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Date: Sat, 23 Jan 2010 02:23:52 +0200
From: Maxim Levitsky <maximlevitsky@...il.com>
To: Artem Bityutskiy <dedekind1@...il.com>
Cc: linux-mtd <linux-mtd@...ts.infradead.org>,
linux-kernel <linux-kernel@...r.kernel.org>,
Alex Dubov <oakad@...oo.com>, joern <joern@...fs.org>,
Thomas Gleixner <tglx@...utronix.de>,
David Woodhouse <dwmw2@...radead.org>
Subject: [PATCH 4/8] MTD: create lockless versions of {get,put}_mtd_device
>>From b7c27159b5540b0951f6b030ffca895f34a3b3d3 Mon Sep 17 00:00:00 2001
From: Maxim Levitsky <maximlevitsky@...il.com>
Date: Sat, 23 Jan 2010 02:04:44 +0200
Subject: [PATCH 4/8] MTD: create lockless versions of {get,put}_mtd_device
This will be used to resolve deadlock in block translation layer.
Signed-off-by: Maxim Levitsky <maximlevitsky@...il.com>
---
drivers/mtd/mtdcore.c | 60 ++++++++++++++++++++++++++++++----------------
include/linux/mtd/mtd.h | 3 +-
2 files changed, 41 insertions(+), 22 deletions(-)
diff --git a/drivers/mtd/mtdcore.c b/drivers/mtd/mtdcore.c
index c356c0a..3bdb7e8 100644
--- a/drivers/mtd/mtdcore.c
+++ b/drivers/mtd/mtdcore.c
@@ -453,27 +453,38 @@ struct mtd_info *get_mtd_device(struct mtd_info *mtd, int num)
ret = NULL;
}
- if (!ret)
- goto out_unlock;
-
- if (!try_module_get(ret->owner))
- goto out_unlock;
-
- if (ret->get_device) {
- err = ret->get_device(ret);
- if (err)
- goto out_put;
+ if (!ret) {
+ ret = ERR_PTR(err);
+ goto out;
}
- ret->usecount++;
+ err = __get_mtd_device(ret);
+ if (err)
+ ret = ERR_PTR(err);
+out:
mutex_unlock(&mtd_table_mutex);
return ret;
+}
-out_put:
- module_put(ret->owner);
-out_unlock:
- mutex_unlock(&mtd_table_mutex);
- return ERR_PTR(err);
+
+int __get_mtd_device(struct mtd_info *mtd)
+{
+ int err;
+
+ if (!try_module_get(mtd->owner))
+ return -ENODEV;
+
+ if (mtd->get_device) {
+
+ err = mtd->get_device(mtd);
+
+ if (err) {
+ module_put(mtd->owner);
+ return err;
+ }
+ }
+ mtd->usecount++;
+ return 0;
}
/**
@@ -524,14 +535,19 @@ out_unlock:
void put_mtd_device(struct mtd_info *mtd)
{
- int c;
-
mutex_lock(&mtd_table_mutex);
- c = --mtd->usecount;
+ __put_mtd_device(mtd);
+ mutex_unlock(&mtd_table_mutex);
+
+}
+
+void __put_mtd_device(struct mtd_info *mtd)
+{
+ --mtd->usecount;
+ BUG_ON(mtd->usecount < 0);
+
if (mtd->put_device)
mtd->put_device(mtd);
- mutex_unlock(&mtd_table_mutex);
- BUG_ON(c < 0);
module_put(mtd->owner);
}
@@ -569,7 +585,9 @@ EXPORT_SYMBOL_GPL(add_mtd_device);
EXPORT_SYMBOL_GPL(del_mtd_device);
EXPORT_SYMBOL_GPL(get_mtd_device);
EXPORT_SYMBOL_GPL(get_mtd_device_nm);
+EXPORT_SYMBOL_GPL(__get_mtd_device);
EXPORT_SYMBOL_GPL(put_mtd_device);
+EXPORT_SYMBOL_GPL(__put_mtd_device);
EXPORT_SYMBOL_GPL(register_mtd_user);
EXPORT_SYMBOL_GPL(unregister_mtd_user);
EXPORT_SYMBOL_GPL(default_mtd_writev);
diff --git a/include/linux/mtd/mtd.h b/include/linux/mtd/mtd.h
index 0f32a9b..662d747 100644
--- a/include/linux/mtd/mtd.h
+++ b/include/linux/mtd/mtd.h
@@ -290,8 +290,9 @@ extern int add_mtd_device(struct mtd_info *mtd);
extern int del_mtd_device (struct mtd_info *mtd);
extern struct mtd_info *get_mtd_device(struct mtd_info *mtd, int num);
+extern int __get_mtd_device(struct mtd_info *mtd);
+extern void __put_mtd_device(struct mtd_info *mtd);
extern struct mtd_info *get_mtd_device_nm(const char *name);
-
extern void put_mtd_device(struct mtd_info *mtd);
--
1.6.3.3
--
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