[patch 5/7] vfs: mountinfo: allow using process root

Allow /proc/<pid>/mountinfo to use the root of <pid> to calculate
mountpoints.

 - move definition of 'struct proc_mounts' to <linux/mnt_namespace.h>
 - add the process's namespace and root to this structure
 - pass a pointer to 'struct proc_mounts' into seq_operations

In addition the following cleanups are made:

 - use a common open function for /proc/<pid>/{mounts,mountstat}
 - surround namespace.c part of these proc files with #ifdef CONFIG_PROC_FS
 - make the seq_operations structures const

Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

1 files changed, 51 insertions, 57 deletions

diff --git a/fs/proc/base.c b/fs/proc/base.c
index 7313c62e3e9d..a04b3db7a296 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -502,17 +502,14 @@ static const struct inode_operations proc_def_inode_operations = {
         .setattr        = proc_setattr,
 };
 
-extern const struct seq_operations mounts_op;
-struct proc_mounts {
-        struct seq_file m;
-        int event;
-};
-
-static int mounts_open(struct inode *inode, struct file *file)
+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(struct inode *inode, struct file *file)
                                 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, &mounts_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);
@@ -573,6 +591,11 @@ static unsigned mounts_poll(struct file *file, poll_table *wait)
         return res;
 }
 
+static int mounts_open(struct inode *inode, struct file *file)
+{
+        return mounts_open_common(inode, file, &mounts_op);
+}
+
 static const struct file_operations proc_mounts_operations = {
         .open           = mounts_open,
         .read           = seq_read,
@@ -581,38 +604,9 @@ static const struct file_operations proc_mounts_operations = {
         .poll           = mounts_poll,
 };
 
-extern const struct seq_operations mountstats_op;
 static int mountstats_open(struct inode *inode, struct file *file)
 {
-        int ret = seq_open(file, &mountstats_op);
-
-        if (!ret) {
-                struct seq_file *m = file->private_data;
-                struct nsproxy *nsp;
-                struct mnt_namespace *mnt_ns = NULL;
-                struct task_struct *task = get_proc_task(inode);
-
-                if (task) {
-                        rcu_read_lock();
-                        nsp = task_nsproxy(task);
-                        if (nsp) {
-                                mnt_ns = nsp->mnt_ns;
-                                if (mnt_ns)
-                                        get_mnt_ns(mnt_ns);
-                        }
-                        rcu_read_unlock();
-
-                        put_task_struct(task);
-                }
-
-                if (mnt_ns)
-                        m->private = mnt_ns;
-                else {
-                        seq_release(inode, file);
-                        ret = -EINVAL;
-                }
-        }
-        return ret;
+        return mounts_open_common(inode, file, &mountstats_op);
 }
 
 static const struct file_operations proc_mountstats_operations = {