This patch brings ability to plug in auxiliary fdinfo providers.
For example in further patches eventfd, evenpoll and fsnotify
will print out information associated with files.
This feature is CONFIG_CHECKPOINT_RESTORE guarded to eliminate
overhead for those who don't need it at all (this
unfortunately makes patch bigger than I wanted).
The basic usage rule is the following
- fdinfo provider should register own "show" method
via proc_register_fdinfo_driver call, where "show"
methods are rather well known seq-file operations
- once the kernel opens /proc/$pid/fdinfo/$fd file
it calls for ->probe() method in registered fdinfo
drivers, and if probe success, then seq-file "show"
operations will be called to provide out additional
infomation
Initially we considered to inject some "show" metod to
file_operations but since there really a number of
file_operations declared inside kernel (and in real the
further patches cover onle eventfd/epoll/inotify) the
waste of memory space will be inacceptable I think.
Signed-off-by: Cyrill Gorcunov <gorcu...@openvz.org>
CC: Al Viro <v...@zeniv.linux.org.uk>
CC: Alexey Dobriyan <adobri...@gmail.com>
CC: Andrew Morton <a...@linux-foundation.org>
CC: Pavel Emelyanov <xe...@parallels.com>
CC: James Bottomley <jbottom...@parallels.com>
---
fs/proc/fd.c | 200 ++++++++++++++++++++++++++++++++++++++++++++++++
include/linux/proc_fs.h | 26 ++++++
2 files changed, 226 insertions(+)
Index: linux-2.6.git/fs/proc/fd.c
===================================================================
--- linux-2.6.git.orig/fs/proc/fd.c
+++ linux-2.6.git/fs/proc/fd.c
@@ -8,12 +8,210 @@
#include <linux/security.h>
#include <linux/file.h>
#include <linux/seq_file.h>
+#include <linux/spinlock.h>
#include <linux/proc_fs.h>
#include "internal.h"
#include "fd.h"
+#ifdef CONFIG_CHECKPOINT_RESTORE
+
+static LIST_HEAD(fdinfo_drivers);
+static DECLARE_RWSEM(fdinfo_drivers_sem);
+
+int proc_register_fdinfo_driver(struct proc_fdinfo_driver *s)
+{
+ struct proc_fdinfo_driver *i;
+ int ret = 0;
+
+ if (!s->ops || !s->probe)
+ return -EINVAL;
+
+ down_write(&fdinfo_drivers_sem);
+ list_for_each_entry(i, &fdinfo_drivers, list) {
+ if (i == s) {
+ WARN_ONCE("Trying reassign fdinfo driver `%s'\n",
+ i->name);
+ ret = -EINVAL;
+ break;
+ }
+ }
+ if (!ret)
+ list_add(&s->list, &fdinfo_drivers);
+ up_write(&fdinfo_drivers_sem);
+
+ return ret;
+}
+
+void proc_unregister_fdinfo_driver(struct proc_fdinfo_driver *s)
+{
+ struct proc_fdinfo_driver *i, *tmp;
+
+ down_write(&fdinfo_drivers_sem);
+ list_for_each_entry_safe(i, tmp, &fdinfo_drivers, list) {
+ if (i == s) {
+ list_del(&i->list);
+ break;
+ }
+ }
+ up_write(&fdinfo_drivers_sem);
+}
+
+static int prep_fdinfo_driver(struct proc_fdinfo_extra *extra)
+{
+ struct proc_fdinfo_driver *s;
+
+ down_read(&fdinfo_drivers_sem);
+ list_for_each_entry(s, &fdinfo_drivers, list) {
+ if (s->probe(extra->f_file)) {
+ extra->driver = s;
+ break;
+ }
+ }
+ up_read(&fdinfo_drivers_sem);
+
+ return 0;
+}
+
+static void *seq_start(struct seq_file *m, loff_t *pos)
+{
+ struct proc_fdinfo_extra *extra = m->private;
+
+ down_read(&fdinfo_drivers_sem);
+ extra->pos = *pos;
+
+ return *pos == 0 ? extra :
+ (extra->driver ? extra->driver->ops->start(m, pos) : NULL);
+}
+
+static void seq_stop(struct seq_file *m, void *v)
+{
+ struct proc_fdinfo_extra *extra = m->private;
+
+ if (extra->driver && extra->pos > 0)
+ extra->driver->ops->stop(m, v);
+ up_read(&fdinfo_drivers_sem);
+}
+
+static void *seq_next(struct seq_file *m, void *p, loff_t *pos)
+{
+ struct proc_fdinfo_extra *extra = m->private;
+ void *v = NULL;
+
+ if (extra->driver) {
+ int ret = 0;
+
+ if (*pos == 0) {
+ v = extra->driver->ops->start(m, pos);
+ if (v) {
+ ret = extra->driver->ops->show(m, v);
+ p = v;
+ } else
+ ret = -1;
+ }
+
+ if (!ret)
+ v = extra->driver->ops->next(m, p, pos);
+ } else
