[ add Gerald and Joao ] On Thu, Aug 19, 2021 at 10:44 PM Christoph Hellwig <hch@xxxxxx> wrote: > > Hi all, > > looking at the recent ZONE_DEVICE related changes we still have a > horrible maze of different code paths. I already suggested to > depend on ARCH_HAS_PTE_SPECIAL for ZONE_DEVICE there, which all modern > architectures have anyway. But the other odd special case is > CONFIG_FS_DAX_LIMITED which is just used for the xpram driver. Does > this driver still see use? If so can we make it behave like the > other DAX drivers and require a pgmap? I think the biggest missing > part would be to implement ARCH_HAS_PTE_DEVMAP for s390. > Gerald, Might you still be looking to help dcssblk get out of FS_DAX_LIMITED jail [1]? I recall Martin saying that 'struct page' overhead was prohibitive. I don't know if Joao's 'struct page' diet patches could help alleviate that at all (would require the filesystem to only allocate blocks in large page sizes). [1]: https://lore.kernel.org/r/20180523205017.0f2bc83e@thinkpad
