patches/old/fs-dax-make-it-possible-to-check-dev-dax-support-without-a-vma.patch

From: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Subject: fs/dax: make it possible to check dev dax support without a VMA
Date: Mon, 16 Jun 2025 20:33:23 +0100

This is a prerequisite for adapting those filesystems to use the
.mmap_prepare() hook for mmap()'ing which invoke this check as this hook
does not have access to a VMA pointer.

To effect this, change the signature of daxdev_mapping_supported() and
update its callers (ext4 and xfs mmap()'ing hook code).

Link: https://lkml.kernel.org/r/b09de1e8544384074165d92d048e80058d971286.1750099179.git.lorenzo.stoakes@oracle.com
Signed-off-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 fs/ext4/file.c      |    2 +-
 fs/xfs/xfs_file.c   |    3 ++-
 include/linux/dax.h |   16 +++++++++-------
 3 files changed, 12 insertions(+), 9 deletions(-)

--- a/fs/ext4/file.c~fs-dax-make-it-possible-to-check-dev-dax-support-without-a-vma
+++ a/fs/ext4/file.c
@@ -821,7 +821,7 @@ static int ext4_file_mmap(struct file *f
 	 * We don't support synchronous mappings for non-DAX files and
 	 * for DAX files if underneath dax_device is not synchronous.
 	 */
-	if (!daxdev_mapping_supported(vma, dax_dev))
+	if (!daxdev_mapping_supported(vma->vm_flags, vma->vm_file, dax_dev))
 		return -EOPNOTSUPP;
 
 	file_accessed(file);
--- a/fs/xfs/xfs_file.c~fs-dax-make-it-possible-to-check-dev-dax-support-without-a-vma
+++ a/fs/xfs/xfs_file.c
@@ -1924,7 +1924,8 @@ xfs_file_mmap(
 	 * We don't support synchronous mappings for non-DAX files and
 	 * for DAX files if underneath dax_device is not synchronous.
 	 */
-	if (!daxdev_mapping_supported(vma, target->bt_daxdev))
+	if (!daxdev_mapping_supported(vma->vm_flags, vma->vm_file,
+				      target->bt_daxdev))
 		return -EOPNOTSUPP;
 
 	file_accessed(file);
--- a/include/linux/dax.h~fs-dax-make-it-possible-to-check-dev-dax-support-without-a-vma
+++ a/include/linux/dax.h
@@ -65,12 +65,13 @@ size_t dax_recovery_write(struct dax_dev
 /*
  * Check if given mapping is supported by the file / underlying device.
  */
-static inline bool daxdev_mapping_supported(struct vm_area_struct *vma,
-					     struct dax_device *dax_dev)
+static inline bool daxdev_mapping_supported(vm_flags_t vm_flags,
+					    struct file *file,
+					    struct dax_device *dax_dev)
 {
-	if (!(vma->vm_flags & VM_SYNC))
+	if (!(vm_flags & VM_SYNC))
 		return true;
-	if (!IS_DAX(file_inode(vma->vm_file)))
+	if (!IS_DAX(file_inode(file)))
 		return false;
 	return dax_synchronous(dax_dev);
 }
@@ -110,10 +111,11 @@ static inline void set_dax_nomc(struct d
 static inline void set_dax_synchronous(struct dax_device *dax_dev)
 {
 }
-static inline bool daxdev_mapping_supported(struct vm_area_struct *vma,
-				struct dax_device *dax_dev)
+static inline bool daxdev_mapping_supported(vm_flags_t vm_flags,
+					    struct file *file,
+					    struct dax_device *dax_dev)
 {
-	return !(vma->vm_flags & VM_SYNC);
+	return !(vm_flags & VM_SYNC);
 }
 static inline size_t dax_recovery_write(struct dax_device *dax_dev,
 		pgoff_t pgoff, void *addr, size_t bytes, struct iov_iter *i)
_