RE: [PATCH 3/6] ceph: return the correct dentry on mkdir

[Viacheslav Dubeyko <Slava.Dubeyko@ibm.com>]

On Mon, 2025-02-24 at 13:15 +1100, NeilBrown wrote:
> On Fri, 21 Feb 2025, Viacheslav Dubeyko wrote:
> > On Fri, 2025-02-21 at 10:36 +1100, NeilBrown wrote:
> > > ceph already splices the correct dentry (in splice_dentry()) from the
> > > result of mkdir but does nothing more with it.
> > > 
> > > Now that ->mkdir can return a dentry, return the correct dentry.
> > > 
> > > Signed-off-by: NeilBrown <neilb@suse.de>
> > > ---
> > >  fs/ceph/dir.c | 9 ++++++++-
> > >  1 file changed, 8 insertions(+), 1 deletion(-)
> > > 
> > > diff --git a/fs/ceph/dir.c b/fs/ceph/dir.c
> > > index 39e0f240de06..c1a1c168bb27 100644
> > > --- a/fs/ceph/dir.c
> > > +++ b/fs/ceph/dir.c
> > > @@ -1099,6 +1099,7 @@ static struct dentry *ceph_mkdir(struct mnt_idmap *idmap, struct inode *dir,
> > >  	struct ceph_client *cl = mdsc->fsc->client;
> > >  	struct ceph_mds_request *req;
> > >  	struct ceph_acl_sec_ctx as_ctx = {};
> > > +	struct dentry *ret = NULL;
> > 
> > I believe that it makes sense to initialize pointer by error here and always
> > return ret as output. If something goes wrong in the logic, then we already have
> > error.
> 
> I'm not certain that I understand, but I have made a change which seems
> to be consistent with the above and included it below.  Please let me
> know if it is what you intended.
> 
> > 
> > >  	int err;
> > >  	int op;
> > >  
> > > @@ -1166,14 +1167,20 @@ static struct dentry *ceph_mkdir(struct mnt_idmap *idmap, struct inode *dir,
> > >  	    !req->r_reply_info.head->is_dentry)
> > >  		err = ceph_handle_notrace_create(dir, dentry);
> > >  out_req:
> > > +	if (!err && req->r_dentry != dentry)
> > > +		/* Some other dentry was spliced in */
> > > +		ret = dget(req->r_dentry);
> > >  	ceph_mdsc_put_request(req);
> > >  out:
> > >  	if (!err)
> > > +		/* Should this use 'ret' ?? */
> > 
> > Could we make a decision should or shouldn't? :)
> > It looks not good to leave this comment instead of proper implementation. Do we
> > have some obstacles to make this decision?
> 
> I suspect we should use ret, but I didn't want to make a change which
> wasn't directly required by my needed.  So I highlighted this which
> looks to me like a possible bug, hoping that someone more familiar with
> the code would give an opinion.  Do you agree that 'ret' (i.e.
> ->r_dentry) should be used when ret is not NULL?
> 

I think if we are going to return ret as a dentry, then it makes sense to call
the ceph_init_inode_acls() for d_inode(ret). I don't see the point to call
ceph_init_inode_acls() for d_inode(dentry) then.

> > 
> > >  		ceph_init_inode_acls(d_inode(dentry), &as_ctx);
> > >  	else
> > >  		d_drop(dentry);
> > >  	ceph_release_acl_sec_ctx(&as_ctx);
> > > -	return ERR_PTR(err);
> > > +	if (err)
> > > +		return ERR_PTR(err);
> > > +	return ret;
> > 
> > What's about this?
> > 
> > return err ? ERR_PTR(err) : ret;
> 
> We could do that, but you said above that you thought we should always
> return 'ret' - which does make some sense.
> 
> What do you think of the following alternate patch?
> 

Patch looks good to me. Thanks.

Reviewed-by: Viacheslav Dubeyko <Slava.Dubeyko@ibm.com>

> Thanks,
> NeilBrown
> 
> diff --git a/fs/ceph/dir.c b/fs/ceph/dir.c
> index 39e0f240de06..d2e5c557df83 100644
> --- a/fs/ceph/dir.c
> +++ b/fs/ceph/dir.c
> @@ -1099,6 +1099,7 @@ static struct dentry *ceph_mkdir(struct mnt_idmap *idmap, struct inode *dir,
>  	struct ceph_client *cl = mdsc->fsc->client;
>  	struct ceph_mds_request *req;
>  	struct ceph_acl_sec_ctx as_ctx = {};
> +	struct dentry *ret;
>  	int err;
>  	int op;
>  
> @@ -1116,32 +1117,32 @@ static struct dentry *ceph_mkdir(struct mnt_idmap *idmap, struct inode *dir,
>  		      ceph_vinop(dir), dentry, dentry, mode);
>  		op = CEPH_MDS_OP_MKDIR;
>  	} else {
> -		err = -EROFS;
> +		ret = ERR_PTR(-EROFS);
>  		goto out;
>  	}
>  
>  	if (op == CEPH_MDS_OP_MKDIR &&
>  	    ceph_quota_is_max_files_exceeded(dir)) {
> -		err = -EDQUOT;
> +		ret = ERR_PTR(-EDQUOT);
>  		goto out;
>  	}
>  	if ((op == CEPH_MDS_OP_MKSNAP) && IS_ENCRYPTED(dir) &&
>  	    !fscrypt_has_encryption_key(dir)) {
> -		err = -ENOKEY;
> +		ret = ERR_PTR(-ENOKEY);
>  		goto out;
>  	}
>  
>  
>  	req = ceph_mdsc_create_request(mdsc, op, USE_AUTH_MDS);
>  	if (IS_ERR(req)) {
> -		err = PTR_ERR(req);
> +		ret = ERR_CAST(req);
>  		goto out;
>  	}
>  
>  	mode |= S_IFDIR;
>  	req->r_new_inode = ceph_new_inode(dir, dentry, &mode, &as_ctx);
>  	if (IS_ERR(req->r_new_inode)) {
> -		err = PTR_ERR(req->r_new_inode);
> +		ret = ERR_CAST(req->r_new_inode);
>  		req->r_new_inode = NULL;
>  		goto out_req;
>  	}
> @@ -1165,15 +1166,23 @@ static struct dentry *ceph_mkdir(struct mnt_idmap *idmap, struct inode *dir,
>  	    !req->r_reply_info.head->is_target &&
>  	    !req->r_reply_info.head->is_dentry)
>  		err = ceph_handle_notrace_create(dir, dentry);
> +	ret = ERR_PTR(err);
>  out_req:
> +	if (!IS_ERR(ret) && req->r_dentry != dentry)
> +		/* Some other dentry was spliced in */
> +		ret = dget(req->r_dentry);
>  	ceph_mdsc_put_request(req);
>  out:
> -	if (!err)
> -		ceph_init_inode_acls(d_inode(dentry), &as_ctx);
> -	else
> +	if (!IS_ERR(ret)) {
> +		if (ret)
> +			ceph_init_inode_acls(d_inode(ret), &as_ctx);
> +		else
> +			ceph_init_inode_acls(d_inode(dentry), &as_ctx);
> +	} else {
>  		d_drop(dentry);
> +	}
>  	ceph_release_acl_sec_ctx(&as_ctx);
> -	return ERR_PTR(err);
> +	return ret;
>  }
>  
>  static int ceph_link(struct dentry *old_dentry, struct inode *dir,
> 

Thanks,
Slava.