On 2021/11/24 14:09, hch@xxxxxxxxxxxxx wrote:
On Wed, Nov 24, 2021 at 07:07:18AM +0800, Qu Wenruo wrote:
In that case, the missing piece seems to be a way to convert a splitted
plain bio into a REQ_OP_ZONE_APPEND bio.
Can this be done without slow bvec copying?
Yes. I have a WIP stacking driver that converts writes to zone appends
and it does just that:
sector_t orig_sector = bio->bi_iter.bi_sector;
unsigned int bio_flags = bio->bi_opf & ~REQ_OP_MASK;
...
clone = bio_clone_fast(bio, GFP_NOIO, &bdev->write_bio_set);
...
clone->bi_opf = REQ_OP_ZONE_APPEND | REQ_NOMERGE | bio_flags;
Just so simple? Then that's super awesome.
But I'm a little concerned about the bio_add_hw_page() call in
bio_add_zoned_append().
It's not exactly the same as bio_add_page().
Does it mean as long as our splitted bio doesn't exceed zone limit, we
can do the convert without any further problem?
Thanks,
Qu
bio_set_dev(clone, dev->lower_bdev);
clone->bi_iter.bi_sector = zone_sector;
trace_block_bio_remap(clone, disk_devt(disk), orig_sector);
Thanks,
Qu
---end quoted text---
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