From: Al Viro <viro@ZenIV.linux.org.uk>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: John Ogness <john.ogness@linutronix.de>,
linux-fsdevel <linux-fsdevel@vger.kernel.org>,
Christoph Hellwig <hch@lst.de>,
Thomas Gleixner <tglx@linutronix.de>,
Peter Zijlstra <peterz@infradead.org>,
Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 4/4] fs/dcache: Avoid the try_lock loops in dentry_kill()
Date: Thu, 22 Feb 2018 05:40:44 +0000 [thread overview]
Message-ID: <20180222054044.GN30522@ZenIV.linux.org.uk> (raw)
In-Reply-To: <CA+55aFyo6jrvU62DiwKJZaTnmwLYQe4krNJCbAUui8R+=bDVdQ@mail.gmail.com>
On Fri, Feb 16, 2018 at 10:03:15AM -0800, Linus Torvalds wrote:
> On Fri, Feb 16, 2018 at 7:09 AM, John Ogness <john.ogness@linutronix.de> wrote:
> > dentry_kill() holds dentry->d_lock and needs to acquire both
> > dentry->d_inode->i_lock and dentry->d_parent->d_lock. This cannot be
> > done with spin_lock() operations because it's the reverse of the
> > regular lock order. To avoid ABBA deadlocks it is done with two
> > trylock loops.
> >
> > Trylock loops are problematic in two scenarios:
>
> I don't mind this patch series per se (although I would really like Al
> to ack it), but this particular patch I hate.
I'm not happy about the previous patch either. Why do we need the users
of that thing to deal with retries? And I'm not even sure we want to
bother with retries on inode change inside dentry_kill() itself - just
unlock, return dentry and let the caller handle that. Callers *must*
handle "need to drop another one" anyway, so...
prev parent reply other threads:[~2018-02-22 5:40 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-02-16 15:09 [PATCH 0/4] fs/dcache: avoid trylock loops John Ogness
2018-02-16 15:09 ` [PATCH 1/4] fs/dcache: Remove stale comment from dentry_kill() John Ogness
2018-02-16 15:09 ` [PATCH 2/4] fs/dcache: Move dentry_kill() below lock_parent() John Ogness
2018-02-16 15:09 ` [PATCH 3/4] fs/dcache: Avoid the try_lock loop in d_delete() John Ogness
2018-02-16 17:10 ` Peter Zijlstra
2018-02-16 17:30 ` Peter Zijlstra
2018-02-22 5:18 ` Al Viro
2018-02-22 8:35 ` John Ogness
2018-02-16 15:09 ` [PATCH 4/4] fs/dcache: Avoid the try_lock loops in dentry_kill() John Ogness
2018-02-16 18:03 ` Linus Torvalds
2018-02-16 22:32 ` John Ogness
2018-02-16 22:42 ` Linus Torvalds
2018-02-16 23:05 ` John Ogness
2018-02-16 23:31 ` Linus Torvalds
2018-02-16 23:49 ` John Ogness
2018-02-17 0:06 ` Linus Torvalds
2018-02-19 23:34 ` John Ogness
2018-02-20 0:42 ` Linus Torvalds
2018-02-20 8:39 ` Peter Zijlstra
2018-02-20 8:43 ` Peter Zijlstra
2018-02-22 5:29 ` Al Viro
2018-02-22 5:40 ` Al Viro [this message]
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20180222054044.GN30522@ZenIV.linux.org.uk \
--to=viro@zeniv.linux.org.uk \
--cc=bigeasy@linutronix.de \
--cc=hch@lst.de \
--cc=john.ogness@linutronix.de \
--cc=linux-fsdevel@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=peterz@infradead.org \
--cc=tglx@linutronix.de \
--cc=torvalds@linux-foundation.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox