linux-ext4 - Re: [PATCH] JBD slab cleanups

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Message-Id: <1190138690.6528.23.camel@norville.austin.ibm.com>
Date:	Tue, 18 Sep 2007 13:04:50 -0500
From:	Dave Kleikamp <shaggy@...ux.vnet.ibm.com>
To:	cmm@...ibm.com
Cc:	Christoph Hellwig <hch@...radead.org>,
	Badari Pulavarty <pbadari@...ibm.com>,
	Christoph Lameter <clameter@....com>,
	linux-fsdevel <linux-fsdevel@...r.kernel.org>,
	ext4 development <linux-ext4@...r.kernel.org>,
	lkml <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] JBD slab cleanups

On Tue, 2007-09-18 at 09:35 -0700, Mingming Cao wrote:
> On Tue, 2007-09-18 at 10:04 +0100, Christoph Hellwig wrote:
> > On Mon, Sep 17, 2007 at 03:57:31PM -0700, Mingming Cao wrote:
> > > Here is the incremental small cleanup patch. 
> > > 
> > > Remove kamlloc usages in jbd/jbd2 and consistently use jbd_kmalloc/jbd2_malloc.
> > 
> > Shouldn't we kill jbd_kmalloc instead?
> > 
> 
> It seems useful to me to keep jbd_kmalloc/jbd_free. They are central
> places to handle memory (de)allocation(<page size) via kmalloc/kfree, so
> in the future if we need to change memory allocation in jbd(e.g. not
> using kmalloc or using different flag), we don't need to touch every
> place in the jbd code calling jbd_kmalloc.

I disagree.  Why would jbd need to globally change the way it allocates
memory?  It currently uses kmalloc (and jbd_kmalloc) for allocating a
variety of structures.  Having to change one particular instance won't
necessarily mean we want to change all of them.  Adding unnecessary
wrappers only obfuscates the code making it harder to understand.  You
wouldn't want every subsystem to have it's own *_kmalloc() that took
different arguments.  Besides, there aren't that many calls to kmalloc
and kfree in the jbd code, so there wouldn't be much pain in changing
GFP flags or whatever, if it ever needed to be done.

Shaggy
-- 
David Kleikamp
IBM Linux Technology Center

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