On Tue, Jan 20, 2026 at 08:41:50PM +1100, NeilBrown wrote: > On Tue, 20 Jan 2026, Christian Brauner wrote: > > On Tue, Jan 20, 2026 at 07:45:35AM +1100, NeilBrown wrote: > > > On Mon, 19 Jan 2026, Christian Brauner wrote: > > > > On Mon, Jan 19, 2026 at 06:22:42PM +1100, NeilBrown wrote: > > > > > On Mon, 19 Jan 2026, Christoph Hellwig wrote: > > > > > > On Mon, Jan 19, 2026 at 10:23:13AM +1100, NeilBrown wrote: > > > > > > > > This was Chuck's suggested name. His point was that STABLE > > > > > > > > means that > > > > > > > > the FH's don't change during the lifetime of the file. > > > > > > > > > > > > > > > > I don't much care about the flag name, so if everyone likes > > > > > > > > PERSISTENT > > > > > > > > better I'll roll with that. > > > > > > > > > > > > > > I don't like PERSISTENT. > > > > > > > I'd rather call a spade a spade. > > > > > > > > > > > > > > EXPORT_OP_SUPPORTS_NFS_EXPORT > > > > > > > or > > > > > > > EXPORT_OP_NOT_NFS_COMPATIBLE > > > > > > > > > > > > > > The issue here is NFS export and indirection doesn't bring any > > > > > > > benefits. > > > > > > > > > > > > No, it absolutely is not. And the whole concept of calling > > > > > > something > > > > > > after the initial or main use is a recipe for a mess. > > > > > > > > > > We are calling it for it's only use. If there was ever another use, > > > > > we > > > > > could change the name if that made sense. It is not a public name, it > > > > > is easy to change. > > > > > > > > > > > > > > > > > Pick a name that conveys what the flag is about, and document those > > > > > > semantics well. This flag is about the fact that for a given file, > > > > > > as long as that file exists in the file system the handle is stable. > > > > > > Both stable and persistent are suitable for that, nfs is everything > > > > > > but. > > > > > > > > > > My understanding is that kernfs would not get the flag. > > > > > kernfs filehandles do not change as long as the file exist. > > > > > But this is not sufficient for the files to be usefully exported. > > > > > > > > > > I suspect kernfs does re-use filehandles relatively soon after the > > > > > file/object has been destroyed. Maybe that is the real problem here: > > > > > filehandle reuse, not filehandle stability. > > > > > > > > > > Jeff: could you please give details (and preserve them in future cover > > > > > letters) of which filesystems are known to have problems and what > > > > > exactly those problems are? > > > > > > > > > > > > > > > > > Remember nfs also support volatile file handles, and other > > > > > > applications > > > > > > might rely on this (I know of quite a few user space applications > > > > > > that > > > > > > do, but they are kinda hardwired to xfs anyway). > > > > > > > > > > The NFS protocol supports volatile file handles. knfsd does not. > > > > > So maybe > > > > > EXPORT_OP_NOT_NFSD_COMPATIBLE > > > > > might be better. or EXPORT_OP_NOT_LINUX_NFSD_COMPATIBLE. > > > > > (I prefer opt-out rather than opt-in because nfsd export was the > > > > > original purpose of export_operations, but it isn't something > > > > > I would fight for) > > > > > > > > I prefer one of the variants you proposed here but I don't particularly > > > > care. It's not a hill worth dying on. So if Christoph insists on the > > > > other name then I say let's just go with it. > > > > > > > > > > This sounds like you are recommending that we give in to bullying. > > > I would rather the decision be made based on the facts of the case, not > > > the opinions that are stated most bluntly. > > > > > > I actually think that what Christoph wants is actually quite different > > > from what Jeff wants, and maybe two flags are needed. But I don't yet > > > have a clear understanding of what Christoph wants, so I cannot be sure. > > > > I've tried to indirectly ask whether you would be willing to compromise > > here or whether you want to insist on your alternative name. Apparently > > that didn't come through. > > This would be the "not a hill worthy dying on" part of your statement. > I think I see that implication now. > But no, I don't think compromise is relevant. I think the problem > statement as originally given by Jeff is misleading, and people have > been misled to an incorrect name. > > > > > I'm unclear what your goal is in suggesting that I recommend "we" give > > into bullying. All it achieved was to further derail this thread. > > > > The "We" is the same as the "us" in "let's just go with it". > > > > I also think it's not very helpful at v6 of the discussion to start > > figuring out what the actual key rift between Jeff's and Christoph's > > position is. If you've figured it out and gotten an agreement and this > > is already in, send a follow-up series. > > v6? v2 was posted today. But maybe you are referring the some other > precursors. > > The introductory statement in v2 is > > This patchset adds a flag that indicates whether the filesystem supports > stable filehandles (i.e. that they don't change over the life of the > file). It then makes any filesystem that doesn't set that flag > ineligible for nfsd export. > > Nobody else questioned the validity of that. I do. > No evidence was given that there are *any* filesystems that don't > support stable filehandles. The only filesystem mentioned is cgroups > and it DOES provide stable filehandles.
Oh yes we did. And this is a merry-go-round. It is very much fine for a filesystems to support file handles without wanting to support exporting via NFS. That is especially true for in-kernel pseudo filesystems. As I've said before multiple times I want a way to allow filesystems such as pidfs and nsfs to use file handles without supporting export. Whatever that fscking flag is called at this point I fundamentally don't care. And we are reliving the same arguments over and over. I will _hard NAK_ anything that starts mandating that export of filesystems must be allowed simply because their file handles fit export criteria. I do not care whether pidfs or nsfs file handles fit the bill. They will not be exported.
