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. > > + * 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.
