On Fri, 11 Nov 2022, Keith Busch wrote:
> > There are other DM targets that override logical_block_size in their
> > .io_hints hook (writecache, ebs, zoned). Have you reasoned through why
> > those do _not_ need updating too?
>
> Yeah, that's a good question. The ones that have a problem all make
> assumptions about a bio's bv_offset being logical block size aligned,
> and each of those is accounted for here. Everything else looks fine with
> respect to handling offsets.
Unaligned bv_offset should work - because XFS is sending such bios. If you
compile the kernel with memory debugging, kmalloc returns unaligned
memory. XFS will allocate a buffer with kmalloc, test if it crosses a page
boundary, if not, use the buffer, if yes, free the buffer and allocate a
full page.
There have been device mapper problems about unaligned bv_offset in the
past and I have fixed them.
Unaligned bv_length is a problem for the affected targets.
Mikulas
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