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From:   Pankaj Gupta <pagupta@redhat.com>
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Subject: [PATCH v3 5/5] xfs: disable map_sync for virtio pmem
Date:   Wed,  9 Jan 2019 20:17:36 +0530
Message-Id: <20190109144736.17452-6-pagupta@redhat.com>
In-Reply-To: <20190109144736.17452-1-pagupta@redhat.com>
References: <20190109144736.17452-1-pagupta@redhat.com>
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

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@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 e474250..eae4aa4 100644
--- a/fs/xfs/xfs_file.c
+++ b/fs/xfs/xfs_file.c
@@ -1190,6 +1190,14 @@ xfs_file_mmap(
 	if (!IS_DAX(file_inode(filp)) && (vma->vm_flags & VM_SYNC))
 		return -EOPNOTSUPP;
 
+	/* We don't support synchronous mappings with guest direct access
+	 * and virtio based host page cache mechanism.
+	 */
+	if (IS_DAX(file_inode(filp)) && virtio_pmem_host_cache_enabled(
+		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)))
-- 
2.9.3