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In-Reply-To: <201011020819.33777.manningc2@actrix.gen.nz>
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Date: Mon, 1 Nov 2010 21:23:33 +0200
Message-ID: <AANLkTimJw8ZMDGu61z8bEvCL8R94xr9GdAnFkQDtMg+V@mail.gmail.com>
Subject: Re: [PATCH 05/29] Staging: yaffs2: yaffs_allocator: Add files
From: Pekka Enberg <penberg@kernel.org>
To: Charles Manning <manningc2@actrix.gen.nz>
Cc: Tracey Dent <tdent48227@gmail.com>, greg@kroah.com,
        linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org
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On Mon, Nov 1, 2010 at 9:19 PM, Charles Manning <manningc2@actrix.gen.nz> wrote:
> On Tuesday 02 November 2010 07:58:49 Pekka Enberg wrote:
>> On Mon, Nov 1, 2010 at 8:40 PM, Tracey Dent <tdent48227@gmail.com> wrote:
>> > Adding files to yaffs2 directory.
>> >
>> > Signed-off-by: Tracey Dent <tdent48227@gmail.com>
>> > ---
>> > ?drivers/staging/yaffs2/yaffs_allocator.c | ?408
>> > ++++++++++++++++++++++++++++++ drivers/staging/yaffs2/yaffs_allocator.h |
>> > ? 30 +++
>> > ?2 files changed, 438 insertions(+), 0 deletions(-)
>> > ?create mode 100644 drivers/staging/yaffs2/yaffs_allocator.c
>> > ?create mode 100644 drivers/staging/yaffs2/yaffs_allocator.h
>> >
>> > diff --git a/drivers/staging/yaffs2/yaffs_allocator.c
>> > b/drivers/staging/yaffs2/yaffs_allocator.c new file mode 100644
>> > index 0000000..024ee2a
>> > --- /dev/null
>> > +++ b/drivers/staging/yaffs2/yaffs_allocator.c
>> > @@ -0,0 +1,408 @@
>> > +/*
>> > + * YAFFS: Yet Another Flash File System. A NAND-flash specific file
>> > system. + *
>> > + * Copyright (C) 2002-2010 Aleph One Ltd.
>> > + * ? for Toby Churchill Ltd and Brightstar Engineering
>> > + *
>> > + * Created by Charles Manning <charles@aleph1.co.uk>
>> > + *
>> > + * This program is free software; you can redistribute it and/or modify
>> > + * it under the terms of the GNU General Public License version 2 as
>> > + * published by the Free Software Foundation.
>> > + */
>> > +
>> > +
>> > +
>> > +#include "yaffs_allocator.h"
>> > +#include "yaffs_guts.h"
>> > +#include "yaffs_trace.h"
>> > +#include "yportenv.h"
>> > +
>> > +#ifdef CONFIG_YAFFS_YMALLOC_ALLOCATOR
>> > +
>> > +void yaffs_deinit_raw_tnodes_and_objs(yaffs_dev_t *dev)
>> > +{
>> > + ? ? ? dev = dev;
>> > +}
>> > +
>> > +void yaffs_init_raw_tnodes_and_objs(yaffs_dev_t *dev)
>> > +{
>> > + ? ? ? dev = dev;
>> > +}
>> > +
>> > +yaffs_tnode_t *yaffs_alloc_raw_tnode(yaffs_dev_t *dev)
>> > +{
>> > + ? ? ? return (yaffs_tnode_t *)YMALLOC(dev->tnode_size);
>> > +}
>> > +
>> > +void yaffs_free_raw_tnode(yaffs_dev_t *dev, yaffs_tnode_t *tn)
>> > +{
>> > + ? ? ? dev = dev;
>> > + ? ? ? YFREE(tn);
>> > +}
>>
>> So you have your own dynamic memory allocator? What's wrong with kmalloc()?
>
> No. YMALLOC() wraps kmalloc() to keep the code portable.
>
> This code does a home-grown slab allocator. The reason for doing this is that
> Linux slab does not allow slab caches to be destroyed while objects exist.
>
> While that might sound like a dangerous practice, it does mean that when yaffs
> unmounts it can drop all the data structures without having to walk all the
> trees freeing the objects.

Either way, your home-grown slab allocator is not going to be merged
this way. You should be using kmem_cache_alloc() and propose proper
patches on top of mm/sl?b.c.
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