linux-kernel - [PATCH RFC v2 02/12] mm: Convert pXd_devmap checks to vma_is

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Message-ID: <5142b971de0a9608147c003953781b34aa6a3a45.1739941374.git-series.apopple@nvidia.com>
Date: Wed, 19 Feb 2025 16:04:46 +1100
From: Alistair Popple <apopple@...dia.com>
To: akpm@...ux-foundation.org,
	linux-mm@...ck.org
Cc: Alistair Popple <apopple@...dia.com>,
	gerald.schaefer@...ux.ibm.com,
	dan.j.williams@...el.com,
	jgg@...pe.ca,
	willy@...radead.org,
	david@...hat.com,
	linux-kernel@...r.kernel.org,
	nvdimm@...ts.linux.dev,
	linux-fsdevel@...r.kernel.org,
	linux-ext4@...r.kernel.org,
	linux-xfs@...r.kernel.org,
	jhubbard@...dia.com,
	hch@....de,
	zhang.lyra@...il.com,
	debug@...osinc.com,
	bjorn@...nel.org,
	balbirs@...dia.com
Subject: [PATCH RFC v2 02/12] mm: Convert pXd_devmap checks to vma_is_dax

Currently dax is the only user of pmd and pud mapped ZONE_DEVICE
pages. Therefore page walkers that want to exclude DAX pages can check
pmd_devmap or pud_devmap. However soon dax will no longer set PFN_DEV,
meaning dax pages are mapped as normal pages.

Ensure page walkers that currently use pXd_devmap to skip DAX pages
continue to do so by adding explicit checks of the VMA instead.

Signed-off-by: Alistair Popple <apopple@...dia.com>
---
 fs/userfaultfd.c | 2 +-
 mm/hmm.c         | 2 +-
 mm/userfaultfd.c | 2 +-
 3 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c
index 97c4d71..27e3ec0 100644
--- a/fs/userfaultfd.c
+++ b/fs/userfaultfd.c
@@ -304,7 +304,7 @@ static inline bool userfaultfd_must_wait(struct userfaultfd_ctx *ctx,
 		goto out;
 
 	ret = false;
-	if (!pmd_present(_pmd) || pmd_devmap(_pmd))
+	if (!pmd_present(_pmd) || vma_is_dax(vmf->vma))
 		goto out;
 
 	if (pmd_trans_huge(_pmd)) {
diff --git a/mm/hmm.c b/mm/hmm.c
index 082f7b7..db12c0a 100644
--- a/mm/hmm.c
+++ b/mm/hmm.c
@@ -429,7 +429,7 @@ static int hmm_vma_walk_pud(pud_t *pudp, unsigned long start, unsigned long end,
 		return hmm_vma_walk_hole(start, end, -1, walk);
 	}
 
-	if (pud_leaf(pud) && pud_devmap(pud)) {
+	if (pud_leaf(pud) && vma_is_dax(walk->vma)) {
 		unsigned long i, npages, pfn;
 		unsigned int required_fault;
 		unsigned long *hmm_pfns;
diff --git a/mm/userfaultfd.c b/mm/userfaultfd.c
index 867898c..cc6dc18 100644
--- a/mm/userfaultfd.c
+++ b/mm/userfaultfd.c
@@ -1710,7 +1710,7 @@ ssize_t move_pages(struct userfaultfd_ctx *ctx, unsigned long dst_start,
 
 		ptl = pmd_trans_huge_lock(src_pmd, src_vma);
 		if (ptl) {
-			if (pmd_devmap(*src_pmd)) {
+			if (vma_is_dax(src_vma)) {
 				spin_unlock(ptl);
 				err = -ENOENT;
 				break;
-- 
git-series 0.9.1