On Tue, Jan 20, 2026 at 03:19:21PM +0800, Gao Xiang wrote: >> It will be very hard to change unless we move to physical indexing of >> the page cache, which has all kinds of downside.s > > I'm not sure if it's really needed: I think the final > folio adaption plan is that folio can be dynamic > allocated? then why not keep multiple folios for a > physical memory, since folios are not order-0 anymore.
Having multiple folios for the same piece of memory can't work, at we'd have unsynchronized state. > Using physical indexing sounds really inflexible on my > side, and it can be even regarded as a regression for me. I'm absolutely not arguing for that.. >>> So that let's face the reality: this feature introduces >>> on-disk xattrs called "fingerprints." --- Since they're >>> just xattrs, the EROFS on-disk format remains unchanged. >> >> I think the concept of using a backing file of some sort for the shared >> pagecache (which I have no problem with at all), vs the imprecise > > In that way (actually Jingbo worked that approach in 2023), > we have to keep the shared data physically contiguous and > even uncompressed, which cannot work for most cases. Why does that matter? > On the other side, I do think `fingerprint` from design > is much like persistent NFS file handles in some aspect > (but I don't want to equal to that concept, but very > similar) for a single trusted domain, we should have to > deal with multiple filesystem sources and mark in a > unique way in a domain. I don't really thing they are similar in any way.
