Messages in this thread | | | Date | Tue, 27 Oct 2020 07:48:32 +0100 | From | Greg KH <> | Subject | problems with splice from /proc (was Linux 5.10-rc1) |
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On Sun, Oct 25, 2020 at 03:40:27PM -0700, Linus Torvalds wrote: > The most interesting - to me - change here is Christoph's setf_fs() > removal (it got merged through Al Viro, as you can see in my mergelog > below). It's not a _huge_ change, but it's interesting because the > whole model of set_fs() to specify whether a userspace copy actually > goes to user space or kernel space goes back to pretty much the > original release of Linux, and while the name is entirely historic (it > hasn't used the %fs segment register in a long time), the concept has > remained. Until now.
I told Al this yesterday, but figured I would mention it here for others to see.
Commit 36e2c7421f02 ("fs: don't allow splice read/write without explicit ops") from this patch series, is breaking the bionic test suite that does the following to verify that splice is working:
int in = open("/proc/cpuinfo", O_RDONLY); ASSERT_NE(in, -1);
TemporaryFile tf; ssize_t bytes_read = splice(in, nullptr, pipe_fds[1], nullptr, 8*1024, SPLICE_F_MORE | SPLICE_F_MOVE); ASSERT_NE(bytes_read, -1);
Before this change, all works well but now splice fails on /proc files (and I'm guessing other virtual filesystems).
I'll ask the bionic developers if they can change their test to some other file, but this is a regression and might show up in other "test platforms" as well. Using /proc for this is just so simple because these files are "always there" and don't require any housekeeping for test suites to worry about .
thanks,
greg k-h
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