linux-kernel - [PATCH 29/52] fuse: add DAX mmap support

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Date:   Mon, 10 Dec 2018 12:12:55 -0500
From:   Vivek Goyal <vgoyal@...hat.com>
To:     linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org
Cc:     vgoyal@...hat.com, miklos@...redi.hu, stefanha@...hat.com,
        dgilbert@...hat.com, sweil@...hat.com, swhiteho@...hat.com
Subject: [PATCH 29/52] fuse: add DAX mmap support

From: Stefan Hajnoczi <stefanha@...hat.com>

Add DAX mmap() support.

Signed-off-by: Stefan Hajnoczi <stefanha@...hat.com>
---
 fs/fuse/file.c | 58 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 57 insertions(+), 1 deletion(-)

diff --git a/fs/fuse/file.c b/fs/fuse/file.c
index 41d773ba2c72..5230f2d84a14 100644
--- a/fs/fuse/file.c
+++ b/fs/fuse/file.c
@@ -2501,9 +2501,65 @@ static int fuse_direct_mmap(struct file *file, struct vm_area_struct *vma)
 	return generic_file_mmap(file, vma);
 }
 
+static int __fuse_dax_fault(struct vm_fault *vmf, enum page_entry_size pe_size,
+			    bool write)
+{
+	int ret;
+	struct inode *inode = file_inode(vmf->vma->vm_file);
+	struct super_block *sb = inode->i_sb;
+	pfn_t pfn;
+
+	if (write)
+		sb_start_pagefault(sb);
+
+	/* TODO inode semaphore to protect faults vs truncate */
+
+	ret = dax_iomap_fault(vmf, pe_size, &pfn, NULL, &fuse_iomap_ops);
+
+	if (ret & VM_FAULT_NEEDDSYNC)
+		ret = dax_finish_sync_fault(vmf, pe_size, pfn);
+
+	if (write)
+		sb_end_pagefault(sb);
+
+	return ret;
+}
+
+static int fuse_dax_fault(struct vm_fault *vmf)
+{
+	return __fuse_dax_fault(vmf, PE_SIZE_PTE,
+				vmf->flags & FAULT_FLAG_WRITE);
+}
+
+static int 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 int fuse_dax_page_mkwrite(struct vm_fault *vmf)
+{
+	return __fuse_dax_fault(vmf, PE_SIZE_PTE, true);
+}
+
+static int 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 = {
+	.fault		= fuse_dax_fault,
+	.huge_fault	= fuse_dax_huge_fault,
+	.page_mkwrite	= fuse_dax_page_mkwrite,
+	.pfn_mkwrite	= 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 = &fuse_dax_vm_ops;
+	vma->vm_flags |= VM_MIXEDMAP | VM_HUGEPAGE;
+	return 0;
 }
 
 static int convert_fuse_file_lock(struct fuse_conn *fc,
-- 
2.13.6