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From:   David Howells <dhowells@redhat.com>
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To:     Linus Torvalds <torvalds@linux-foundation.org>
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        Al Viro <viro@zeniv.linux.org.uk>, dray@redhat.com,
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        Christian Brauner <christian.brauner@ubuntu.com>,
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Subject: Re: [GIT PULL] General notification queue and key notifications
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Date:   Sat, 13 Jun 2020 14:04:52 +0100
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Linus Torvalds <torvalds@linux-foundation.org> wrote:

> I'm not even convinced O_NOTIFICATION_PIPE is necessary, but at worst
> it will be a useful marker. I think the only real reason for it was to
> avoid any clashes with splice(), which has more complex use of the
> pipe buffers.

The main reason is to prevent splice because the iov_iter rewind for splice
gets quite tricky if the kernel can randomly insert packets into the pipe
buffer in between what splice is inserting.

> I'm so far just reading this thread and the arguments for users, and I
> haven't yet looked at all the actual details in the pull request - but
> last time I had objections to things it wasn't the code, it was the
> lack of any use.

Would you be willing at this point to consider pulling the mount notifications
and fsinfo() which helps support that?  I could whip up pull reqs for those
two pieces - or do you want to see more concrete patches that use it?

David