+ ++*pos;
+
+ extra->pos = *pos;
+ return v;
+}
+
+static int seq_show(struct seq_file *m, void *v)
+{
+ struct proc_fdinfo_extra *extra = m->private;
+
+ if (extra->driver && extra->pos > 0)
+ return extra->driver->ops->show(m, v);
+
+ seq_printf(m, "pos:\t%lli\nflags:\t0%o\n",
+ (long long)extra->f_file->f_pos,
+ extra->f_flags);
+ return 0;
+}
+
+static const struct seq_operations fdinfo_seq_ops = {
+ .start = seq_start,
+ .next = seq_next,
+ .stop = seq_stop,
+ .show = seq_show,
+};
+
+static int seq_fdinfo_open(struct inode *inode, struct file *file)
+{
+ struct files_struct *files = NULL;
+ struct proc_fdinfo_extra *extra;
+ struct task_struct *task;
+ struct seq_file *m;
+ int ret;
+
+ extra = kzalloc(sizeof(*extra), GFP_KERNEL);
+ if (!extra)
+ return -ENOMEM;
+
+ ret = seq_open(file, &fdinfo_seq_ops);
+ if (!ret) {
+ ret = -ENOENT;
+ m = file->private_data;
+ m->private = extra;
+
+ task = get_proc_task(inode);
+ if (task) {
+ files = get_files_struct(task);
+ put_task_struct(task);
+ }
+
+ if (files) {
+ int fd = proc_fd(inode);
+
+ spin_lock(&files->file_lock);
+ extra->f_file = fcheck_files(files, fd);
+ if (extra->f_file) {
+ struct fdtable *fdt = files_fdtable(files);
+
+ extra->f_flags = extra->f_file->f_flags &
~O_CLOEXEC;
+ if (close_on_exec(fd, fdt))
+ extra->f_flags |= O_CLOEXEC;
+ get_file(extra->f_file);
+ }
+ spin_unlock(&files->file_lock);
+ put_files_struct(files);
+
+ ret = prep_fdinfo_driver(extra);
+ }
+ }
+
+ if (ret) {
+ if (extra->f_file)
+ put_filp(extra->f_file);
+ kfree(extra);
+ }
+ return ret;
+}
+
+static int seq_fdinfo_release(struct inode *inode, struct file *file)
+{
+ struct seq_file *m = file->private_data;
+ struct proc_fdinfo_extra *extra = m->private;
+
+ put_filp(extra->f_file);
+ kfree(m->private);
+
+ return seq_release(inode, file);
+}
+
+static const struct file_operations proc_fdinfo_file_operations = {
+ .open = seq_fdinfo_open,
+ .read = seq_read,
+ .llseek = seq_lseek,
+ .release = seq_fdinfo_release,
+};
+
+#else /* CONFIG_CHECKPOINT_RESTORE */
+
struct proc_fdinfo {
loff_t f_pos;
int f_flags;
@@ -90,6 +288,8 @@ static const struct file_operations proc
.release = seq_fdinfo_release,
};
+#endif /* CONFIG_CHECKPOINT_RESTORE */
+
static int tid_fd_revalidate(struct dentry *dentry, struct nameidata *nd)
{
struct files_struct *files;
Index: linux-2.6.git/include/linux/proc_fs.h
===================================================================
--- linux-2.6.git.orig/include/linux/proc_fs.h
+++ linux-2.6.git/include/linux/proc_fs.h
@@ -100,6 +100,24 @@ struct vmcore {
loff_t offset;
};
+struct seq_operations;
+
+/* fdinfo auxiliary information drivers */
+struct proc_fdinfo_driver {
+ struct list_head list;
+ const char *name;
+ const struct seq_operations *ops;
+ int (*probe)(struct file *file);
+};
+
+/* auxiliary data allocated per fdinfo reader */
+struct proc_fdinfo_extra {
+ struct proc_fdinfo_driver *driver;
+ loff_t pos;
+ struct file *f_file;
+ unsigned int f_flags;
+};
+
#ifdef CONFIG_PROC_FS
extern void proc_root_init(void);
@@ -175,6 +193,11 @@ extern struct proc_dir_entry *proc_net_m
extern struct file *proc_ns_fget(int fd);
+#ifdef CONFIG_CHECKPOINT_RESTORE
+extern int proc_register_fdinfo_driver(struct proc_fdinfo_driver *s);
+extern void proc_unregister_fdinfo_driver(struct proc_fdinfo_driver *s);
+#endif /* CONFIG_CHECKPOINT_RESTORE */
+
#else
#define proc_net_fops_create(net, name, mode, fops) ({ (void)(mode), NULL; })
@@ -229,6 +252,9 @@ static inline struct file *proc_ns_fget(
return ERR_PTR(-EINVAL);
}
+static inline int proc_register_fdinfo_driver(struct proc_fdinfo_driver *s) {
return -EINVAL; }
+static inline void proc_unregister_fdinfo_driver(struct proc_fdinfo_driver *s)
{ }
+
#endif /* CONFIG_PROC_FS */
#if !defined(CONFIG_PROC_KCORE)
--
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