On Mon, Mar 23, 2015 at 5:36 PM, Xie, Huawei <huawei.xie at intel.com> wrote:
> On 3/23/2015 11:27 PM, Pavel Boldin wrote: > > > On Mon, Mar 23, 2015 at 5:16 PM, Xie, Huawei <huawei.xie at intel.com<mailto: > huawei.xie at intel.com>> wrote: > On 3/23/2015 10:52 PM, Pavel Boldin wrote: > > > On Mon, Mar 23, 2015 at 4:41 PM, Xie, Huawei <huawei.xie at intel.com<mailto: > huawei.xie at intel.com><mailto:huawei.xie at intel.com<mailto: > huawei.xie at intel.com>>> wrote: > On 3/23/2015 10:37 PM, Pavel Boldin wrote: > > > On Mon, Mar 23, 2015 at 4:21 PM, Xie, Huawei <huawei.xie at intel.com<mailto: > huawei.xie at intel.com><mailto:huawei.xie at intel.com<mailto: > huawei.xie at intel.com>><mailto:huawei.xie at intel.com<mailto: > huawei.xie at intel.com><mailto:huawei.xie at intel.com<mailto: > huawei.xie at intel.com>>>> wrote: > On 3/23/2015 8:54 PM, Pavel Boldin wrote: > > Due to increased `struct file's reference counter subsequent call > > to `filp_close' does not free the `struct file'. Prepend `fput' call > > to decrease the reference counter. > > > > Signed-off-by: Pavel Boldin <pboldin at mirantis.com<mailto: > pboldin at mirantis.com><mailto:pboldin at mirantis.com<mailto: > pboldin at mirantis.com>><mailto:pboldin at mirantis.com<mailto: > pboldin at mirantis.com><mailto:pboldin at mirantis.com<mailto: > pboldin at mirantis.com>>>> > > --- > > lib/librte_vhost/eventfd_link/eventfd_link.c | 1 + > > 1 file changed, 1 insertion(+) > > > > diff --git a/lib/librte_vhost/eventfd_link/eventfd_link.c > b/lib/librte_vhost/eventfd_link/eventfd_link.c > > index 7755dd6..62c45c8 100644 > > --- a/lib/librte_vhost/eventfd_link/eventfd_link.c > > +++ b/lib/librte_vhost/eventfd_link/eventfd_link.c > > @@ -117,6 +117,7 @@ eventfd_link_ioctl(struct file *f, unsigned int > ioctl, unsigned long arg) > > * Release the existing eventfd in the source process > > */ > > spin_lock(&files->file_lock); > > + fput(file); > Could we just call atomic_long_dec here? > > We can but I don't like breaking encapsulation (which is broken anyway by > the code). So, there is a special method and we should use it in my opinion. > it is increased by atomic_long_inc_not_zero so why don't we use the > symmetric function? > The code with `atomic_long_inc_not_zero' call is a copy-paste of the > `fget' function. If we want to make it clear we should make a separate > function and name it so: `fget_from_files'. > > I don't understand why there is a (exact?) copy&paste of fget there. :). > Maybe you could post a patchset, first replace the copy/paste with fget > and then this patch. It will looks much clearer. > The code of this module received little to none review and requires some > love at the moment. > > I wanted to refactor the module completely but Thomas said it is not going > to go into the 2.0. So I decided to make a simple one-line fix. > Another isse is do we really need a src fd here? Could we just allocate a > unsed fd in the kernel and installed it with the target eventfd. > This is for DPDK team to decide and should be discussed separately. Pavel > > If you are interested this [0] is the latest version of the refactoring > patch. > > I can provide you with an application that checks that there is indeed no > leakage and ensures that the `eventfd' moving works. It is being used in > our builds as a test [1]. The code is "heredoc"ed in [2] > > [0] http://dpdk.org/dev/patchwork/patch/4113/ > [1] https://review.fuel-infra.org/#/c/4639/ > [2] https://review.fuel-infra.org/#/c/4639/3/tests/runtests.sh > > Pavel > > Second thing is: another thread of the same processor can call the > `sys_close' on the `fd' and this will dereference counter so `fput' will > correctly free the `struct file'. Using `atomic_long_dec' will leak a > `struct file' and print a KERN_ERR message by `filp_close'. > > So, the common thing is to use appropriate functions and don't reinvent > the wheel. > > Pavel > > > > Pavel > > > filp_close(file, files); > > fdt = files_fdtable(files); > > fdt->fd[eventfd_copy.source_fd] = NULL; > > > > > > > >
