Re: [PATCH v3 8/9] btrfs: prepare btrfs_end_repair_bio() for larger data folios

[Christoph Hellwig <hch@infradead.org>]

On Mon, Mar 17, 2025 at 05:40:53PM +1030, Qu Wenruo wrote:
> In above case, the real folio should be folio_b, and offset inside that
> folio should be:
> 
>   bv_offset - ((&folio_b->page - &folio_a->page) << PAGE_SHIFT).
> 
> With these changes, now btrfs_end_repair_bio() is able to handle larger
> folios properly.

Please stop messing with internals like bv_offset and bv_page entirely
if you can, as that makes the pending conversion of the bio_vec to store
a physical address much harder.

Looking at the code the best way to handle this would be to simply
split btrfs_repair_io_failure so that there is a helper for the code
before the bio_init call.  btrfs_repair_eb_io_failure (or a new helper
called by it) then open codes the existing logic using bio_add_folio
(it could in fact use bio_add_folio_nofail instead), while
btrfs_end_repair_bio should just copy the existing bio_vec over
using an assignment or mempcy.