[One more RFC for mountinfo, and then I'll really send them to
Andrew.]
Two changes:
1. Only show reachable mounts in /proc/<pid>/mountinfo, this makes
mountpoints unambiguous for chrooted processes.
2. Instead of showing mountpoints relative to the current root, always
show them relative to the queried task's root.
This means, that a particular mountinfo file will always have the same
contents, regardless of which process is reading the file. Which is a
lot more consistent, than the current behavior of /proc/<pid>/mounts.
Comments?
Thanks,
Miklos
Index: linux/fs/dcache.c
===================================================================
--- linux.orig/fs/dcache.c 2008-03-11 12:40:55.000000000 +0100
+++ linux/fs/dcache.c 2008-03-11 16:22:08.000000000 +0100
@@ -1774,9 +1774,10 @@ static int prepend(char **buffer, int *b
*
* "buflen" should be positive. Caller holds the dcache_lock.
*/
-static char *__d_path(struct dentry *dentry, struct vfsmount *vfsmnt,
- struct path *root, char *buffer, int buflen)
+char *__d_path(struct path *path, struct path *root, char *buffer, int buflen)
{
+ struct dentry *dentry = path->dentry;
+ struct vfsmount *vfsmnt = path->mnt;
char * end = buffer+buflen;
char * retval;
@@ -1863,7 +1864,7 @@ char *d_path(struct path *path, char *bu
path_get(¤t->fs->root);
read_unlock(¤t->fs->lock);
spin_lock(&dcache_lock);
- res = __d_path(path->dentry, path->mnt, &root, buf, buflen);
+ res = __d_path(path, &root, buf, buflen);
spin_unlock(&dcache_lock);
path_put(&root);
return res;
@@ -1976,7 +1977,7 @@ asmlinkage long sys_getcwd(char __user *
unsigned long len;
char * cwd;
- cwd = __d_path(pwd.dentry, pwd.mnt, &root, page, PAGE_SIZE);
+ cwd = __d_path(&pwd, &root, page, PAGE_SIZE);
spin_unlock(&dcache_lock);
error = PTR_ERR(cwd);
Index: linux/fs/namespace.c
===================================================================
--- linux.orig/fs/namespace.c 2008-03-11 12:39:15.000000000 +0100
+++ linux/fs/namespace.c 2008-03-11 17:00:11.000000000 +0100
@@ -683,17 +683,17 @@ EXPORT_SYMBOL(save_mount_options);
/* iterator */
static void *m_start(struct seq_file *m, loff_t *pos)
{
- struct mnt_namespace *n = m->private;
+ struct proc_mounts *p = m->private;
down_read(&namespace_sem);
- return seq_list_start(&n->list, *pos);
+ return seq_list_start(&p->ns->list, *pos);
}
static void *m_next(struct seq_file *m, void *v, loff_t *pos)
{
- struct mnt_namespace *n = m->private;
+ struct proc_mounts *p = m->private;
- return seq_list_next(v, &n->list, pos);
+ return seq_list_next(v, &p->ns->list, pos);
}
static void m_stop(struct seq_file *m, void *v)
@@ -777,13 +777,52 @@ const struct seq_operations mounts_op =
.show = show_vfsmnt
};
+/*
+ * Return true if 'path' is reachable from 'root'
+ */
+static bool is_path_reachable(const struct path *path, const struct path *root)
+{
+ struct dentry *dentry = path->dentry;
+ struct vfsmount *mnt = path->mnt;
+ bool res = false;
+
+ spin_lock(&dcache_lock);
+ for (;;) {
+ if (dentry == root->dentry && mnt == root->mnt) {
+ res = true;
+ break;
+ }
+ if (dentry == mnt->mnt_root || IS_ROOT(dentry)) {
+ /* Global root? */
+ spin_lock(&vfsmount_lock);
+ if (mnt->mnt_parent == mnt) {
+ spin_unlock(&vfsmount_lock);
+ break;
+ }
+ dentry = mnt->mnt_mountpoint;
+ mnt = mnt->mnt_parent;
+ spin_unlock(&vfsmount_lock);
+ continue;
+ }
+ dentry = dentry->d_parent;
+ }
+ spin_unlock(&dcache_lock);
+
+ return res;
+}
+
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 };
int err = 0;
+ /* Skip unreachable mounts */
+ if (!is_path_reachable(&mnt_path, &p->root))
+ return 0;
+
seq_printf(m, "%i %i %u:%u ", mnt->mnt_id, mnt->mnt_parent->mnt_id,
MAJOR(sb->s_dev), MINOR(sb->s_dev));
show_type(m, sb);
@@ -792,7 +831,7 @@ static int show_mountinfo(struct seq_fil
seq_putc(m, ' ');
seq_dentry(m, mnt->mnt_root, " \t\n\\");
seq_putc(m, ' ');
- seq_path(m, &mnt_path, " \t\n\\");
+ seq_path_root(m, &mnt_path, &p->root, " \t\n\\");
seq_puts(m, mnt->mnt_flags & MNT_READONLY ? " ro" : " rw");
show_mnt_opts(m, mnt);
seq_puts(m, sb->s_flags & MS_RDONLY ? " ro" : " rw");
Index: linux/fs/proc/base.c
===================================================================
--- linux.orig/fs/proc/base.c 2008-03-11 12:38:48.000000000 +0100
+++ linux/fs/proc/base.c 2008-03-11 16:22:08.000000000 +0100
@@ -502,17 +502,14 @@ static const struct inode_operations pro
.setattr = proc_setattr,
};
-struct proc_mounts {
- struct seq_file m;
- int event;
-};
-
static int mounts_open_common(struct inode *inode, struct file *file,
const struct seq_operations *op)
