Re: [PATCH trivial] kernel.h: Make container_of_safe type safe
On Mon, Jan 28, 2019 at 06:44:24PM +, Jason Gunthorpe wrote: > On Mon, Jan 28, 2019 at 05:42:42AM -0800, Christoph Hellwig wrote: > > On Thu, Jan 24, 2019 at 08:55:05PM +, Jason Gunthorpe wrote: > > > The final ternary expression is given void * and type * as arguments, so > > > the resulting type of the macro ends up being void *. > > > > > > container_of returns a type which maches the argument, this provides type > > > safety and allows the expression to be immediately used as the target > > > type. > > > > > > Explicitly cast ERR_CAST() to get the correct type. > > > > I think we should just kill off container_of_safe - it has no user > > in the tree, is grossly misnamed and not really all that useful to start > > with. > > I see it open coded from time to time, here someone sent a patch > open-coding it yesterday (with the same bug even): > > https://patchwork.kernel.org/patch/10783535/ > > I noticed it didn't work right because I had a use for it.. And the patch is a good example for an anti-pattern to avoid, I'll chime in there..
Re: [PATCH trivial] kernel.h: Make container_of_safe type safe
On Mon, Jan 28, 2019 at 05:42:42AM -0800, Christoph Hellwig wrote: > On Thu, Jan 24, 2019 at 08:55:05PM +, Jason Gunthorpe wrote: > > The final ternary expression is given void * and type * as arguments, so > > the resulting type of the macro ends up being void *. > > > > container_of returns a type which maches the argument, this provides type > > safety and allows the expression to be immediately used as the target > > type. > > > > Explicitly cast ERR_CAST() to get the correct type. > > I think we should just kill off container_of_safe - it has no user > in the tree, is grossly misnamed and not really all that useful to start > with. I see it open coded from time to time, here someone sent a patch open-coding it yesterday (with the same bug even): https://patchwork.kernel.org/patch/10783535/ I noticed it didn't work right because I had a use for it.. Jason
Re: [PATCH trivial] kernel.h: Make container_of_safe type safe
On Thu, Jan 24, 2019 at 08:55:05PM +, Jason Gunthorpe wrote: > The final ternary expression is given void * and type * as arguments, so > the resulting type of the macro ends up being void *. > > container_of returns a type which maches the argument, this provides type > safety and allows the expression to be immediately used as the target > type. > > Explicitly cast ERR_CAST() to get the correct type. I think we should just kill off container_of_safe - it has no user in the tree, is grossly misnamed and not really all that useful to start with.
[PATCH trivial] kernel.h: Make container_of_safe type safe
The final ternary expression is given void * and type * as arguments, so
the resulting type of the macro ends up being void *.
container_of returns a type which maches the argument, this provides type
safety and allows the expression to be immediately used as the target
type.
Explicitly cast ERR_CAST() to get the correct type.
Fixes: 05e6557b8ed8 ("staging: lustre: add container_of_safe()")
Signed-off-by: Jason Gunthorpe
---
include/linux/kernel.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
Jiri, can you take this? Thanks
Jason
diff --git a/include/linux/kernel.h b/include/linux/kernel.h
index 8f0e68e250a760..7b85aa607eb876 100644
--- a/include/linux/kernel.h
+++ b/include/linux/kernel.h
@@ -1013,7 +1013,7 @@ static inline void ftrace_dump(enum ftrace_dump_mode
oops_dump_mode) { }
BUILD_BUG_ON_MSG(!__same_type(*(ptr), ((type *)0)->member) && \
!__same_type(*(ptr), void),\
"pointer type mismatch in container_of()");\
- IS_ERR_OR_NULL(__mptr) ? ERR_CAST(__mptr) : \
+ IS_ERR_OR_NULL(__mptr) ? ((type *)ERR_CAST(__mptr)) : \
((type *)(__mptr - offsetof(type, member))); })
/* Rebuild everything on CONFIG_FTRACE_MCOUNT_RECORD */
--
2.20.1
