[Qemu-devel] [PATCH v4 4/5] ext4: disable map_sync for async flush

[Pankaj Gupta]

Virtio pmem provides asynchronous host page cache flush
mechanism. We don't support 'MAP_SYNC' with virtio pmem 
and ext4. 

Signed-off-by: Pankaj Gupta <address@hidden>
---
 fs/ext4/file.c | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/fs/ext4/file.c b/fs/ext4/file.c
index 69d65d49837b..86e4bf464320 100644
--- a/fs/ext4/file.c
+++ b/fs/ext4/file.c
@@ -360,8 +360,10 @@ static const struct vm_operations_struct ext4_file_vm_ops 
= {
 static int ext4_file_mmap(struct file *file, struct vm_area_struct *vma)
 {
        struct inode *inode = file->f_mapping->host;
+       struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);
+       struct dax_device *dax_dev = sbi->s_daxdev;
 
-       if (unlikely(ext4_forced_shutdown(EXT4_SB(inode->i_sb))))
+       if (unlikely(ext4_forced_shutdown(sbi)))
                return -EIO;
 
        /*
@@ -371,6 +373,13 @@ static int ext4_file_mmap(struct file *file, struct 
vm_area_struct *vma)
        if (!IS_DAX(file_inode(file)) && (vma->vm_flags & VM_SYNC))
                return -EOPNOTSUPP;
 
+       /* We don't support synchronous mappings with DAX files if
+        * dax_device is not synchronous.
+        */
+       if (IS_DAX(file_inode(file)) && !dax_synchronous(dax_dev)
+                                               && (vma->vm_flags & VM_SYNC))
+               return -EOPNOTSUPP;
+
        file_accessed(file);
        if (IS_DAX(file_inode(file))) {
                vma->vm_ops = &ext4_dax_vm_ops;
-- 
2.20.1