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Date:   Tue, 29 Mar 2022 11:24:00 -0400
From:   "J. Bruce Fields" <bfields@fieldses.org>
To:     Dai Ngo <dai.ngo@oracle.com>
Cc:     chuck.lever@oracle.com, jlayton@redhat.com,
        viro@zeniv.linux.org.uk, linux-nfs@vger.kernel.org,
        linux-fsdevel@vger.kernel.org
Subject: Re: [PATCH RFC v18 05/11] NFSD: Update nfs4_get_vfs_file() to handle
 courtesy client
Message-ID: <20220329152400.GD29634@fieldses.org>
References: <1648182891-32599-1-git-send-email-dai.ngo@oracle.com>
 <1648182891-32599-6-git-send-email-dai.ngo@oracle.com>
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On Thu, Mar 24, 2022 at 09:34:45PM -0700, Dai Ngo wrote:
> Update nfs4_get_vfs_file and nfs4_upgrade_open to handle share
> reservation conflict with courtesy client.
> 
> Update nfs4_get_vfs_file and nfs4_upgrade_open to handle share
> reservation conflict with courtesy client.
> 
> When we have deny/access conflict we walk the fi_stateids of the
> file in question, looking for open stateid and check the deny/access
> of that stateid against the one from the open request. If there is
> a conflict then we check if the client that owns that stateid is
> a courtesy client. If it is then we set the client state to
> CLIENT_EXPIRED and allow the open request to continue. We have
> to scan all the stateid's of the file since the conflict can be
> caused by multiple open stateid's.
> 
> Client with CLIENT_EXPIRED is expired by the laundromat.
> 
> Signed-off-by: Dai Ngo <dai.ngo@oracle.com>
> ---
>  fs/nfsd/nfs4state.c | 85 +++++++++++++++++++++++++++++++++++++++++++++--------
>  1 file changed, 72 insertions(+), 13 deletions(-)
> 
> diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
> index f20c75890594..fe8969ba94b3 100644
> --- a/fs/nfsd/nfs4state.c
> +++ b/fs/nfsd/nfs4state.c
> @@ -701,9 +701,56 @@ __nfs4_file_get_access(struct nfs4_file *fp, u32 access)
>  		atomic_inc(&fp->fi_access[O_RDONLY]);
>  }
>  
> +/*
> + * Check if courtesy clients have conflicting access and resolve it if possible
> + *
> + * access:  is op_share_access if share_access is true.
> + *	    Check if access mode, op_share_access, would conflict with
> + *	    the current deny mode of the file 'fp'.
> + * access:  is op_share_deny if share_access is false.
> + *	    Check if the deny mode, op_share_deny, would conflict with
> + *	    current access of the file 'fp'.
> + * stp:     skip checking this entry.
> + * new_stp: normal open, not open upgrade.
> + *
> + * Function returns:
> + *	false - access/deny mode conflict with normal client.
> + *	true  - no conflict or conflict with courtesy client(s) is resolved.
> + */
> +static bool
> +nfs4_resolve_deny_conflicts_locked(struct nfs4_file *fp, bool new_stp,
> +		struct nfs4_ol_stateid *stp, u32 access, bool share_access)
> +{
> +	struct nfs4_ol_stateid *st;
> +	struct nfs4_client *clp;
> +	bool conflict = true;
> +	unsigned char bmap;
> +
> +	lockdep_assert_held(&fp->fi_lock);
> +	list_for_each_entry(st, &fp->fi_stateids, st_perfile) {
> +		/* ignore lock stateid */
> +		if (st->st_openstp)
> +			continue;
> +		if (st == stp && new_stp)
> +			continue;
> +		/* check file access against deny mode or vice versa */
> +		bmap = share_access ? st->st_deny_bmap : st->st_access_bmap;
> +		if (!(access & bmap_to_share_mode(bmap)))
> +			continue;

As I said before, I recommend just doing *both* checks here.  Then you
can remove the "bool share_access" argument.  I think that'll make the
code easier to read.

Otherwise, this version looks OK to me, thanks for the revisions.

--b.

