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    SubjectRe: [PATCH 1/2] blkdev: fix merge_bvec_fn return value checks
    Date
    Mike Snitzer <snitzer@redhat.com> writes:

    > Linux has all sorts of internal interfaces that are "odd"... the current
    > 'q->merge_bvec_fn' interface included. But odd is not a problem (nor is
    > it "broken") unless you make changes that don't consider how the current
    > interface is defined.
    Ok. then cant you please explain more historical questions
    1) Why bio_add_page() can not add less data than requested?
    Seems that it doesn't make caller's code much complicate
    Off course barrier bio is special case. I don't consider it here.

    2) What statement "bio_add_page() must accept at least one page"
    exactly means?
    IMHO this means that bio_add_page() must accept at least
    one page with len (PAGE_SIZE - offset). Or more restricted
    statemnt that first bio_add_page() must be always successfull.

    But currently in some places this rule treated as what all bio
    which has size less whan PAGE_SIZE are accepted. And in x86 such
    bio may has up to 8 pages/bvecs.
    >
    > But I digress...
    >
    > Mike


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