From: Al Viro <viro@ZenIV.linux.org.uk>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Dave Chinner <david@fromorbit.com>, CAI Qian <caiqian@redhat.com>,
linux-xfs <linux-xfs@vger.kernel.org>,
xfs@oss.sgi.com, Jens Axboe <axboe@kernel.dk>,
Nick Piggin <npiggin@gmail.com>,
linux-fsdevel@vger.kernel.org
Subject: [RFC][CFT] splice_read reworked
Date: Fri, 23 Sep 2016 20:00:32 +0100 [thread overview]
Message-ID: <20160923190032.GA25771@ZenIV.linux.org.uk> (raw)
In-Reply-To: <20160917190023.GA8039@ZenIV.linux.org.uk>
The series is supposed to solve the locking order problems for
->splice_read() and get rid of code duplication between the read-side
methods.
pipe_lock is lifted out of ->splice_read() instances, along with
waiting for empty space in pipe, etc. - we do that stuff in callers.
A new variant of iov_iter is introduced - it's backed by a pipe,
copy_to_iter() results in allocating pages and copying into those,
copy_page_to_iter() just sticks a reference to that page into pipe.
Running out of space in pipe yields a short read, as a fault in iovec-backed
iov_iter would have. Enough primitives are implemented for normal
->read_iter() instances to work.
generic_file_splice_read() switched to feeding such iov_iter to
->read_iter() instance. That turns out to be enough to kill almost all
->splice_read() instances; the only ones _not_ using generic_file_splice_read()
or default_file_splice_read() (== no zero-copy fallback) are
fuse_dev_splice_read(), 3 instances in kernel/{relay.c,trace/trace.c} and
sock_splice_read(). It's almost certainly possible to convert fuse one
and the same might be possible to do to socket one. relay and tracing
stuff is just plain weird; might or might not be doable.
Something hopefully working is in
git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs.git #work.splice_read
Several commits in that pipe (#1, #8 and #9) are trivial cleanups and fixes
for crap caught while doing the rest, probably ought to be separated.
Shortlog:
Al Viro (11):
fix memory leaks in tracing_buffers_splice_read()
splice_to_pipe(): don't open-code wakeup_pipe_readers()
splice: switch get_iovec_page_array() to iov_iter
splice: lift pipe_lock out of splice_to_pipe()
skb_splice_bits(): get rid of callback
new helper: add_to_pipe()
fuse_dev_splice_read(): switch to add_to_pipe()
cifs: don't use memcpy() to copy struct iov_iter
fuse_ioctl_copy_user(): don't open-code copy_page_{to,from}_iter()
new iov_iter flavour: pipe-backed
switch generic_file_splice_read() to use of ->read_iter()
Diffstat:
drivers/staging/lustre/lustre/llite/file.c | 70 +--
.../staging/lustre/lustre/llite/llite_internal.h | 15 +-
drivers/staging/lustre/lustre/llite/vvp_internal.h | 14 -
drivers/staging/lustre/lustre/llite/vvp_io.c | 45 +-
fs/cifs/file.c | 14 +-
fs/coda/file.c | 23 +-
fs/fuse/dev.c | 48 +-
fs/fuse/file.c | 30 +-
fs/gfs2/file.c | 28 +-
fs/nfs/file.c | 25 +-
fs/nfs/internal.h | 2 -
fs/nfs/nfs4file.c | 2 +-
fs/ocfs2/file.c | 34 +-
fs/ocfs2/ocfs2_trace.h | 2 -
fs/splice.c | 578 +++++++--------------
fs/xfs/xfs_file.c | 41 +-
fs/xfs/xfs_trace.h | 1 -
include/linux/fs.h | 2 -
include/linux/skbuff.h | 8 +-
include/linux/splice.h | 3 +
include/linux/uio.h | 14 +-
kernel/trace/trace.c | 14 +-
lib/iov_iter.c | 390 +++++++++++++-
mm/shmem.c | 115 +---
net/core/skbuff.c | 28 +-
net/ipv4/tcp.c | 3 +-
net/kcm/kcmsock.c | 16 +-
net/unix/af_unix.c | 17 +-
28 files changed, 648 insertions(+), 934 deletions(-)
It's not all I would like to do there (in particular, I hadn't
done fuse splice_read conversion to read_iter, even though it does appear
to be doable; that'll take copy_page_to_iter_nosteal() as a new primitive
+ considerable amount of massage in fs/fuse/dev.c), but it should at least
* make pipe lock the outermost
* switch generic_file_splice_read() to ->read_iter(), making
it suitable for lustre/coda/gfs2/ocfs2/xfs/shmem without any wrappers
* somewhat simplify socket ->splice_read() guts (not by much - to
start doing that right we'd need the same new primitive)
* remove a considerable pile of code.
