From 1e8f889b10d8d2223105719e36ce45688fedbd59 Mon Sep 17 00:00:00 2001 From: David Gibson Date: Fri, 6 Jan 2006 00:10:44 -0800 Subject: [PATCH] Hugetlb: Copy on Write support Implement copy-on-write support for hugetlb mappings so MAP_PRIVATE can be supported. This helps us to safely use hugetlb pages in many more applications. The patch makes the following changes. If needed, I also have it broken out according to the following paragraphs. 1. Add a pair of functions to set/clear write access on huge ptes. The writable check in make_huge_pte is moved out to the caller for use by COW later. 2. Hugetlb copy-on-write requires special case handling in the following situations: - copy_hugetlb_page_range() - Copied pages must be write protected so a COW fault will be triggered (if necessary) if those pages are written to. - find_or_alloc_huge_page() - Only MAP_SHARED pages are added to the page cache. MAP_PRIVATE pages still need to be locked however. 3. Provide hugetlb_cow() and calls from hugetlb_fault() and hugetlb_no_page() which handles the COW fault by making the actual copy. 4. Remove the check in hugetlbfs_file_map() so that MAP_PRIVATE mmaps will be allowed. Make MAP_HUGETLB exempt from the depricated VM_RESERVED mapping check. Signed-off-by: David Gibson Signed-off-by: Adam Litke Cc: William Lee Irwin III Cc: "Seth, Rohit" Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- fs/hugetlbfs/inode.c | 3 --- 1 file changed, 3 deletions(-) (limited to 'fs') diff --git a/fs/hugetlbfs/inode.c b/fs/hugetlbfs/inode.c index 8c1cef3..8c41315 100644 --- a/fs/hugetlbfs/inode.c +++ b/fs/hugetlbfs/inode.c @@ -100,9 +100,6 @@ static int hugetlbfs_file_mmap(struct file *file, struct vm_area_struct *vma) loff_t len, vma_len; int ret; - if ((vma->vm_flags & (VM_MAYSHARE | VM_WRITE)) == VM_WRITE) - return -EINVAL; - if (vma->vm_pgoff & (HPAGE_SIZE / PAGE_SIZE - 1)) return -EINVAL; -- cgit v1.1