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    SubjectRe: [PATCH 2/4] block: use the same failfast bits for bio and request
    Hello, Boaz.

    Boaz Harrosh wrote:
    >>> flags as bit positions generally only make sense if you use
    >>> test/set/clear_bit, otherwise they just confuse things.
    >
    > first please make a distinction between test/set/clear_bit and
    > test/__set/__clear_bit the former is not an option since it's not what
    > we need.

    Block flags look like the way they do today because a while back they
    were accessed with atomic bitops (the versions w/o the underbars).
    Now that they're all inside spinlocks, it all became moot.

    > What can be more clear then rq_set_flags(req, QUEUE_FLAG_QUEUED) then
    > rq_clear_flags(req, QUEUE_FLAG_QUEUED) later.

    req->cmd_flags |= QUEUE_FLAG_QUEUED / &= ~QUEUE_FLAG_QUEUED might not
    be as clear but should be sufficient, I suppose.

    > That's why I suggested the set/clear_flags() variable size macro
    > which can set/clear multiple bit-flags at same cost of masks, only
    > that the compiler calculates the mask in compile time.
    >
    > This can also be good for the greps above. .eg:
    > test_flags(&rq->cmd_flags, REQ_FAILFAST_DEV, REQ_FAILFAST_TRANSPORT, REQ_FAILFAST_DRIVER);
    ...
    > As said, yes, the the lower-case accessors for upper-case bits does nothing,
    > but use __set/__clear/test is a different matter that can also replace the
    > sugary need of these.

    Heh.. I don't know. What about things like flags & mask == mask2
    test? The vararg macros would work for most cases and I wouldn't be
    violently against them if they were already in place but I don't see
    much benefit of all those when people are already very accustomed to
    using c bitops to handle flags.

    Thanks.

    --
    tejun


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