From: Dave Chinner <david@fromorbit.com>
To: "Darrick J. Wong" <darrick.wong@oracle.com>
Cc: linux-xfs@vger.kernel.org
Subject: Re: [PATCH 10/27] libxfs: add kernel-compatible completion API
Date: Tue, 20 Oct 2020 09:21:31 +1100 [thread overview]
Message-ID: <20201019222131.GM7391@dread.disaster.area> (raw)
In-Reply-To: <20201015170917.GU9832@magnolia>
On Thu, Oct 15, 2020 at 10:09:17AM -0700, Darrick J. Wong wrote:
> On Thu, Oct 15, 2020 at 06:21:38PM +1100, Dave Chinner wrote:
> > From: Dave Chinner <dchinner@redhat.com>
> >
> > This is needed for the kernel buffer cache conversion to be able
> > to wait on IO synchrnously. It is implemented with pthread mutexes
> > and conditional variables.
> >
> > Signed-off-by: Dave Chinner <dchinner@redhat.com>
> > ---
> > include/Makefile | 1 +
> > include/completion.h | 61 ++++++++++++++++++++++++++++++++++++++++++++
> > include/libxfs.h | 1 +
> > libxfs/libxfs_priv.h | 1 +
> > 4 files changed, 64 insertions(+)
> > create mode 100644 include/completion.h
> >
> > diff --git a/include/Makefile b/include/Makefile
> > index f7c40a5ce1a1..98031e70fa0d 100644
> > --- a/include/Makefile
> > +++ b/include/Makefile
> > @@ -12,6 +12,7 @@ LIBHFILES = libxfs.h \
> > atomic.h \
> > bitops.h \
> > cache.h \
> > + completion.h \
> > hlist.h \
> > kmem.h \
> > list.h \
> > diff --git a/include/completion.h b/include/completion.h
> > new file mode 100644
> > index 000000000000..92194c3f1484
> > --- /dev/null
> > +++ b/include/completion.h
> > @@ -0,0 +1,61 @@
> > +// SPDX-License-Identifier: GPL-2.0
> > +/*
> > + * Copyright (c) 2019 RedHat, Inc.
> > + * All Rights Reserved.
> > + */
> > +#ifndef __LIBXFS_COMPLETION_H__
> > +#define __LIBXFS_COMPLETION_H__
> > +
> > +/*
> > + * This implements kernel compatible completion semantics. This is slightly
> > + * different to the way pthread conditional variables work in that completions
> > + * can be signalled before the waiter tries to wait on the variable. In the
> > + * pthread case, the completion is ignored and the waiter goes to sleep, whilst
> > + * the kernel will see that the completion has already been completed and so
> > + * will not block. This is handled through the addition of the the @signalled
> > + * flag in the struct completion.
>
> Hmm... do any of the existing pthread_cond_t users need these semantics?
No idea. I haven't done an audit, and that's outside the scope of
what I'm doing here...
> I suspect the ones in scrub/vfs.c might actually be vulnerable to the
> signal-before-wait race that this completion structure solves.
>
> In any case, seeing as this primitive isn't inherent to the xfs disk
> format, maybe these new concurrency management things belong in libfrog?
I've just mirrored all the other kernel wrapper headers by placing
them in include/. I don't see much point in moving these to libfrog,
because they have no actual built object code that needs to be
linked. i.e. they are included globally for everything via
libxfs/libxfs_priv.h and include/libxfs.h, and that's all that is
needed to use these APIs. If they get more complex and require
actual object files to be built, then it's time to reconsider...
Cheers,
Dave.
