Commit 2d4d4864 authored by Ram Pai's avatar Ram Pai Committed by Al Viro

[patch 6/7] vfs: mountinfo: add /proc/<pid>/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/<pid>/mountinfo which attempts to address
all these deficiencies.

Code shared between /proc/<pid>/mounts and /proc/<pid>/mountinfo is
extracted into separate functions.

Thanks to Al Viro for the help in getting the design right.
Signed-off-by: default avatarRam Pai <linuxram@us.ibm.com>
Signed-off-by: default avatarMiklos Szeredi <mszeredi@suse.cz>
Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
parent a1a2c409
......@@ -43,6 +43,7 @@ Table of Contents
2.13 /proc/<pid>/oom_score - Display current oom-killer score
2.14 /proc/<pid>/io - Display the IO accounting fields
2.15 /proc/<pid>/coredump_filter - Core dump filtering settings
2.16 /proc/<pid>/mountinfo - Information about mounts
------------------------------------------------------------------------------
Preface
......@@ -2348,4 +2349,35 @@ For example:
$ echo 0x7 > /proc/self/coredump_filter
$ ./some_program
2.16 /proc/<pid>/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
------------------------------------------------------------------------------
......@@ -746,20 +746,30 @@ static void m_stop(struct seq_file *m, void *v)
up_read(&namespace_sem);
}
static int show_vfsmnt(struct seq_file *m, void *v)
struct proc_fs_info {
int flag;
const char *str;
};
static void show_sb_opts(struct seq_file *m, struct super_block *sb)
{
struct vfsmount *mnt = list_entry(v, struct vfsmount, mnt_list);
int err = 0;
static struct proc_fs_info {
int flag;
char *str;
} fs_info[] = {
static const struct proc_fs_info fs_info[] = {
{ MS_SYNCHRONOUS, ",sync" },
{ MS_DIRSYNC, ",dirsync" },
{ MS_MANDLOCK, ",mand" },
{ 0, NULL }
};
static struct proc_fs_info mnt_info[] = {
const struct proc_fs_info *fs_infop;
for (fs_infop = fs_info; fs_infop->flag; fs_infop++) {
if (sb->s_flags & fs_infop->flag)
seq_puts(m, fs_infop->str);
}
}
static void show_mnt_opts(struct seq_file *m, struct vfsmount *mnt)
{
static const struct proc_fs_info mnt_info[] = {
{ MNT_NOSUID, ",nosuid" },
{ MNT_NODEV, ",nodev" },
{ MNT_NOEXEC, ",noexec" },
......@@ -768,27 +778,37 @@ static int show_vfsmnt(struct seq_file *m, void *v)
{ MNT_RELATIME, ",relatime" },
{ 0, NULL }
};
struct proc_fs_info *fs_infop;
const struct proc_fs_info *fs_infop;
for (fs_infop = mnt_info; fs_infop->flag; fs_infop++) {
if (mnt->mnt_flags & fs_infop->flag)
seq_puts(m, fs_infop->str);
}
}
static void show_type(struct seq_file *m, struct super_block *sb)
{
mangle(m, sb->s_type->name);
if (sb->s_subtype && sb->s_subtype[0]) {
seq_putc(m, '.');
mangle(m, sb->s_subtype);
}
}
static int show_vfsmnt(struct seq_file *m, void *v)
{
struct vfsmount *mnt = list_entry(v, struct vfsmount, mnt_list);
int err = 0;
struct path mnt_path = { .dentry = mnt->mnt_root, .mnt = mnt };
mangle(m, mnt->mnt_devname ? mnt->mnt_devname : "none");
seq_putc(m, ' ');
seq_path(m, &mnt_path, " \t\n\\");
seq_putc(m, ' ');
mangle(m, mnt->mnt_sb->s_type->name);
if (mnt->mnt_sb->s_subtype && mnt->mnt_sb->s_subtype[0]) {
seq_putc(m, '.');
mangle(m, mnt->mnt_sb->s_subtype);
}
show_type(m, mnt->mnt_sb);
seq_puts(m, __mnt_is_readonly(mnt) ? " ro" : " rw");
for (fs_infop = fs_info; fs_infop->flag; fs_infop++) {
if (mnt->mnt_sb->s_flags & fs_infop->flag)
seq_puts(m, fs_infop->str);
}
for (fs_infop = mnt_info; fs_infop->flag; fs_infop++) {
if (mnt->mnt_flags & fs_infop->flag)
