Re: [PATCH] btrfs: use IOMAP_DIO_BOUNCE flag for direct reads

[Christoph Hellwig <hch@infradead.org>]

On Mon, Aug 31, 2026 at 05:01:21PM +0930, Qu Wenruo wrote:
> However it only shows up in lore, but not in my inbox at all, and I have no
> idea why.
> 
> And lore is never a good way to review patches, nor easy to reply.

I got it brack through all the usual lists, so this must be some kind
of filtering on your side.

> > For one this removes the read-side IOMAP_DIO_BOUNCE support you are
> > using here, because it had problems.  The alternative is iomap-based
> > and better at building large, aligned read bios which matter for HDD.
> > It also introduces the concept of lazy bouncing where it only bounce
> > buffers after a checksum failure happens by default, which means you
> > only pay an overhead for misbehaving applications.
> 
> In that case I'm afraid btrfs may need some way to integrate the checksum
> handling into iomap.
> As the btrfs has a very internal handling for repairing each block.

The only iomap path is the bounce buffering, the checksum handling is
still left to the file systems.  The code will probably need some
minor tweaks for btrfs, like passing in a bio_set to use for the clones,
but it shouldn't be too bad.