mtd: mtdblock: introduce mtdblks_lock

The mtdblks array and its content are prone to race conditions. Introduce
the mutex mtdblks_lock in order to solve this.

[Amended by Artem Bityutskiy]

Signed-off-by: Matthias Kaehlcke <matthias@kaehlcke.net>
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>

diff --git a/drivers/mtd/mtdblock.c b/drivers/mtd/mtdblock.c
index 208c6faa0358afe995608599ea7e39dc4a405e6d..77db5ce24d92b9fed41970d83bb1346a95740d85 100644 (file)
--- a/drivers/mtd/mtdblock.c
+++ b/drivers/mtd/mtdblock.c
@@ -29,6 +29,8 @@ static struct mtdblk_dev {
        enum { STATE_EMPTY, STATE_CLEAN, STATE_DIRTY } cache_state;
 } *mtdblks[MAX_MTD_DEVICES];
 
+static struct mutex mtdblks_lock;
+
 /*
  * Cache stuff...
  *
@@ -270,15 +272,19 @@ static int mtdblock_open(struct mtd_blktrans_dev *mbd)
 
        DEBUG(MTD_DEBUG_LEVEL1,"mtdblock_open\n");
 
+       mutex_lock(&mtdblks_lock);
        if (mtdblks[dev]) {
                mtdblks[dev]->count++;
+               mutex_unlock(&mtdblks_lock);
                return 0;
        }
 
        /* OK, it's not open. Create cache info for it */
        mtdblk = kzalloc(sizeof(struct mtdblk_dev), GFP_KERNEL);
-       if (!mtdblk)
+       if (!mtdblk) {
+               mutex_unlock(&mtdblks_lock);
                return -ENOMEM;
+       }
 
        mtdblk->count = 1;
        mtdblk->mtd = mtd;
@@ -291,6 +297,7 @@ static int mtdblock_open(struct mtd_blktrans_dev *mbd)
        }
 
        mtdblks[dev] = mtdblk;
+       mutex_unlock(&mtdblks_lock);
 
        DEBUG(MTD_DEBUG_LEVEL1, "ok\n");
 
@@ -304,6 +311,8 @@ static int mtdblock_release(struct mtd_blktrans_dev *mbd)
 
        DEBUG(MTD_DEBUG_LEVEL1, "mtdblock_release\n");
 
+       mutex_lock(&mtdblks_lock);
+
        mutex_lock(&mtdblk->cache_mutex);
        write_cached_data(mtdblk);
        mutex_unlock(&mtdblk->cache_mutex);
@@ -316,6 +325,9 @@ static int mtdblock_release(struct mtd_blktrans_dev *mbd)
                vfree(mtdblk->cache_data);
                kfree(mtdblk);
        }
+
+       mutex_unlock(&mtdblks_lock);
+
        DEBUG(MTD_DEBUG_LEVEL1, "ok\n");
 
        return 0;
@@ -376,6 +388,8 @@ static struct mtd_blktrans_ops mtdblock_tr = {
 
 static int __init init_mtdblock(void)
 {
+       mutex_init(&mtdblks_lock);
+
        return register_mtd_blktrans(&mtdblock_tr);
 }