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From:   "Benjamin Coddington" <bcodding@redhat.com>
To:     trond.myklebust@hammerspace.com, anna.schumaker@netapp.com
Cc:     linux-nfs@vger.kernel.org
Subject: Re: [PATCH 2/3] NFSv4: Refactor nfs_need_update_open_stateid()
Date:   Mon, 21 Sep 2020 07:17:36 -0400
Message-ID: <61369AD2-60E8-4B10-8AB5-DAA9BEAE257D@redhat.com>
In-Reply-To: <d6c4cd73c3546057edfe8d80512b274bb431d68e.1600686204.git.bcodding@redhat.com>
References: <5a7f6bbf4cf2038634a572f42ad80e95a8d0ae9c.1600686204.git.bcodding@redhat.com>
 <d6c4cd73c3546057edfe8d80512b274bb431d68e.1600686204.git.bcodding@redhat.com>
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NACK.  Please drop this patch..  This is a junk version of this patch 
that I was
using for debugging that I sent by mistake.  I'll send a cleaned up 
version separately.

Ben

On 21 Sep 2020, at 7:04, Benjamin Coddington wrote:

> The logic was becoming difficult to follow.  Add some comments and 
> local
> variables to clarify the behavior.
>
> Signed-off-by: Benjamin Coddington <bcodding@redhat.com>
> ---
>  fs/nfs/nfs4proc.c | 39 +++++++++++++++++++++++++--------------
>  1 file changed, 25 insertions(+), 14 deletions(-)
>
> diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c
> index 9ced7a62c05e..499f978d48aa 100644
> --- a/fs/nfs/nfs4proc.c
> +++ b/fs/nfs/nfs4proc.c
> @@ -1568,23 +1568,34 @@ static void 
> nfs_test_and_clear_all_open_stateid(struct nfs4_state *state)
>  static bool nfs_need_update_open_stateid(struct nfs4_state *state,
>  		const nfs4_stateid *stateid)
>  {
> -	if (test_bit(NFS_OPEN_STATE, &state->flags) == 0 ||
> -	    !nfs4_stateid_match_other(stateid, &state->open_stateid)) {
> -		if (stateid->seqid == cpu_to_be32(1)) {
> +	bool state_matches_other = nfs4_stateid_match_other(stateid, 
> &state->open_stateid);
> +	bool seqid_one = stateid->seqid == cpu_to_be32(1);
> +
> +	if (test_bit(NFS_OPEN_STATE, &state->flags)) {
> +		/* The common case - we're updating to a new sequence number */
> +		if (state_matches_other && nfs4_stateid_is_newer(stateid, 
> &state->open_stateid)) {
> +			nfs_state_log_out_of_order_open_stateid(state, stateid);
> +			return true;
> +		}
> +		/* We lost a race with a self-bumping close, do recovery */
> +		if (!state_matches_other) {
> +			trace_printk("lost race to self-bump close\n");
> +			return false;
> +		}
> +	} else {
> +		/* The common case, this is the first OPEN */
> +		if (!state_matches_other && seqid_one) {
>  			nfs_state_log_update_open_stateid(state);
> -		} else {
> -			if (!nfs4_stateid_match_other(stateid, &state->open_stateid))
> -				return false;
> -			else
> -				set_bit(NFS_STATE_CHANGE_WAIT, &state->flags);
> +			return true;
> +		}
> +		/* We lost a race either with a self-bumping close, OR with the 
> first OPEN */
> +		if (!state_matches_other && !seqid_one) {
> +			trace_printk("lost race to self-bump close OR first OPEN\n");
> +			set_bit(NFS_STATE_CHANGE_WAIT, &state->flags);
> +			return true;
>  		}
> -		return true;
> -	}
> -
> -	if (nfs4_stateid_is_newer(stateid, &state->open_stateid)) {
> -		nfs_state_log_out_of_order_open_stateid(state, stateid);
> -		return true;
>  	}
> +	/* Should be impossible to reach: */
>  	return false;
>  }
>
> -- 
> 2.20.1