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    SubjectRe: [PATCH v2 15/26] block: Add bio_copy_data()
    On Thu, Sep 20, 2012 at 05:09:45PM -0700, Kent Overstreet wrote:
    > On Thu, Sep 20, 2012 at 05:06:32PM -0700, Tejun Heo wrote:
    > > Hello,
    > >
    > > On Mon, Sep 10, 2012 at 05:22:26PM -0700, Kent Overstreet wrote:
    > > > +void bio_copy_data(struct bio *dst, struct bio *src)
    > > > +{
    > > ...
    > > > + src_p = kmap_atomic(src_bv->bv_page);
    > > > + dst_p = kmap_atomic(dst_bv->bv_page);
    > > > +
    > > > + memcpy(dst_p + dst_bv->bv_offset,
    > > > + src_p + src_bv->bv_offset,
    > > > + bytes);
    > > > +
    > > > + kunmap_atomic(dst_p);
    > > > + kunmap_atomic(src_p);
    > >
    > > Wrap these in preempt_disable/enable() to allow the function to be
    > > called from any context?
    >
    > I checked the implementation of kmap_atomic(), it already does
    > preempt_disable() so it's safe in process context - if I understand
    > correctly it needs local_irq_save()/restore() to be safe in any context
    > and I figured calling this from irq context is not the norm so that
    > should be the caller's responsibility.

    Ooh, that means the patch I just sent Andrew about sg_mapping_iter is
    still too strict.

    Thanks.

    --
    tejun


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