linux-kernel - Re: [PATCH v3 1/1] dcache: Translating dentry into pathname without taking rename

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Date:	Fri, 06 Sep 2013 22:24:01 -0400
From:	Waiman Long <waiman.long@...com>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
CC:	Alexander Viro <viro@...iv.linux.org.uk>,
	linux-fsdevel <linux-fsdevel@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	"Chandramouleeswaran, Aswin" <aswin@...com>,
	"Norton, Scott J" <scott.norton@...com>,
	George Spelvin <linux@...izon.com>,
	John Stoffel <john@...ffel.org>
Subject: Re: [PATCH v3 1/1] dcache: Translating dentry into pathname without
 taking rename_lock

On 09/06/2013 04:52 PM, Linus Torvalds wrote:
> On Fri, Sep 6, 2013 at 9:08 AM, Waiman Long<Waiman.Long@...com>  wrote:
>> This patch will replace the writer's write_seqlock/write_sequnlock
>> sequence of the rename_lock of the callers of the prepend_path() and
>> __dentry_path() functions with the reader's read_seqbegin/read_seqretry
>> sequence within these 2 functions.
> Ok, this actually looks really good.
>
> I do have one comment, from just reading the patch:
>
> I would really like the stuff inside the
>
>     restart:
>        bptr = *buffer;
>        blen = *buflen;
>        if (retry_cnt) {
>              seq = read_seqbegin(&rename_lock);
>              rcu_read_lock();
>        } else
>              write_seqlock(&rename_lock);
>
>        ... guts of path generation ...
>
>        if (retry_cnt) {
>              retry_cnt--;
>              rcu_read_unlock();
>              if (read_seqretry(&rename_lock, seq))
>                    goto restart;
>        } else
>              write_sequnlock(&rename_lock);
>
> could possible be done as a separate function?
>
> Alternatively (or perhaps additionally), maybe the locking could be
> done as an inline function too (taking the retry count as an argument)
> to make things a bit more easy to understand.

I would prefer putting the begin and end blocks into 2 helper inlined 
helper functions to make code easier to look at. I will work on this 
over the weekend.

-Longman

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