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Date: Mon, 7 Feb 2011 19:31:25 +0100
From: Jiri Olsa <jolsa@...hat.com>
To: alan@...rguk.ukuu.org.uk, gregkh@...e.de
Cc: linux-kernel@...r.kernel.org, Jiri Olsa <jolsa@...hat.com>
Subject: [PATCH 2/2] tty,vcs removing con_buf/conf_buf_mtx
hi,
seems there's no longer need for using con_buf/conf_buf_mtx
as vcs_read/vcs_write buffer for user's data.
The do_con_write function, that was the other user of this,
is currently using its own kmalloc-ed buffer.
Not sure when this got changed, as I was able to find this code
in 2.6.9, but it's already gone as far as current git history
goes - 2.6.12-rc2.
AFAICS there's a behaviour change with the current change.
The lseek is not completely mutually exclusive with the
vcs_read/vcs_write - the file->f_pos might get updated
via lseek callback during the vcs_read/vcs_write processing.
I tried to find out if the prefered behaviour is to keep
this in sync within read/write/lseek functions, but I did
not find any pattern on different places.
I guess if user end up calling write/lseek from different
threads she should know what she's doing. If needed we
could use dedicated fd mutex/buffer.
wbr,
jirka
Signed-off-by: Jiri Olsa <jolsa@...hat.com>
---
drivers/tty/vt/vc_screen.c | 98 +++++++++++++++++++++++--------------------
drivers/tty/vt/vt.c | 12 -----
include/linux/vt_kern.h | 8 ----
3 files changed, 52 insertions(+), 66 deletions(-)
diff --git a/drivers/tty/vt/vc_screen.c b/drivers/tty/vt/vc_screen.c
index 3c27c4b..7b3bfbe 100644
--- a/drivers/tty/vt/vc_screen.c
+++ b/drivers/tty/vt/vc_screen.c
@@ -28,7 +28,6 @@
#include <linux/interrupt.h>
#include <linux/mm.h>
#include <linux/init.h>
-#include <linux/mutex.h>
#include <linux/vt_kern.h>
#include <linux/selection.h>
#include <linux/kbd_kern.h>
@@ -51,6 +50,8 @@
#undef addr
#define HEADER_SIZE 4
+#define CON_BUF_SIZE (CONFIG_BASE_SMALL ? 256 : PAGE_SIZE)
+
struct vcs_poll_data {
struct notifier_block notifier;
unsigned int cons_num;
@@ -131,21 +132,45 @@ vcs_poll_data_get(struct file *file)
return poll;
}
+/*
+ * Returns VC for inode.
+ * Must be called with console_lock.
+ */
+static struct vc_data*
+vcs_vc(struct inode *inode, int *viewed)
+{
+ unsigned int currcons = iminor(inode) & 127;
+
+ WARN_CONSOLE_UNLOCKED();
+
+ if (currcons == 0) {
+ currcons = fg_console;
+ if (viewed)
+ *viewed = 1;
+ } else {
+ currcons--;
+ if (viewed)
+ *viewed = 0;
+ }
+ return vc_cons[currcons].d;
+}
+
+/*
+ * Returns size for VC carried by inode.
+ * Must be called with console_lock.
+ */
static int
vcs_size(struct inode *inode)
{
int size;
int minor = iminor(inode);
- int currcons = minor & 127;
struct vc_data *vc;
- if (currcons == 0)
- currcons = fg_console;
- else
- currcons--;
- if (!vc_cons_allocated(currcons))
+ WARN_CONSOLE_UNLOCKED();
+
+ vc = vcs_vc(inode, NULL);
+ if (!vc)
return -ENXIO;
- vc = vc_cons[currcons].d;
size = vc->vc_rows * vc->vc_cols;
@@ -158,17 +183,13 @@ static loff_t vcs_lseek(struct file *file, loff_t offset, int orig)
{
int size;
- mutex_lock(&con_buf_mtx);
console_lock();
size = vcs_size(file->f_path.dentry->d_inode);
console_unlock();
- if (size < 0) {
- mutex_unlock(&con_buf_mtx);
+ if (size < 0)
return size;
- }
switch (orig) {
default:
- mutex_unlock(&con_buf_mtx);
return -EINVAL;
case 2:
offset += size;
@@ -179,11 +200,9 @@ static loff_t vcs_lseek(struct file *file, loff_t offset, int orig)
break;
}
if (offset < 0 || offset > size) {
- mutex_unlock(&con_buf_mtx);
return -EINVAL;
}
file->f_pos = offset;
- mutex_unlock(&con_buf_mtx);
return file->f_pos;
}
@@ -196,12 +215,15 @@ vcs_read(struct file *file, char __user *buf, size_t count, loff_t *ppos)
struct vc_data *vc;
struct vcs_poll_data *poll;
