From: Al Viro <viro@ZenIV.linux.org.uk>
To: Jens Axboe <axboe@kernel.dk>
Cc: linux-fsdevel@vger.kernel.org,
Nicholas Piggin <npiggin@gmail.com>,
Miklos Szeredi <mszeredi@redhat.com>
Subject: [RFC] vmsplice() and ->steal()
Date: Sat, 10 Dec 2016 02:38:49 +0000 [thread overview]
Message-ID: <20161210023849.GH1555@ZenIV.linux.org.uk> (raw)
vmsplice() generates pipe_bufs with ->steal() set to
user_page_pipe_buf_steal(). What should happen when the source pages
had code from an mmapped area and why shouldn't their ->steal()
do what page_cache_pipe_buf_release() does in that case?
As it is, e.g. fuse_dev_splice_write() getting fed that stuff could,
AFAICS, clear MappedToDisk on such a page, scream about weird pages
(upon noticing non-NULL ->mapping) and fall back to copying (thankfully).
We don't have that many ->steal() users (as the matter of fact, I've
discovered that while trying to debug the breakage in one I'd been
trying to add), but I really wonder about the intended semantics of
->steal().
Comments?
next reply other threads:[~2016-12-10 2:38 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-12-10 2:38 Al Viro [this message]
2016-12-10 3:03 ` [RFC] vmsplice() and ->steal() Al Viro
2016-12-10 5:28 ` Nicholas Piggin
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