Re: [PATCH v4 5/5] xfs: disable map_sync for async flush
On Wed, Apr 03, 2019 at 04:10:18PM +0530, Pankaj Gupta wrote:
Virtio pmem provides asynchronous host page cache flush
mechanism. we don't support 'MAP_SYNC' with virtio pmem
and xfs.
Signed-off-by: Pankaj Gupta <pagupta(a)redhat.com>
---
fs/xfs/xfs_file.c | 8 ++++++++
1 file changed, 8 insertions(+)
diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c
index 1f2e2845eb76..dced2eb8c91a 100644
--- a/fs/xfs/xfs_file.c
+++ b/fs/xfs/xfs_file.c
@@ -1203,6 +1203,14 @@ xfs_file_mmap(
if (!IS_DAX(file_inode(filp)) && (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(filp)) && !dax_synchronous(
+ xfs_find_daxdev_for_inode(file_inode(filp))) &&
+ (vma->vm_flags & VM_SYNC))
+ return -EOPNOTSUPP;
+
file_accessed(filp);
vma->vm_ops = &xfs_file_vm_ops;
if (IS_DAX(file_inode(filp)))
All this ad hoc IS_DAX conditional logic is getting pretty nasty.
xfs_file_mmap(
....
{
struct inode *inode = file_inode(filp);
if (vma->vm_flags & VM_SYNC) {
if (!IS_DAX(inode))
return -EOPNOTSUPP;
if (!dax_synchronous(xfs_find_daxdev_for_inode(inode))
return -EOPNOTSUPP;
}
file_accessed(filp);
vma->vm_ops = &xfs_file_vm_ops;
if (IS_DAX(inode))
vma->vm_flags |= VM_HUGEPAGE;
return 0;
}
Even better, factor out all the "MAP_SYNC supported" checks into a
helper so that the filesystem code just doesn't have to care about
the details of checking for DAX+MAP_SYNC support....
Cheers,
Dave.
--
Dave Chinner
david(a)fromorbit.com