long pos;
- long viewed, attr, read;
- int col, maxcol;
+ long attr, read;
+ int col, maxcol, viewed;
unsigned short *org = NULL;
ssize_t ret;
+ char *con_buf;
- mutex_lock(&con_buf_mtx);
+ con_buf = (char *) __get_free_page(GFP_KERNEL);
+ if (!con_buf)
+ return -ENOMEM;
pos = *ppos;
@@ -211,18 +233,10 @@ vcs_read(struct file *file, char __user *buf, size_t count, loff_t *ppos)
console_lock();
attr = (currcons & 128);
- currcons = (currcons & 127);
- if (currcons == 0) {
- currcons = fg_console;
- viewed = 1;
- } else {
- currcons--;
- viewed = 0;
- }
ret = -ENXIO;
- if (!vc_cons_allocated(currcons))
+ vc = vcs_vc(inode, &viewed);
+ if (!vc)
goto unlock_out;
- vc = vc_cons[currcons].d;
ret = -EINVAL;
if (pos < 0)
@@ -367,7 +381,7 @@ vcs_read(struct file *file, char __user *buf, size_t count, loff_t *ppos)
ret = read;
unlock_out:
console_unlock();
- mutex_unlock(&con_buf_mtx);
+ free_page((unsigned long) con_buf);
return ret;
}
@@ -378,13 +392,16 @@ vcs_write(struct file *file, const char __user *buf, size_t count, loff_t *ppos)
unsigned int currcons = iminor(inode);
struct vc_data *vc;
long pos;
- long viewed, attr, size, written;
+ long attr, size, written;
char *con_buf0;
- int col, maxcol;
+ int col, maxcol, viewed;
u16 *org0 = NULL, *org = NULL;
size_t ret;
+ char *con_buf;
- mutex_lock(&con_buf_mtx);
+ con_buf = (char *) __get_free_page(GFP_KERNEL);
+ if (!con_buf)
+ return -ENOMEM;
pos = *ppos;
@@ -394,19 +411,10 @@ vcs_write(struct file *file, const char __user *buf, size_t count, loff_t *ppos)
console_lock();
attr = (currcons & 128);
- currcons = (currcons & 127);
-
- if (currcons == 0) {
- currcons = fg_console;
- viewed = 1;
- } else {
- currcons--;
- viewed = 0;
- }
ret = -ENXIO;
- if (!vc_cons_allocated(currcons))
+ vc = vcs_vc(inode, &viewed);
+ if (!vc)
goto unlock_out;
- vc = vc_cons[currcons].d;
size = vcs_size(inode);
ret = -EINVAL;
@@ -561,9 +569,7 @@ vcs_write(struct file *file, const char __user *buf, size_t count, loff_t *ppos)
unlock_out:
console_unlock();
-
- mutex_unlock(&con_buf_mtx);
-
+ free_page((unsigned long) con_buf);
return ret;
}
diff --git a/drivers/tty/vt/vt.c b/drivers/tty/vt/vt.c
index 147ede3..0fd6df5 100644
--- a/drivers/tty/vt/vt.c
+++ b/drivers/tty/vt/vt.c
@@ -2068,18 +2068,6 @@ static void do_con_trol(struct tty_struct *tty, struct vc_data *vc, int c)
}
}
-/* This is a temporary buffer used to prepare a tty console write
- * so that we can easily avoid touching user space while holding the
- * console spinlock. It is allocated in con_init and is shared by
- * this code and the vc_screen read/write tty calls.
- *
- * We have to allocate this statically in the kernel data section
- * since console_init (and thus con_init) are called before any
- * kernel memory allocation is available.
- */
-char con_buf[CON_BUF_SIZE];
-DEFINE_MUTEX(con_buf_mtx);
-
/* is_double_width() is based on the wcwidth() implementation by
* Markus Kuhn -- 2007-05-26 (Unicode 5.0)
* Latest version: http://www.cl.cam.ac.uk/~mgk25/ucs/wcwidth.c
diff --git a/include/linux/vt_kern.h b/include/linux/vt_kern.h
index 6625cc1..4d05e14 100644
--- a/include/linux/vt_kern.h
+++ b/include/linux/vt_kern.h
@@ -142,14 +142,6 @@ static inline bool vt_force_oops_output(struct vc_data *vc)
return false;
}
-/*
- * vc_screen.c shares this temporary buffer with the console write code so that
- * we can easily avoid touching user space while holding the console spinlock.
- */
-
-#define CON_BUF_SIZE (CONFIG_BASE_SMALL ? 256 : PAGE_SIZE)
-extern char con_buf[CON_BUF_SIZE];
-extern struct mutex con_buf_mtx;
extern char vt_dont_switch;
extern int default_utf8;
extern int global_cursor_default;
--
1.7.1
--
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