--
Dave Chinner
david@fromorbit.com
next prev parent reply other threads:[~2020-10-19 22:21 UTC|newest]
Thread overview: 49+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-10-15 7:21 [PATCH 00/27] [RFC, WIP] xfsprogs: xfs_buf unification and AIO Dave Chinner
2020-10-15 7:21 ` [PATCH 01/27] xfsprogs: remove unused buffer tracing code Dave Chinner
2020-10-15 7:21 ` [PATCH 02/27] xfsprogs: remove unused IO_DEBUG functionality Dave Chinner
2020-11-16 2:31 ` Eric Sandeen
2020-10-15 7:21 ` [PATCH 03/27] libxfs: get rid of b_bcount from xfs_buf Dave Chinner
2020-11-23 19:53 ` Eric Sandeen
2020-10-15 7:21 ` [PATCH 04/27] libxfs: rename buftarg->dev to btdev Dave Chinner
2020-11-16 2:33 ` Eric Sandeen
2020-10-15 7:21 ` [PATCH 05/27] xfsprogs: get rid of ancient btree tracing fragments Dave Chinner
2020-11-16 2:35 ` Eric Sandeen
2020-10-15 7:21 ` [PATCH 06/27] xfsprogs: remove xfs_buf_t typedef Dave Chinner
2020-10-15 15:22 ` Darrick J. Wong
2020-10-15 20:54 ` Dave Chinner
2020-10-15 7:21 ` [PATCH 07/27] xfsprogs: introduce liburcu support Dave Chinner
2020-10-15 7:21 ` [PATCH 08/27] libxfs: add spinlock_t wrapper Dave Chinner
2020-10-15 7:21 ` [PATCH 09/27] atomic: convert to uatomic Dave Chinner
2020-10-15 7:21 ` [PATCH 10/27] libxfs: add kernel-compatible completion API Dave Chinner
2020-10-15 17:09 ` Darrick J. Wong
2020-10-19 22:21 ` Dave Chinner [this message]
2020-10-15 7:21 ` [PATCH 11/27] libxfs: add wrappers for kernel semaphores Dave Chinner
2020-10-15 7:21 ` [PATCH 12/27] xfsprogs: convert use-once buffer reads to uncached IO Dave Chinner
2020-10-15 17:12 ` Darrick J. Wong
2020-10-19 22:36 ` Dave Chinner
2020-10-15 7:21 ` [PATCH 13/27] libxfs: introduce userspace buftarg infrastructure Dave Chinner
2020-10-15 7:21 ` [PATCH 14/27] xfs: rename libxfs_buftarg_init to libxfs_open_devices() Dave Chinner
2020-10-15 7:21 ` [PATCH 15/27] libxfs: introduce userspace buftarg infrastructure Dave Chinner
2020-10-15 17:16 ` Darrick J. Wong
2020-10-15 7:21 ` [PATCH 16/27] libxfs: add a synchronous IO engine to the buftarg Dave Chinner
2020-10-15 7:21 ` [PATCH 17/27] xfsprogs: convert libxfs_readbufr to libxfs_buf_read_uncached Dave Chinner
2020-10-15 7:21 ` [PATCH 18/27] libxfs: convert libxfs_bwrite to buftarg IO Dave Chinner
2020-10-15 7:21 ` [PATCH 19/27] libxfs: add cache infrastructure to buftarg Dave Chinner
2020-10-15 7:21 ` [PATCH 20/27] libxfs: add internal lru to btcache Dave Chinner
2020-10-15 7:21 ` [PATCH 21/27] libxfs: Add kernel list_lru wrapper Dave Chinner
2020-10-15 7:21 ` [PATCH 22/27] libxfs: introduce new buffer cache infrastructure Dave Chinner
2020-10-15 17:46 ` Darrick J. Wong
2020-10-15 7:21 ` [PATCH 23/27] libxfs: use PSI information to detect memory pressure Dave Chinner
2020-10-15 17:56 ` Darrick J. Wong
2020-10-15 21:20 ` Dave Chinner
2020-10-15 7:21 ` [PATCH 24/27] libxfs: add a buftarg cache shrinker implementation Dave Chinner
2020-10-15 18:01 ` Darrick J. Wong
2020-10-15 21:33 ` Dave Chinner
2020-10-15 7:21 ` [PATCH 25/27] libxfs: switch buffer cache implementations Dave Chinner
2020-10-15 7:21 ` [PATCH 26/27] build: set platform_defs.h.in dependency correctly Dave Chinner
2020-10-15 7:21 ` [PATCH 27/27] libxfs: convert sync IO buftarg engine to AIO Dave Chinner
2020-10-15 18:26 ` Darrick J. Wong
2020-10-15 21:42 ` Dave Chinner
2020-10-15 7:29 ` [PATCH 00/27] [RFC, WIP] xfsprogs: xfs_buf unification and AIO Dave Chinner
2020-10-15 18:37 ` Darrick J. Wong
2020-10-15 22:35 ` Dave Chinner
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