Re: [PATCH 1/2] fix bad behavior in use_hierarchy file

[Tejun Heo <tj@kernel.org>]

(cc'ing Li)

Hello, Andrew.

On Tue, Jun 26, 2012 at 03:25:22PM -0700, Andrew Morton wrote:
> hm.  The various .write_u64() implementations go and return zero on
> success and cgroup_write_X64() sees this and rewrites the return value
> to `nbytes'.
> 
> That was a bit naughty of us - it prevents a .write_u64() instance from
> being able to fully implement a partial write.  We can *partially*
> implement a partial write, by returning a value between 1 and nbytes-1,
> but we can't return zero.  It's a weird interface, it's a surprising
> interface and it was quite unnecessary to do it this way.  Someone
> please slap Paul.
> 
> It's hardly a big problem I, but that's why the unix write() interface
> was designed the way it is.

The whole file interface is severely over-designed like a lot of other
things in cgorup.  I'm thinking about consolidating all the different
read/write methods into one generic pair, likely based on seq_file and
make all others helpers.

Thanks.

-- 
tejun

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