Re: [PATCH 1/1] xfs: introduce new file range commit ioctls

Christoph Hellwig
2024-08-23T04:12:54Z

On Thu, Aug 22, 2024 at 05:01:22PM -0700, Darrick J. Wong wrote:
> From: Darrick J. Wong <djwong@kernel.org>
>
> This patch introduces two more new ioctls to manage atomic updates to
> file contents -- XFS_IOC_START_COMMIT and XFS_IOC_COMMIT_RANGE. The
> commit mechanism here is exactly the same as what XFS_IOC_EXCHANGE_RANGE
> does, but with the additional requirement that file2 cannot have changed
> since some sampling point. The start-commit ioctl performs the sampling
> of file attributes.

The code itself looks simply enough now, but how do we guarantee
that ctime actually works as a full change count and not just by
chance here?