* get rid of a bunch of splice_{grow,shrink}_spd/splice_to_pipe
callers; remaining ones are in default_file_splice_read() (trivially
killable by conversion to iov_iter_get_pages_alloc(), followed by the same
build iovec array + use kernel_readv as we do now + iov_iter_advance to
the length returned by kernel_readv), kernel/relay and kernel/trace/trace.c
ones (should switch to add_to_pipe(), AFAICS) and skb_splice_bits()
(again, a matter of copy_page_to_iter_nosteal(), which will take out
spd_can_coalesce/spd_fill_page in there as well). Once the remaining ones
are taken care of, splice_pipe_desc and friends will go away.
In its current form it survives LTP, xfstests and overlayfs testsuite;
if anybody has additional tests for splice and friends, I would like to hear
about such. It really needs more beating, though.
Please, help with review and testing.
next prev parent reply other threads:[~2016-09-23 19:00 UTC|newest]
Thread overview: 104+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20160908235521.GL2356@ZenIV.linux.org.uk>
[not found] ` <20160909015324.GD30056@dastard>
[not found] ` <CA+55aFzohsUXj_3BeFNr2t50Wm=G+7toRDEz=Tk7VJqP3n1hXQ@mail.gmail.com>
[not found] ` <CA+55aFxrqCng2Qxasc9pyMrKUGFjo==fEaFT1vkH9Lncte3RgQ@mail.gmail.com>
[not found] ` <20160909023452.GO2356@ZenIV.linux.org.uk>
[not found] ` <CA+55aFwHQMjO4-vtfB9-ytc=o+DRo-HXVGckvXLboUxgpwb7_g@mail.gmail.com>
[not found] ` <20160909221945.GQ2356@ZenIV.linux.org.uk>
[not found] ` <CA+55aFzTOOB6oEVaaGD0N7Uznk-W9+ULPwzsxS_L_oZqGVSeLA@mail.gmail.com>
[not found] ` <20160914031648.GB2356@ZenIV.linux.org.uk>
[not found] ` <20160914133925.2fba4629@roar.ozlabs.ibm.com>
2016-09-18 5:33 ` xfs_file_splice_read: possible circular locking dependency detected Al Viro
2016-09-19 3:08 ` Nicholas Piggin
2016-09-19 6:11 ` Al Viro
2016-09-19 7:26 ` Nicholas Piggin
[not found] ` <CA+55aFznQaOWoSMNphgGJJWZ=8-odrc0DAUMzfGPQe+_N4UgNA@mail.gmail.com>
[not found] ` <20160914042559.GC2356@ZenIV.linux.org.uk>
[not found] ` <20160917082007.GA6489@ZenIV.linux.org.uk>
[not found] ` <20160917190023.GA8039@ZenIV.linux.org.uk>
2016-09-18 19:31 ` skb_splice_bits() and large chunks in pipe (was " Al Viro
2016-09-18 20:12 ` Linus Torvalds
2016-09-18 22:31 ` Al Viro
2016-09-19 0:18 ` Linus Torvalds
2016-09-19 0:22 ` Al Viro
2016-09-20 9:51 ` Herbert Xu
2016-09-23 19:00 ` Al Viro [this message]
2016-09-23 19:01 ` [PATCH 01/11] fix memory leaks in tracing_buffers_splice_read() Al Viro
2016-09-23 19:02 ` [PATCH 02/11] splice_to_pipe(): don't open-code wakeup_pipe_readers() Al Viro
2016-09-23 19:02 ` [PATCH 03/11] splice: switch get_iovec_page_array() to iov_iter Al Viro
2016-09-23 19:03 ` [PATCH 04/11] splice: lift pipe_lock out of splice_to_pipe() Al Viro
2016-09-23 19:45 ` Linus Torvalds
2016-09-23 20:10 ` Al Viro
2016-09-23 20:36 ` Linus Torvalds
2016-09-24 3:59 ` Al Viro
2016-09-24 17:29 ` Al Viro
2016-09-27 15:38 ` Nicholas Piggin
2016-09-27 15:53 ` Chuck Lever
2016-09-24 3:59 ` [PATCH 04/12] " Al Viro
2016-09-26 13:35 ` Miklos Szeredi
2016-09-27 4:14 ` Al Viro
2016-12-17 19:54 ` Andreas Schwab
2016-12-18 19:28 ` Linus Torvalds
2016-12-18 19:57 ` Andreas Schwab
2016-12-18 20:12 ` Al Viro
2016-12-18 20:30 ` Al Viro
