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Date:   Wed,  9 Jan 2019 20:17:35 +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 4/5] ext4: 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 ext4. 

Signed-off-by: Pankaj Gupta <pagupta@...hat.com>
---
 fs/ext4/file.c | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/fs/ext4/file.c b/fs/ext4/file.c
index 69d65d4..e54f48b 100644
--- a/fs/ext4/file.c
+++ b/fs/ext4/file.c
@@ -360,8 +360,10 @@ static const struct vm_operations_struct ext4_file_vm_ops = {
 static int ext4_file_mmap(struct file *file, struct vm_area_struct *vma)
 {
 	struct inode *inode = file->f_mapping->host;
+	struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);
+	struct dax_device *dax_dev = sbi->s_daxdev;
 
-	if (unlikely(ext4_forced_shutdown(EXT4_SB(inode->i_sb))))
+	if (unlikely(ext4_forced_shutdown(sbi)))
 		return -EIO;
 
 	/*
@@ -371,6 +373,13 @@ static int ext4_file_mmap(struct file *file, struct vm_area_struct *vma)
 	if (!IS_DAX(file_inode(file)) && (vma->vm_flags & VM_SYNC))
 		return -EOPNOTSUPP;
 
+	/* We don't support synchronous mappings with guest direct access
+	 * and virtio based host page cache flush mechanism.
+	 */
+	if (IS_DAX(file_inode(file)) && virtio_pmem_host_cache_enabled(dax_dev)
+						&& (vma->vm_flags & VM_SYNC))
+		return -EOPNOTSUPP;
+
 	file_accessed(file);
 	if (IS_DAX(file_inode(file))) {
 		vma->vm_ops = &ext4_dax_vm_ops;
-- 
2.9.3

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