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From: Al Viro <viro@zeniv.linux.org.uk>
To: Steven Rostedt <rostedt@goodmis.org>
Cc: Greg KH <gregkh@linuxfoundation.org>,
	yu kuai <yukuai3@huawei.com>,
	rafael@kernel.org, oleg@redhat.com, mchehab+samsung@kernel.org,
	corbet@lwn.net, tytso@mit.edu, jmorris@namei.org,
	linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org,
	zhengbin13@huawei.com, yi.zhang@huawei.com,
	chenxiang66@hisilicon.com, xiexiuqi@huawei.com
Subject: Re: [PATCH 1/3] dcache: add a new enum type for 'dentry_d_lock_class'
Date: Fri, 15 Nov 2019 13:48:23 +0000	[thread overview]
Message-ID: <20191115134823.GQ26530@ZenIV.linux.org.uk> (raw)
In-Reply-To: <20191115083813.65f5523c@gandalf.local.home>

On Fri, Nov 15, 2019 at 08:38:13AM -0500, Steven Rostedt wrote:
> On Fri, 15 Nov 2019 13:16:25 +0000
> Al Viro <viro@zeniv.linux.org.uk> wrote:
> 
> > I want to understand the overall situation.  No argument, list_empty()
> > in there is BS, for many reasons.  But I wonder if trying to keep the
> > current structure of the iterator _and_ the use of simple_rmdir()/simple_unlink()
> > is the right approach.
> 
> My guess is that debugfs was written to be as simple as possible.
> Nothing too complex. And in doing so, may have issues as you are
> pointing out. Just a way to allow communications between user space and
> kernel space (as tracefs started out).
> 
> BTW, what do you mean by "can debugfs_remove_recursive() rely upon the
> lack of attempts to create new entries inside the subtree it's trying
> to kill?"

Is it possible for something to call e.g. debugfs_create_dir() (or any
similar primitive) with parent inside the subtree that has been
passed to debugfs_remove_recursive() call that is still in progress?

If debugfs needs to cope with that, debugfs_remove_recursive() needs
considerably heavier locking, to start with.

  parent reply	other threads:[~2019-11-15 13:49 UTC|newest]

Thread overview: 24+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-11-15  3:27 [PATCH 0/3] fix potential infinite loop in debugfs_remove_recursive yu kuai
2019-11-15  3:27 ` [PATCH 1/3] dcache: add a new enum type for 'dentry_d_lock_class' yu kuai
2019-11-15  3:27   ` Greg KH
2019-11-15  4:12     ` Al Viro
2019-11-15  7:20       ` Greg KH
2019-11-15 10:08         ` yukuai (C)
2019-11-15 13:16         ` Al Viro
2019-11-15 13:38           ` Steven Rostedt
2019-11-15 13:39             ` Steven Rostedt
2019-11-15 13:48             ` Al Viro [this message]
2019-11-15 13:58               ` Steven Rostedt
2019-11-15 14:17                 ` Al Viro
2019-11-15 17:54                   ` Al Viro
2019-11-15 18:42                     ` [RFC] simple_recursive_removal() Al Viro
2019-11-15 19:41                       ` Al Viro
2019-11-15 21:18                         ` Al Viro
2019-11-15 21:26                           ` Steven Rostedt
2019-11-15 22:10                             ` Al Viro
2019-11-16 12:04                               ` Greg KH
2019-11-17 22:24                               ` Al Viro
2019-11-18  6:37                                 ` Greg KH
2019-11-15 10:02     ` [PATCH 1/3] dcache: add a new enum type for 'dentry_d_lock_class' yukuai (C)
2019-11-15  3:27 ` [PATCH 2/3] fs/libfs.c: use 'spin_lock_nested' when taking 'd_lock' for dentry in simple_empty yu kuai
2019-11-15  3:27 ` [PATCH 3/3] debugfs: fix potential infinite loop in debugfs_remove_recursive yu kuai

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