From: Miklos Szeredi Add a stable identifier for shared mounts. Signed-off-by: Miklos Szeredi --- Documentation/filesystems/proc.txt | 12 +------ fs/namespace.c | 7 ++-- fs/pnode.c | 63 ++++++++++++++++++++++++------------- fs/pnode.h | 1 include/linux/mount.h | 1 5 files changed, 52 insertions(+), 32 deletions(-) Index: linux/fs/pnode.c =================================================================== --- linux.orig/fs/pnode.c 2008-03-13 20:45:49.000000000 +0100 +++ linux/fs/pnode.c 2008-03-13 20:45:50.000000000 +0100 @@ -9,8 +9,12 @@ #include #include #include +#include #include "pnode.h" +static DEFINE_SPINLOCK(mnt_pgid_lock); +static DEFINE_IDA(mnt_pgid_ida); + /* return the next shared peer mount of @p */ static inline struct vfsmount *next_peer(struct vfsmount *p) { @@ -27,47 +31,58 @@ static inline struct vfsmount *next_slav return list_entry(p->mnt_slave.next, struct vfsmount, mnt_slave); } -void set_mnt_shared(struct vfsmount *mnt) +static void __set_mnt_shared(struct vfsmount *mnt) { mnt->mnt_flags &= ~MNT_PNODE_MASK; mnt->mnt_flags |= MNT_SHARED; } -void clear_mnt_shared(struct vfsmount *mnt) +void set_mnt_shared(struct vfsmount *mnt) { - mnt->mnt_flags &= ~MNT_SHARED; + int res; + + retry: + spin_lock(&mnt_pgid_lock); + if (IS_MNT_SHARED(mnt)) { + spin_unlock(&mnt_pgid_lock); + return; + } + + res = ida_get_new(&mnt_pgid_ida, &mnt->mnt_pgid); + spin_unlock(&mnt_pgid_lock); + if (res == -EAGAIN) { + if (ida_pre_get(&mnt_pgid_ida, GFP_KERNEL)) + goto retry; + } + __set_mnt_shared(mnt); } -static int __peer_group_id(struct vfsmount *mnt) +void clear_mnt_shared(struct vfsmount *mnt) { - struct vfsmount *m; - int id = mnt->mnt_id; - - for (m = next_peer(mnt); m != mnt; m = next_peer(m)) - id = min(id, m->mnt_id); + if (IS_MNT_SHARED(mnt)) { + mnt->mnt_flags &= ~MNT_SHARED; + mnt->mnt_pgid = -1; + } +} - return id; +void make_mnt_peer(struct vfsmount *old, struct vfsmount *mnt) +{ + mnt->mnt_pgid = old->mnt_pgid; + list_add(&mnt->mnt_share, &old->mnt_share); + __set_mnt_shared(mnt); } -/* return the smallest ID within the peer group */ int get_peer_group_id(struct vfsmount *mnt) { - int id; - - spin_lock(&vfsmount_lock); - id = __peer_group_id(mnt); - spin_unlock(&vfsmount_lock); - - return id; + return mnt->mnt_pgid; } -/* return the smallest ID within the master's peer group */ int get_master_id(struct vfsmount *mnt) { int id; spin_lock(&vfsmount_lock); - id = __peer_group_id(mnt->mnt_master); + id = get_peer_group_id(mnt->mnt_master); spin_unlock(&vfsmount_lock); return id; @@ -91,7 +106,13 @@ static int do_make_slave(struct vfsmount if (peer_mnt == mnt) peer_mnt = NULL; } - list_del_init(&mnt->mnt_share); + if (!list_empty(&mnt->mnt_share)) + list_del_init(&mnt->mnt_share); + else if (IS_MNT_SHARED(mnt)) { + spin_lock(&mnt_pgid_lock); + ida_remove(&mnt_pgid_ida, mnt->mnt_pgid); + spin_unlock(&mnt_pgid_lock); + } if (peer_mnt) master = peer_mnt; Index: linux/include/linux/mount.h =================================================================== --- linux.orig/include/linux/mount.h 2008-03-13 20:45:15.000000000 +0100 +++ linux/include/linux/mount.h 2008-03-13 20:45:50.000000000 +0100 @@ -57,6 +57,7 @@ struct vfsmount { struct vfsmount *mnt_master; /* slave is on master->mnt_slave_list */ struct mnt_namespace *mnt_ns; /* containing namespace */ int mnt_id; /* mount identifier */ + int mnt_pgid; /* peer group identifier */ /* * We put mnt_count & mnt_expiry_mark at the end of struct vfsmount * to let these frequently modified fields in a separate cache line Index: linux/fs/namespace.c =================================================================== --- linux.orig/fs/namespace.c 2008-03-13 20:45:49.000000000 +0100 +++ linux/fs/namespace.c 2008-03-13 20:45:50.000000000 +0100 @@ -95,6 +95,7 @@ struct vfsmount *alloc_vfsmnt(const char return NULL; } + mnt->mnt_pgid = -1; atomic_set(&mnt->mnt_count, 1); INIT_LIST_HEAD(&mnt->mnt_hash); INIT_LIST_HEAD(&mnt->mnt_child); @@ -539,8 +540,10 @@ static struct vfsmount *clone_mnt(struct mnt->mnt_master = old; clear_mnt_shared(mnt); } else if (!(flag & CL_PRIVATE)) { - if ((flag & CL_PROPAGATION) || IS_MNT_SHARED(old)) - list_add(&mnt->mnt_share, &old->mnt_share); + if (flag & CL_PROPAGATION) + set_mnt_shared(old); + if (IS_MNT_SHARED(old)) + make_mnt_peer(old, mnt); if (IS_MNT_SLAVE(old)) list_add(&mnt->mnt_slave, &old->mnt_slave); mnt->mnt_master = old->mnt_master; Index: linux/Documentation/filesystems/proc.txt =================================================================== --- linux.orig/Documentation/filesystems/proc.txt 2008-03-13 20:45:15.000000000 +0100 +++ linux/Documentation/filesystems/proc.txt 2008-03-13 20:45:50.000000000 +0100 @@ -2367,18 +2367,12 @@ MNTOPTS: per mount options SBOPTS: per super block options PROPAGATION: propagation type -propagation type: [:][,...] - note: 'shared' flag is followed by the mntid of its peer mount - 'slave' flag is followed by the mntid of its master mount +propagation type: [:][,...] + 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 'private' flag stands by itself 'unbindable' flag stands by itself -The 'mntid' used in the propagation type is a canonical ID of the peer -group (currently the smallest ID within the group is used for this -purpose, but this should not be relied on). Since mounts can be added -or removed from the peer group, this ID only guaranteed to stay the -same on a static propagation tree. - For more information see: Documentation/filesystems/sharedsubtree.txt Index: linux/fs/pnode.h =================================================================== --- linux.orig/fs/pnode.h 2008-03-13 20:45:49.000000000 +0100 +++ linux/fs/pnode.h 2008-03-13 20:45:50.000000000 +0100 @@ -25,6 +25,7 @@ void set_mnt_shared(struct vfsmount *); void clear_mnt_shared(struct vfsmount *); +void make_mnt_peer(struct vfsmount *, struct vfsmount *); void change_mnt_propagation(struct vfsmount *, int); int propagate_mnt(struct vfsmount *, struct dentry *, struct vfsmount *, struct list_head *); -- -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/