page flow in IO flow

 

1. page add to bio

int f2fs_submit_page_bio(struct f2fs_io_info *fio)
    /* Allocate a new bio */
    bio = __bio_alloc(fio, 1);

    if (bio_add_page(bio, page, PAGE_SIZE, 0) < PAGE_SIZE) {
        bio_put(bio);
        return -EFAULT;
    }
    __submit_bio(fio->sbi, bio, fio->type);

 

2. blo map to scatterlist(sg)

blk_rq_map_sg

blk_rq_map_sg+0x0/0x544
mmc_blk_data_prep+0x220/0x2c8
mmc_blk_rw_rq_prep+0x50/0x16c
mmc_blk_mq_issue_rq+0x238/0xd88
mmc_mq_queue_rq+0x1fc/0x26c
blk_mq_dispatch_rq_list+0x154/0x4ec
blk_mq_do_dispatch_sched+0x64/0x1e8
blk_mq_sched_dispatch_requests+0x12c/0x1b0
__blk_mq_run_hw_queue+0xe4/0x11c
blk_mq_run_work_fn+0x18/0x20

 这里的scatterlist应该是在init的时候alloc的(而不需要runtime处理request时再不断地去alloc)，mmc_mq_init_request里根据hostg的max_segs调用mmc_alloc_sg分配scatterlist数组，数组大小是host driver里定义的max_segs，分配的scatterlist数组指针保存到mmc_queue_req.sg，调用mmc_alloc_sg的callstack：

[    0.274469] dump_stack+0xac/0x104
[    0.274472] mmc_mq_init_request+0x44/0x84
[    0.274475] blk_mq_alloc_rqs+0x1ac/0x238
[    0.274478] blk_mq_alloc_tag_set+0x1b0/0x370
[    0.274480] mmc_init_queue+0xf0/0x354
[    0.274483] mmc_blk_alloc_req+0xdc/0x2bc
[    0.274485] mmc_blk_probe+0x418/0x66c
[    0.274488] mmc_bus_probe+0x34/0x64
[    0.274491] really_probe+0x244/0x640
[    0.274494] driver_probe_device+0x60/0xf8
[    0.274497] __device_attach_driver+0x128/0x164
[    0.274499] bus_for_each_drv+0x98/0x108
[    0.274502] __device_attach.llvm.6744517518758298417+0xb4/0x14c
[    0.274505] bus_probe_device+0x38/0xd4
[    0.274507] device_add+0x910/0xb38
[    0.274509] mmc_add_card+0x210/0x230
[    0.274512] mmc_attach_mmc+0xc4/0x16c
[    0.274514] mmc_rescan+0x2e0/0x41c
[    0.274516] process_one_work+0x208/0x558
[    0.274519] worker_thread+0x27c/0x504
[    0.274523] kthread+0x14c/0x184
[    0.274525] ret_from_fork+0x10/0x18

 

3. dma_map_sg，get dma_address