Re: [PATCH RFC v18 05/11] NFSD: Update nfs4_get_vfs_file() to handle courtesy client

[dai.ngo@xxxxxxxxxx]

On 3/29/22 8:24 AM, J. Bruce Fields wrote:
> 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@xxxxxxxxxx>
> > ---
> >   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.

Bruce, I'm not clear how to check both here as I mentioned in my previous
email.

nfs4_resolve_deny_conflicts_locked is called from nfs4_file_get_access
and nfs4_file_check_deny to check either access or deny mode separately
so how do we check both access and deny in nfs4_resolve_deny_conflicts_locked?

Thanks,
-Dai

> 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