On Sat, May 20, 2023 at 03:03:48PM +0200, Christian Brauner wrote:
> On Sat, Apr 29, 2023 at 05:49:54AM +0000, aloktiagi wrote:
> > Introduce a mechanism to replace a file linked in the epoll interface with a new
> > file.
> >
> > eventpoll_replace() finds all instances of the file to be replaced and replaces
> > them with the new file and the interested events.
> >
> > Signed-off-by: aloktiagi <aloktiagi@xxxxxxxxx>
> > ---
> > Changes in v5:
> > - address review comments and move the call to replace old file in each
> > subsystem (epoll, io_uring, etc.) outside the fdtable helpers like
> > replace_fd().
> >
> > Changes in v4:
> > - address review comment to remove the redundant eventpoll_replace() function.
> > - removed an extra empty line introduced in include/linux/file.h
> >
> > Changes in v3:
> > - address review comment and iterate over the file table while holding the
> > spin_lock(&files->file_lock).
> > - address review comment and call filp_close() outside the
> > spin_lock(&files->file_lock).
> > ---
> > fs/eventpoll.c | 65 +++++++++++++++++++++++++++++++++++++++
> > include/linux/eventpoll.h | 8 +++++
> > 2 files changed, 73 insertions(+)
> >
> > diff --git a/fs/eventpoll.c b/fs/eventpoll.c
> > index 64659b110973..be9d192b223d 100644
> > --- a/fs/eventpoll.c
> > +++ b/fs/eventpoll.c
> > @@ -935,6 +935,71 @@ void eventpoll_release_file(struct file *file)
> > mutex_unlock(&epmutex);
> > }
> >
> > +static int ep_insert(struct eventpoll *ep, const struct epoll_event *event,
> > + struct file *tfile, int fd, int full_check);
> > +
> > +/*
> > + * This is called from eventpoll_replace() to replace a linked file in the epoll
> > + * interface with a new file received from another process. This is useful in
> > + * cases where a process is trying to install a new file for an existing one
> > + * that is linked in the epoll interface
> > + */
> > +int eventpoll_replace_file(struct file *toreplace, struct file *file, int tfd)
> > +{
> > + int fd;
> > + int error = 0;
> > + struct eventpoll *ep;
> > + struct epitem *epi;
> > + struct hlist_node *next;
> > + struct epoll_event event;
> > + struct hlist_head *to_remove = toreplace->f_ep;
> > +
> > + if (!file_can_poll(file))
> > + return 0;
> > +
> > + mutex_lock(&epmutex);
>
> Sorry, I missed that you send a new version somehow.
>
> So, I think I mentioned this last time: The locking has changed to
> reduce contention on the global mutex. Both epmutex and ep_remove() are
> gone. So this doesn't even compile anymore...
>
> CC fs/eventpoll.o
> ../fs/eventpoll.c: In function ‘eventpoll_replace_file’:
> ../fs/eventpoll.c:998:21: error: ‘epmutex’ undeclared (first use in this function); did you mean ‘mutex’?
> 998 | mutex_lock(&epmutex);
> | ^~~~~~~
> | mutex
> ../fs/eventpoll.c:998:21: note: each undeclared identifier is reported only once for each function it appears in
> ../fs/eventpoll.c:1034:17: error: implicit declaration of function ‘ep_remove’; did you mean ‘idr_remove’? [-Werror=implicit-function-declaration]
> 1034 | ep_remove(ep, epi);
> | ^~~~~~~~~
> | idr_remove
>
> on current mainline. So please send a new version for this.
Apologies, I didn't realize the change had been merged. Will send out a new version.