seq_puts(m, fs_infop->str);
}
show_sb_opts(m, mnt->mnt_sb);
show_mnt_opts(m, mnt);
if (mnt->mnt_sb->s_op->show_options)
err = mnt->mnt_sb->s_op->show_options(m, mnt);
seq_puts(m, " 0 0\n");
......@@ -802,6 +822,59 @@ const struct seq_operations mounts_op = {
.show = show_vfsmnt
};
static int show_mountinfo(struct seq_file *m, void *v)
{
struct proc_mounts *p = m->private;
struct vfsmount *mnt = list_entry(v, struct vfsmount, mnt_list);
struct super_block *sb = mnt->mnt_sb;
struct path mnt_path = { .dentry = mnt->mnt_root, .mnt = mnt };
struct path root = p->root;
int err = 0;
seq_printf(m, "%i %i %u:%u ", mnt->mnt_id, mnt->mnt_parent->mnt_id,
MAJOR(sb->s_dev), MINOR(sb->s_dev));
seq_dentry(m, mnt->mnt_root, " \t\n\\");
seq_putc(m, ' ');
seq_path_root(m, &mnt_path, &root, " \t\n\\");
if (root.mnt != p->root.mnt || root.dentry != p->root.dentry) {
/*
* Mountpoint is outside root, discard that one. Ugly,
* but less so than trying to do that in iterator in a
* race-free way (due to renames).
*/
return SEQ_SKIP;
}
seq_puts(m, mnt->mnt_flags & MNT_READONLY ? " ro" : " rw");
show_mnt_opts(m, mnt);
/* 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_UNBINDABLE(mnt))
seq_puts(m, " unbindable");
/* Filesystem specific data */
seq_puts(m, " - ");
show_type(m, sb);
seq_putc(m, ' ');
mangle(m, mnt->mnt_devname ? mnt->mnt_devname : "none");
seq_puts(m, sb->s_flags & MS_RDONLY ? " ro" : " rw");
show_sb_opts(m, sb);
if (sb->s_op->show_options)
err = sb->s_op->show_options(m, mnt);
seq_putc(m, '\n');
return err;
}
const struct seq_operations mountinfo_op = {
.start = m_start,
.next = m_next,
.stop = m_stop,
.show = show_mountinfo,
};
static int show_vfsstat(struct seq_file *m, void *v)
{
struct vfsmount *mnt = list_entry(v, struct vfsmount, mnt_list);
......@@ -822,7 +895,7 @@ static int show_vfsstat(struct seq_file *m, void *v)
/* file system type */
seq_puts(m, "with fstype ");
mangle(m, mnt->mnt_sb->s_type->name);
show_type(m, mnt->mnt_sb);
/* optional statistics */
if (mnt->mnt_sb->s_op->show_stats) {
......
......@@ -604,6 +604,19 @@ static const struct file_operations proc_mounts_operations = {
.poll = mounts_poll,
};
static int mountinfo_open(struct inode *inode, struct file *file)
{
return mounts_open_common(inode, file, &mountinfo_op);
}
static const struct file_operations proc_mountinfo_operations = {
.open = mountinfo_open,
.read = seq_read,
.llseek = seq_lseek,
.release = mounts_release,
.poll = mounts_poll,
};
static int mountstats_open(struct inode *inode, struct file *file)
{
return mounts_open_common(inode, file, &mountstats_op);
......@@ -2303,6 +2316,7 @@ static const struct pid_entry tgid_base_stuff[] = {
LNK("root", root),
LNK("exe", exe),
REG("mounts", S_IRUGO, mounts),
REG("mountinfo", S_IRUGO, mountinfo),
REG("mountstats", S_IRUSR, mountstats),
#ifdef CONFIG_PROC_PAGE_MONITOR
REG("clear_refs", S_IWUSR, clear_refs),
......@@ -2635,6 +2649,7 @@ static const struct pid_entry tid_base_stuff[] = {
LNK("root", root),
LNK("exe", exe),
REG("mounts", S_IRUGO, mounts),
REG("mountinfo", S_IRUGO, mountinfo),
#ifdef CONFIG_PROC_PAGE_MONITOR
REG("clear_refs", S_IWUSR, clear_refs),
REG("smaps", S_IRUGO, smaps),
......
......@@ -46,6 +46,7 @@ static inline void get_mnt_ns(struct mnt_namespace *ns)
}
extern const struct seq_operations mounts_op;
extern const struct seq_operations mountinfo_op;
extern const struct seq_operations mountstats_op;
#endif
......
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