On Thu, 2020-07-23 at 13:46 +0900, Stafford Horne wrote:
> On Wed, Jul 22, 2020 at 03:11:35PM +0000, Atish Patra wrote:
> > On Wed, 2020-07-22 at 14:48 +0200, Greg KH wrote:
> > > On Tue, Jul 21, 2020 at 03:50:35PM -0700, Palmer Dabbelt wrote:
> > > > On Mon, 20 Jul 2020 12:14:03 PDT (-0700), Greg KH wrote:
> > > > > On Mon, Jul 20, 2020 at 06:50:10PM +0000, Atish Patra wrote:
> > > > > > On Mon, 2020-07-20 at 23:11 +0530, Naresh Kamboju wrote:
> > > > > > > RISC-V build breaks on stable-rc 5.7 branch.
> > > > > > > build failed with gcc-8, gcc-9 and gcc-9.
> > > > > > >
> > > > > >
> > > > > > Sorry for the compilation issue.
> > > > > >
> > > > > > mmap_read_lock was intrdouced in the following commit.
> > > > > >
> > > > > > commit 9740ca4e95b4
> > > > > > Author: Michel Lespinasse <walken@xxxxxxxxxx>
> > > > > > Date: Mon Jun 8 21:33:14 2020 -0700
> > > > > >
> > > > > > mmap locking API: initial implementation as rwsem
> > > > > > wrappers
> > > > > >
> > > > > > The following two commits replaced the usage of mmap_sem
> > > > > > rwsem
> > > > > > calls
> > > > > > with mmap_lock.
> > > > > >
> > > > > > d8ed45c5dcd4 (mmap locking API: use coccinelle to convert
> > > > > > mmap_sem
> > > > > > rwsem call sites)
> > > > > > 89154dd5313f (mmap locking API: convert mmap_sem call sites
> > > > > > missed by
> > > > > > coccinelle)
> > > > > >
> > > > > > The first commit is not present in stale 5.7-y for obvious
> > > > > > reasons.
> > > > > >
> > > > > > Do we need to send a separate patch only for stable branch
> > > > > > with
> > > > > > mmap_sem ? I am not sure if that will cause a conflict
> > > > > > again in
> > > > > > future.
> > > > >
> > > > > I do not like taking odd backports, and would rather take the
> > > > > real patch
> > > > > that is upstream.
> > > >
> > > > I guess I'm a bit new to stable backports so I'm not sure
> > > > what's
> > > > expected here.
> > > > The failing patch fixes a bug by using a new interface. The
> > > > smallest diff fix
> > > > for the stable kernels would be to construct a similar fix
> > > > without
> > > > the new
> > > > interface, which in this case is very easy as the new interface
> > > > just converted
> > > > some generic locking calls to one-line functions. It seems
> > > > somewhat circuitous
> > > > to land that in Linus' tree, though, as it would require
> > > > breaking
> > > > our port
> > > > before fixing it to use the old interfaces and then cleaning it
> > > > up
> > > > to use the
> > > > new interfaces.
> > > >
> > > > Are we expected to pull the new interface onto stable in
> > > > addition
> > > > to this fix?
> > >
> > > If it really does fix a big issue, yes, that is fine to do.
> > >
> >
> > The original issue was manifests only for certain rootfs with
> > CONFIG_DEBUG_VM enabled in kernel. I am not sure if that qualfies
> > for a
> > big issue :). But there was a similar fix for OpenRISC as well.
> >
> > +stafford (who fixed the issue for OpenRISC)
> >
> > @stafford Was there a request to backport the fix to stable ?
>
> I have not requested pulling my patch to stable. Mine is this one:
>
> 313a5257b84c2 ("openrisc: fix boot oops when DEBUG_VM is enabled")
>
> If you cat request that would be great.
>
> > I can combine all the git ids that needs to be pulled in.
>
> Note, mine lists:
>
> Fixes: 42fc541404f2 ("mmap locking API: add mmap_assert_locked()
> and mmap_assert_write_locked()")
>
> while your's lists:
>
> Fixes: 395a21ff859c(riscv: add ARCH_HAS_SET_DIRECT_MAP support)
>
> That is when the code was introduced to the riscv port, but not the
> commit that
> broke booting.
>
> I think if you list the Fixes as I did when backporting to stable
> Greg, or his
> tools, would also know that the patch depends on the the 42fc541404f2
> commit.
>
> Also, I guess there is no problem with listing 2 "Fixes" in the
> future.
>
Thanks. I will keep that in mind in future.
Backporting the RISC-V fix would require the original commit to be
backported as well.
commit 9740ca4e95b4 (mmap locking API: initial implementation as rwsem
wrappers)
However, that is the first commit for big cleanup 12 patch series.
https://lkml.org/lkml/2020/5/20/56
While backporting the first commit (9740ca4e95b4) would solve the
problem for RISC-V, all other architecture fixes won't be there.
Do we want that in stable tree?
> Thanks Atish and Palmer.
>
> -Stafford
>
> > > > The new interface doesn't actually fix anything itself, but it
> > > > would allow a
> > > > functional kernel to be constructed that consisted of only
> > > > backports from
> > > > Linus' tree (which would also make further fixes easier).
> > >
> > > That's fine.
> > >
> > > > It seems safe to
> > > > just pull in 9740ca4e95b4 ("mmap locking API: initial
> > > > implementation as rwsem
> > > > wrappers") before this failing patch, as in this case the new
> > > > interface will
> > > > function correctly with only a subset of callers having been
> > > > converted. Of
> > > > course that's not a generally true statement so I don't know if
> > > > future code
> > > > will behave that way, but pulling in those conversion patches
> > > > is
> > > > definitely
> > > > unnecessary diff right now.
> > >
> > > If someone wants to send me a full set of the git ids that need
> > > to be
> > > pulled in, I will be glad to do so.
> > >
> > > thanks,
> > >
> > > greg k-h
> >
> > --
> > Regards,
> > Atish
--
Regards,
Atish
