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SubjectRe: [PATCH resend] rmap: recompute pgoff for unmapping huge page
On Mon, 4 Mar 2013 20:47:31 +0800 Hillf Danton <dhillf@gmail.com> wrote:

> [Resend due to error in delivering to linux-kernel@vger.kernel.org,
> caused probably by the rich format provided by the mail agent by default.]
>
> We have to recompute pgoff if the given page is huge, since result based on
> HPAGE_SIZE is not approapriate for scanning the vma interval tree, as shown
> by commit 36e4f20af833(hugetlb: do not use vma_hugecache_offset() for
> vma_prio_tree_foreach)
>
> Signed-off-by: Hillf Danton <dhillf@gmail.com>
> ---
>
> --- a/mm/rmap.c Mon Mar 4 20:00:00 2013
> +++ b/mm/rmap.c Mon Mar 4 20:02:16 2013
> @@ -1513,6 +1513,9 @@ static int try_to_unmap_file(struct page
> unsigned long max_nl_size = 0;
> unsigned int mapcount;
>
> + if (PageHuge(page))
> + pgoff = page->index << compound_order(page);
> +
> mutex_lock(&mapping->i_mmap_mutex);
> vma_interval_tree_foreach(vma, &mapping->i_mmap, pgoff, pgoff) {
> unsigned long address = vma_address(page, vma);

How are we getting here for hugepages? Trying to migrate a hugetlbfs
page?

Can we just do this?

--- a/mm/rmap.c~a
+++ a/mm/rmap.c
@@ -1505,7 +1505,7 @@ static int try_to_unmap_anon(struct page
static int try_to_unmap_file(struct page *page, enum ttu_flags flags)
{
struct address_space *mapping = page->mapping;
- pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
+ pgoff_t pgoff;
struct vm_area_struct *vma;
int ret = SWAP_AGAIN;
unsigned long cursor;
@@ -1513,6 +1513,7 @@ static int try_to_unmap_file(struct page
unsigned long max_nl_size = 0;
unsigned int mapcount;

+ pgoff = page->index << compound_order(page);
mutex_lock(&mapping->i_mmap_mutex);
vma_interval_tree_foreach(vma, &mapping->i_mmap, pgoff, pgoff) {
unsigned long address = vma_address(page, vma);
_
It's a lot less fuss.


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