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'? > + * 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.
