> > > > Even if allocation is done synchronously, data would be lost except on > > actual pmem. Explicit msync()s don't need MAP_SYNC, and don't require > > a sync per page. > > > > Signed-off-by: Adam Borowski <kilobyte@xxxxxxxxxx> > > --- > > MAP_SYNC can't be allowed unconditionally, as cacheline flushes don't help > > guarantee persistency in page cache. This fixes an error in my earlier > > patch "btrfs: allow MAP_SYNC mmap" -- you'd probably want to amend that. > > > > > > fs/btrfs/file.c | 7 +++++++ > > 1 file changed, 7 insertions(+) > > > > diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c > > index 362a9cf9dcb2..0bc5428037ba 100644 > > --- a/fs/btrfs/file.c > > +++ b/fs/btrfs/file.c > > @@ -2233,6 +2233,13 @@ static int btrfs_file_mmap(struct file *filp, > > struct vm_area_struct *vma) > > if (!IS_DAX(inode) && !mapping->a_ops->readpage) > > return -ENOEXEC; > > > > + /* > > + * Normal operation of btrfs is pretty much an antithesis of > > MAP_SYNC; > > + * supporting it outside DAX is pointless. > > + */ > > + if (!IS_DAX(inode) && (vma->vm_flags & VM_SYNC)) > > + return -EOPNOTSUPP; > > + > > If the virtio-pmem patch set goes upstream prior to btrfs-dax support > this will need to switch over to the new daxdev_mapping_supported() > helper. I was planning to do changes for virtio pmem & BTRFS. I was waiting for DAX support for BTRFS to merge upstream. Thank you, Pankaj > > https://lore.kernel.org/lkml/20190426050039.17460-5-pagupta@xxxxxxxxxx/ >
