From: Nick Piggin Date: Sat, 9 Feb 2008 00:15:19 +0000 (+0100) Subject: mm: special mapping nopage X-Git-Url: https://git.stricted.de/?a=commitdiff_plain;h=b1d0e4f535e10775cffde922208b49629169aeaa;p=GitHub%2FLineageOS%2FG12%2Fandroid_kernel_amlogic_linux-4.9.git mm: special mapping nopage Convert special mapping install from nopage to fault. Because the "vm_file" is NULL for the special mapping, the generic VM code has messed up "vm_pgoff" thinking that it's an anonymous mapping and the offset does't matter. For that reason, we need to undo the vm_pgoff offset that got added into vmf->pgoff. [ We _really_ should clean that up - either by making this whole special mapping code just use a real file entry rather than that ugly array of "struct page" pointers, or by just making the VM code realize that even if vm_file is NULL it may not be a regular anonymous mmap. - Linus ] Signed-off-by: Nick Piggin Cc: linux-mm@kvack.org Cc: linux-kernel@vger.kernel.org Signed-off-by: Linus Torvalds --- diff --git a/mm/mmap.c b/mm/mmap.c index ad6e4eaf34f8..a32d28ce31cd 100644 --- a/mm/mmap.c +++ b/mm/mmap.c @@ -2165,24 +2165,31 @@ int may_expand_vm(struct mm_struct *mm, unsigned long npages) } -static struct page *special_mapping_nopage(struct vm_area_struct *vma, - unsigned long address, int *type) +static int special_mapping_fault(struct vm_area_struct *vma, + struct vm_fault *vmf) { + pgoff_t pgoff; struct page **pages; - BUG_ON(address < vma->vm_start || address >= vma->vm_end); + /* + * special mappings have no vm_file, and in that case, the mm + * uses vm_pgoff internally. So we have to subtract it from here. + * We are allowed to do this because we are the mm; do not copy + * this code into drivers! + */ + pgoff = vmf->pgoff - vma->vm_pgoff; - address -= vma->vm_start; - for (pages = vma->vm_private_data; address > 0 && *pages; ++pages) - address -= PAGE_SIZE; + for (pages = vma->vm_private_data; pgoff && *pages; ++pages) + pgoff--; if (*pages) { struct page *page = *pages; get_page(page); - return page; + vmf->page = page; + return 0; } - return NOPAGE_SIGBUS; + return VM_FAULT_SIGBUS; } /* @@ -2194,7 +2201,7 @@ static void special_mapping_close(struct vm_area_struct *vma) static struct vm_operations_struct special_mapping_vmops = { .close = special_mapping_close, - .nopage = special_mapping_nopage, + .fault = special_mapping_fault, }; /*