[PATCH v4 1/6] userfaultfd: convert mfill_atomic_pte_copy() to use a folio

Peng Zhang
2023-03-30T13:41:40Z

From: ZhangPeng <zhangpeng362@huawei.com>

Call vma_alloc_folio() directly instead of alloc_page_vma(). Add an
assertion that this is a single-page folio and removes several calls to
compound_head().

Signed-off-by: ZhangPeng <zhangpeng362@huawei.com>
---
mm/userfaultfd.c | 25 +++++++++++++------------
1 file changed, 13 insertions(+), 12 deletions(-)

diff --git a/mm/userfaultfd.c b/mm/userfaultfd.c
index 7f1b5f8b712c..efa9e1d681ee 100644
--- a/mm/userfaultfd.c
+++ b/mm/userfaultfd.c
@@ -137,15 +137,15 @@ static int mfill_atomic_pte_copy(pmd_t *dst_pmd,
{
void *page_kaddr;
int ret;
- struct page *page;
+ struct folio *folio;

if (!*pagep) {
ret = -ENOMEM;
- page = alloc_page_vma(GFP_HIGHUSER_MOVABLE, dst_vma, dst_addr);
- if (!page)
+ folio = vma_alloc_folio(GFP_HIGHUSER_MOVABLE, 0, dst_vma, dst_addr, false);
+ if (!folio)
goto out;

- page_kaddr = kmap_local_page(page);
+ page_kaddr = kmap_local_folio(folio, 0);
/*
* The read mmap_lock is held here. Despite the
* mmap_lock being read recursive a deadlock is still
@@ -171,36 +171,37 @@ static int mfill_atomic_pte_copy(pmd_t *dst_pmd,
/* fallback to copy_from_user outside mmap_lock */
if (unlikely(ret)) {
ret = -ENOENT;
- *pagep = page;
+ *pagep = &folio->page;
/* don't free the page */
goto out;
}

- flush_dcache_page(page);
+ flush_dcache_folio(folio);
} else {
- page = *pagep;
+ folio = page_folio(*pagep);
+ VM_BUG_ON_FOLIO(folio_test_large(folio), folio);
*pagep = NULL;
}

/*
- * The memory barrier inside __SetPageUptodate makes sure that
+ * The memory barrier inside __folio_mark_uptodate makes sure that
* preceding stores to the page contents become visible before
* the set_pte_at() write.
*/
- __SetPageUptodate(page);
+ __folio_mark_uptodate(folio);

ret = -ENOMEM;
- if (mem_cgroup_charge(page_folio(page), dst_vma->vm_mm, GFP_KERNEL))
+ if (mem_cgroup_charge(folio, dst_vma->vm_mm, GFP_KERNEL))
goto out_release;

ret = mfill_atomic_install_pte(dst_pmd, dst_vma, dst_addr,
- page, true, flags);
+ &folio->page, true, flags);
if (ret)
goto out_release;
out:
return ret;
out_release:
- put_page(page);
+ folio_put(folio);
goto out;
}

--
2.25.1