Re: [PATCH 2/3] mds: fix cap revoke race

["Yan, Zheng" <zheng.z.yan@intel.com>]

This patch's title is wrong, please ignore it.

Thanks
Yan, Zheng

On 06/24/2013 02:41 PM, Yan, Zheng wrote:
> From: "Yan, Zheng" <zheng.z.yan@intel.com>
> 
> If caps are been revoking by the auth MDS, don't consider them as
> issued even they are still issued by non-auth MDS. The non-auth
> MDS should also be revoking/exporting these caps, the client just
> hasn't received the cap revoke/export message.
> 
> The race I encountered is: When caps are exporting to new MDS, the
> client receives cap import message and cap revoke message from the
> new MDS, then receives cap export message from the old MDS. When
> the client receives cap revoke message from the new MDS, the revoking
> caps are still issued by the old MDS, so the client does nothing.
> Later when the cap export message is received, the client removes
> the caps issued by the old MDS. (Another way to fix the race is
> calling ceph_check_caps() in handle_cap_export())
> 
> Signed-off-by: Yan, Zheng <zheng.z.yan@intel.com>
> ---
>  fs/ceph/caps.c | 9 +++++++++
>  1 file changed, 9 insertions(+)
> 
> diff --git a/fs/ceph/caps.c b/fs/ceph/caps.c
> index 9a5ccc9..a8c616b 100644
> --- a/fs/ceph/caps.c
> +++ b/fs/ceph/caps.c
> @@ -697,6 +697,15 @@ int __ceph_caps_issued(struct ceph_inode_info *ci, int *implemented)
>  		if (implemented)
>  			*implemented |= cap->implemented;
>  	}
> +	/*
> +	 * exclude caps issued by non-auth MDS, but are been revoking
> +	 * by the auth MDS. The non-auth MDS should be revoking/exporting
> +	 * these caps, but the message is delayed.
> +	 */
> +	if (ci->i_auth_cap) {
> +		cap = ci->i_auth_cap;
> +		have &= ~cap->implemented | cap->issued;
> +	}
>  	return have;
>  }
>  
>