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Subject[PATCH v3 4/5] ext4: disable map_sync for virtio pmem
Date
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@redhat.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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