From 719f5d7f0b90ac2c8f8ca4232eb322b266fea01e Mon Sep 17 00:00:00 2001 From: Miklos Szeredi <mszeredi@suse.cz> Date: Thu, 27 Mar 2008 13:06:23 +0100 Subject: [patch 4/7] vfs: mountinfo: add mount peer group ID Add a unique ID to each peer group using the IDR infrastructure. The identifiers are reused after the peer group dissolves. The IDR structures are protected by holding namepspace_sem for write while allocating or deallocating IDs. IDs are allocated when a previously unshared vfsmount becomes the first member of a peer group. When a new member is added to an existing group, the ID is copied from one of the old members. IDs are freed when the last member of a peer group is unshared. Setting the MNT_SHARED flag on members of a subtree is done as a separate step, after all the IDs have been allocated. This way an allocation failure can be cleaned up easilty, without affecting the propagation state. Based on design sketch by Al Viro. Signed-off-by: Miklos Szeredi <mszeredi@suse.cz> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk> --- fs/pnode.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) (limited to 'fs/pnode.c') diff --git a/fs/pnode.c b/fs/pnode.c index f968e35d978..d18d66491a0 100644 --- a/fs/pnode.c +++ b/fs/pnode.c @@ -46,7 +46,11 @@ static int do_make_slave(struct vfsmount *mnt) if (peer_mnt == mnt) peer_mnt = NULL; } + if (IS_MNT_SHARED(mnt) && list_empty(&mnt->mnt_share)) + mnt_release_group_id(mnt); + list_del_init(&mnt->mnt_share); + mnt->mnt_group_id = 0; if (peer_mnt) master = peer_mnt; @@ -68,7 +72,6 @@ static int do_make_slave(struct vfsmount *mnt) } mnt->mnt_master = master; CLEAR_MNT_SHARED(mnt); - INIT_LIST_HEAD(&mnt->mnt_slave_list); return 0; } -- cgit v1.2.3-70-g09d2 From 97e7e0f71d6d948c25f11f0a33878d9356d9579e Mon Sep 17 00:00:00 2001 From: Miklos Szeredi <mszeredi@suse.cz> Date: Thu, 27 Mar 2008 13:06:26 +0100 Subject: [patch 7/7] vfs: mountinfo: show dominating group id Show peer group ID of nearest dominating group that has intersection with the mount's namespace. Signed-off-by: Miklos Szeredi <mszeredi@suse.cz> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk> --- Documentation/filesystems/proc.txt | 6 +++++ fs/namespace.c | 9 +++++-- fs/pnode.c | 51 ++++++++++++++++++++++++++++++++++++++ fs/pnode.h | 1 + 4 files changed, 65 insertions(+), 2 deletions(-) (limited to 'fs/pnode.c') diff --git a/Documentation/filesystems/proc.txt b/Documentation/filesystems/proc.txt index 2cd920f92e5..2a99116edc4 100644 --- a/Documentation/filesystems/proc.txt +++ b/Documentation/filesystems/proc.txt @@ -2374,8 +2374,14 @@ possible optional fields are: shared:X mount is shared in peer group X master:X mount is slave to peer group X +propagate_from:X mount is slave and receives propagation from peer group X (*) unbindable mount is unbindable +(*) X is the closest dominant peer group under the process's root. If +X is the immediate master of the mount, or if there's no dominant peer +group under the same root, then only the "master:X" field is present +and not the "propagate_from:X" field. + For more information on mount propagation see: Documentation/filesystems/sharedsubtree.txt diff --git a/fs/namespace.c b/fs/namespace.c index c807b8d5f89..0505fb61aa7 100644 --- a/fs/namespace.c +++ b/fs/namespace.c @@ -850,8 +850,13 @@ static int show_mountinfo(struct seq_file *m, void *v) /* Tagged fields ("foo:X" or "bar") */ if (IS_MNT_SHARED(mnt)) seq_printf(m, " shared:%i", mnt->mnt_group_id); - if (IS_MNT_SLAVE(mnt)) - seq_printf(m, " master:%i", mnt->mnt_master->mnt_group_id); + if (IS_MNT_SLAVE(mnt)) { + int master = mnt->mnt_master->mnt_group_id; + int dom = get_dominating_id(mnt, &p->root); + seq_printf(m, " master:%i", master); + if (dom && dom != master) + seq_printf(m, " propagate_from:%i", dom); + } if (IS_MNT_UNBINDABLE(mnt)) seq_puts(m, " unbindable"); diff --git a/fs/pnode.c b/fs/pnode.c index d18d66491a0..8d5f392ec3d 100644 --- a/fs/pnode.c +++ b/fs/pnode.c @@ -28,6 +28,57 @@ static inline struct vfsmount *next_slave(struct vfsmount *p) return list_entry(p->mnt_slave.next, struct vfsmount, mnt_slave); } +/* + * Return true if path is reachable from root + * + * namespace_sem is held, and mnt is attached + */ +static bool is_path_reachable(struct vfsmount *mnt, struct dentry *dentry, + const struct path *root) +{ + while (mnt != root->mnt && mnt->mnt_parent != mnt) { + dentry = mnt->mnt_mountpoint; + mnt = mnt->mnt_parent; + } + return mnt == root->mnt && is_subdir(dentry, root->dentry); +} + +static struct vfsmount *get_peer_under_root(struct vfsmount *mnt, + struct mnt_namespace *ns, + const struct path *root) +{ + struct vfsmount *m = mnt; + + do { + /* Check the namespace first for optimization */ + if (m->mnt_ns == ns && is_path_reachable(m, m->mnt_root, root)) + return m; + + m = next_peer(m); + } while (m != mnt); + + return NULL; +} + +/* + * Get ID of closest dominating peer group having a representative + * under the given root. + * + * Caller must hold namespace_sem + */ +int get_dominating_id(struct vfsmount *mnt, const struct path *root) +{ + struct vfsmount *m; + + for (m = mnt->mnt_master; m != NULL; m = m->mnt_master) { + struct vfsmount *d = get_peer_under_root(m, mnt->mnt_ns, root); + if (d) + return d->mnt_group_id; + } + + return 0; +} + static int do_make_slave(struct vfsmount *mnt) { struct vfsmount *peer_mnt = mnt, *master = mnt->mnt_master; diff --git a/fs/pnode.h b/fs/pnode.h index 973c3f825e7..958665d662a 100644 --- a/fs/pnode.h +++ b/fs/pnode.h @@ -36,4 +36,5 @@ int propagate_mnt(struct vfsmount *, struct dentry *, struct vfsmount *, int propagate_umount(struct list_head *); int propagate_mount_busy(struct vfsmount *, int); void mnt_release_group_id(struct vfsmount *); +int get_dominating_id(struct vfsmount *mnt, const struct path *root); #endif /* _LINUX_PNODE_H */ -- cgit v1.2.3-70-g09d2