vfs: take /proc/*/mounts and friends to fs/proc_namespace.c

rationale: that stuff is far tighter bound to fs/namespace.c than to
the guts of procfs proper.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

1 files changed, 331 insertions, 0 deletions

diff --git a/fs/proc_namespace.c b/fs/proc_namespace.c
new file mode 100644
index 00000000000..9dcd9543ca1
--- /dev/null
+++ b/fs/proc_namespace.c
@@ -0,0 +1,331 @@
+/*
+ * fs/proc_namespace.c - handling of /proc/<pid>/{mounts,mountinfo,mountstats}
+ *
+ * In fact, that's a piece of procfs; it's *almost* isolated from
+ * the rest of fs/proc, but has rather close relationships with
+ * fs/namespace.c, thus here instead of fs/proc
+ *
+ */
+#include <linux/mnt_namespace.h>
+#include <linux/nsproxy.h>
+#include <linux/security.h>
+#include <linux/fs_struct.h>
+#include "proc/internal.h" /* only for get_proc_task() in ->open() */
+
+#include "pnode.h"
+#include "internal.h"
+
+static unsigned mounts_poll(struct file *file, poll_table *wait)
+{
+	struct proc_mounts *p = file->private_data;
+	struct mnt_namespace *ns = p->ns;
+	unsigned res = POLLIN | POLLRDNORM;
+
+	poll_wait(file, &p->ns->poll, wait);
+
+	br_read_lock(vfsmount_lock);
+	if (p->m.poll_event != ns->event) {
+		p->m.poll_event = ns->event;
+		res |= POLLERR | POLLPRI;
+	}
+	br_read_unlock(vfsmount_lock);
+
+	return res;
+}
+
+struct proc_fs_info {
+	int flag;
+	const char *str;
+};
+
+static int show_sb_opts(struct seq_file *m, struct super_block *sb)
+{
+	static const struct proc_fs_info fs_info[] = {
+		{ MS_SYNCHRONOUS, ",sync" },
+		{ MS_DIRSYNC, ",dirsync" },
+		{ MS_MANDLOCK, ",mand" },
+		{ 0, NULL }
+	};
+	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);
+	}
+
+	return security_sb_show_options(m, sb);
+}
+
+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" },
+		{ MNT_NOATIME, ",noatime" },
+		{ MNT_NODIRATIME, ",nodiratime" },
+		{ MNT_RELATIME, ",relatime" },
+		{ 0, NULL }
+	};
+	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 inline void mangle(struct seq_file *m, const char *s)
+{
+	seq_escape(m, s, " \t\n\\");
+}
+
+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, struct vfsmount *mnt)
+{
+	struct mount *r = real_mount(mnt);
+	int err = 0;
+	struct path mnt_path = { .dentry = mnt->mnt_root, .mnt = mnt };
+
+	if (mnt->mnt_sb->s_op->show_devname) {
+		err = mnt->mnt_sb->s_op->show_devname(m, mnt);
+		if (err)
+			goto out;
+	} else {
+		mangle(m, r->mnt_devname ? r->mnt_devname : "none");
+	}
+	seq_putc(m, ' ');
+	seq_path(m, &mnt_path, " \t\n\\");
+	seq_putc(m, ' ');
+	show_type(m, mnt->mnt_sb);
+	seq_puts(m, __mnt_is_readonly(mnt) ? " ro" : " rw");
+	err = show_sb_opts(m, mnt->mnt_sb);
+	if (err)
+		goto out;
+	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");
+out:
+	return err;
+}
+
+static int show_mountinfo(struct seq_file *m, struct vfsmount *mnt)
+{
+	struct proc_mounts *p = m->private;
+	struct mount *r = real_mount(mnt);
+	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 ", r->mnt_id, r->mnt_parent->mnt_id,
+		   MAJOR(sb->s_dev), MINOR(sb->s_dev));
+	if (sb->s_op->show_path)
+		err = sb->s_op->show_path(m, mnt);
+	else
+		seq_dentry(m, mnt->mnt_root, " \t\n\\");
+	if (err)
+		goto out;
+	seq_putc(m, ' ');
+
+	/* mountpoints outside of chroot jail will give SEQ_SKIP on this */
+	err = seq_path_root(m, &mnt_path, &root, " \t\n\\");
+	if (err)
+		goto out;
+
+	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(r))
+		seq_printf(m, " shared:%i", r->mnt_group_id);
+	if (IS_MNT_SLAVE(r)) {
+		int master = r->mnt_master->mnt_group_id;
+		int dom = get_dominating_id(r, &p->root);