{
struct task_struct *task = get_proc_task(inode);
struct nsproxy *nsp;
struct mnt_namespace *ns = NULL;
+ struct fs_struct *fs = NULL;
+ struct path root;
struct proc_mounts *p;
int ret = -EINVAL;
@@ -525,40 +522,61 @@ static int mounts_open_common(struct ino
get_mnt_ns(ns);
}
rcu_read_unlock();
-
+ if (ns)
+ fs = get_fs_struct(task);
put_task_struct(task);
}
- if (ns) {
- ret = -ENOMEM;
- p = kmalloc(sizeof(struct proc_mounts), GFP_KERNEL);
- if (p) {
- file->private_data = &p->m;
- ret = seq_open(file, op);
- if (!ret) {
- p->m.private = ns;
- p->event = ns->event;
- return 0;
- }
- kfree(p);
- }
- put_mnt_ns(ns);
- }
+ if (!ns)
+ goto err;
+ if (!fs)
+ goto err_put_ns;
+
+ read_lock(&fs->lock);
+ root = fs->root;
+ path_get(&root);
+ read_unlock(&fs->lock);
+ put_fs_struct(fs);
+
+ ret = -ENOMEM;
+ p = kmalloc(sizeof(struct proc_mounts), GFP_KERNEL);
+ if (!p)
+ goto err_put_path;
+
+ file->private_data = &p->m;
+ ret = seq_open(file, op);
+ if (ret)
+ goto err_free;
+
+ p->m.private = p;
+ p->ns = ns;
+ p->root = root;
+ p->event = ns->event;
+
+ return 0;
+
+ err_free:
+ kfree(p);
+ err_put_path:
+ path_put(&root);
+ err_put_ns:
+ put_mnt_ns(ns);
+ err:
return ret;
}
static int mounts_release(struct inode *inode, struct file *file)
{
- struct seq_file *m = file->private_data;
- struct mnt_namespace *ns = m->private;
- put_mnt_ns(ns);
+ struct proc_mounts *p = file->private_data;
+ path_put(&p->root);
+ put_mnt_ns(p->ns);
return seq_release(inode, file);
}
static unsigned mounts_poll(struct file *file, poll_table *wait)
{
struct proc_mounts *p = file->private_data;
- struct mnt_namespace *ns = p->m.private;
+ struct mnt_namespace *ns = p->ns;
unsigned res = 0;
poll_wait(file, &ns->poll, wait);
Index: linux/fs/seq_file.c
===================================================================
--- linux.orig/fs/seq_file.c 2008-03-11 12:39:15.000000000 +0100
+++ linux/fs/seq_file.c 2008-03-11 16:22:08.000000000 +0100
@@ -392,6 +392,29 @@ int seq_path(struct seq_file *m, struct
EXPORT_SYMBOL(seq_path);
#ifdef CONFIG_PROC_FS
+int seq_path_root(struct seq_file *m, struct path *path, struct path *root,
+ char *esc)
+{
+ if (m->count < m->size) {
+ char *s = m->buf + m->count;
+ char *p;
+
+ spin_lock(&dcache_lock);
+ p = __d_path(path, root, s, m->size - m->count);
+ spin_unlock(&dcache_lock);
+ if (!IS_ERR(p)) {
+ s = mangle_path(s, p, esc);
+ if (s) {
+ p = m->buf + m->count;
+ m->count = s - m->buf;
+ return s - p;
+ }
+ }
+ }
+ m->count = m->size;
+ return -1;
+}
+
/*
* returns the path of the 'dentry' from the root of its filesystem.
*/
Index: linux/include/linux/dcache.h
===================================================================
--- linux.orig/include/linux/dcache.h 2008-03-11 12:39:15.000000000 +0100
+++ linux/include/linux/dcache.h 2008-03-11 16:22:08.000000000 +0100
@@ -302,6 +302,7 @@ extern int d_validate(struct dentry *, s
*/
extern char *dynamic_dname(struct dentry *, char *, int, const char *, ...);
+extern char *__d_path(struct path *path, struct path *root, char *, int);
extern char *d_path(struct path *, char *, int);
#ifdef CONFIG_PROC_FS
Index: linux/include/linux/mnt_namespace.h
===================================================================
--- linux.orig/include/linux/mnt_namespace.h 2008-03-11 12:38:48.000000000 +0100
+++ linux/include/linux/mnt_namespace.h 2008-03-11 16:22:08.000000000 +0100
@@ -5,6 +5,7 @@
#include <linux/mount.h>
#include <linux/sched.h>
#include <linux/nsproxy.h>
+#include <linux/seq_file.h>
struct mnt_namespace {
atomic_t count;
@@ -14,6 +15,13 @@ struct mnt_namespace {
int event;
};
+struct proc_mounts {
+ struct seq_file m; /* must be the first element */
+ struct mnt_namespace *ns;
+ struct path root;
+ int event;
+};
+
extern struct mnt_namespace *copy_mnt_ns(unsigned long, struct mnt_namespace *,
struct fs_struct *);
extern void __put_mnt_ns(struct mnt_namespace *ns);
Index: linux/include/linux/seq_file.h
===================================================================
--- linux.orig/include/linux/seq_file.h 2008-03-11 12:39:15.000000000 +0100
+++ linux/include/linux/seq_file.h 2008-03-11 16:22:08.000000000 +0100
@@ -46,6 +46,8 @@ int seq_printf(struct seq_file *, const
int seq_path(struct seq_file *, struct path *, char *);
#ifdef CONFIG_PROC_FS
+int seq_path_root(struct seq_file *m, struct path *path, struct path *root,
+ char *esc);
int seq_dentry(struct seq_file *, struct dentry *, char *);
#endif /* CONFIG_PROC_FS */
--
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