[dm-devel] Question about end_clone_bio()

[Dong Robin]

Hi

There are codes in end_clone_bio():

static void end_clone_bio(struct bio *clone, int error)
{
....
        /*
         * bios are processed from the head of the list.
         * So the completing bio should always be rq->bio.
         * If it's not, something wrong is happening.
         */
        if (tio->orig->bio != bio)
                DMERR("bio completion is going in the middle of the request");
....

My question is: why the completing bio should always be rq->bio? If
the driver of a block device dispatchs all the bios belong to a
request,
how should it make sure the first completing bio is the first bio in
bio list of request ?



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Best Regard
Robin Dong