+		seq_printf(m, " master:%i", master);
+		if (dom && dom != master)
+			seq_printf(m, " propagate_from:%i", dom);
+	}
+	if (IS_MNT_UNBINDABLE(r))
+		seq_puts(m, " unbindable");
+
+	/* Filesystem specific data */
+	seq_puts(m, " - ");
+	show_type(m, sb);
+	seq_putc(m, ' ');
+	if (sb->s_op->show_devname)
+		err = sb->s_op->show_devname(m, mnt);
+	else
+		mangle(m, r->mnt_devname ? r->mnt_devname : "none");
+	if (err)
+		goto out;
+	seq_puts(m, sb->s_flags & MS_RDONLY ? " ro" : " rw");
+	err = show_sb_opts(m, sb);
+	if (err)
+		goto out;
+	if (sb->s_op->show_options)
+		err = sb->s_op->show_options(m, mnt);
+	seq_putc(m, '\n');
+out:
+	return err;
+}
+
+static int show_vfsstat(struct seq_file *m, struct vfsmount *mnt)
+{
+	struct mount *r = real_mount(mnt);
+	struct path mnt_path = { .dentry = mnt->mnt_root, .mnt = mnt };
+	int err = 0;
+
+	/* device */
+	if (mnt->mnt_sb->s_op->show_devname) {
+		seq_puts(m, "device ");
+		err = mnt->mnt_sb->s_op->show_devname(m, mnt);
+	} else {
+		if (r->mnt_devname) {
+			seq_puts(m, "device ");
+			mangle(m, r->mnt_devname);
+		} else
+			seq_puts(m, "no device");
+	}
+
+	/* mount point */
+	seq_puts(m, " mounted on ");
+	seq_path(m, &mnt_path, " \t\n\\");
+	seq_putc(m, ' ');
+
+	/* file system type */
+	seq_puts(m, "with fstype ");
+	show_type(m, mnt->mnt_sb);
+
+	/* optional statistics */
+	if (mnt->mnt_sb->s_op->show_stats) {
+		seq_putc(m, ' ');
+		if (!err)
+			err = mnt->mnt_sb->s_op->show_stats(m, mnt);
+	}
+
+	seq_putc(m, '\n');
+	return err;
+}
+
+static int mounts_open_common(struct inode *inode, struct file *file,
+			      int (*show)(struct seq_file *, struct vfsmount *))
+{
+	struct task_struct *task = get_proc_task(inode);
+	struct nsproxy *nsp;
+	struct mnt_namespace *ns = NULL;
+	struct path root;
+	struct proc_mounts *p;
+	int ret = -EINVAL;
+
+	if (!task)
+		goto err;
+
+	rcu_read_lock();
+	nsp = task_nsproxy(task);
+	if (!nsp) {
+		rcu_read_unlock();
+		put_task_struct(task);
+		goto err;
+	}
+	ns = nsp->mnt_ns;
+	if (!ns) {
+		rcu_read_unlock();
+		put_task_struct(task);
+		goto err;
+	}
+	get_mnt_ns(ns);
+	rcu_read_unlock();
+	task_lock(task);
+	if (!task->fs) {
+		task_unlock(task);
+		put_task_struct(task);
+		ret = -ENOENT;
+		goto err_put_ns;
+	}
+	get_fs_root(task->fs, &root);
+	task_unlock(task);
+	put_task_struct(task);
+
+	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, &mounts_op);
+	if (ret)
+		goto err_free;
+
+	p->m.private = p;
+	p->ns = ns;
+	p->root = root;
+	p->m.poll_event = ns->event;
+	p->show = show;
+
+	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 proc_mounts *p = file->private_data;
+	path_put(&p->root);
+	put_mnt_ns(p->ns);
+	return seq_release(inode, file);
+}
+
+static int mounts_open(struct inode *inode, struct file *file)
+{
+	return mounts_open_common(inode, file, show_vfsmnt);
+}
+
+static int mountinfo_open(struct inode *inode, struct file *file)
+{
+	return mounts_open_common(inode, file, show_mountinfo);
+}
+
+static int mountstats_open(struct inode *inode, struct file *file)
+{
+	return mounts_open_common(inode, file, show_vfsstat);
+}
+
+const struct file_operations proc_mounts_operations = {
+	.open		= mounts_open,
+	.read		= seq_read,
+	.llseek		= seq_lseek,
+	.release	= mounts_release,
+	.poll		= mounts_poll,
+};
+
+const struct file_operations proc_mountinfo_operations = {
+	.open		= mountinfo_open,
+	.read		= seq_read,
+	.llseek		= seq_lseek,
+	.release	= mounts_release,
+	.poll		= mounts_poll,
+};
+
+const struct file_operations proc_mountstats_operations = {
+	.open		= mountstats_open,
+	.read		= seq_read,
+	.llseek		= seq_lseek,
+	.release	= mounts_release,
+};