From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Date: Mon, 12 Aug 2019 10:28:27 -0700 From: Ira Weiny Subject: Re: [RFC PATCH v2 16/19] RDMA/uverbs: Add back pointer to system file object Message-ID: <20190812172826.GA19746@iweiny-DESK2.sc.intel.com> References: <20190809225833.6657-1-ira.weiny@intel.com> <20190809225833.6657-17-ira.weiny@intel.com> <20190812130039.GD24457@ziepe.ca> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190812130039.GD24457@ziepe.ca> Sender: owner-linux-mm@kvack.org To: Jason Gunthorpe Cc: Andrew Morton , Dan Williams , Matthew Wilcox , Jan Kara , Theodore Ts'o , John Hubbard , Michal Hocko , Dave Chinner , linux-xfs@vger.kernel.org, linux-rdma@vger.kernel.org, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-nvdimm@lists.01.org, linux-ext4@vger.kernel.org, linux-mm@kvack.org List-ID: On Mon, Aug 12, 2019 at 10:00:40AM -0300, Jason Gunthorpe wrote: > On Fri, Aug 09, 2019 at 03:58:30PM -0700, ira.weiny@intel.com wrote: > > From: Ira Weiny > > > > In order for MRs to be tracked against the open verbs context the ufile > > needs to have a pointer to hand to the GUP code. > > > > No references need to be taken as this should be valid for the lifetime > > of the context. > > > > Signed-off-by: Ira Weiny > > drivers/infiniband/core/uverbs.h | 1 + > > drivers/infiniband/core/uverbs_main.c | 1 + > > 2 files changed, 2 insertions(+) > > > > diff --git a/drivers/infiniband/core/uverbs.h b/drivers/infiniband/core/uverbs.h > > index 1e5aeb39f774..e802ba8c67d6 100644 > > +++ b/drivers/infiniband/core/uverbs.h > > @@ -163,6 +163,7 @@ struct ib_uverbs_file { > > struct page *disassociate_page; > > > > struct xarray idr; > > + struct file *sys_file; /* backpointer to system file object */ > > }; > > The 'struct file' has a lifetime strictly shorter than the > ib_uverbs_file, which is kref'd on its own lifetime. Having a back > pointer like this is confouding as it will be invalid for some of the > lifetime of the struct. Ah... ok. I really thought it was the other way around. __fput() should not call ib_uverbs_close() until the last reference on struct file is released... What holds references to struct ib_uverbs_file past that? Perhaps I need to add this (untested)? diff --git a/drivers/infiniband/core/uverbs_main.c b/drivers/infiniband/core/uverbs_main.c index f628f9e4c09f..654e774d9cf2 100644 --- a/drivers/infiniband/core/uverbs_main.c +++ b/drivers/infiniband/core/uverbs_main.c @@ -1125,6 +1125,8 @@ static int ib_uverbs_close(struct inode *inode, struct file *filp) list_del_init(&file->list); mutex_unlock(&file->device->lists_mutex); + file->sys_file = NULL; + kref_put(&file->ref, ib_uverbs_release_file); return 0;