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From:   Vivek Goyal <vgoyal@redhat.com>
To:     linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
        linux-nvdimm@lists.01.org, virtio-fs@redhat.com, miklos@szeredi.hu
Cc:     vgoyal@redhat.com, stefanha@redhat.com, dgilbert@redhat.com,
        mst@redhat.com
Subject: [PATCH 14/20] fuse,dax: add DAX mmap support
Date:   Wed,  4 Mar 2020 11:58:39 -0500
Message-Id: <20200304165845.3081-15-vgoyal@redhat.com>
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From: Stefan Hajnoczi <stefanha@redhat.com>

Add DAX mmap() support.

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
---
 fs/fuse/file.c | 62 +++++++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 61 insertions(+), 1 deletion(-)

diff --git a/fs/fuse/file.c b/fs/fuse/file.c
index 9effdd3dc6d6..303496e6617f 100644
--- a/fs/fuse/file.c
+++ b/fs/fuse/file.c
@@ -2870,10 +2870,15 @@ static const struct vm_operations_struct fuse_fil=
e_vm_ops =3D {
 	.page_mkwrite	=3D fuse_page_mkwrite,
 };
=20
+static int fuse_dax_mmap(struct file *file, struct vm_area_struct *vma);
 static int fuse_file_mmap(struct file *file, struct vm_area_struct *vma)
 {
 	struct fuse_file *ff =3D file->private_data;
=20
+	/* DAX mmap is superior to direct_io mmap */
+	if (IS_DAX(file_inode(file)))
+		return fuse_dax_mmap(file, vma);
+
 	if (ff->open_flags & FOPEN_DIRECT_IO) {
 		/* Can't provide the coherency needed for MAP_SHARED */
 		if (vma->vm_flags & VM_MAYSHARE)
@@ -2892,9 +2897,63 @@ static int fuse_file_mmap(struct file *file, struc=
t vm_area_struct *vma)
 	return 0;
 }
=20
+static vm_fault_t __fuse_dax_fault(struct vm_fault *vmf,
+				   enum page_entry_size pe_size, bool write)
+{
+	vm_fault_t ret;
+	struct inode *inode =3D file_inode(vmf->vma->vm_file);
+	struct super_block *sb =3D inode->i_sb;
+	pfn_t pfn;
+
+	if (write)
+		sb_start_pagefault(sb);
+
+	ret =3D dax_iomap_fault(vmf, pe_size, &pfn, NULL, &fuse_iomap_ops);
+
+	if (ret & VM_FAULT_NEEDDSYNC)
+		ret =3D dax_finish_sync_fault(vmf, pe_size, pfn);
+
+	if (write)
+		sb_end_pagefault(sb);
+
+	return ret;
+}
+
+static vm_fault_t fuse_dax_fault(struct vm_fault *vmf)
+{
+	return __fuse_dax_fault(vmf, PE_SIZE_PTE,
+				vmf->flags & FAULT_FLAG_WRITE);
+}
+
+static vm_fault_t fuse_dax_huge_fault(struct vm_fault *vmf,
+			       enum page_entry_size pe_size)
+{
+	return __fuse_dax_fault(vmf, pe_size, vmf->flags & FAULT_FLAG_WRITE);
+}
+
+static vm_fault_t fuse_dax_page_mkwrite(struct vm_fault *vmf)
+{
+	return __fuse_dax_fault(vmf, PE_SIZE_PTE, true);
+}
+
+static vm_fault_t fuse_dax_pfn_mkwrite(struct vm_fault *vmf)
+{
+	return __fuse_dax_fault(vmf, PE_SIZE_PTE, true);
+}
+
+static const struct vm_operations_struct fuse_dax_vm_ops =3D {
+	.fault		=3D fuse_dax_fault,
+	.huge_fault	=3D fuse_dax_huge_fault,
+	.page_mkwrite	=3D fuse_dax_page_mkwrite,
+	.pfn_mkwrite	=3D fuse_dax_pfn_mkwrite,
+};
+
 static int fuse_dax_mmap(struct file *file, struct vm_area_struct *vma)
 {
-	return -EINVAL; /* TODO */
+	file_accessed(file);
+	vma->vm_ops =3D &fuse_dax_vm_ops;
+	vma->vm_flags |=3D VM_MIXEDMAP | VM_HUGEPAGE;
+	return 0;
 }
=20
 static int convert_fuse_file_lock(struct fuse_conn *fc,
@@ -3940,6 +3999,7 @@ static const struct file_operations fuse_file_opera=
tions =3D {
 	.release	=3D fuse_release,
 	.fsync		=3D fuse_fsync,
 	.lock		=3D fuse_file_lock,
+	.get_unmapped_area =3D thp_get_unmapped_area,
 	.flock		=3D fuse_file_flock,
 	.splice_read	=3D generic_file_splice_read,
 	.splice_write	=3D iter_file_splice_write,
--=20
2.20.1