On Wed, Nov 14, 2012 at 08:03:49AM +0100, Stefani Seibold wrote:
> Am Freitag, den 09.11.2012, 10:32 +0800 schrieb Yuanhan Liu:
> > On Thu, Nov 08, 2012 at 01:37:15PM +0100, Stefani Seibold wrote:
> > > Am Donnerstag, den 08.11.2012, 20:24 +0800 schrieb Yuanhan Liu:
>
> > Yes, it is. I will try log API then.
> >
> > Stefani, I found an issue while rework to current API. Say the current
> > code of __kfifo_init:
> > int __kfifo_init(struct __kfifo *fifo, void *buffer,
> > unsigned int size, size_t esize)
> > {
> > size /= esize;
> >
> > if (!is_power_of_2(size))
> > size = rounddown_pow_of_two(size);
> > ....
> > }
> >
> > Even thought I changed the API to something like:
> > int __kfifo_init(struct __kfifo *fifo, void *buffer,
> > int size_order, size_t esize)
> > {
> > unsigned int size = 1 << size_order;
> >
> > size /= esize;
> > ...
> > }
> >
> > See? There is still a divide and we can't make it sure that it will be
> > power of 2 after that.
> >
> > So, I came up 2 proposal to fix this.
> >
> > 1. refactor the meaning of 'size' argument first.
> >
> > 'size' means the size of pre-allocated buffer. We can refactor it to
> > meaning of 'the number of fifo elements' just like __kfifo_alloc, so
> > that we don't need do the size /= esize stuff.
> >
> > 2. remove kfifo_init
> >
> > As we can't make sure that kfifo will do exactly what users asked(in
> > the way of fifo size). It would be safe and good to maintain buffer
> > and buffer size inside kfifo. So, I propose to remove it and use
> > kfifo_alloc instead.
> >
> > git grep 'kfifo_init\>' shows that we currently have 2 users only.
> >
> >
> > The first way is hacky, and it doesn't make much sense to me. Since
> > buffer is pre-allocated by user but not kfifo. User has to calculate
> > element size and the number of elements, which is not friendly.
> >
> > The second way does make more sense to me.
>
> kfifo_init() was requested by some kernel developers, i never liked it.
> If you have a better and cleaner solution than do it, otherwise kick it
> away if you like.
There are only 2 kfifo_init users: libiscsi.c and libsrp.c under
drivers/scsi/, and they are with same logic.
I propose to replace them with kfifo_alloc. I will make patch for
this later to see if scsi guys OK with it or not. If OK, we can
remove kfifo_init.
--yliu
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