Commit fcdba07e authored by Jiri Olsa's avatar Jiri Olsa Committed by Greg Kroah-Hartman
Browse files

tty,vcs removing con_buf/conf_buf_mtx 



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.

Signed-off-by: default avatarJiri Olsa <jolsa@redhat.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@suse.de>
parent dc1892c4

drivers/tty/vt/vc_screen.c

+52 −46
Original line number Diff line number Diff line
@@ -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;

}

drivers/tty/vt/vt.c

+0 −12
Original line number Diff line number Diff line
@@ -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

include/linux/vt_kern.h

+0 −8
Original line number Diff line number Diff line
@@ -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;

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