From: Waiman Long <waiman.long@hp.com>
To: George Spelvin <linux@horizon.com>
Cc: torvalds@linux-foundation.org, viro@ZenIV.linux.org.uk,
aswin@hp.com, john@stoffel.org, linux-fsdevel@vger.kernel.org,
linux-kernel@vger.kernel.org, scott.norton@hp.com
Subject: Re: [PATCH v4 1/1] dcache: Translating dentry into pathname without taking rename_lock
Date: Mon, 09 Sep 2013 23:57:40 -0400 [thread overview]
Message-ID: <522E98B4.1050906@hp.com> (raw)
In-Reply-To: <20130910004020.29299.qmail@science.horizon.com>
On 09/09/2013 08:40 PM, George Spelvin wrote:
> I'm really wondering about only trying once before taking the write lock.
> Yes, using the lsbit is a cute hack, but are we using it for its cuteness
> rather than its effectiveness?
>
> Renames happen occasionally. If that causes all the current pathname
> translations to fall back to the write lock, that is fairly heavy.
> Worse, all of those translations will (unnecessarily) bump the write
> seqcount, triggering *other* translations to fail back to the write-lock
> path.
>
> One patch to fix this would be to have the fallback read algorithm take
> sl->lock but *not* touch sl->seqcount, so it wouldn't break concurrent
> readers.
Actually, a follow-up patch that I am planning to do is to introduce a
read_seqlock() primitive in seqlock.h that does exactly that. Then the
write_seqlock() in this patch will be modified to read_seqlock().
-Longman
next prev parent reply other threads:[~2013-09-10 3:57 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-09-09 16:18 [PATCH v4 0/1] dcache: Translating dentry into pathname without taking rename_lock Waiman Long
2013-09-09 16:18 ` [PATCH v4 1/1] " Waiman Long
2013-09-09 17:29 ` Al Viro
2013-09-09 17:45 ` Linus Torvalds
2013-09-09 17:56 ` Waiman Long
2013-09-09 18:06 ` Al Viro
2013-09-09 18:15 ` Linus Torvalds
2013-09-09 18:21 ` Al Viro
2013-09-09 18:36 ` Al Viro
2013-09-09 18:46 ` Al Viro
2013-09-09 18:46 ` Waiman Long
2013-09-09 19:10 ` Al Viro
2013-09-09 19:28 ` Al Viro
2013-09-09 22:57 ` Waiman Long
2013-09-10 0:40 ` George Spelvin
2013-09-10 0:57 ` Al Viro
2013-09-10 1:15 ` Ramkumar Ramachandra
2013-09-10 1:34 ` Linus Torvalds
2013-09-10 2:25 ` Al Viro
2013-09-10 2:33 ` Linus Torvalds
2013-09-10 3:12 ` Ramkumar Ramachandra
2013-09-10 8:24 ` George Spelvin
2013-09-10 3:57 ` Waiman Long [this message]
2013-09-09 17:55 ` Waiman Long
2013-09-09 18:07 ` Al Viro
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