[PATCH] remove active field from tty buffer structure

Remove 'active' field from tty buffer structure.  This was added in 2.6.16
as part of a patch to make the new tty buffering SMP safe.  This field is
unnecessary with the more intelligently written flush_to_ldisc that adds
receive_room handling.

Removing this field reverts to simpler logic where the tail buffer is
always the 'active' buffer, which should not be freed by flush_to_ldisc.
(active == buffer being filled with new data)

The result is simpler, smaller, and faster tty buffer code.

Signed-off-by: Paul Fulghum <paulkf@microgate.com>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Cc: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

4 files changed, 6 insertions, 17 deletions

diff --git a/drivers/char/tty_io.c b/drivers/char/tty_io.c
index 1f03ebf165d9..8d19f7281f0b 100644
--- a/drivers/char/tty_io.c
+++ b/drivers/char/tty_io.c
@@ -267,7 +267,6 @@ static struct tty_buffer *tty_buffer_alloc(size_t size)
         p->used = 0;
         p->size = size;
         p->next = NULL;
-        p->active = 0;
         p->commit = 0;
         p->read = 0;
         p->char_buf_ptr = (char *)(p->data);
@@ -327,10 +326,9 @@ int tty_buffer_request_room(struct tty_struct *tty, size_t size)
         /* OPTIMISATION: We could keep a per tty "zero" sized buffer to
            remove this conditional if its worth it. This would be invisible
            to the callers */
-        if ((b = tty->buf.tail) != NULL) {
+        if ((b = tty->buf.tail) != NULL)
                 left = b->size - b->used;
-                b->active = 1;
-        } else
+        else
                 left = 0;
 
         if (left < size) {
@@ -338,12 +336,10 @@ int tty_buffer_request_room(struct tty_struct *tty, size_t size)
                 if ((n = tty_buffer_find(tty, size)) != NULL) {
                         if (b != NULL) {
                                 b->next = n;
-                                b->active = 0;
                                 b->commit = b->used;
                         } else
                                 tty->buf.head = n;
                         tty->buf.tail = n;
-                        n->active = 1;
                 } else
                         size = left;
         }
@@ -404,10 +400,8 @@ void tty_schedule_flip(struct tty_struct *tty)
 {
         unsigned long flags;
         spin_lock_irqsave(&tty->buf.lock, flags);
-        if (tty->buf.tail != NULL) {
-                tty->buf.tail->active = 0;
+        if (tty->buf.tail != NULL)
                 tty->buf.tail->commit = tty->buf.tail->used;
-        }
         spin_unlock_irqrestore(&tty->buf.lock, flags);
         schedule_delayed_work(&tty->buf.work, 1);
 }
@@ -2902,10 +2896,8 @@ void tty_flip_buffer_push(struct tty_struct *tty)
 {
         unsigned long flags;
         spin_lock_irqsave(&tty->buf.lock, flags);
-        if (tty->buf.tail != NULL) {
-                tty->buf.tail->active = 0;
+        if (tty->buf.tail != NULL)
                 tty->buf.tail->commit = tty->buf.tail->used;
-        }
         spin_unlock_irqrestore(&tty->buf.lock, flags);
 
         if (tty->low_latency)
diff --git a/include/linux/kbd_kern.h b/include/linux/kbd_kern.h
index 4eb851ece080..efe0ee4cc80b 100644
--- a/include/linux/kbd_kern.h
+++ b/include/linux/kbd_kern.h
@@ -155,10 +155,8 @@ static inline void con_schedule_flip(struct tty_struct *t)
 {
         unsigned long flags;
         spin_lock_irqsave(&t->buf.lock, flags);
-        if (t->buf.tail != NULL) {
-                t->buf.tail->active = 0;
+        if (t->buf.tail != NULL)
                 t->buf.tail->commit = t->buf.tail->used;
-        }
         spin_unlock_irqrestore(&t->buf.lock, flags);
         schedule_work(&t->buf.work);
 }
diff --git a/include/linux/tty.h b/include/linux/tty.h
index 341cc4552c00..b3b807e4b050 100644
--- a/include/linux/tty.h
+++ b/include/linux/tty.h
@@ -57,7 +57,6 @@ struct tty_buffer {
         unsigned char *flag_buf_ptr;
         int used;
         int size;
-        int active;
         int commit;
         int read;
         /* Data points here */
diff --git a/include/linux/tty_flip.h b/include/linux/tty_flip.h
index 31548303ee37..eb677cf56106 100644
--- a/include/linux/tty_flip.h
+++ b/include/linux/tty_flip.h
@@ -12,7 +12,7 @@ static inline int tty_insert_flip_char(struct tty_struct *tty,
                                         unsigned char ch, char flag)
 {
         struct tty_buffer *tb = tty->buf.tail;
-        if (tb && tb->active && tb->used < tb->size) {
+        if (tb && tb->used < tb->size) {
                 tb->flag_buf_ptr[tb->used] = flag;
                 tb->char_buf_ptr[tb->used++] = ch;
                 return 1;