linux-kernel - [PATCH] de-semaphorize smackfs

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Date:	Mon, 17 Mar 2008 17:14:40 -0600
From:	Jonathan Corbet <corbet@....net>
To:	linux-kernel@...r.kernel.org
cc:	Casey Schaufler <casey@...aufler-ca.com>
Subject: [PATCH] de-semaphorize smackfs

While looking at the generic semaphore patch, I came to wonder what the
remaining semaphore users in the kernel were actually doing.  After a
quick grep for down_interruptible(), smackfs remained at the bottom of
my screen.  It seems like a straightforward mutex case - low-hanging
fruit.  So here's a conversion patch; compile-tested only, but what
could go wrong?

jon

Convert smackfs from a semaphore to a mutex

Signed-off-by: Jonathan Corbet <corbet@....net>

diff --git a/security/smack/smackfs.c b/security/smack/smackfs.c
index afe7c9b..6e09cec 100644
--- a/security/smack/smackfs.c
+++ b/security/smack/smackfs.c
@@ -76,7 +76,7 @@ struct smk_list_entry *smack_list;
 /*
  * Disable concurrent writing open() operations
  */
-static struct semaphore smack_write_sem;
+static DEFINE_MUTEX(smack_write_mutex);
 
 /*
  * Values for parsing cipso rules
@@ -171,7 +171,7 @@ static int smk_open_load(struct inode *inode, struct file *file)
 	if ((file->f_flags & O_ACCMODE) == O_RDONLY)
 		return seq_open(file, &load_seq_ops);
 
-	if (down_interruptible(&smack_write_sem))
+	if (mutex_lock_interruptible(&smack_write_mutex))
 		return -ERESTARTSYS;
 
 	return 0;
@@ -192,7 +192,7 @@ static int smk_release_load(struct inode *inode, struct file *file)
 	if ((file->f_flags & O_ACCMODE) == O_RDONLY)
 		return seq_release(inode, file);
 
-	up(&smack_write_sem);
+	mutex_unlock(&smack_write_mutex);
 	return 0;
 }
 
@@ -1011,7 +1011,7 @@ static int __init init_smk_fs(void)
 		}
 	}
 
-	sema_init(&smack_write_sem, 1);
+	mutex_init(&smack_write_mutex);
 	smk_cipso_doi();
 	smk_unlbl_ambient(NULL);
 
--
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