linux-kernel - [PATCH v3 5/5] xfs: disable map

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Date:   Wed,  9 Jan 2019 19:26:06 +0530
From:   Pankaj Gupta <pagupta@...hat.com>
To:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        qemu-devel@...gnu.org, linux-nvdimm@...1.01.org,
        linux-fsdevel@...r.kernel.org,
        virtualization@...ts.linux-foundation.org,
        linux-acpi@...r.kernel.org, linux-ext4@...r.kernel.org,
        linux-xfs@...r.kernel.org
Cc:     jack@...e.cz, stefanha@...hat.com, dan.j.williams@...el.com,
        riel@...riel.com, nilal@...hat.com, kwolf@...hat.com,
        pbonzini@...hat.com, zwisler@...nel.org, vishal.l.verma@...el.com,
        dave.jiang@...el.com, david@...hat.com, jmoyer@...hat.com,
        xiaoguangrong.eric@...il.com, hch@...radead.org, mst@...hat.com,
        jasowang@...hat.com, lcapitulino@...hat.com, imammedo@...hat.com,
        eblake@...hat.com, willy@...radead.org, tytso@....edu,
        adilger.kernel@...ger.ca, darrick.wong@...cle.com,
        rjw@...ysocki.net, pagupta@...hat.com
Subject: [PATCH v3 5/5] xfs: disable map_sync for virtio pmem

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@...hat.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