On Thu, Dec 12, 2024 at 10:05:47AM -0800, Darrick J. Wong wrote:
> On Wed, Dec 11, 2024 at 09:53:43AM +0100, Christoph Hellwig wrote:
> > This doesn't much - just always returns the start block number for each
>
> "This doesn't much" - I don't understand the sentence very well. How
> about:
>
> "Add a new IOMAP_F_ZONE_APPEND flag for the filesystem to indicate that
> the storage device must inform us where it wrote the data, so that the
> filesystem can update its own internal mapping metadata. The filesystem
> should set the starting address of the zone in iomap::addr, and extract
> the LBA address from the bio during ioend processing. iomap builds
> bios unconstrained by the hardware limits and will split them in the bio
> submission handler."
Sounds reasonable.
> The splitting happens whenever IOMAP_F_BOUNDARY gets set by
> ->map_blocks, right?
The splitting happens when:
(a) we run out of enough space in one zone and have to switch to another
one. That then most likely picks an new zone, in which case
IOMAP_F_BOUNDARY will be set
(b) if the hardware I/O constraints require splitting the I/O (typically
because it's too larger)
