Re: [PATCH v2] fs: ntfs: Disable NTFS_RW for PPC

[Guenter Roeck]

On 11/22/21 5:15 PM, Joel Stanley wrote:
> On Mon, 22 Nov 2021 at 23:58, Guenter Roeck <linux@xxxxxxxxxxxx> wrote:
> > NTFS_RW code allocates page size dependent arrays on the stack. This
> > results in build failures if the page size is 64k, which is now the
> > default for PPC.
>
> It became the default for PPC_BOOK3S_64, which doesn't include all of
> PPC, in f22969a66041 ("powerpc/64s: Default to 64K pages for 64 bit
> book3s").
>
> You might want to add a mention of this commit in your commit message.
>
> > fs/ntfs/aops.c: In function 'ntfs_write_mst_block':
> > fs/ntfs/aops.c:1311:1: error:
> >          the frame size of 2240 bytes is larger than 2048 bytes
> >
> > Increasing the maximum frame size for PPC just to silence this error does
> > not really help. It would have to be set to a really large value for 256k
> > pages. Such a large frame size could potentially result in stack overruns
> > in this code and elsewhere and is therefore not desirable. Disable NTFS_RW
> > for PPC instead.
> >
> > Cc: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
> > Cc: Stephen Rothwell <sfr@xxxxxxxxxxxxxxxx>
> > Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
> > Signed-off-by: Guenter Roeck <linux@xxxxxxxxxxxx>
> > ---
> > v2: Introduce new configuration flag DISABLE_NTFS_RW and use it to disable NTFS_RW
> >      for PPC
> >
> >   fs/ntfs/Kconfig | 5 +++++
> >   1 file changed, 5 insertions(+)
> >
> > diff --git a/fs/ntfs/Kconfig b/fs/ntfs/Kconfig
> > index 1667a7e590d8..324224febb6a 100644
> > --- a/fs/ntfs/Kconfig
> > +++ b/fs/ntfs/Kconfig
> > @@ -49,8 +49,13 @@ config NTFS_DEBUG
> >            When reporting bugs, please try to have available a full dump of
> >            debugging messages while the misbehaviour was occurring.
> >
> > +config DISABLE_NTFS_RW
> > +       bool
> > +       default y if PPC
>
> PPC_64K_PAGES would be more accurate.
>
> I think arm64 was seeing a similar build error, so you could include
> ARM64_64K_PAGES as well?
Yes, you are correct.

fs/ntfs/aops.c: In function 'ntfs_write_mst_block':
fs/ntfs/aops.c:1311:1: error: the frame size of 2608 bytes is larger than 2048 bytes

Ok, I'll do that. And, digging for it, I see

config VMXNET3
        tristate "VMware VMXNET3 ethernet driver"
        depends on PCI && INET
        depends on !(PAGE_SIZE_64KB || ARM64_64K_PAGES || \
                     IA64_PAGE_SIZE_64KB || PARISC_PAGE_SIZE_64KB || \
                     PPC_64K_PAGES)

That adds hexagon, ia64, mips, parisc, and sh to the list of affected architectures.
Plus, of course, there is PAGE_SIZE_256KB and PPC_256K_PAGES.

So we are looking for something like

config DISABLE_NTFS_RW
	bool
	default y if PAGE_SIZE_256KB || PPC_256K_PAGES || \
		PAGE_SIZE_64KB || ARM64_64K_PAGES || IA64_PAGE_SIZE_64KB || \
		PARISC_PAGE_SIZE_64KB || PPC_64K_PAGES

Anything else ?

Guenter


> > +
> >   config NTFS_RW
> >          bool "NTFS write support"
> > +       depends on !DISABLE_NTFS_RW
> >          depends on NTFS_FS
> >          help
> >            This enables the partial, but safe, write support in the NTFS driver.
> > --
> > 2.33.0