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Message-ID: <20080416221723.GB7112@us.ibm.com>
Date: Wed, 16 Apr 2008 15:17:23 -0700
From: sukadev@...ibm.com
To: Andrew Morton <akpm@...l.org>
Cc: serue@...ibm.com, "Eric W. Biederman" <ebiederm@...ssion.com>,
hpa@...or.com, Containers <containers@...ts.osdl.org>,
linux-kernel@...r.kernel.org
Subject: [PATCH]: Factor out PTY index allocation
We noticed this while working on pts namespaces and believe this might
be an useful change even as we rework our pts/device namespace approach.
---
From: Sukadev Bhattiprolu <sukadev@...ibm.com>
Subject: [PATCH]: Factor out PTY index allocation
Factor out the code used to allocate/free a pts index into new interfaces,
devpts_new_index() and devpts_kill_index(). This localizes the external
data structures used in managing the pts indices.
Signed-off-by: Sukadev Bhattiprolu <sukadev@...ibm.com>
Signed-off-by: Serge Hallyn<serue@...ibm.com>
Signed-off-by: Matt Helsley<matthltc@...ibm.com>
---
drivers/char/tty_io.c | 40 ++++++----------------------------------
fs/devpts/inode.c | 42 +++++++++++++++++++++++++++++++++++++++++-
include/linux/devpts_fs.h | 4 ++++
3 files changed, 51 insertions(+), 35 deletions(-)
Index: 2.6.25-rc8-mm2/include/linux/devpts_fs.h
===================================================================
--- 2.6.25-rc8-mm2.orig/include/linux/devpts_fs.h 2008-01-26 09:49:16.000000000 -0800
+++ 2.6.25-rc8-mm2/include/linux/devpts_fs.h 2008-04-16 09:51:15.000000000 -0700
@@ -17,6 +17,8 @@
#ifdef CONFIG_UNIX98_PTYS
+int devpts_new_index(void);
+void devpts_kill_index(int idx);
int devpts_pty_new(struct tty_struct *tty); /* mknod in devpts */
struct tty_struct *devpts_get_tty(int number); /* get tty structure */
void devpts_pty_kill(int number); /* unlink */
@@ -24,6 +26,8 @@ void devpts_pty_kill(int number); /* u
#else
/* Dummy stubs in the no-pty case */
+static inline int devpts_new_index(void) { return -EINVAL; }
+static inline void devpts_kill_index(int idx) { }
static inline int devpts_pty_new(struct tty_struct *tty) { return -EINVAL; }
static inline struct tty_struct *devpts_get_tty(int number) { return NULL; }
static inline void devpts_pty_kill(int number) { }
Index: 2.6.25-rc8-mm2/drivers/char/tty_io.c
===================================================================
--- 2.6.25-rc8-mm2.orig/drivers/char/tty_io.c 2008-04-16 09:51:11.000000000 -0700
+++ 2.6.25-rc8-mm2/drivers/char/tty_io.c 2008-04-16 09:51:15.000000000 -0700
@@ -91,7 +91,6 @@
#include <linux/module.h>
#include <linux/smp_lock.h>
#include <linux/device.h>
-#include <linux/idr.h>
#include <linux/wait.h>
#include <linux/bitops.h>
#include <linux/delay.h>
@@ -137,9 +136,6 @@ EXPORT_SYMBOL(tty_mutex);
#ifdef CONFIG_UNIX98_PTYS
extern struct tty_driver *ptm_driver; /* Unix98 pty masters; for /dev/ptmx */
-extern int pty_limit; /* Config limit on Unix98 ptys */
-static DEFINE_IDR(allocated_ptys);
-static DEFINE_MUTEX(allocated_ptys_lock);
static int ptmx_open(struct inode *, struct file *);
#endif
@@ -2636,15 +2632,9 @@ static void release_dev(struct file *fil
*/
release_tty(tty, idx);
