Re: [PATCH v3 7/7] NFSD: Pass share reservations flags to VFS

[Jeff Layton <jlayton@redhat.com>]

On Thu, 28 Feb 2013 19:25:33 +0400
Pavel Shilovsky <piastry@etersoft.ru> wrote:

> that maps them into O_DENY flags and make them visible for
> applications that use O_DENYMAND opens.
> 
> Signed-off-by: Pavel Shilovsky <piastry@etersoft.ru>
> ---
>  fs/locks.c          |  1 +
>  fs/nfsd/nfs4state.c | 46 +++++++++++++++++++++++++++++++++++++++++++++-
>  2 files changed, 46 insertions(+), 1 deletion(-)
> 
> diff --git a/fs/locks.c b/fs/locks.c
> index 0cc7d1b..593d464 100644
> --- a/fs/locks.c
> +++ b/fs/locks.c
> @@ -874,6 +874,7 @@ deny_lock_file(struct file *filp)
>  	locks_free_lock(lock);
>  	return error;
>  }
> +EXPORT_SYMBOL(deny_lock_file);
>  
>  static int __posix_lock_file(struct inode *inode, struct file_lock *request, struct file_lock *conflock)
>  {
> diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
> index ac8ed96c..766256a 100644
> --- a/fs/nfsd/nfs4state.c
> +++ b/fs/nfsd/nfs4state.c
> @@ -476,6 +476,19 @@ test_deny(u32 access, struct nfs4_ol_stateid *stp)
>  	return test_bit(access, &stp->st_deny_bmap);
>  }
>  
> +static int nfs4_deny_to_odeny(u32 access)
> +{
> +	switch (access & NFS4_SHARE_DENY_BOTH) {
> +	case NFS4_SHARE_DENY_READ:
> +		return O_DENYMAND | O_DENYREAD;
> +	case NFS4_SHARE_DENY_WRITE:
> +		return O_DENYWRITE | O_DENYMAND;
> +	case NFS4_SHARE_DENY_BOTH:
> +		return O_DENYREAD | O_DENYWRITE | O_DENYMAND;
> +	}
> +	return O_DENYMAND;
> +}
> +
>  static int nfs4_access_to_omode(u32 access)
>  {
>  	switch (access & NFS4_SHARE_ACCESS_BOTH) {
> @@ -2793,6 +2806,21 @@ nfsd4_truncate(struct svc_rqst *rqstp, struct svc_fh *fh,
>  }
>  
>  static __be32
> +nfs4_vfs_set_deny(struct nfs4_file *fp, unsigned long share_access,
> +		  unsigned long deny_access)
> +{
> +	int oflag, rc;
> +	__be32 status = nfs_ok;
> +
> +	oflag = nfs4_access_to_omode(share_access);
> +	fp->fi_fds[oflag]->f_flags |= nfs4_deny_to_odeny(deny_access);
> +	rc = deny_lock_file(fp->fi_fds[oflag]);
> +	if (rc)
> +		status = nfserrno(rc);
> +	return status;
> +}
> +
> +static __be32
>  nfs4_upgrade_open(struct svc_rqst *rqstp, struct nfs4_file *fp, struct svc_fh *cur_fh, struct nfs4_ol_stateid *stp, struct nfsd4_open *open)
>  {
>  	u32 op_share_access = open->op_share_access;
> @@ -2813,6 +2841,14 @@ nfs4_upgrade_open(struct svc_rqst *rqstp, struct nfs4_file *fp, struct svc_fh *c
>  		}
>  		return status;
>  	}
> +	status = nfs4_vfs_set_deny(fp, op_share_access, open->op_share_deny);
> +	if (status) {
> +		if (new_access) {
> +			int oflag = nfs4_access_to_omode(op_share_access);
> +			nfs4_file_put_access(fp, oflag);
> +		}
> +		return status;
> +	}
>  	/* remember the open */
>  	set_access(op_share_access, stp);
>  	set_deny(open->op_share_deny, stp);
> @@ -3046,7 +3082,7 @@ nfsd4_process_open2(struct svc_rqst *rqstp, struct svc_fh *current_fh, struct nf
>  
>  	/*
>  	 * OPEN the file, or upgrade an existing OPEN.
> -	 * If truncate fails, the OPEN fails.
> +	 * If truncate or setting deny fails, the OPEN fails.
>  	 */
>  	if (stp) {
>  		/* Stateid was found, this is an OPEN upgrade */
> @@ -3060,6 +3096,10 @@ nfsd4_process_open2(struct svc_rqst *rqstp, struct svc_fh *current_fh, struct nf
>  		status = nfsd4_truncate(rqstp, current_fh, open);
>  		if (status)
>  			goto out;
> +		status = nfs4_vfs_set_deny(fp, open->op_share_access,
> +					   open->op_share_deny);
> +		if (status)
> +			goto out;
>  		stp = open->op_stp;
>  		open->op_stp = NULL;
>  		init_open_stateid(stp, fp, open);
> @@ -3758,6 +3798,10 @@ nfsd4_open_downgrade(struct svc_rqst *rqstp,
>  	}
>  	nfs4_stateid_downgrade(stp, od->od_share_access);
>  
> +	status = nfs4_vfs_set_deny(stp->st_file, od->od_share_access,
> +				   od->od_share_deny);
> +	if (status)
> +		goto out;
>  	reset_union_bmap_deny(od->od_share_deny, stp);
>  
>  	update_stateid(&stp->st_stid.sc_stateid);

knfsd has some code already to handle share reservations internally.
Nothing outside of knfsd is aware of these reservations, of course so
moving to a vfs-level object for it would be a marked improvement.

It doesn't look like this patch removes any of that old code though. I
think it probably should, or there ought to be some consideration of
how this new stuff will mesh with it.

I think you have 2 choices here:

1/ rip out the old share reservation code altogether and require that
filesystems mount with -o sharemand or whatever if they want to allow
their enforcement

2/ make knfsd fall back to using the internal share reservation code
when the mount option isn't enabled

Personally, I think #1 would be fine, but Bruce may want to weigh in on
what he'd prefer.

-- 
Jeff Layton <jlayton@redhat.com>