proc: implement proc_single_file_operations

Currently many /proc/pid files use a crufty precursor to the current seq_file
api, and they don't have direct access to the pid_namespace or the pid of for
which they are displaying data.

So implement proc_single_file_operations to make the seq_file routines easy to
use, and to give access to the full state of the pid of we are displaying data
for.

Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Cc: Oleg Nesterov <oleg@tv-sign.ru>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 43 insertions, 0 deletions

diff --git a/fs/proc/base.c b/fs/proc/base.c
index c59852b38787..f4b1e14bd95b 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -121,6 +121,10 @@ struct pid_entry {
         NOD(NAME, (S_IFREG|(MODE)),                     \
                 NULL, &proc_info_file_operations,       \
                 { .proc_read = &proc_##OTYPE } )
+#define ONE(NAME, MODE, OTYPE)                          \
+        NOD(NAME, (S_IFREG|(MODE)),                     \
+                NULL, &proc_single_file_operations,     \
+                { .proc_show = &proc_##OTYPE } )
 
 int maps_protect;
 EXPORT_SYMBOL(maps_protect);
@@ -658,6 +662,45 @@ static const struct file_operations proc_info_file_operations = {
         .read           = proc_info_read,
 };
 
+static int proc_single_show(struct seq_file *m, void *v)
+{
+        struct inode *inode = m->private;
+        struct pid_namespace *ns;
+        struct pid *pid;
+        struct task_struct *task;
+        int ret;
+
+        ns = inode->i_sb->s_fs_info;
+        pid = proc_pid(inode);
+        task = get_pid_task(pid, PIDTYPE_PID);
+        if (!task)
+                return -ESRCH;
+
+        ret = PROC_I(inode)->op.proc_show(m, ns, pid, task);
+
+        put_task_struct(task);
+        return ret;
+}
+
+static int proc_single_open(struct inode *inode, struct file *filp)
+{
+        int ret;
+        ret = single_open(filp, proc_single_show, NULL);
+        if (!ret) {
+                struct seq_file *m = filp->private_data;
+
+                m->private = inode;
+        }
+        return ret;
+}
+
+static const struct file_operations proc_single_file_operations = {
+        .open           = proc_single_open,
+        .read           = seq_read,
+        .llseek         = seq_lseek,
+        .release        = single_release,
+};
+
 static int mem_open(struct inode* inode, struct file* file)
 {
         file->private_data = (void*)((long)current->self_exec_id);