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Subject[patch 4/6] vfs: mountinfo show dominating group id
From: Miklos Szeredi <mszeredi@suse.cz>

Show peer group ID of nearest dominating group that has intersection
with the mount's namespace.

See the the documentation update for details.

Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
---
Documentation/filesystems/proc.txt | 11 ++++++++---
fs/namespace.c | 24 ++++++++++++++++--------
fs/pnode.c | 32 ++++++++++++++++++++++++++++++++
fs/pnode.h | 1 +
4 files changed, 57 insertions(+), 11 deletions(-)

Index: linux/fs/namespace.c
===================================================================
--- linux.orig/fs/namespace.c 2008-03-13 20:45:50.000000000 +0100
+++ linux/fs/namespace.c 2008-03-13 20:45:51.000000000 +0100
@@ -798,16 +798,24 @@ static int show_mountinfo(struct seq_fil
show_sb_opts(m, sb);
if (sb->s_op->show_options)
err = sb->s_op->show_options(m, mnt);
- if (IS_MNT_SHARED(mnt)) {
- seq_printf(m, " shared:%i", get_peer_group_id(mnt));
- if (IS_MNT_SLAVE(mnt))
- seq_printf(m, ",slave:%i", get_master_id(mnt));
- } else if (IS_MNT_SLAVE(mnt)) {
- seq_printf(m, " slave:%i", get_master_id(mnt));
+ seq_putc(m, ' ');
+ if (IS_MNT_SHARED(mnt) || IS_MNT_SLAVE(mnt)) {
+ if (IS_MNT_SHARED(mnt))
+ seq_printf(m, "shared:%i", get_peer_group_id(mnt));
+ if (IS_MNT_SLAVE(mnt)) {
+ int dominator_id = get_dominator_id_same_ns(mnt);
+
+ if (IS_MNT_SHARED(mnt))
+ seq_putc(m, ',');
+
+ seq_printf(m, "slave:%i", get_master_id(mnt));
+ if (dominator_id != -1)
+ seq_printf(m, ":%i", dominator_id);
+ }
} else if (IS_MNT_UNBINDABLE(mnt)) {
- seq_printf(m, " unbindable");
+ seq_printf(m, "unbindable");
} else {
- seq_printf(m, " private");
+ seq_printf(m, "private");
}
seq_putc(m, '\n');
return err;
Index: linux/fs/pnode.c
===================================================================
--- linux.orig/fs/pnode.c 2008-03-13 20:45:50.000000000 +0100
+++ linux/fs/pnode.c 2008-03-13 20:45:51.000000000 +0100
@@ -88,6 +88,38 @@ int get_master_id(struct vfsmount *mnt)
return id;
}

+static struct vfsmount *get_peer_in_ns(struct vfsmount *mnt,
+ struct mnt_namespace *ns)
+{
+ struct vfsmount *m = mnt;
+
+ do {
+ if (m->mnt_ns == ns)
+ return m;
+ m = next_peer(m);
+ } while (m != mnt);
+
+ return NULL;
+}
+
+int get_dominator_id_same_ns(struct vfsmount *mnt)
+{
+ int id = -1;
+ struct vfsmount *m;
+
+ spin_lock(&vfsmount_lock);
+ for (m = mnt->mnt_master; m != NULL; m = m->mnt_master) {
+ struct vfsmount *d = get_peer_in_ns(m, mnt->mnt_ns);
+ if (d) {
+ id = d->mnt_pgid;
+ break;
+ }
+ }
+ spin_unlock(&vfsmount_lock);
+
+ return id;
+}
+
static int do_make_slave(struct vfsmount *mnt)
{
struct vfsmount *peer_mnt = mnt, *master = mnt->mnt_master;
Index: linux/fs/pnode.h
===================================================================
--- linux.orig/fs/pnode.h 2008-03-13 20:45:50.000000000 +0100
+++ linux/fs/pnode.h 2008-03-13 20:45:51.000000000 +0100
@@ -33,4 +33,5 @@ int propagate_umount(struct list_head *)
int propagate_mount_busy(struct vfsmount *, int);
int get_peer_group_id(struct vfsmount *);
int get_master_id(struct vfsmount *);
+int get_dominator_id_same_ns(struct vfsmount *);
#endif /* _LINUX_PNODE_H */
Index: linux/Documentation/filesystems/proc.txt
===================================================================
--- linux.orig/Documentation/filesystems/proc.txt 2008-03-13 20:45:50.000000000 +0100
+++ linux/Documentation/filesystems/proc.txt 2008-03-13 20:45:51.000000000 +0100
@@ -2367,15 +2367,20 @@ MNTOPTS: per mount options
SBOPTS: per super block options
PROPAGATION: propagation type

-propagation type: <propagation_flag>[:<peergrpid>][,...]
+propagation type: <propagation_flag>[:<peergrpid>[:<domgrpid>]][,...]
note: 'shared' flag is followed by the id of this mount's peer group
- 'slave' flag is followed by the peer group id of its master mount
+ 'slave' flag is followed by the peer group id of its master mount,
+ optionally followed by the id of the closest dominant(*)
+ peer group in the same namespace, if one exists.
'private' flag stands by itself
'unbindable' flag stands by itself

+(*) A dominant peer group is an ancestor of this mount in the
+propagation tree, in other words, this mount receives propagation from
+the dominant peer group, but not the other way round.
+
For more information see:

Documentation/filesystems/sharedsubtree.txt

-
------------------------------------------------------------------------------
--


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