From: John Ogness <john.ogness@linutronix.de>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: linux-fsdevel <linux-fsdevel@vger.kernel.org>,
Al Viro <viro@zeniv.linux.org.uk>, 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: Sat, 17 Feb 2018 00:49:35 +0100 [thread overview]
Message-ID: <87lgfs3374.fsf@linutronix.de> (raw)
In-Reply-To: <CA+55aFzfug3S_dRrHDh=Zdat0KZVar13NQVzyqXd3-xHLzeSjA@mail.gmail.com> (Linus Torvalds's message of "Fri, 16 Feb 2018 15:31:22 -0800")
On 2018-02-17, Linus Torvalds <torvalds@linux-foundation.org> wrote:
>> dentry_kill() calls both dentry_lock_inode() and lock_parent() in the
>> common case. So by changing the semantics of lock_parent(), I am
>> removing two "recheck in case I dropped" in the common case rather
>> than just the one you pointed out.
>
> Ok, that would be lovely, but doesn't that end up being a nasty patch?
After reading your initial feedback my idea was to change both
lock_parent() and dentry_lock_inode() to not only communicate _if_ the
lock was successful, but also if d_lock was dropped in the process. (For
example, with a tristate rather than boolean return value.) Then callers
would know if they needed to recheck the dentry contents.
> So it may be that my dislike of the "re-check after possibly dropping
> the lock" is not really about the re-checking, but about just how it
> made that function look much more complicated.
I understand what you are saying and I appreciate the comments. I will
code up some variations for myself and try to pick the one that is the
least complicated for my v2.
John Ogness
next prev parent reply other threads:[~2018-02-16 23:49 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 [this message]
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
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