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    SubjectRe: [PATCH][v3] blktrace: conversion to tracepoints
    Em Thu, Oct 30, 2008 at 12:11:45PM +0100, Jens Axboe escreveu:
    > On Thu, Oct 30 2008, Arnaldo Carvalho de Melo wrote:
    > > Yes, I tested it, run 'btrace /dev/sda' several times, while doing a
    > > 45 GB backup using rsync over NFS, etc. So it should have exercised the
    > > tracepoints use and repeated registrater/unregister cycles.
    >
    > Awesome, just wanted to know what level of testing you had done (from
    > "none" to "doesn't crash" to "actually works"), so thanks for that.

    Jens,

    Now I'm working on the marker glue code for systemtap to use
    these tracepoints and I noticed that one important piece of information
    is not available unless one first uses blk_trace_ioctl to fill in
    request_queue->blk_trace, that is request_queue->blk_trace->dev, i.e.
    the device associated with the request_queue.

    Is there a way to, from the request_queue, get the dev? I guess
    not, as if there would be you wouldn't have added it to struct
    blk_trace...

    Would it be sane to add get struct block_device->bd_dev dev_t
    info into struct request_queue at sd_probe time or most probably at some
    more suitable routine in the device/disk registration sequence of
    events?

    I am certainly missing lots of connections here, there are many
    objects and relationships among these objects that may make the
    association of a block_device with a request_queue not to be fixed all
    the time, thus requiring the struct blk_trace ->dev field to be set up
    at ioctl time, but I'm just trying to figure out how to remove the
    requirement of a setup routine for the tracepoints to know what is the
    dev_t associated with the request_queue they are getting as a parameter.

    Best Regards,

    - Arnaldo


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