diff options
Diffstat (limited to 'mm/mmap.c')
| -rw-r--r-- | mm/mmap.c | 34 |
1 files changed, 34 insertions, 0 deletions
diff --git a/mm/mmap.c b/mm/mmap.c index 7afc7a7cec6..b6537211b9c 100644 --- a/mm/mmap.c +++ b/mm/mmap.c @@ -1029,6 +1029,40 @@ unsigned long do_mmap_pgoff(struct file * file, unsigned long addr, } EXPORT_SYMBOL(do_mmap_pgoff); +/* + * Some shared mappigns will want the pages marked read-only + * to track write events. If so, we'll downgrade vm_page_prot + * to the private version (using protection_map[] without the + * VM_SHARED bit). + */ +int vma_wants_writenotify(struct vm_area_struct *vma) +{ + unsigned int vm_flags = vma->vm_flags; + + /* If it was private or non-writable, the write bit is already clear */ + if ((vm_flags & (VM_WRITE|VM_SHARED)) != ((VM_WRITE|VM_SHARED))) + return 0; + + /* The backer wishes to know when pages are first written to? */ + if (vma->vm_ops && vma->vm_ops->page_mkwrite) + return 1; + + /* The open routine did something to the protections already? */ + if (pgprot_val(vma->vm_page_prot) != + pgprot_val(protection_map[vm_flags & + (VM_READ|VM_WRITE|VM_EXEC|VM_SHARED)])) + return 0; + + /* Specialty mapping? */ + if (vm_flags & (VM_PFNMAP|VM_INSERTPAGE)) + return 0; + + /* Can the mapping track the dirty pages? */ + return vma->vm_file && vma->vm_file->f_mapping && + mapping_cap_account_dirty(vma->vm_file->f_mapping); +} + + unsigned long mmap_region(struct file *file, unsigned long addr, unsigned long len, unsigned long flags, unsigned int vm_flags, unsigned long pgoff, |