On 07/05/2021 19:21, Kees Cook wrote: > On Fri, May 07, 2021 at 07:05:51PM +0100, Colin Ian King wrote: >> Hi, >> >> While doing some micro benchmarking with stress-ng I discovered that >> since linux 5.9 the splicing from /dev/zero to a pipe now fails with >> -EINVAL. >> >> I bisected this down to the following commit: >> >> 36e2c7421f02a22f71c9283e55fdb672a9eb58e7 is the first bad commit >> commit 36e2c7421f02a22f71c9283e55fdb672a9eb58e7 >> Author: Christoph Hellwig <hch@xxxxxx> >> Date: Thu Sep 3 16:22:34 2020 +0200 >> >> fs: don't allow splice read/write without explicit ops >> >> I'm not sure if this has been reported before, or if it's intentional >> behavior or not. As it stands, it's a regression in the stress-ng splice >> test case. > > The general loss of generic splice read/write is known. Here's some > early conversations I was involved in: > > https://lore.kernel.org/lkml/20200818200725.GA1081@xxxxxx/ > https://lore.kernel.org/lkml/202009181443.C2179FB@keescook/ > https://lore.kernel.org/lkml/20201005204517.2652730-1-keescook@xxxxxxxxxxxx/ > > And it's been getting re-implemented in individual places: > > $ git log --oneline --no-merges --grep 36e2c742 > 42984af09afc jffs2: Hook up splice_write callback > a35d8f016e0b nilfs2: make splice write available again > f8ad8187c3b5 fs/pipe: allow sendfile() to pipe again > f2d6c2708bd8 kernfs: wire up ->splice_read and ->splice_write > 9bb48c82aced tty: implement write_iter > dd78b0c483e3 tty: implement read_iter > 14e3e989f6a5 proc mountinfo: make splice available again > c1048828c3db orangefs: add splice file operations > 960f4f8a4e60 fs: 9p: add generic splice_write file operation > cf03f316ad20 fs: 9p: add generic splice_read file operations > 06a17bbe1d47 afs: Fix copy_file_range() Ah..so this explains why copy_file_range() also returns -EINVAL now on some file systems, such a minix since that uses splicing too via do_splice_direct(). :-/ > > So the question is likely, "do we want this for /dev/zero?" >
