Hi Matthew, On Sun, Nov 4, 2018 at 2:06 PM Mike Rapoport <rppt@xxxxxxxxxxxxx> wrote: > > On Sat, Nov 03, 2018 at 05:02:36AM -0700, Matthew Wilcox wrote: > > On Sat, Nov 03, 2018 at 10:35:04AM +0530, Souptick Joarder wrote: > > > Page fault handlers are supposed to return VM_FAULT codes, > > > but some drivers/file systems mistakenly return error > > > numbers. Now that all drivers/file systems have been converted > > > to use the vm_fault_t return type, change the type definition > > > to no longer be compatible with 'int'. By making it an unsigned > > > int, the function prototype becomes incompatible with a function > > > which returns int. Sparse will detect any attempts to return a > > > value which is not a VM_FAULT code. > > > > > > > -/* Encode hstate index for a hwpoisoned large page */ > > > -#define VM_FAULT_SET_HINDEX(x) ((x) << 12) > > > -#define VM_FAULT_GET_HINDEX(x) (((x) >> 12) & 0xf) > > ... > > > +/* Encode hstate index for a hwpoisoned large page */ > > > +#define VM_FAULT_SET_HINDEX(x) ((__force vm_fault_t)((x) << 16)) > > > +#define VM_FAULT_GET_HINDEX(x) (((x) >> 16) & 0xf) > > > > I think it's important to mention in the changelog that these values > > have been changed to avoid conflicts with other VM_FAULT codes. > > > > > +/** > > > + * typedef vm_fault_t - __bitwise unsigned int > > > + * > > > + * vm_fault_t is the new unsigned int type to return VM_FAULT > > > + * code by page fault handlers of drivers/file systems. Now if > > > + * any page fault handlers returns non VM_FAULT code instead > > > + * of VM_FAULT code, it will be a mismatch with function > > > + * prototype and sparse will detect it. > > > + */ > > > > The first line should be what the typedef *means*, not repeat the > > compiler's definition. The rest of the description should be information > > for someone coming to the type for the first time; what you've written > > here is changelog material. > > > > /** > > * typedef vm_fault_t - Return type for page fault handlers. > > * > > * Page fault handlers return a bitmask of %VM_FAULT values. > > */ > > > > > +typedef __bitwise unsigned int vm_fault_t; > > > + > > > +/** > > > + * enum - VM_FAULT code > > > > Can you document an anonymous enum? I've never tried. Did you run this > > through 'make htmldocs'? > > You cannot document an anonymous enum. I assume, you are pointing to Document folder and I don't know if this enum need to be documented or not. I didn't run 'make htmldocs' as there is no document related changes. > > > > + * This enum is used to track the VM_FAULT code return by page > > > + * fault handlers. > > > > * Page fault handlers return a bitmask of these values to tell the > > * core VM what happened when handling the fault. > > > > -- > Sincerely yours, > Mike. >