> +		clp = st->st_stid.sc_client;
> +		if (nfsd4_expire_courtesy_clnt(clp))
> +			continue;
> +		conflict = false;
> +		break;
> +	}
> +	return conflict;
> +}
> +
>  static __be32
> -nfs4_file_get_access(struct nfs4_file *fp, u32 access)
> +nfs4_file_get_access(struct nfs4_file *fp, u32 access,
> +		struct nfs4_ol_stateid *stp, bool new_stp)
>  {
> +
>  	lockdep_assert_held(&fp->fi_lock);
>  
>  	/* Does this access mode make sense? */
> @@ -711,15 +758,21 @@ nfs4_file_get_access(struct nfs4_file *fp, u32 access)
>  		return nfserr_inval;
>  
>  	/* Does it conflict with a deny mode already set? */
> -	if ((access & fp->fi_share_deny) != 0)
> -		return nfserr_share_denied;
> +	if ((access & fp->fi_share_deny) != 0) {
> +		if (!nfs4_resolve_deny_conflicts_locked(fp, new_stp,
> +				stp, access, true))
> +			return nfserr_share_denied;
> +	}
>  
>  	__nfs4_file_get_access(fp, access);
>  	return nfs_ok;
>  }
>  
> -static __be32 nfs4_file_check_deny(struct nfs4_file *fp, u32 deny)
> +static __be32 nfs4_file_check_deny(struct nfs4_file *fp, u32 deny,
> +		struct nfs4_ol_stateid *stp, bool new_stp)
>  {
> +	__be32 rc = nfs_ok;
> +
>  	/* Common case is that there is no deny mode. */
>  	if (deny) {
>  		/* Does this deny mode make sense? */
> @@ -728,13 +781,19 @@ static __be32 nfs4_file_check_deny(struct nfs4_file *fp, u32 deny)
>  
>  		if ((deny & NFS4_SHARE_DENY_READ) &&
>  		    atomic_read(&fp->fi_access[O_RDONLY]))
> -			return nfserr_share_denied;
> +			rc = nfserr_share_denied;
>  
>  		if ((deny & NFS4_SHARE_DENY_WRITE) &&
>  		    atomic_read(&fp->fi_access[O_WRONLY]))
> -			return nfserr_share_denied;
> +			rc = nfserr_share_denied;
> +
> +		if (rc == nfserr_share_denied) {
> +			if (nfs4_resolve_deny_conflicts_locked(fp, new_stp,
> +					stp, deny, false))
> +				rc = nfs_ok;
> +		}
>  	}
> -	return nfs_ok;
> +	return rc;
>  }
>  
>  static void __nfs4_file_put_access(struct nfs4_file *fp, int oflag)
> @@ -4952,7 +5011,7 @@ nfsd4_truncate(struct svc_rqst *rqstp, struct svc_fh *fh,
>  
>  static __be32 nfs4_get_vfs_file(struct svc_rqst *rqstp, struct nfs4_file *fp,
>  		struct svc_fh *cur_fh, struct nfs4_ol_stateid *stp,
> -		struct nfsd4_open *open)
> +		struct nfsd4_open *open, bool new_stp)
>  {
>  	struct nfsd_file *nf = NULL;
>  	__be32 status;
> @@ -4966,14 +5025,14 @@ static __be32 nfs4_get_vfs_file(struct svc_rqst *rqstp, struct nfs4_file *fp,
>  	 * Are we trying to set a deny mode that would conflict with
>  	 * current access?
>  	 */
> -	status = nfs4_file_check_deny(fp, open->op_share_deny);
> +	status = nfs4_file_check_deny(fp, open->op_share_deny, stp, new_stp);
>  	if (status != nfs_ok) {
>  		spin_unlock(&fp->fi_lock);
>  		goto out;
>  	}
>  
>  	/* set access to the file */
> -	status = nfs4_file_get_access(fp, open->op_share_access);
> +	status = nfs4_file_get_access(fp, open->op_share_access, stp, new_stp);
>  	if (status != nfs_ok) {
>  		spin_unlock(&fp->fi_lock);
>  		goto out;
> @@ -5027,11 +5086,11 @@ nfs4_upgrade_open(struct svc_rqst *rqstp, struct nfs4_file *fp, struct svc_fh *c
>  	unsigned char old_deny_bmap = stp->st_deny_bmap;
>  
>  	if (!test_access(open->op_share_access, stp))
> -		return nfs4_get_vfs_file(rqstp, fp, cur_fh, stp, open);
> +		return nfs4_get_vfs_file(rqstp, fp, cur_fh, stp, open, false);
>  
>  	/* test and set deny mode */
>  	spin_lock(&fp->fi_lock);
> -	status = nfs4_file_check_deny(fp, open->op_share_deny);
> +	status = nfs4_file_check_deny(fp, open->op_share_deny, stp, false);
>  	if (status == nfs_ok) {
>  		set_deny(open->op_share_deny, stp);
>  		fp->fi_share_deny |=
> @@ -5376,7 +5435,7 @@ nfsd4_process_open2(struct svc_rqst *rqstp, struct svc_fh *current_fh, struct nf
>  			goto out;
>  		}
>  	} else {
> -		status = nfs4_get_vfs_file(rqstp, fp, current_fh, stp, open);
> +		status = nfs4_get_vfs_file(rqstp, fp, current_fh, stp, open, true);
>  		if (status) {
>  			stp->st_stid.sc_type = NFS4_CLOSED_STID;
>  			release_open_stateid(stp);
> -- 
> 2.9.5