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Subject[PATCH 04/79] tty-ldisc: make /proc/tty/ldiscs use ldisc_ops instead of ldiscs
Date
From: Linus Torvalds <torvalds@linux-foundation.org>

The /proc/tty/ldiscs file is totally and utterly un-interested in the
"struct tty_ldisc" structures, and only cares about the underlying ldisc
operations.

So don't make it create a dummy 'struct ldisc' only to get a pointer to
the operations, and then destroy it. Instead, we split up the function
'tty_ldisc_try_get()', and create a 'get_ldops()' helper that just looks
up the ldisc operations based on the ldisc number.

That makes the code simpler to read (smaller and more well-defined
helper functions), and allows the /proc functions to avoid creating that
useless dummy only to immediately free it again.

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Tested-by: Sergey Senozhatsky <sergey.senozhatsky@mail.by>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Cc: OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
---
drivers/char/tty_ldisc.c | 65 +++++++++++++++++++++++++++------------------
1 files changed, 39 insertions(+), 26 deletions(-)
diff --git a/drivers/char/tty_ldisc.c b/drivers/char/tty_ldisc.c
index e48af9f..cbfacc0 100644
--- a/drivers/char/tty_ldisc.c
+++ b/drivers/char/tty_ldisc.c
@@ -145,6 +145,34 @@ int tty_unregister_ldisc(int disc)
}
EXPORT_SYMBOL(tty_unregister_ldisc);

+static struct tty_ldisc_ops *get_ldops(int disc)
+{
+ unsigned long flags;
+ struct tty_ldisc_ops *ldops, *ret;
+
+ spin_lock_irqsave(&tty_ldisc_lock, flags);
+ ret = ERR_PTR(-EINVAL);
+ ldops = tty_ldiscs[disc];
+ if (ldops) {
+ ret = ERR_PTR(-EAGAIN);
+ if (try_module_get(ldops->owner)) {
+ ldops->refcount++;
+ ret = ldops;
+ }
+ }
+ spin_unlock_irqrestore(&tty_ldisc_lock, flags);
+ return ret;
+}
+
+static void put_ldops(struct tty_ldisc_ops *ldops)
+{
+ unsigned long flags;
+
+ spin_lock_irqsave(&tty_ldisc_lock, flags);
+ ldops->refcount--;
+ module_put(ldops->owner);
+ spin_unlock_irqrestore(&tty_ldisc_lock, flags);
+}

/**
* tty_ldisc_try_get - try and reference an ldisc
@@ -156,36 +184,21 @@ EXPORT_SYMBOL(tty_unregister_ldisc);

static struct tty_ldisc *tty_ldisc_try_get(int disc)
{
- unsigned long flags;
struct tty_ldisc *ld;
struct tty_ldisc_ops *ldops;
- int err = -EINVAL;

ld = kmalloc(sizeof(struct tty_ldisc), GFP_KERNEL);
if (ld == NULL)
return ERR_PTR(-ENOMEM);

- spin_lock_irqsave(&tty_ldisc_lock, flags);
- ld->ops = NULL;
- ldops = tty_ldiscs[disc];
- /* Check the entry is defined */
- if (ldops) {
- /* If the module is being unloaded we can't use it */
- if (!try_module_get(ldops->owner))
- err = -EAGAIN;
- else {
- /* lock it */
- ldops->refcount++;
- ld->ops = ldops;
- atomic_set(&ld->users, 1);
- err = 0;
- }
- }
- spin_unlock_irqrestore(&tty_ldisc_lock, flags);
- if (err) {
+ ldops = get_ldops(disc);
+ if (IS_ERR(ldops)) {
kfree(ld);
- return ERR_PTR(err);
+ return ERR_CAST(ldops);
}
+
+ ld->ops = ldops;
+ atomic_set(&ld->users, 1);
return ld;
}

@@ -234,13 +247,13 @@ static void tty_ldiscs_seq_stop(struct seq_file *m, void *v)
static int tty_ldiscs_seq_show(struct seq_file *m, void *v)
{
int i = *(loff_t *)v;
- struct tty_ldisc *ld;
+ struct tty_ldisc_ops *ldops;

- ld = tty_ldisc_try_get(i);
- if (IS_ERR(ld))
+ ldops = get_ldops(i);
+ if (IS_ERR(ldops))
return 0;
- seq_printf(m, "%-10s %2d\n", ld->ops->name ? ld->ops->name : "???", i);
- put_ldisc(ld);
+ seq_printf(m, "%-10s %2d\n", ldops->name ? ldops->name : "???", i);
+ put_ldops(ldops);
return 0;
}

--
1.6.4.2


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