linux-kernel - Re: [fuse-devel] [PATCH 0/5] fuse: close file synchronously

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Message-ID: <51669CA6.7000007@parallels.com>
Date:	Thu, 11 Apr 2013 15:21:10 +0400
From:	"Maxim V. Patlasov" <mpatlasov@...allels.com>
To:	"miklos@...redi.hu" <miklos@...redi.hu>
CC:	<dev@...allels.com>, <xemul@...allels.com>,
	<fuse-devel@...ts.sourceforge.net>, <linux-kernel@...r.kernel.org>,
	<devel@...nvz.org>
Subject: Re: [fuse-devel] [PATCH 0/5] fuse: close file synchronously

Hi Miklos,

Any feedback would be highly appreciated.

Thanks,
Maxim

12/20/2012 04:30 PM, Maxim Patlasov пишет:
> Hi,
>
> There is a long-standing demand for syncronous behaviour of fuse_release:
>
> http://sourceforge.net/mailarchive/message.php?msg_id=19343889
> http://sourceforge.net/mailarchive/message.php?msg_id=29814693
>
> A few months ago Avati and me explained why such a feature would be useful:
>
> http://sourceforge.net/mailarchive/message.php?msg_id=29889055
> http://sourceforge.net/mailarchive/message.php?msg_id=29867423
>
> In short, the problem is that fuse_release (that's called on last user
> close(2)) sends FUSE_RELEASE to userspace and returns without waiting for
> ACK from userspace. Consequently, there is a gap when user regards the
> file released while userspace fuse is still working on it. An attempt to
> access the file from another node leads to complicated synchronization
> problems because the first node still "holds" the file.
>
> The patch-set resolves the problem by making fuse_release synchronous:
> wait for ACK from userspace for FUSE_RELEASE if the feature is ON.
>
> To keep single-threaded userspace implementations happy the patch-set
> ensures that by the time fuse_release_common calls fuse_file_put, no
> more in-flight I/O exists. Asynchronous fuse callbacks (like
> fuse_readpages_end) cannot trigger FUSE_RELEASE anymore. Hence, we'll
> never block in contexts other than close().
>
> Thanks,
> Maxim
>
> ---
>
> Maxim Patlasov (5):
>        fuse: add close_wait flag to fuse_conn
>        fuse: cosmetic rework of fuse_send_readpages
>        fuse: wait for end of IO on release
>        fuse: enable close_wait feature
>        fuse: fix synchronous case of fuse_file_put()
>
>
>   fs/fuse/file.c            |   82 ++++++++++++++++++++++++++++++++++++++-------
>   fs/fuse/fuse_i.h          |    3 ++
>   fs/fuse/inode.c           |    5 ++-
>   include/uapi/linux/fuse.h |    7 +++-
>   4 files changed, 82 insertions(+), 15 deletions(-)
>

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