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Commit 97e7e0f7 authored by Miklos Szeredi's avatar Miklos Szeredi Committed by Al Viro
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[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: default avatarMiklos Szeredi <mszeredi@suse.cz>
Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
parent 2d4d4864

Documentation/filesystems/proc.txt

+6 −0
Original line number Diff line number Diff line
@@ -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

fs/namespace.c

+7 −2
Original line number Diff line number Diff line
@@ -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");

fs/pnode.c

+51 −0
Original line number Diff line number Diff line
@@ -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;

fs/pnode.h

+1 −0
Original line number Diff line number Diff line
@@ -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 */