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

[Ira Weiny]

Alison Schofield wrote:
> On Fri, Mar 27, 2026 at 09:03:26PM +0000, John Groves wrote:
> > From: John Groves <john@xxxxxxxxxx>
> > 
> > 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???

John have you been able to reproduce this?

Ira

> 
> Let me know if you need more info.
> 
> -- Alison
> 
>