[Ocfs2-devel] [PATCH] ocfs2: retry once dlm_dispatch_assert_master failed with ENOMEM

[Wengang]

O2net is using a single threaded work queue to process network requests. 
Blocking in a handler would block whole network processing.
As you see, the memory allocation is with GFP_NOFS, if the first try 
failed, the following retries may still fail. Thus it could block a 
while which is not good.

How about to limit the retries, say, 3 or 5 times. If it still failed to 
get memory, return an error to peer and peer decides to retry or give up.

thanks,
wengang

于 2014年04月03日 20:45, Joseph Qi 写道:
> Once dlm_dispatch_assert_master failed in dlm_master_requery_handler,
> the only reason is ENOMEM. So just retry it instead of BUG().
>
> Signed-off-by: Joseph Qi <joseph.qi at huawei.com>
> ---
>   fs/ocfs2/dlm/dlmrecovery.c | 11 ++++++++---
>   1 file changed, 8 insertions(+), 3 deletions(-)
>
> diff --git a/fs/ocfs2/dlm/dlmrecovery.c b/fs/ocfs2/dlm/dlmrecovery.c
> index 7035af0..f772d64 100644
> --- a/fs/ocfs2/dlm/dlmrecovery.c
> +++ b/fs/ocfs2/dlm/dlmrecovery.c
> @@ -1685,6 +1685,7 @@ int dlm_master_requery_handler(struct o2net_msg *msg, u32 len, void *data,
>   
>   	hash = dlm_lockid_hash(req->name, req->namelen);
>   
> +retry:
>   	spin_lock(&dlm->spinlock);
>   	res = __dlm_lookup_lockres(dlm, req->name, req->namelen, hash);
>   	if (res) {
> @@ -1693,10 +1694,14 @@ int dlm_master_requery_handler(struct o2net_msg *msg, u32 len, void *data,
>   		if (master == dlm->node_num) {
>   			int ret = dlm_dispatch_assert_master(dlm, res,
>   							     0, 0, flags);
> +			/* ENOMEM returns, just retry */
>   			if (ret < 0) {
> -				mlog_errno(-ENOMEM);
> -				/* retry!? */
> -				BUG();
> +				spin_unlock(&res->spinlock);
> +				dlm_lockres_put(res);
> +				spin_unlock(&dlm->spinlock);
> +				mlog_errno(ret);
> +				msleep(50);
> +				goto retry;
>   			}
>   		} else /* put.. incase we are not the master */
>   			dlm_lockres_put(res);