Re: [PATCH] gfs2: add missing __rcu annotation to i_gl in incore.h

[Andreas Gruenbacher]

On Fri, Jul 24, 2026 at 6:05 PM Adrián García Casado
<adriangarciacasado42@xxxxxxxxx> wrote:
> Hi Andreas,
>
> Thanks for applying the patch!

No, I'm not applying that patch. As I said, it's not really fixing
anything, it's only trading two errors against 200 warnings.

> For the record, I have successfully boot-tested the patched v7.2-rc4+
> kernel on bare-metal x86_64 (Debian 13 native on an ASUS Vivobook).
>
> To stress-test the kernel stability under load, I ran some heavy workloads:
> - A standalone loopback mount of GFS2 (using lock_nolock) with I/O stress
>   tests (100+ concurrent files).
> - A full multi-threaded compilation of the PCSX2 emulator (using CMake
>   and Ninja) with all CPU cores sustained at 100% load.
>
> The system behaved completely stable with no deadlocks, hangs, or OOM.
>
> Tested-by: Adrian Garcia Casado <adriangarciacasado42@xxxxxxxxx>
>
> Best regards,
> Adrian

Andreas

> El vie, 24 jul 2026, 17:33, Andreas Gruenbacher <agruenba@xxxxxxxxxx> escribió:
>>
>> On Tue, Jun 30, 2026 at 12:03 PM Adrian Garcia Casado
>> <adriangarciacasado42@xxxxxxxxx> wrote:
>> > In gfs2_inode_lookup() and other parts of the GFS2 filesystem,
>> > ip->i_gl is accessed and dereferenced via RCU helpers like
>> > rcu_dereference_check() and rcu_access_pointer(). However, the
>> > actual i_gl pointer in struct gfs2_inode was never annotated
>> > with __rcu in incore.h.
>> >
>> > This missing annotation causes Sparse to throw multiple
>> > "incompatible types in comparison expression (different address spaces)"
>> > warnings and compilation-blocking errors under strict static analysis builds.
>>
>> Indeed, there are two sparse errors related to i_gl.
>>
>> > Fix this by adding the __rcu annotation to i_gl in struct gfs2_inode.
>>
>> With this fix, I get about 200 sparse warnings instead of the two
>> errors. So thanks for pointing out that there are errors, but without
>> fixing any of the underlying problems, this patch isn't very useful.
>>
>> Andreas
>>
>> > Signed-off-by: Adrian Garcia Casado <adriangarciacasado42@xxxxxxxxx>
>> > Tested-by: Adrian Garcia Casado <adriangarciacasado42@xxxxxxxxx>
>> > ---
>> >
>> > diff --git a/fs/gfs2/incore.h b/fs/gfs2/incore.h
>> > index 6146577..16df753 100644
>> > --- a/fs/gfs2/incore.h
>> > +++ b/fs/gfs2/incore.h
>> > @@ -392,7 +392,7 @@ struct gfs2_inode {
>> >         u64 i_generation;
>> >         u64 i_eattr;
>> >         unsigned long i_flags;          /* GIF_... */
>> > -       struct gfs2_glock *i_gl;
>> > +       struct gfs2_glock __rcu *i_gl;
>> >         struct gfs2_holder i_iopen_gh;
>> >         struct gfs2_qadata *i_qadata; /* quota allocation data */
>> >         struct gfs2_holder i_rgd_gh;
>>
>> Applied, thanks.
>>
>>
>>
>> Andreas
>>