Re: [PATCH V10 0/8] dax: prepare for famfs

[Alison Schofield <alison.schofield@intel.com>]

On Fri, Mar 27, 2026 at 09:03:26PM +0000, John Groves wrote:
> From: John Groves <john@groves.net>
> 
> This patch series along with the bundled patches to fuse are available
> as a git tag at [0].
> 
> Dropped the "bundle" thread. If this submission goes smoothly, I'll update
> the fuse patches to v10 (very little change there as yet).
> 
> Changes v9 -> v10
> - Minor modernizations per comments from (mostly) Jonathan
> - Minor Kconfig simplification
> - bus.c:dax_match_type(): don't make fsdev_dax eligible for automatic binding
>   where devdax would otherwise bind
> - dax-private.h: add missing kerneldoc comment for field cached_size in
>   struct dev_dax_range (thanks Dave)
> - fsdev_write_dax(): s/pmem_addr/addr/ (thanks Dave)
> - include/linux/dax.h: remove a spuriously-added declaration of inode_dax()
>   (thanks Jonathan)
> 
> Description:
> 
> This patch series introduces the required dax support for famfs.
> Previous versions of the famfs series included both dax and fuse patches.
> This series separates them into separate patch series' (and the fuse
> series dependends on this dax series).
> 
> The famfs user space code can be found at [1]
> 
> Dax Overview:
> 
> This series introduces a new "famfs mode" of devdax, whose driver is
> drivers/dax/fsdev.c. This driver supports dax_iomap_rw() and
> dax_iomap_fault() calls against a character dax instance. A dax device
> now can be converted among three modes: 'system-ram', 'devdax' and
> 'famfs' via daxctl or sysfs (e.g. unbind devdax and bind famfs instead).
> 
> In famfs mode, a dax device initializes its pages consistent with the
> fsdaxmode of pmem. Raw read/write/mmap are not supported in this mode,
> but famfs is happy in this mode - using dax_iomap_rw() for read/write and
> dax_iomap_fault() for mmap faults.
> 

Here's what I found:

famfs-v10 on 7.0-rc5 + ndctl v84:
	dax suite all pass 13/13, so no regression appears

famfs-v10 on 7.0-rc5 +
(ndctl v84 w https://github.com/jagalactic/ndctl/tree/famfs
top 3 patches + edit daxctl-famfs.sh to use cxl-test:

	existing dax suite keeps passing
	daxctl-famfs.sh oops w the new test at # Restore original mode"
	seems easy to repoduce, maybe cannot go back to system-ram???

Let me know if you need more info.

-- Alison