On Sat, Jan 5, 2019 at 4:22 PM Linus Torvalds
<torvalds@xxxxxxxxxxxxxxxxxxxx> wrote:
>
> But I think my patch to just rip out all that page lookup, and just
> base it on the page table state has the fundamental advantage that it
> gets rid of code. Maybe I should jst commit it, and see if anything
> breaks? We do have options in case things break, and then we'd at
> least know who cares (and perhaps a lot more information of _why_ they
> care).
Slightly updated patch in case somebody wants to try things out.
Also, any comments about the pmd_trans_unstable() case?
Linus
mm/mincore.c | 94 +++++++++---------------------------------------------------
1 file changed, 13 insertions(+), 81 deletions(-)
diff --git a/mm/mincore.c b/mm/mincore.c
index 218099b5ed31..f0f91461a9f4 100644
--- a/mm/mincore.c
+++ b/mm/mincore.c
@@ -42,72 +42,14 @@ static int mincore_hugetlb(pte_t *pte, unsigned long hmask, unsigned long addr,
return 0;
}
-/*
- * Later we can get more picky about what "in core" means precisely.
- * For now, simply check to see if the page is in the page cache,
- * and is up to date; i.e. that no page-in operation would be required
- * at this time if an application were to map and access this page.
- */
-static unsigned char mincore_page(struct address_space *mapping, pgoff_t pgoff)
-{
- unsigned char present = 0;
- struct page *page;
-
- /*
- * When tmpfs swaps out a page from a file, any process mapping that
- * file will not get a swp_entry_t in its pte, but rather it is like
- * any other file mapping (ie. marked !present and faulted in with
- * tmpfs's .fault). So swapped out tmpfs mappings are tested here.
- */
-#ifdef CONFIG_SWAP
- if (shmem_mapping(mapping)) {
- page = find_get_entry(mapping, pgoff);
- /*
- * shmem/tmpfs may return swap: account for swapcache
- * page too.
- */
- if (xa_is_value(page)) {
- swp_entry_t swp = radix_to_swp_entry(page);
- page = find_get_page(swap_address_space(swp),
- swp_offset(swp));
- }
- } else
- page = find_get_page(mapping, pgoff);
-#else
- page = find_get_page(mapping, pgoff);
-#endif
- if (page) {
- present = PageUptodate(page);
- put_page(page);
- }
-
- return present;
-}
-
-static int __mincore_unmapped_range(unsigned long addr, unsigned long end,
- struct vm_area_struct *vma, unsigned char *vec)
-{
- unsigned long nr = (end - addr) >> PAGE_SHIFT;
- int i;
-
- if (vma->vm_file) {
- pgoff_t pgoff;
-
- pgoff = linear_page_index(vma, addr);
- for (i = 0; i < nr; i++, pgoff++)
- vec[i] = mincore_page(vma->vm_file->f_mapping, pgoff);
- } else {
- for (i = 0; i < nr; i++)
- vec[i] = 0;
- }
- return nr;
-}
-
static int mincore_unmapped_range(unsigned long addr, unsigned long end,
struct mm_walk *walk)
{
- walk->private += __mincore_unmapped_range(addr, end,
- walk->vma, walk->private);
+ unsigned char *vec = walk->private;
+ unsigned long nr = (end - addr) >> PAGE_SHIFT;
+
+ memset(vec, 0, nr);
+ walk->private += nr;
return 0;
}
@@ -127,8 +69,9 @@ static int mincore_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end,
goto out;
}
+ /* We'll consider a THP page under construction to be there */
if (pmd_trans_unstable(pmd)) {
- __mincore_unmapped_range(addr, end, vma, vec);
+ memset(vec, 1, nr);
goto out;
}
@@ -137,28 +80,17 @@ static int mincore_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end,
pte_t pte = *ptep;
if (pte_none(pte))
- __mincore_unmapped_range(addr, addr + PAGE_SIZE,
- vma, vec);
+ *vec = 0;
else if (pte_present(pte))
*vec = 1;
else { /* pte is a swap entry */
swp_entry_t entry = pte_to_swp_entry(pte);
- if (non_swap_entry(entry)) {
- /*
- * migration or hwpoison entries are always
- * uptodate
- */
- *vec = 1;
- } else {
-#ifdef CONFIG_SWAP
- *vec = mincore_page(swap_address_space(entry),
- swp_offset(entry));
-#else
- WARN_ON(1);
- *vec = 1;
-#endif
- }
+ /*
+ * migration or hwpoison entries are always
+ * uptodate
+ */
+ *vec = !!non_swap_entry(entry);
}
vec++;
}
