[Ocfs2-devel] [PATCH v2] ocfs2/cluster: unlock the o2hb_live_lock before the o2nm_depend_item()
Joseph Qi
jiangqi903 at gmail.com
Mon Nov 6 01:37:06 PST 2017
Hi Alex,
For local heartbeat mode, I understand that if the region is not found,
o2hb_live_lock won't be released. And if the region is found, it doesn't
have to iterate the next region. So I agree with your fix in this case.
But I still don't get how to make sure the safe iteration in case of
global heartbeat mode.
Thanks,
Joseph
On 17/11/2 14:00, alex chen wrote:
> In the following situation, the down_write() will be called under
> the spin_lock(), which may lead a soft lockup:
> o2hb_region_inc_user
> spin_lock(&o2hb_live_lock)
> o2hb_region_pin
> o2nm_depend_item
> configfs_depend_item
> inode_lock
> down_write
> -->here may sleep and reschedule
>
> So we should unlock the o2hb_live_lock before the o2nm_depend_item(), and
> get item reference in advance to prevent the region to be released.
>
> Signed-off-by: Alex Chen <alex.chen at huawei.com>
> Reviewed-by: Yiwen Jiang <jiangyiwen at huawei.com>
> Reviewed-by: Jun Piao <piaojun at huawei.com>
> ---
> fs/ocfs2/cluster/heartbeat.c | 7 +++++++
> 1 file changed, 7 insertions(+)
>
> diff --git a/fs/ocfs2/cluster/heartbeat.c b/fs/ocfs2/cluster/heartbeat.c
> index d020604..07b2fdc 100644
> --- a/fs/ocfs2/cluster/heartbeat.c
> +++ b/fs/ocfs2/cluster/heartbeat.c
> @@ -2399,8 +2399,15 @@ static int o2hb_region_pin(const char *region_uuid)
> if (reg->hr_item_pinned || reg->hr_item_dropped)
> goto skip_pin;
>
> + config_item_get(®->hr_item);
> + spin_unlock(&o2hb_live_lock);
> +
> /* Ignore ENOENT only for local hb (userdlm domain) */
> ret = o2nm_depend_item(®->hr_item);
> +
> + config_item_put(®->hr_item);
> + spin_lock(&o2hb_live_lock);
> +
> if (!ret) {
> mlog(ML_CLUSTER, "Pin region %s\n", uuid);
> reg->hr_item_pinned = 1;
>
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