From df820f8de4e481222b17f9bcee7b909ae8167529 Mon Sep 17 00:00:00 2001 From: Miklos Szeredi Date: Thu, 4 Jun 2020 10:48:19 +0200 Subject: ovl: make private mounts longterm Overlayfs is using clone_private_mount() to create internal mounts for underlying layers. These are used for operations requiring a path, such as dentry_open(). Since these private mounts are not in any namespace they are treated as short term, "detached" mounts and mntput() involves taking the global mount_lock, which can result in serious cacheline pingpong. Make these private mounts longterm instead, which trade the penalty on mntput() for a slightly longer shutdown time due to an added RCU grace period when putting these mounts. Introduce a new helper kern_unmount_many() that can take care of multiple longterm mounts with a single RCU grace period. Cc: Al Viro Signed-off-by: Miklos Szeredi --- include/linux/mount.h | 2 ++ 1 file changed, 2 insertions(+) (limited to 'include/linux/mount.h') diff --git a/include/linux/mount.h b/include/linux/mount.h index bf8cc4108b8f..8de95a0bec8d 100644 --- a/include/linux/mount.h +++ b/include/linux/mount.h @@ -109,4 +109,6 @@ extern unsigned int sysctl_mount_max; extern bool path_is_mountpoint(const struct path *path); +extern void kern_unmount_array(struct vfsmount *mnt[], unsigned int num); + #endif /* _LINUX_MOUNT_H */ -- cgit v1.2.3-59-g8ed1b