Re: [PATCH v5 03/10] xfs: Refactor xfs_reflink_end_cow_extent()

[John Garry]

On 12/03/2025 07:24, Christoph Hellwig wrote:
> On Mon, Mar 10, 2025 at 06:39:39PM +0000, John Garry wrote:
> > Refactor xfs_reflink_end_cow_extent() into separate parts which process
> > the CoW range and commit the transaction.
> >
> > This refactoring will be used in future for when it is required to commit
> > a range of extents as a single transaction, similar to how it was done
> > pre-commit d6f215f359637.
>
> Darrick pointed out that if you do more than just a tiny number
> of extents per transactions you run out of log reservations very
> quickly here:
>
> https://urldefense.com/v3/__https://lore.kernel.org/all/20240329162936.GI6390@frogsfrogsfrogs/__;!!ACWV5N9M2RV99hQ!PWLcBof1tKimKUObvCj4vOhljWjFmjtzVHLx9apcU5Rah1xZnmp_3PIq6eSwx6TdEXzMLYYyBfmZLgvj$
>
> how does your scheme deal with that?
The resblks calculation in xfs_reflink_end_atomic_cow() takes care of 
this, right? Or does the log reservation have a hard size limit, 
regardless of that calculation?

Thanks,
John