Re: [RFC PATCH] sysfs: refill attribute buffer when reading fromoffset 0

[Tejun Heo]

Hello,

Andrew Morton wrote:
> >  The application for this change is to allow a userspace
> > RAID metadata handler to check the state of an array without causing any
> > memory allocations.  Thus not causing writeback to a raid array that might
> > be blocked waiting for userspace to take action.
>
> Although that sounds like a rather, umm, optimistic application.  I guess
> if everything's mlocked you might get lucky.
>
> > Cc: NeilBrown <neilb@xxxxxxx>
> > Cc: Tejun Heo <htejun@xxxxxxxxx>
> > Signed-off-by: Dan Williams <dan.j.williams@xxxxxxxxx>

Acked-by: Tejun Heo <htejun@xxxxxxxxx>

> Has this been tested with pread()?  That should work - doing an lseek+read
> is plain dopey.
>
> Can we now remove need_read_fill?  Not if we want to support
> open+lseek+read, I guess - this initial read might not be at offset
> zero.

Heh.. needs_read_fill is set after read and poll regardless of file pos 
and I bet there are applications depending on it.  :-(

--
tejun
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