linux-kernel - [RFC][PATCH 0/4] No I/O from mntput

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Message-ID: <87y4z8uzqw.fsf_-_@x220.int.ebiederm.org>
Date:	Mon, 14 Apr 2014 00:38:47 -0700
From:	ebiederm@...ssion.com (Eric W. Biederman)
To:	Al Viro <viro@...IV.linux.org.uk>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	"Serge E. Hallyn" <serge@...lyn.com>,
	Linux-Fsdevel <linux-fsdevel@...r.kernel.org>,
	Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Andy Lutomirski <luto@...capital.net>,
	Rob Landley <rob@...dley.net>,
	Miklos Szeredi <miklos@...redi.hu>,
	Christoph Hellwig <hch@...radead.org>,
	Karel Zak <kzak@...hat.com>,
	"J. Bruce Fields" <bfields@...ldses.org>,
	Fengguang Wu <fengguang.wu@...el.com>, tytso@....edu
Subject: [RFC][PATCH 0/4] No I/O from mntput

There are a lot of ways we could approach this, and I sat down and wrote
the simplest variant I could think of, so hopefully there are not silly
bugs that get overlooked.

The code move all cleanup from mntput that would do filesystem I/O into
work queues.

The code waits in mntput for that I/O to complete if we wait today.

The code has been tested and it works, and it succeeds in running
deactivate_super in a stack from with just short of 7500 bytes free.
7500 bytes should be enough for anybody!

I want to double check that I am using work queues correctly, they used
to be deadlock prone, and sleep on everything before I commit to a final
version but this version is probably good enough.

I may be going overboard in the case where we auto close BSD accounting
files, but at this point I figure better safe than sorry. 

Eric W. Biederman (4):
      vfs: Remove useless loop in mntput_no_expire
      vfs: Move autoclose of BSD accounting into a work queue
      vfs: In mntput run deactivate_super on a shallow stack.
      vfs: Block intuitively in the case of BSD accounting files

 fs/mount.h     | 14 +++++++++++---
 fs/namespace.c | 43 +++++++++++++++++++++++++++++++++++--------
 kernel/acct.c  | 25 ++++++++++++++++++++-----
 3 files changed, 66 insertions(+), 16 deletions(-)

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