From: Christoph Hellwig <hch@xxxxxx> Subject: mm: simplify gup_fast_permitted Pass in the already calculated end value instead of recomputing it, and leave the end > start check in the callers instead of duplicating them in the arch code. Link: http://lkml.kernel.org/r/20190625143715.1689-3-hch@xxxxxx Signed-off-by: Christoph Hellwig <hch@xxxxxx> Reviewed-by: Jason Gunthorpe <jgg@xxxxxxxxxxxx> Cc: Andrey Konovalov <andreyknvl@xxxxxxxxxx> Cc: Benjamin Herrenschmidt <benh@xxxxxxxxxxxxxxxxxxx> Cc: David Miller <davem@xxxxxxxxxxxxx> Cc: James Hogan <jhogan@xxxxxxxxxx> Cc: Khalid Aziz <khalid.aziz@xxxxxxxxxx> Cc: Michael Ellerman <mpe@xxxxxxxxxxxxxx> Cc: Nicholas Piggin <npiggin@xxxxxxxxx> Cc: Paul Burton <paul.burton@xxxxxxxx> Cc: Paul Mackerras <paulus@xxxxxxxxx> Cc: Ralf Baechle <ralf@xxxxxxxxxxxxxx> Cc: Rich Felker <dalias@xxxxxxxx> Cc: Yoshinori Sato <ysato@xxxxxxxxxxxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- arch/s390/include/asm/pgtable.h | 8 +------- arch/x86/include/asm/pgtable_64.h | 8 +------- mm/gup.c | 17 +++++++---------- 3 files changed, 9 insertions(+), 24 deletions(-) --- a/arch/s390/include/asm/pgtable.h~mm-simplify-gup_fast_permitted +++ a/arch/s390/include/asm/pgtable.h @@ -1270,14 +1270,8 @@ static inline pte_t *pte_offset(pmd_t *p #define pte_offset_map(pmd, address) pte_offset_kernel(pmd, address) #define pte_unmap(pte) do { } while (0) -static inline bool gup_fast_permitted(unsigned long start, int nr_pages) +static inline bool gup_fast_permitted(unsigned long start, unsigned long end) { - unsigned long len, end; - - len = (unsigned long) nr_pages << PAGE_SHIFT; - end = start + len; - if (end < start) - return false; return end <= current->mm->context.asce_limit; } #define gup_fast_permitted gup_fast_permitted --- a/arch/x86/include/asm/pgtable_64.h~mm-simplify-gup_fast_permitted +++ a/arch/x86/include/asm/pgtable_64.h @@ -259,14 +259,8 @@ extern void init_extra_mapping_uc(unsign extern void init_extra_mapping_wb(unsigned long phys, unsigned long size); #define gup_fast_permitted gup_fast_permitted -static inline bool gup_fast_permitted(unsigned long start, int nr_pages) +static inline bool gup_fast_permitted(unsigned long start, unsigned long end) { - unsigned long len, end; - - len = (unsigned long)nr_pages << PAGE_SHIFT; - end = start + len; - if (end < start) - return false; if (end >> __VIRTUAL_MASK_SHIFT) return false; return true; --- a/mm/gup.c~mm-simplify-gup_fast_permitted +++ a/mm/gup.c @@ -2123,13 +2123,9 @@ static void gup_pgd_range(unsigned long * Check if it's allowed to use __get_user_pages_fast() for the range, or * we need to fall back to the slow version: */ -bool gup_fast_permitted(unsigned long start, int nr_pages) +static bool gup_fast_permitted(unsigned long start, unsigned long end) { - unsigned long len, end; - - len = (unsigned long) nr_pages << PAGE_SHIFT; - end = start + len; - return end >= start; + return true; } #endif @@ -2150,6 +2146,8 @@ int __get_user_pages_fast(unsigned long len = (unsigned long) nr_pages << PAGE_SHIFT; end = start + len; + if (end <= start) + return 0; if (unlikely(!access_ok((void __user *)start, len))) return 0; @@ -2165,7 +2163,7 @@ int __get_user_pages_fast(unsigned long * block IPIs that come from THPs splitting. */ - if (gup_fast_permitted(start, nr_pages)) { + if (gup_fast_permitted(start, end)) { local_irq_save(flags); gup_pgd_range(start, end, write ? FOLL_WRITE : 0, pages, &nr); local_irq_restore(flags); @@ -2224,13 +2222,12 @@ int get_user_pages_fast(unsigned long st len = (unsigned long) nr_pages << PAGE_SHIFT; end = start + len; - if (nr_pages <= 0) + if (end <= start) return 0; - if (unlikely(!access_ok((void __user *)start, len))) return -EFAULT; - if (gup_fast_permitted(start, nr_pages)) { + if (gup_fast_permitted(start, end)) { local_irq_disable(); gup_pgd_range(addr, end, gup_flags, pages, &nr); local_irq_enable(); _
