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authorLinus Torvalds <torvalds@g5.osdl.org>2005-12-11 20:38:17 -0800
committerLinus Torvalds <torvalds@g5.osdl.org>2005-12-11 20:38:17 -0800
commit67121172f9753f38689651b613a4850e0e75876f (patch)
treecfb6ea8365c44a43ee254385c7d246f0418cedd0
parent913f2d792ff584bf9ebf5968472b3e4ffe0fd9c8 (diff)
downloadop-kernel-dev-67121172f9753f38689651b613a4850e0e75876f.zip
op-kernel-dev-67121172f9753f38689651b613a4850e0e75876f.tar.gz
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>
-rw-r--r--mm/memory.c11
1 files changed, 8 insertions, 3 deletions
diff --git a/mm/memory.c b/mm/memory.c
index 430a72e..47c533e 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;
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