-#ifdef CONFIG_UNIX98_PTYS
/* Make this pty number available for reallocation */
- if (devpts) {
- mutex_lock(&allocated_ptys_lock);
- idr_remove(&allocated_ptys, idx);
- mutex_unlock(&allocated_ptys_lock);
- }
-#endif
-
+ if (devpts)
+ devpts_kill_index(idx);
}
/**
@@ -2800,29 +2790,13 @@ static int ptmx_open(struct inode *inode
struct tty_struct *tty;
int retval;
int index;
- int idr_ret;
nonseekable_open(inode, filp);
/* find a device that is not in use. */
- mutex_lock(&allocated_ptys_lock);
- if (!idr_pre_get(&allocated_ptys, GFP_KERNEL)) {
- mutex_unlock(&allocated_ptys_lock);
- return -ENOMEM;
- }
- idr_ret = idr_get_new(&allocated_ptys, NULL, &index);
- if (idr_ret < 0) {
- mutex_unlock(&allocated_ptys_lock);
- if (idr_ret == -EAGAIN)
- return -ENOMEM;
- return -EIO;
- }
- if (index >= pty_limit) {
- idr_remove(&allocated_ptys, index);
- mutex_unlock(&allocated_ptys_lock);
- return -EIO;
- }
- mutex_unlock(&allocated_ptys_lock);
+ index = devpts_new_index();
+ if (index < 0)
+ return index;
mutex_lock(&tty_mutex);
retval = init_dev(ptm_driver, index, &tty);
@@ -2847,9 +2821,7 @@ out1:
release_dev(filp);
return retval;
out:
- mutex_lock(&allocated_ptys_lock);
- idr_remove(&allocated_ptys, index);
- mutex_unlock(&allocated_ptys_lock);
+ devpts_kill_index(index);
return retval;
}
#endif
Index: 2.6.25-rc8-mm2/fs/devpts/inode.c
===================================================================
--- 2.6.25-rc8-mm2.orig/fs/devpts/inode.c 2008-02-27 15:17:59.000000000 -0800
+++ 2.6.25-rc8-mm2/fs/devpts/inode.c 2008-04-16 09:51:15.000000000 -0700
@@ -17,6 +17,7 @@
#include <linux/namei.h>
#include <linux/mount.h>
#include <linux/tty.h>
+#include <linux/idr.h>
#include <linux/devpts_fs.h>
#include <linux/parser.h>
#include <linux/fsnotify.h>
@@ -26,6 +27,10 @@
#define DEVPTS_DEFAULT_MODE 0600
+extern int pty_limit; /* Config limit on Unix98 ptys */
+static DEFINE_IDR(allocated_ptys);
+static DECLARE_MUTEX(allocated_ptys_lock);
+
static struct vfsmount *devpts_mnt;
static struct dentry *devpts_root;
@@ -171,9 +176,44 @@ static struct dentry *get_node(int num)
return lookup_one_len(s, root, sprintf(s, "%d", num));
}
+int devpts_new_index(void)
+{
+ int index;
+ int idr_ret;
+
+retry:
+ if (!idr_pre_get(&allocated_ptys, GFP_KERNEL)) {
+ return -ENOMEM;
+ }
+
+ down(&allocated_ptys_lock);
+ idr_ret = idr_get_new(&allocated_ptys, NULL, &index);
+ if (idr_ret < 0) {
+ up(&allocated_ptys_lock);
+ if (idr_ret == -EAGAIN)
+ goto retry;
+ return -EIO;
+ }
+
+ if (index >= pty_limit) {
+ idr_remove(&allocated_ptys, index);
+ up(&allocated_ptys_lock);
+ return -EIO;
+ }
+ up(&allocated_ptys_lock);
+ return index;
+}
+
+void devpts_kill_index(int idx)
+{
+ down(&allocated_ptys_lock);
+ idr_remove(&allocated_ptys, idx);
+ up(&allocated_ptys_lock);
+}
+
int devpts_pty_new(struct tty_struct *tty)
{
- int number = tty->index;
+ int number = tty->index; /* tty layer puts index from devpts_new_index() in here */
struct tty_driver *driver = tty->driver;
dev_t device = MKDEV(driver->major, driver->minor_start+number);
struct dentry *dentry;
--
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