From 2d4d4864ac08caff5c204a752bd004eed4f08760 Mon Sep 17 00:00:00 2001 From: Ram Pai Date: Thu, 27 Mar 2008 13:06:25 +0100 Subject: [patch 6/7] vfs: mountinfo: add /proc//mountinfo [mszeredi@suse.cz] rewrite and split big patch into managable chunks /proc/mounts in its current form lacks important information: - propagation state - root of mount for bind mounts - the st_dev value used within the filesystem - identifier for each mount and it's parent It also suffers from the following problems: - not easily extendable - ambiguity of mountpoints within a chrooted environment - doesn't distinguish between filesystem dependent and independent options - doesn't distinguish between per mount and per super block options This patch introduces /proc//mountinfo which attempts to address all these deficiencies. Code shared between /proc//mounts and /proc//mountinfo is extracted into separate functions. Thanks to Al Viro for the help in getting the design right. Signed-off-by: Ram Pai Signed-off-by: Miklos Szeredi Signed-off-by: Al Viro --- Documentation/filesystems/proc.txt | 32 ++++++++++++++++++++++++++++++++ 1 file changed, 32 insertions(+) (limited to 'Documentation/filesystems/proc.txt') diff --git a/Documentation/filesystems/proc.txt b/Documentation/filesystems/proc.txt index 518ebe609e2..2cd920f92e5 100644 --- a/Documentation/filesystems/proc.txt +++ b/Documentation/filesystems/proc.txt @@ -43,6 +43,7 @@ Table of Contents 2.13 /proc//oom_score - Display current oom-killer score 2.14 /proc//io - Display the IO accounting fields 2.15 /proc//coredump_filter - Core dump filtering settings + 2.16 /proc//mountinfo - Information about mounts ------------------------------------------------------------------------------ Preface @@ -2348,4 +2349,35 @@ For example: $ echo 0x7 > /proc/self/coredump_filter $ ./some_program +2.16 /proc//mountinfo - Information about mounts +-------------------------------------------------------- + +This file contains lines of the form: + +36 35 98:0 /mnt1 /mnt2 rw,noatime master:1 - ext3 /dev/root rw,errors=continue +(1)(2)(3) (4) (5) (6) (7) (8) (9) (10) (11) + +(1) mount ID: unique identifier of the mount (may be reused after umount) +(2) parent ID: ID of parent (or of self for the top of the mount tree) +(3) major:minor: value of st_dev for files on filesystem +(4) root: root of the mount within the filesystem +(5) mount point: mount point relative to the process's root +(6) mount options: per mount options +(7) optional fields: zero or more fields of the form "tag[:value]" +(8) separator: marks the end of the optional fields +(9) filesystem type: name of filesystem of the form "type[.subtype]" +(10) mount source: filesystem specific information or "none" +(11) super options: per super block options + +Parsers should ignore all unrecognised optional fields. Currently the +possible optional fields are: + +shared:X mount is shared in peer group X +master:X mount is slave to peer group X +unbindable mount is unbindable + +For more information on mount propagation see: + + Documentation/filesystems/sharedsubtree.txt + ------------------------------------------------------------------------------ -- cgit v1.2.3-70-g09d2 From 97e7e0f71d6d948c25f11f0a33878d9356d9579e Mon Sep 17 00:00:00 2001 From: Miklos Szeredi 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 Signed-off-by: Al Viro --- 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 'Documentation/filesystems/proc.txt') 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