On 28/06/2023 03:20, Yin Fengwei wrote:
On 6/27/23 16:09, Ryan Roberts wrote:
On 27/06/2023 08:08, Yu Zhao wrote:
On Mon, Jun 26, 2023 at 11:14 AM Ryan Roberts <ryan.roberts@xxxxxxx> wrote:
Like folio_add_new_anon_rmap() but batch-rmaps a range of pages
belonging to a folio, for effciency savings. All pages are accounted as
small pages.
Signed-off-by: Ryan Roberts <ryan.roberts@xxxxxxx>
---
include/linux/rmap.h | 2 ++
mm/rmap.c | 43 +++++++++++++++++++++++++++++++++++++++++++
2 files changed, 45 insertions(+)
diff --git a/include/linux/rmap.h b/include/linux/rmap.h
index a3825ce81102..15433a3d0cbf 100644
--- a/include/linux/rmap.h
+++ b/include/linux/rmap.h
@@ -196,6 +196,8 @@ void page_add_new_anon_rmap(struct page *, struct vm_area_struct *,
unsigned long address);
void folio_add_new_anon_rmap(struct folio *, struct vm_area_struct *,
unsigned long address);
+void folio_add_new_anon_rmap_range(struct folio *folio, struct page *page,
+ int nr, struct vm_area_struct *vma, unsigned long address);
We should update folio_add_new_anon_rmap() to support large() &&
!folio_test_pmd_mappable() folios instead.
I double checked all places currently using folio_add_new_anon_rmap(),
and as expected, none actually allocates large() &&
!folio_test_pmd_mappable() and maps it one by one, which makes the
cases simpler, i.e.,
if (!large())
// the existing basepage case
else if (!folio_test_pmd_mappable())
// our new case
else
// the existing THP case
I don't have a strong opinion either way. Happy to go with this suggestion. But
the reason I did it as a new function was because I was following the pattern in
[1] which adds a new folio_add_file_rmap_range() function.
[1] https://lore.kernel.org/linux-mm/20230315051444.3229621-35-willy@xxxxxxxxxxxxx/
Oh. There is different here:
For page cache, large folio could be created by previous file access. But later
file access by other process just need map partial large folio. In this case, we need
_range for filemap.
But for anonymous, I suppose we always map whole folio in. So I agree with Yu. We
don't need _range for folio_add_new_anon_rmap(). Thanks.
Yes that makes sense - thanks. I'll merge the new case into
folio_add_new_anon_rmap() for v2.
Regards
Yin, Fengwei
void page_add_file_rmap(struct page *, struct vm_area_struct *,
bool compound);
void folio_add_file_rmap_range(struct folio *, struct page *, unsigned int nr,
diff --git a/mm/rmap.c b/mm/rmap.c
index 1d8369549424..4050bcea7ae7 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -1305,6 +1305,49 @@ void folio_add_new_anon_rmap(struct folio *folio, struct vm_area_struct *vma,
__page_set_anon_rmap(folio, &folio->page, vma, address, 1);
}
+/**
+ * folio_add_new_anon_rmap_range - Add mapping to a set of pages within a new
+ * anonymous potentially large folio.
+ * @folio: The folio containing the pages to be mapped
+ * @page: First page in the folio to be mapped
+ * @nr: Number of pages to be mapped
+ * @vma: the vm area in which the mapping is added
+ * @address: the user virtual address of the first page to be mapped
+ *
+ * Like folio_add_new_anon_rmap() but batch-maps a range of pages within a folio
+ * using non-THP accounting. Like folio_add_new_anon_rmap(), the inc-and-test is
+ * bypassed and the folio does not have to be locked. All pages in the folio are
+ * individually accounted.
+ *
+ * As the folio is new, it's assumed to be mapped exclusively by a single
+ * process.
+ */
+void folio_add_new_anon_rmap_range(struct folio *folio, struct page *page,
+ int nr, struct vm_area_struct *vma, unsigned long address)
+{
+ int i;
+
+ VM_BUG_ON_VMA(address < vma->vm_start ||
+ address + (nr << PAGE_SHIFT) > vma->vm_end, vma);
BTW, VM_BUG_ON* shouldn't be used in new code:
Documentation/process/coding-style.rst
Thanks, sorry about that. Was copy-pasting from folio_add_new_anon_rmap().
