From: Chengguang Xu cgxu519@zoho.com.cn
[ Upstream commit c87a37ebd40b889178664c2c09cc187334146292 ]
Currently on mmap cache policy, we always attach writeback_fid whether mmap type is SHARED or PRIVATE. However, in the use case of kata-container which combines 9p(Guest OS) with overlayfs(Host OS), this behavior will trigger overlayfs' copy-up when excute command inside container.
Link: http://lkml.kernel.org/r/20190820100325.10313-1-cgxu519@zoho.com.cn Signed-off-by: Chengguang Xu cgxu519@zoho.com.cn Signed-off-by: Dominique Martinet dominique.martinet@cea.fr Signed-off-by: Sasha Levin sashal@kernel.org --- fs/9p/vfs_file.c | 3 +++ 1 file changed, 3 insertions(+)
diff --git a/fs/9p/vfs_file.c b/fs/9p/vfs_file.c index 373cc50544e91..9dbf371471261 100644 --- a/fs/9p/vfs_file.c +++ b/fs/9p/vfs_file.c @@ -528,6 +528,7 @@ v9fs_mmap_file_mmap(struct file *filp, struct vm_area_struct *vma) v9inode = V9FS_I(inode); mutex_lock(&v9inode->v_mutex); if (!v9inode->writeback_fid && + (vma->vm_flags & VM_SHARED) && (vma->vm_flags & VM_WRITE)) { /* * clone a fid and add it to writeback_fid @@ -629,6 +630,8 @@ static void v9fs_mmap_vm_close(struct vm_area_struct *vma) (vma->vm_end - vma->vm_start - 1), };
+ if (!(vma->vm_flags & VM_SHARED)) + return;
p9_debug(P9_DEBUG_VFS, "9p VMA close, %p, flushing", vma);