2016-12-18 22:10 ` Linus Torvalds
2016-12-18 22:18 ` Al Viro
2016-12-18 22:22 ` Linus Torvalds
2016-12-18 22:49 ` Andreas Schwab
2016-12-21 18:56 ` Andreas Schwab
2016-12-21 19:12 ` Linus Torvalds
2016-09-24 4:00 ` [PATCH 06/12] new helper: add_to_pipe() Al Viro
2016-09-26 13:49 ` Miklos Szeredi
2016-09-24 4:01 ` [PATCH 10/12] new iov_iter flavour: pipe-backed Al Viro
2016-09-29 20:53 ` Miklos Szeredi
2016-09-29 22:50 ` Al Viro
2016-09-30 7:30 ` Miklos Szeredi
2016-10-03 3:34 ` [RFC] O_DIRECT vs EFAULT (was Re: [PATCH 10/12] new iov_iter flavour: pipe-backed) Al Viro
2016-10-03 17:07 ` Linus Torvalds
2016-10-03 18:54 ` Al Viro
2016-09-24 4:01 ` [PATCH 11/12] switch generic_file_splice_read() to use of ->read_iter() Al Viro
2016-09-24 4:02 ` [PATCH 12/12] switch default_file_splice_read() to use of pipe-backed iov_iter Al Viro
2016-09-23 19:03 ` [PATCH 05/11] skb_splice_bits(): get rid of callback Al Viro
2016-09-23 19:04 ` [PATCH 06/11] new helper: add_to_pipe() Al Viro
2016-09-23 19:04 ` [PATCH 07/11] fuse_dev_splice_read(): switch to add_to_pipe() Al Viro
2016-09-23 19:06 ` [PATCH 08/11] cifs: don't use memcpy() to copy struct iov_iter Al Viro
2016-09-23 19:08 ` [PATCH 09/11] fuse_ioctl_copy_user(): don't open-code copy_page_{to,from}_iter() Al Viro
2016-09-26 9:31 ` Miklos Szeredi
2016-09-23 19:09 ` [PATCH 10/11] new iov_iter flavour: pipe-backed Al Viro
2016-09-23 19:10 ` [PATCH 11/11] switch generic_file_splice_read() to use of ->read_iter() Al Viro
2016-09-30 13:32 ` [RFC][CFT] splice_read reworked CAI Qian
2016-09-30 17:42 ` CAI Qian
2016-09-30 18:33 ` CAI Qian
2016-10-03 1:37 ` Al Viro
2016-10-03 17:49 ` CAI Qian
2016-10-04 17:39 ` local DoS - systemd hang or timeout (WAS: Re: [RFC][CFT] splice_read reworked) CAI Qian
2016-10-04 21:42 ` tj
2016-10-05 14:09 ` CAI Qian
2016-10-05 15:30 ` tj
2016-10-05 15:54 ` CAI Qian
2016-10-05 18:57 ` CAI Qian
2016-10-05 20:05 ` Al Viro
2016-10-06 12:20 ` CAI Qian
2016-10-06 12:25 ` CAI Qian
2016-10-06 16:11 ` CAI Qian
2016-10-06 17:00 ` Linus Torvalds
2016-10-06 18:12 ` CAI Qian
2016-10-07 9:57 ` Dave Chinner
2016-10-07 15:25 ` Linus Torvalds
2016-10-07 7:08 ` Jan Kara
2016-10-07 14:43 ` CAI Qian
2016-10-07 15:27 ` CAI Qian
2016-10-07 18:56 ` CAI Qian
2016-10-09 21:54 ` Dave Chinner
2016-10-10 14:10 ` CAI Qian
2016-10-10 20:14 ` CAI Qian
2016-10-10 21:57 ` Dave Chinner
2016-10-12 19:50 ` [bisected] " CAI Qian
2016-10-12 20:59 ` Dave Chinner
2016-10-13 16:25 ` CAI Qian
2016-10-13 20:49 ` Dave Chinner
2016-10-13 20:56 ` CAI Qian
2016-10-09 21:51 ` Dave Chinner
2016-10-21 15:38 ` [4.9-rc1+] overlayfs lockdep CAI Qian
2016-10-24 12:57 ` Miklos Szeredi
2016-10-07 9:27 ` local DoS - systemd hang or timeout (WAS: Re: [RFC][CFT] splice_read reworked) Dave Chinner
2016-10-03 1:42 ` [RFC][CFT] splice_read reworked Al Viro
2016-10-03 14:06 ` CAI Qian
2016-10-03 15:20 ` CAI Qian
2016-10-03 21:12 ` Dave Chinner
2016-10-04 13:57 ` CAI Qian
2016-10-03 20:32 ` CAI Qian
2016-10-03 20:35 ` Al Viro
2016-10-04 13:29 ` CAI Qian
2016-10-04 14:28 ` Al Viro
2016-10-04 16:21 ` CAI Qian
2016-10-04 20:12 ` Al Viro
2016-10-05 14:30 ` CAI Qian
2016-10-05 16:07 ` Al Viro
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