如何在Linux内核中使用生物请求阅读一个部门

我想只读一个扇区从硬盘到内存中的一个特定的页面,这个页面是保留的,没有映射到任何地址映射.我发现 this solution,但我不知道如何将文件翻译成块设备和扇区.例如,在文件mm / filemap.c中的函数do_generic_file_read中有这样一行：

error = mapping->a_ops->readpage(filp,page);

由于目标页面不是任何映射,所以我无法使用相同的功能,但是我需要将filp转换为设备和扇区,以便生成自己的生物请求.我该怎么办？

编辑1

我试过这个可能的解决方案,通过添加它,它首先计算扇区,然后直接调用ext2_get_block来获取设备,然后添加所需的页面位置并提交生物请求：

struct page *myPage;
int myRet;
struct buffer_head bh;
struct bio *bio = bio_alloc(GFP_NOIO,1);
myPage = pfn_to_page(Some_Location);
bio_init(bio);
bio->bi_sector = (sector_t)page_offset << (PAGE_CACHE_SHIFT - mapping->host->i_blkbits);
myRet = ext2_get_block(mapping->host,bio->bi_sector,&bh,0);
bio->bi_bdev = bh.b_bdev;
bio->bi_next = NULL;
bio->bi_size = PAGE_SIZE;
bio_add_page(bio,myPage,PAGE_SIZE,0);
submit_bio(READ,bio);

这使用函数中的现有地址映射来创建生物请求,因为所需的页面没有地址映射.它只有一个问题,submit_bio行导致：

[    4.792142] ------------[ cut here ]------------
[    4.792892] WARNING: at arch/x86/kernel/pci-nommu.c:63 nommu_map_sg+0xd9/0x100()
[    4.793674] Hardware name: Standard PC (i440FX + PIIX,1996)
[    4.794149] Modules linked in:
[    4.794607] Pid: 153,comm: kblockd/0 Not tainted 2.6.32.65 #308
[    4.795077] Call Trace:
[    4.795545]  [<ffffffff81056875>] ? warn_slowpath_common+0x65/0xa0
[    4.796024]  [<ffffffff810380a9>] ? nommu_map_sg+0xd9/0x100
[    4.796446]  [<ffffffff8121ef4a>] ? ide_dma_prepare+0xda/0x180
[    4.796900]  [<ffffffff81219923>] ? do_rw_taskfile+0x253/0x330
[    4.797532]  [<ffffffff8122311c>] ? ide_do_rw_disk+0x22c/0x320
[    4.797983]  [<ffffffff81215c3a>] ? do_ide_request+0x11a/0x600
[    4.798416]  [<ffffffff81051450>] ? __dequeue_entity+0x30/0x40
[    4.798854]  [<ffffffff810519a1>] ? finish_task_switch.constprop.110+0x31/0xc0
[    4.799391]  [<ffffffff8141fdd6>] ? thread_return+0x2a/0x1d4
[    4.799816]  [<ffffffff81052116>] ? check_preempt_wakeup+0x76/0xe0
[    4.800279]  [<ffffffff811a3be0>] ? blk_unplug_work+0x0/0x20
[    4.800754]  [<ffffffff811a5b2a>] ? generic_unplug_device+0x1a/0x30
[    4.801218]  [<ffffffff810661dc>] ? worker_thread+0x13c/0x210
[    4.802710]  [<ffffffff81069cb0>] ? autoremove_wake_function+0x0/0x30
[    4.804130]  [<ffffffff810660a0>] ? worker_thread+0x0/0x210
[    4.805357]  [<ffffffff810660a0>] ? worker_thread+0x0/0x210
[    4.806356]  [<ffffffff81069907>] ? kthread+0x77/0x80
[    4.807302]  [<ffffffff81033eaa>] ? child_rip+0xa/0x20
[    4.808500]  [<ffffffff81069890>] ? kthread+0x0/0x80
[    4.809060]  [<ffffffff81033ea0>] ? child_rip+0x0/0x20
[    4.809620] ---[ end trace 61d7e1478dbb58eb ]---

后来导致这个：

[    4.871857] hda: task_pio_intr: status=0x58 { DriveReady SeekComplete DataRequest }
[    4.872553] hda: possibly failed opcode: 0x29
[    4.873346] hda: DMA disabled
[    4.885478] Clocksource tsc unstable (delta = 115822911 ns)
[    4.886364] Switching to clocksource jiffies
[    4.919051] ide0: reset: success

和这个：

[   48.957807] hda: lost interrupt

我添加到函数__do_page_cache_readahead在mm / readahead.c,但它可以添加类似于mm / filemap.c或类似的功能.也许有人可以解决这个问题！

bio.bi_bdev = I_BDEV(mapping->host);