Re: [PATCH] ceph: add get_name() NFS export callback

From: Sage Weil <sage@inktank.com>
To: "Yan, Zheng" <zheng.z.yan@intel.com>
Cc: ceph-devel@vger.kernel.org
Subject: Re: [PATCH] ceph: add get_name() NFS export callback
Date: Thu, 6 Mar 2014 08:45:28 -0800 (PST)	[thread overview]
Message-ID: <alpine.DEB.2.00.1403060832170.316@cobra.newdream.net> (raw)
In-Reply-To: <1394111946-13754-1-git-send-email-zheng.z.yan@intel.com>

On Thu, 6 Mar 2014, Yan, Zheng wrote:
> Set WANT_DENTRY flag for the LOOKUPINO MDS request. The flag makes
> MDS reply contain dentry trace.
> 
> Signed-off-by: Yan, Zheng <zheng.z.yan@intel.com>
> ---
>  fs/ceph/export.c | 45 +++++++++++++++++++++++++++++++++++++++++++++
>  fs/ceph/inode.c  | 51 ++++++++++++++++++++++++++++++++++++++++++++++++++-
>  2 files changed, 95 insertions(+), 1 deletion(-)
> 
> diff --git a/fs/ceph/export.c b/fs/ceph/export.c
> index 4ec1fd5..3c84b49 100644
> --- a/fs/ceph/export.c
> +++ b/fs/ceph/export.c
> @@ -183,9 +183,54 @@ static struct dentry *ceph_get_parent(struct dentry *child)
>  	return dentry;
>  }
>  
> +static int ceph_get_name(struct dentry *parent, char *name,
> +			 struct dentry *child)
> +{
> +	struct ceph_mds_client *mdsc;
> +	struct ceph_mds_request *req;
> +	int err;
> +
> +	mdsc = ceph_inode_to_client(child->d_inode)->mdsc;
> +	req = ceph_mdsc_create_request(mdsc, CEPH_MDS_OP_LOOKUPINO,
> +				       USE_ANY_MDS);
> +	if (IS_ERR(req))
> +		return PTR_ERR(req);
> +
> +	mutex_lock(&parent->d_inode->i_mutex);
> +
> +	req->r_inode = child->d_inode;
> +	ihold(child->d_inode);
> +	req->r_ino2 = ceph_vino(parent->d_inode);
> +	req->r_locked_dir = parent->d_inode;
> +	req->r_num_caps = 1;
> +	err = ceph_mdsc_do_request(mdsc, NULL, req);

This one also worries me.  If the r_locked_dir isn't the current parent 
anymore, then below in ceph_fill_trace we will be doing a d_alloc etc in 
the wrong directory... at least with the current version of LOOKUPINO.  Is 
there an MDS patch that is verifying ino2 is correct?  Otherwise, we might 
be creating a dentry and setting up a lease etc in a different directory  
than what the MDS has.

Sigh... the nfsd's behavior when trying to reconnect things is clearly 
confusing to me.  Even reading through 
Documentation/filesystems/nfs/Exporting it isn't obvious what nfsd is 
actually doing with these methods, or what happens if the filesystem isn't 
in the state it expects it to be.

Anyway, it sounds like as long as we prevent ceph_fill_inode from putting 
a dentry in the wrong directory then this is good!

sage

> +
> +	mutex_unlock(&parent->d_inode->i_mutex);
> +
> +	if (!err) {
> +		struct ceph_mds_reply_info_parsed *rinfo = &req->r_reply_info;
> +		if (rinfo->head->is_dentry) {
> +			memcpy(name, rinfo->dname, rinfo->dname_len);
> +			name[rinfo->dname_len] = 0;
> +		} else {
> +			err = -EOPNOTSUPP;
> +		}
> +	}
> +	ceph_mdsc_put_request(req);
> +
> +	if (!err)
> +		dout("get_name child %p ino %llx.%llx name %s\n",
> +		     child, ceph_vinop(child->d_inode), name);
> +	else
> +		dout("get_name child %p ino %llx.%llx err %d\n",
> +		     child, ceph_vinop(child->d_inode), err);
> +	return err;
> +}
> +
>  const struct export_operations ceph_export_ops = {
>  	.encode_fh = ceph_encode_fh,
>  	.fh_to_dentry = ceph_fh_to_dentry,
>  	.fh_to_parent = ceph_fh_to_parent,
>  	.get_parent = ceph_get_parent,
> +	.get_name = ceph_get_name,
>  };
> diff --git a/fs/ceph/inode.c b/fs/ceph/inode.c
> index 8bf2384..ff3ee3e 100644
> --- a/fs/ceph/inode.c
> +++ b/fs/ceph/inode.c
> @@ -1044,10 +1044,59 @@ int ceph_fill_trace(struct super_block *sb, struct ceph_mds_request *req,
>  					 session, req->r_request_started, -1,
>  					 &req->r_caps_reservation);
>  			if (err < 0)
> -				return err;
> +				goto done;
>  		} else {
>  			WARN_ON_ONCE(1);
>  		}
> +
> +		if (dir && req->r_op == CEPH_MDS_OP_LOOKUPINO) {
> +			struct qstr dname;
> +			struct dentry *dn, *parent;
> +
> +			BUG_ON(!rinfo->head->is_target);
> +			BUG_ON(req->r_dentry);
> +
> +			parent = d_find_any_alias(dir);
> +			BUG_ON(!parent);
> +
> +			dname.name = rinfo->dname;
> +			dname.len = rinfo->dname_len;
> +			dname.hash = full_name_hash(dname.name, dname.len);
> +			vino.ino = le64_to_cpu(rinfo->targeti.in->ino);
> +			vino.snap = le64_to_cpu(rinfo->targeti.in->snapid);
> +retry_lookup:
> +			dn = d_lookup(parent, &dname);
> +			dout("d_lookup on parent=%p name=%.*s got %p\n",
> +			     parent, dname.len, dname.name, dn);
> +
> +			if (!dn) {
> +				dn = d_alloc(parent, &dname);
> +				dout("d_alloc %p '%.*s' = %p\n", parent,
> +				     dname.len, dname.name, dn);
> +				if (dn == NULL) {
> +					dput(parent);
> +					err = -ENOMEM;
> +					goto done;
> +				}
> +				err = ceph_init_dentry(dn);
> +				if (err < 0) {
> +					dput(dn);
> +					dput(parent);
> +					goto done;
> +				}
> +			} else if (dn->d_inode &&
> +				   (ceph_ino(dn->d_inode) != vino.ino ||
> +				    ceph_snap(dn->d_inode) != vino.snap)) {
> +				dout(" dn %p points to wrong inode %p\n",
> +				     dn, dn->d_inode);
> +				d_delete(dn);
> +				dput(dn);
> +				goto retry_lookup;
> +			}
> +
> +			req->r_dentry = dn;
> +			dput(parent);
> +		}
>  	}
>  
>  	if (rinfo->head->is_target) {
> -- 
> 1.8.5.3
> 
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