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    SubjectRe: [PATCH] change gen_pool allocator to not touch managed memory
    Dean Nelson wrote:
    >>> Both Andrey Volkov and Jes Sorensen have expressed a desire that the
    >>> gen_pool allocator not write to the memory being managed. See the
    >>> following:
    >>>
    >>> http://marc.theaimsgroup.com/?l=linux-kernel&m=113518602713125&w=2
    >>> http://marc.theaimsgroup.com/?l=linux-kernel&m=113533568827916&w=2
    >> hm, fair enough.
    >>
    >> The patch is fairly large+intrusive. I trust it's been broadly tested?
    >
    > Yes, it was thoroughly tested. I even pulled the bitmap manipulation code
    > into a user app with which I could pre-set bits of a bitmap in order to
    > test boundary conditions with various contiguous bit lengths.

    I haven't been directly involved in this work, but I am very confident
    in Dean's work in this.

    Just a few minor nits below:

    > -unsigned long gen_pool_alloc(struct gen_pool *poolp, int size)
    > +int gen_pool_add(struct gen_pool *pool, unsigned long addr, size_t size,
    > + int nid)
    > {
    > - int j, i, s, max_chunk_size;
    > - unsigned long a, flags;
    > - struct gen_pool_link *h = poolp->h;
    > + struct gen_pool_chunk *chunk;
    > + int nbits = size >> pool->min_alloc_order;
    > + int nbytes = sizeof(struct gen_pool_chunk) +
    > + (nbits + BITS_PER_BYTE - 1) / BITS_PER_BYTE;
    > +
    > + if (nbytes > PAGE_SIZE) {
    > + chunk = vmalloc_node(nbytes, nid);
    > + } else {
    > + chunk = kmalloc_node(nbytes, GFP_KERNEL, nid);
    > + }

    Any patch that adds vmalloc() calls to code always makes the little
    hairs on the back of my neck stand up. Any chance we could get away with
    alloc_pages_node() for this?

    > ia64_pal_mc_drain();
    > - status = smp_call_function(uncached_ipi_mc_drain, NULL, 0, 1);
    > - if (status)
    > - printk(KERN_WARNING "smp_call_function failed for "
    > - "uncached_ipi_mc_drain! (%i)\n", status);
    > + (void) smp_call_function(uncached_ipi_mc_drain, NULL, 0, 1);

    This thing could in theory fail so having the error check there seems
    the right thing to me. In either case, please don't (void) the function
    return (this is a style issue, I know).

    > Index: linux-2.6/arch/ia64/sn/kernel/sn2/cache.c
    > ===================================================================
    > --- linux-2.6.orig/arch/ia64/sn/kernel/sn2/cache.c 2006-04-24 12:25:36.234717101 -0500
    > +++ linux-2.6/arch/ia64/sn/kernel/sn2/cache.c 2006-04-24 12:27:56.012899026 -0500

    This part we should maybe do in a seperate patch? It seems valid on it's
    own?

    Cheers,
    Jes
    -
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