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| author | Miklos Szeredi <mszeredi@redhat.com> | 2020-06-04 10:48:19 +0200 |
|---|---|---|
| committer | Miklos Szeredi <mszeredi@redhat.com> | 2020-06-04 10:48:19 +0200 |
| commit | df820f8de4e481222b17f9bcee7b909ae8167529 (patch) | |
| tree | 8410725a7cd85f540f59120710b8617c18348670 /include/linux/mount.h | |
| parent | b8e42a651bdee06202ebdd96cff64fdeabd5b1d6 (diff) | |
| download | lwn-df820f8de4e481222b17f9bcee7b909ae8167529.tar.gz lwn-df820f8de4e481222b17f9bcee7b909ae8167529.zip | |
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 <viro@zeniv.linux.org.uk>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Diffstat (limited to 'include/linux/mount.h')
| -rw-r--r-- | include/linux/mount.h | 2 |
1 files changed, 2 insertions, 0 deletions
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 */ |