Fix up mm/mincore.c error value cases (4fb23e43) · Commits · 戴 / test

Hugh Dickins correctly points out that mincore() is actually _supposed_ to fail on an unmapped hole in the user address space, rather than return valid ("empty") information about the hole. This just simplifies the problem further (I had been misled by our previous confusing and complicated way of doing mincore()). Also, in the unlikely situation that we can't allocate a temporary kernel buffer, we should actually return EAGAIN, not ENOMEM, to keep the "unmapped hole" and "allocation failure" error cases separate. Finally, add a comment about our stupid historical lack of support for anonymous mappings. I'll fix that if somebody reminds me after 2.6.20 is out. Acked-by:

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

Linus Torvalds <torvalds@osdl.org>

mm/mincore.c

+10 −19

Original line number	Diff line number	Diff line
		@@ -49,29 +49,20 @@ static long do_mincore(unsigned long addr, unsigned char *vec, unsigned long pag
		struct vm_area_struct *vma = find_vma(current->mm, addr);

		/*
		* find_vma() didn't find anything: the address
		* is above everything we have mapped.
		* find_vma() didn't find anything above us, or we're
		* in an unmapped hole in the address space: ENOMEM.
		*/
		if (!vma) {
		memset(vec, 0, pages);
		return pages;
		}

		/*
		* find_vma() found something, but we might be
		* below it: check for that.
		*/
		if (addr < vma->vm_start) {
		unsigned long gap = (vma->vm_start - addr) >> PAGE_SHIFT;
		if (gap > pages)
		gap = pages;
		memset(vec, 0, gap);
		return gap;
		}
		if (!vma \|\| addr < vma->vm_start)
		return -ENOMEM;

		/*
		* Ok, got it. But check whether it's a segment we support
		* mincore() on. Right now, we don't do any anonymous mappings.
		*
		* FIXME: This is just stupid. And returning ENOMEM is
		* stupid too. We should just look at the page tables. But
		* this is what we've traditionally done, so we'll just
		* continue doing it.
		*/
		if (!vma->vm_file)
		return -ENOMEM;
		@@ -142,7 +133,7 @@ asmlinkage long sys_mincore(unsigned long start, size_t len,

		tmp = (void *) __get_free_page(GFP_USER);
		if (!tmp)
		return -ENOMEM;
		return -EAGAIN;

		retval = 0;
		while (pages) {

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