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SubjectRe: [PATCH v3 14/15] fs/files: export close_fd() symbol
On Thu, Sep 07, 2017 at 03:42:25PM -0300, Gustavo Padovan wrote:
> From: Gustavo Padovan <gustavo.padovan@collabora.com>
>
> Rename __close_fd() to close_fd() and export it to be able close files
> in modules using file descriptors.
>
> The usecase that motivates this change happens in V4L2 where we send
> events to userspace with a fd that has file installed in it. But if for
> some reason we have to cancel the video stream we need to close the files
> that haven't been shared with userspace yet. Thus the export of
> close_fd() becomes necessary.
>
> fd_install() happens when we call an ioctl to queue a buffer, but we only
> share the fd with userspace later, and that may happen in a kernel thread
> instead.

NAK. As soon as the reference is in descriptor table, you *can't* do anything
to it. This "sharing" part is complete BS - being _told_ that descriptor is
there does not matter at all. That descriptor might be hit with dup2() as
soon as fd_install() has happened. Or be closed, or any number of other things.

You can not take it back. Once fd_install() is done, it's fucking done, period.
If V4L2 requires removing it from descriptor table, it's a shitty API and needs
to be fixed.

Again, NAK.

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