To fix issue #99, we only need to add MAP_SYNC in the mmap_supported_flags. The following condition to indicate synchronous page fault by VFS does not change, so the execution path of page fault in mmap remains the same.
// in fs/dax.c
/*
* MAP_SYNC on a dax mapping guarantees dirty metadata is
* flushed on write-faults (non-cow), but not read-faults.
*/
static bool dax_fault_is_synchronous(unsigned long flags,
struct vm_area_struct *vma, struct iomap *iomap)
{
return (flags & IOMAP_WRITE) && (vma->vm_flags & VM_SYNC)
&& (iomap->flags & IOMAP_F_DIRTY);
}
IOMAP_F_DIRTY indicates the inode has uncommitted metadata requiring fdatasync, which will not be set by NOVA. So dax_fault_is_synchronous still returns 0 whether VM_SYNC is 0 or 1.
To fix issue #99, we only need to add
MAP_SYNCin themmap_supported_flags. The following condition to indicate synchronous page fault by VFS does not change, so the execution path of page fault in mmap remains the same.IOMAP_F_DIRTY indicates the inode has uncommitted metadata requiring fdatasync, which will not be set by NOVA. So
dax_fault_is_synchronousstill returns 0 whether VM_SYNC is 0 or 1.