procfs: Convert /proc/pid/fdinfo/ handling routines to seq-file v2

This patch converts /proc/pid/fdinfo/ handling routines to seq-file which
is needed to extend seq operations and plug in auxiliary fdinfo provides
from subsystems like eventfd/eventpoll/fsnotify.

Note the proc_fd_link no longer call for proc_fd_info, simply because
the guts of proc_fd_info() got merged into ->show() of that seq_file

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

diff --git a/fs/proc/fd.c b/fs/proc/fd.c
index 1b0f932b4bd98026ebed5b5e7042a8081e48c076..9cef449c0f76fa68569b70e28514557442a16338 100644 (file)
--- a/fs/proc/fd.c
+++ b/fs/proc/fd.c
@@ -6,61 +6,68 @@
 #include <linux/namei.h>
 #include <linux/pid.h>
 #include <linux/security.h>
+#include <linux/file.h>
+#include <linux/seq_file.h>
 
 #include <linux/proc_fs.h>
 
 #include "internal.h"
 #include "fd.h"
 
-#define PROC_FDINFO_MAX 64
-
-static int proc_fd_info(struct inode *inode, struct path *path, char *info)
+static int seq_show(struct seq_file *m, void *v)
 {
-       struct task_struct *task = get_proc_task(inode);
        struct files_struct *files = NULL;
-       int fd = proc_fd(inode);
-       struct file *file;
+       int f_flags = 0, ret = -ENOENT;
+       struct file *file = NULL;
+       struct task_struct *task;
+
+       task = get_proc_task(m->private);
+       if (!task)
+               return -ENOENT;
+
+       files = get_files_struct(task);
+       put_task_struct(task);
 
-       if (task) {
-               files = get_files_struct(task);
-               put_task_struct(task);
-       }
        if (files) {
-               /*
-                * We are not taking a ref to the file structure, so we must
-                * hold ->file_lock.
-                */
+               int fd = proc_fd(m->private);
+
                spin_lock(&files->file_lock);
                file = fcheck_files(files, fd);
                if (file) {
-                       unsigned int f_flags;
-                       struct fdtable *fdt;
+                       struct fdtable *fdt = files_fdtable(files);
 
-                       fdt = files_fdtable(files);
                        f_flags = file->f_flags & ~O_CLOEXEC;
                        if (close_on_exec(fd, fdt))
                                f_flags |= O_CLOEXEC;
 
-                       if (path) {
-                               *path = file->f_path;
-                               path_get(&file->f_path);
-                       }
-                       if (info)
-                               snprintf(info, PROC_FDINFO_MAX,
-                                        "pos:\t%lli\n"
-                                        "flags:\t0%o\n",
-                                        (long long) file->f_pos,
-                                        f_flags);
-                       spin_unlock(&files->file_lock);
-                       put_files_struct(files);
-                       return 0;
+                       get_file(file);
+                       ret = 0;
                }
                spin_unlock(&files->file_lock);
                put_files_struct(files);
        }
-       return -ENOENT;
+
+       if (!ret) {
+                seq_printf(m, "pos:\t%lli\nflags:\t0%o\n",
+                          (long long)file->f_pos, f_flags);
+               fput(file);
+       }
+
+       return ret;
 }
 
+static int seq_fdinfo_open(struct inode *inode, struct file *file)
+{
+       return single_open(file, seq_show, inode);
+}
+
+static const struct file_operations proc_fdinfo_file_operations = {
+       .open           = seq_fdinfo_open,
+       .read           = seq_read,
+       .llseek         = seq_lseek,
+       .release        = single_release,
+};
+
 static int tid_fd_revalidate(struct dentry *dentry, unsigned int flags)
 {
        struct files_struct *files;
@@ -130,7 +137,32 @@ static const struct dentry_operations tid_fd_dentry_operations = {
 
 static int proc_fd_link(struct dentry *dentry, struct path *path)
 {
-       return proc_fd_info(dentry->d_inode, path, NULL);
+       struct files_struct *files = NULL;
+       struct task_struct *task;
+       int ret = -ENOENT;
+
+       task = get_proc_task(dentry->d_inode);
+       if (task) {
+               files = get_files_struct(task);
+               put_task_struct(task);
+       }
+
+       if (files) {
+               int fd = proc_fd(dentry->d_inode);
+               struct file *fd_file;
+
+               spin_lock(&files->file_lock);
+               fd_file = fcheck_files(files, fd);
+               if (fd_file) {
+                       *path = fd_file->f_path;
+                       path_get(&fd_file->f_path);
+                       ret = 0;
+               }
+               spin_unlock(&files->file_lock);
+               put_files_struct(files);
+       }
+
+       return ret;
 }
 
 static struct dentry *
@@ -245,22 +277,6 @@ out_no_task:
        return retval;
 }
 
-static ssize_t proc_fdinfo_read(struct file *file, char __user *buf,
-                               size_t len, loff_t *ppos)
-{
-       char tmp[PROC_FDINFO_MAX];
-       int err = proc_fd_info(file->f_path.dentry->d_inode, NULL, tmp);
-       if (!err)
-               err = simple_read_from_buffer(buf, len, ppos, tmp, strlen(tmp));
-       return err;
-}
-
-static const struct file_operations proc_fdinfo_file_operations = {
-       .open           = nonseekable_open,
-       .read           = proc_fdinfo_read,
-       .llseek         = no_llseek,
-};
-
 static int proc_readfd(struct file *filp, void *dirent, filldir_t filldir)
 {
        return proc_readfd_common(filp, dirent, filldir, proc_fd_instantiate);