linux内核之块设备一---通用块层bio处理

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于 2016-07-23 13:08:28 发布 · 4.2k 阅读

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#linux kernel

本文详细介绍了Linux内核中通用块层的bio处理接口generic_make_request的实现过程，包括bio列表的管理、设备请求队列的查找、扇区重映射以及错误处理等关键步骤，旨在理解块设备驱动的内部工作机制。

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通用块层bio处理的接口generic_make_request

void generic_make_request(struct bio *bio)
{
    if (current->bio_tail) {
        /* make_request is active */
        *(current->bio_tail) = bio;
        bio->bi_next = NULL;
        current->bio_tail = &bio->bi_next;
        return;
    }
    /* following loop may be a bit non-obvious, and so deserves some
     * explanation.
     * Before entering the loop, bio->bi_next is NULL (as all callers
     * ensure that) so we have a list with a single bio.
     * We pretend that we have just taken it off a longer list, so
     * we assign bio_list to the next (which is NULL) and bio_tail
     * to &bio_list, thus initialising the bio_list of new bios to be
     * added.  __generic_make_request may indeed add some more bios
     * through a recursive call to generic_make_request.  If it
     * did, we find a non-NULL value in bio_list and re-enter the loop