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* bio -> bi_bdev
@ 2007-01-24 13:46 Jochen Oekonomopulos
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From: Jochen Oekonomopulos @ 2007-01-24 13:46 UTC (permalink / raw)
  To: linux-kernel


I am working on a module to redirect a bio request from one block device
to another. Therefore, I catch every bio from one device, clone it and
change the underlying block_device bi_bdev to the other block device.
Everything works fine, except that the first page read is always filled
with random data. Everything else works fine. So I am wondering, if
there is something I did not take into consideration.

I tested it under 2.6.8 and 2.6.19 with the same results.

Below is the essence of my redirection code.

"device" is the instance of my device structure. The original read was
made to it and I want to redirect it to the block_device linked in

struct bio bio, cloned_bio;
int sect = 0;

rq_for_each_bio(bio, req) {
		cloned_bio = bio_clone(bio, GFP_NOIO);
		cloned_bio -> bi_private = bio;
		cloned_bio -> bi_bdev = device -> bdev;
		if(bio_data_dir(cloned_bio) == WRITE) {

			submit_bio(WRITE, cloned_bio);
		else {

			submit_bio(READ, cloned_bio);
		sect += cloned_bio->bi_size/KERNEL_SECTOR_SIZE;


thanks in advance for any feedback,

Jochen Oekonomopulos

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