Re: [PATCH v2 07/10] mm/shmem_luo: Retrieve tmpfs files onto a tmpfs mount chosen by userspace

[Pasha Tatashin]

On 10-28 23:09, David Matlack wrote:
> On 2026-10-28 06:02 PM, Pasha Tatashin wrote:
> 
> > > +/*
> > > + * Whether @inode is on the internal shmem mount, which is used by
> > > + * shmem_file_setup() and thus by memfd_create().
> > > + */
> > > +bool shmem_inode_on_internal_mount(const struct inode *inode)
> > > +{
> > > +	return inode->i_sb == shm_mnt->mnt_sb;
> > > +}
> > 
> > Please fix the warning reported by kernel test robot.
> 
> Will do.
> 
> The prototype for shmem_inode_on_internal_mount() is in mm/internal.h,
> which mm/shmem.c only includes if CONFIG_SHMEM=y, but the robot was
> building without CONFIG_SHMEM. I've moved the definition of this
> function into CONFIG_SHMEM in v3 to fix this.
> 
> > Looking at this together with Pratyush's mapping-freeze series ([PATCH
> > 0/3] mm: allow freezing mappings), I think we should extend the mapping
> > freeze lifecycle from preserve() -> retrieve() to preserve() ->
> > finish().
> >
> > When retrieve() returns an fd, its mapping should still come out frozen
> > and only become fully user-owned/mutable once a successful session
> > finish() happens. That keeps the index -> folio mapping invariant across
> > the entire live update until every fd in the session (e.g. vmfd,
> > iommufd, vfiofd that depend on the memfd) has been retrieved, passed
> > can_finish(), and been finalized together in finish().
> >
> > (Doesn't have to block this series, we can do it on top or as part of
> > Pratyush's AS_FROZEN series.), but I think we must fix it either here or
> > there.)
> 
> Ok that sounds reasonable. Should we do that as part of Pratyush's
> series then?
> 
> Pratyuh's series replaces shmem_freeze() with mapping_set_frozen(), so
> retrieve() would freeze the new file and finish() would unfreeze it.
> That should work the same for memfds and tmpfs files..
> 
> BTW, this tmpfs series does a lot of renames and code motion so it
> conflicts with Pratyush's series. How should we order these?

Initially, I thought Pratyush's patch series would land after yours. 
However, since he plans to separate the LU changes from the rest, I 
expect both series to land in this cycle. The order does not matter; 
whoever lands in liveupdate/next first, the other will need to resolve 
the merge conflicts.

-- 
Pasha