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| author | Linus Torvalds <torvalds@g5.osdl.org> | 2005-12-11 20:38:17 -0800 |
|---|---|---|
| committer | Linus Torvalds <torvalds@g5.osdl.org> | 2005-12-11 20:38:17 -0800 |
| commit | 67121172f9753f38689651b613a4850e0e75876f (patch) | |
| tree | cfb6ea8365c44a43ee254385c7d246f0418cedd0 /mm/memory.c | |
| parent | 913f2d792ff584bf9ebf5968472b3e4ffe0fd9c8 (diff) | |
| download | lwn-67121172f9753f38689651b613a4850e0e75876f.tar.gz lwn-67121172f9753f38689651b613a4850e0e75876f.zip | |
Allow arbitrary read-only shared pfn-remapping too
The VM layer (for historical reasons) turns a read-only shared mmap into
a private-like mapping with the VM_MAYWRITE bit clear. Thus checking
just VM_SHARED isn't actually sufficient.
So use a trivial helper function for the cases where we wanted to inquire
if a mapping was COW-like or not.
Moo!
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Diffstat (limited to 'mm/memory.c')
| -rw-r--r-- | mm/memory.c | 11 |
1 files changed, 8 insertions, 3 deletions
diff --git a/mm/memory.c b/mm/memory.c index 430a72ed08d5..47c533eaa072 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -349,6 +349,11 @@ void print_bad_pte(struct vm_area_struct *vma, pte_t pte, unsigned long vaddr) dump_stack(); } +static inline int is_cow_mapping(unsigned int flags) +{ + return (flags & (VM_SHARED | VM_MAYWRITE)) == VM_MAYWRITE; +} + /* * This function gets the "struct page" associated with a pte. * @@ -377,7 +382,7 @@ struct page *vm_normal_page(struct vm_area_struct *vma, unsigned long addr, pte_ unsigned long off = (addr - vma->vm_start) >> PAGE_SHIFT; if (pfn == vma->vm_pgoff + off) return NULL; - if (vma->vm_flags & VM_SHARED) + if (!is_cow_mapping(vma->vm_flags)) return NULL; } @@ -439,7 +444,7 @@ copy_one_pte(struct mm_struct *dst_mm, struct mm_struct *src_mm, * If it's a COW mapping, write protect it both * in the parent and the child */ - if ((vm_flags & (VM_SHARED | VM_MAYWRITE)) == VM_MAYWRITE) { + if (is_cow_mapping(vm_flags)) { ptep_set_wrprotect(src_mm, addr, src_pte); pte = *src_pte; } @@ -1319,7 +1324,7 @@ int remap_pfn_range(struct vm_area_struct *vma, unsigned long addr, * behaviour that some programs depend on. We mark the "original" * un-COW'ed pages by matching them up with "vma->vm_pgoff". */ - if (!(vma->vm_flags & VM_SHARED)) { + if (is_cow_mapping(vma->vm_flags)) { if (addr != vma->vm_start || end != vma->vm_end) return -EINVAL; vma->vm_pgoff = pfn; |