On Wed, Apr 10, 2024 at 05:59:41PM -0700, Darrick J. Wong wrote: > I thought about designing this interface that way, where userspace > passes a pointer to an empty buffer, and the kernel formats that with > xfs_scrub_vecs that tell userspace what it scrubbed and what the outcome > was. I didn't like that, because now the kernel has to have a way to > communicate that the buffer needed to have been at least X size, even > though for our cases XFS_SCRUB_TYPE_NR + 2 would always be enough. > > Better, I thought, to let userspace figure out what it wants to run, and > tell that explicitly to the kernel, and then the kernel can just do > that. The downside is that now we need the barriers. And the downside is the userspace needs to known about all the passes and dependencies. Which I guess it does anyway due to the older scrub interface, but maybe that's worth documenting? > > > > + BUILD_BUG_ON(sizeof(struct xfs_scrub_vec_head) == > > > + sizeof(struct xfs_scrub_metadata)); > > > + BUILD_BUG_ON(XFS_IOC_SCRUB_METADATA == XFS_IOC_SCRUBV_METADATA); > > > > What is the point of these BUILD_BUG_ONs? > > Reusing the same ioctl number instead of burning another one. It's not > really necessary I suppose. I find reusing the numbers really confusings even if it does work due to the size encoding. If you're fine with getting rid of it I'm all for it.
