[V9fs-developer][PATCH v2] 9p: create writeback fid on shared writable mmap

[Chengguang Xu]

If vma is shared and the file was opened for writing,
we should also create writeback fid because vma may be
mprotected writable even if now readonly.

Signed-off-by: Chengguang Xu <cgxu...@mykernel.net>
---
 fs/9p/vfs_file.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/9p/vfs_file.c b/fs/9p/vfs_file.c
index b177fd3b1eb3..e4256dbcb754 100644
--- a/fs/9p/vfs_file.c
+++ b/fs/9p/vfs_file.c
@@ -517,7 +517,7 @@ v9fs_mmap_file_mmap(struct file *filp, struct 
vm_area_struct *vma)
        mutex_lock(&v9inode->v_mutex);
        if (!v9inode->writeback_fid &&
            (vma->vm_flags & VM_SHARED) &&
-           (vma->vm_flags & VM_WRITE)) {
+           (vma->vm_flags & VM_MAYWRITE)) {
                /*
                 * clone a fid and add it to writeback_fid
                 * we do it during mmap instead of
-- 
2.26.2