[PATCH] unpaged: private write VM_RESERVED (83e9b7e9) · Commits · 戴 / test

The PageReserved removal in 2.6.15-rc1 issued a "deprecated" message when you tried to mmap or mprotect MAP_PRIVATE PROT_WRITE a VM_RESERVED, and failed with -EACCES: because do_wp_page lacks the refinement to COW pages in those areas, nor do we expect to find anonymous pages in them; and it seemed just bloat to add code for handling such a peculiar case. But immediately it caused vbetool and ddcprobe (using lrmi) to fail. So revert the "deprecated" messages, letting mmap and mprotect succeed. But leave do_wp_page's BUG_ON(vma->vm_flags & VM_RESERVED) in place until we've added the code to do it right: so this particular patch is only good if the app doesn't really need to write to that private area. Signed-off-by:

Hugh Dickins <hugh@veritas.com> Signed-off-by:

Andrew Morton <akpm@osdl.org> Signed-off-by:

Linus Torvalds <torvalds@osdl.org>

mm/mmap.c

+0 −11

Original line number	Diff line number	Diff line
		@@ -1076,17 +1076,6 @@ munmap_back:
		error = file->f_op->mmap(file, vma);
		if (error)
		goto unmap_and_free_vma;
		if ((vma->vm_flags & (VM_SHARED \| VM_WRITE \| VM_RESERVED))
		== (VM_WRITE \| VM_RESERVED)) {
		printk(KERN_WARNING "program %s is using MAP_PRIVATE, "
		"PROT_WRITE mmap of VM_RESERVED memory, which "
		"is deprecated. Please report this to "
		"linux-kernel@vger.kernel.org\n",current->comm);
		if (vma->vm_ops && vma->vm_ops->close)
		vma->vm_ops->close(vma);
		error = -EACCES;
		goto unmap_and_free_vma;
		}
		} else if (vm_flags & VM_SHARED) {
		error = shmem_zero_setup(vma);
		if (error)

mm/mprotect.c

+0 −8

Original line number	Diff line number	Diff line
		@@ -124,14 +124,6 @@ mprotect_fixup(struct vm_area_struct vma, struct vm_area_struct *pprev,
		* a MAP_NORESERVE private mapping to writable will now reserve.
		*/
		if (newflags & VM_WRITE) {
		if (oldflags & VM_RESERVED) {
		BUG_ON(oldflags & VM_WRITE);
		printk(KERN_WARNING "program %s is using MAP_PRIVATE, "
		"PROT_WRITE mprotect of VM_RESERVED memory, "
		"which is deprecated. Please report this to "
		"linux-kernel@vger.kernel.org\n",current->comm);
		return -EACCES;
		}
		if (!(oldflags & (VM_ACCOUNT\|VM_WRITE\|VM_SHARED\|VM_HUGETLB))) {
		charged = nrpages;
		if (security_vm_enough_memory(charged))

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