reitz
2020-01-30 21:44 ` [PATCH v3 01/21] blockdev: Allow external snapshots everywhere Max Reitz
2020-01-30 21:44 ` [PATCH v3 02/21] blockdev: Allow resizing everywhere Max Reitz
2020-01-30 21:44 ` [PATCH v3 03/21] block: Drop bdrv_is_first_non_filter() Max Reitz
2020-01-30 21:44 ` [PATCH v3 04/21] iotests: Let 041 use -blockdev for quorum children Max Reitz
2020-01-30 21:44 ` [PATCH v3 05/21] quorum: Fix child permissions Max Reitz
2020-01-30 21:44 ` [PATCH v3 06/21] block: Add bdrv_recurse_can_replace() Max Reitz
2020-01-30 21:44 ` [PATCH v3 07/21] blkverify: Implement .bdrv_recurse_can_replace() Max Reitz
2020-01-30 21:44 ` [PATCH v3 08/21] quorum: Store children in own structure Max Reitz
2020-01-30 21:44 ` [PATCH v3 09/21] quorum: Add QuorumChild.to_be_replaced Max Reitz
2020-02-04  9:33   ` Vladimir Sementsov-Ogievskiy
2020-02-05 15:38   ` Kevin Wolf [this message]
2020-02-06 10:11     ` Max Reitz
2020-02-06 14:58       ` Kevin Wolf
2020-02-06 15:21         ` Max Reitz
2020-02-06 15:51           ` Kevin Wolf
2020-02-06 16:43             ` Max Reitz
2020-02-06 16:47               ` Max Reitz
2020-02-06 16:58                 ` Kevin Wolf
2020-02-06 16:57               ` Kevin Wolf
2020-02-06 17:06                 ` Max Reitz
2020-02-06 17:41                   ` Kevin Wolf
2020-01-30 21:44 ` [PATCH v3 10/21] quorum: Implement .bdrv_recurse_can_replace() Max Reitz
2020-02-04  9:37   ` Vladimir Sementsov-Ogievskiy
2020-01-30 21:44 ` [PATCH v3 11/21] block: Use bdrv_recurse_can_replace() Max Reitz
2020-01-30 21:44 ` [PATCH v3 12/21] block: Remove bdrv_recurse_is_first_non_filter() Max Reitz
2020-02-04  9:45   ` Vladimir Sementsov-Ogievskiy
2020-01-30 21:44 ` [PATCH v3 13/21] mirror: Double-check immediately before replacing Max Reitz
2020-01-30 21:44 ` [PATCH v3 14/21] quorum: Stop marking it as a filter Max Reitz
2020-01-30 21:44 ` [PATCH v3 15/21] iotests: Use complete_and_wait() in 155 Max Reitz
2020-01-30 21:44 ` [PATCH v3 16/21] iotests: Add VM.assert_block_path() Max Reitz
2020-02-04 10:33   ` Vladimir Sementsov-Ogievskiy
2020-02-04 14:09   ` Vladimir Sementsov-Ogievskiy
2020-01-30 21:44 ` [PATCH v3 17/21] iotests/041: Drop superfluous shutdowns Max Reitz
2020-02-04 11:40   ` Vladimir Sementsov-Ogievskiy
2020-01-30 21:44 ` [PATCH v3 18/21] iotests: Resolve TODOs in 041 Max Reitz
2020-02-04  9:54   ` Vladimir Sementsov-Ogievskiy
2020-01-30 21:44 ` [PATCH v3 19/21] iotests: Use self.image_len in TestRepairQuorum Max Reitz
2020-01-30 21:44 ` [PATCH v3 20/21] iotests: Add tests for invalid Quorum @replaces Max Reitz
2020-01-30 21:44 ` [PATCH v3 21/21] iotests: Check that @replaces can replace filters Max Reitz
2020-02-04  9:56   ` Vladimir Sementsov-Ogievskiy

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