net: autoconvert trivial BKL users to private mutex

All these files use the big kernel lock in a trivial
way to serialize their private file operations,
typically resulting from an earlier semi-automatic
pushdown from VFS.

None of these drivers appears to want to lock against
other code, and they all use the BKL as the top-level
lock in their file operations, meaning that there
is no lock-order inversion problem.

Consequently, we can remove the BKL completely,
replacing it with a per-file mutex in every case.
Using a scripted approach means we can avoid
typos.

file=$1
name=$2
if grep -q lock_kernel ${file} ; then
    if grep -q 'include.*linux.mutex.h' ${file} ; then
            sed -i '/include.*<linux\/smp_lock.h>/d' ${file}
    else
            sed -i 's/include.*<linux\/smp_lock.h>.*$/include <linux\/mutex.h>/g' ${file}
    fi
    sed -i ${file} \
        -e "/^#include.*linux.mutex.h/,$ {
                1,/^\(static\|int\|long\)/ {
                     /^\(static\|int\|long\)/istatic DEFINE_MUTEX(${name}_mutex);

} }"  \
    -e "s/\(un\)*lock_kernel\>[ ]*()/mutex_\1lock(\&${name}_mutex)/g" \
    -e '/[      ]*cycle_kernel_lock();/d'
else
    sed -i -e '/include.*\<smp_lock.h\>/d' ${file}  \
                -e '/cycle_kernel_lock()/d'
fi

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: netdev@vger.kernel.org
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ppp_generic.c

@@ -40,7 +40,6 @@
 #include <linux/if_arp.h>
 #include <linux/ip.h>
 #include <linux/tcp.h>
-#include <linux/smp_lock.h>
 #include <linux/spinlock.h>
 #include <linux/rwsem.h>
 #include <linux/stddef.h>
@@ -180,6 +179,7 @@ struct channel {
  * channel.downl.
  */
 
+static DEFINE_MUTEX(ppp_mutex);
 static atomic_t ppp_unit_count = ATOMIC_INIT(0);
 static atomic_t channel_count = ATOMIC_INIT(0);
 
@@ -362,7 +362,6 @@ static const int npindex_to_ethertype[NUM_NP] = {
  */
 static int ppp_open(struct inode *inode, struct file *file)
 {
-	cycle_kernel_lock();
 	/*
 	 * This could (should?) be enforced by the permissions on /dev/ppp.
 	 */
@@ -582,7 +581,7 @@ static long ppp_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 		 * this fd and reopening /dev/ppp.
 		 */
 		err = -EINVAL;
-		lock_kernel();
+		mutex_lock(&ppp_mutex);
 		if (pf->kind == INTERFACE) {
 			ppp = PF_TO_PPP(pf);
 			if (file == ppp->owner)
@@ -594,7 +593,7 @@ static long ppp_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 		} else
 			printk(KERN_DEBUG "PPPIOCDETACH file->f_count=%ld\n",
 			       atomic_long_read(&file->f_count));
-		unlock_kernel();
+		mutex_unlock(&ppp_mutex);
 		return err;
 	}
 
@@ -602,7 +601,7 @@ static long ppp_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 		struct channel *pch;
 		struct ppp_channel *chan;
 
-		lock_kernel();
+		mutex_lock(&ppp_mutex);
 		pch = PF_TO_CHANNEL(pf);
 
 		switch (cmd) {
@@ -624,7 +623,7 @@ static long ppp_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 				err = chan->ops->ioctl(chan, cmd, arg);
 			up_read(&pch->chan_sem);
 		}
-		unlock_kernel();
+		mutex_unlock(&ppp_mutex);
 		return err;
 	}
 
@@ -634,7 +633,7 @@ static long ppp_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 		return -EINVAL;
 	}
 
-	lock_kernel();
+	mutex_lock(&ppp_mutex);
 	ppp = PF_TO_PPP(pf);
 	switch (cmd) {
 	case PPPIOCSMRU:
@@ -782,7 +781,7 @@ static long ppp_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 	default:
 		err = -ENOTTY;
 	}
-	unlock_kernel();
+	mutex_unlock(&ppp_mutex);
 	return err;
 }
 
@@ -795,7 +794,7 @@ static int ppp_unattached_ioctl(struct net *net, struct ppp_file *pf,
 	struct ppp_net *pn;
 	int __user *p = (int __user *)arg;
 
-	lock_kernel();
+	mutex_lock(&ppp_mutex);
 	switch (cmd) {
 	case PPPIOCNEWUNIT:
 		/* Create a new ppp unit */
@@ -846,7 +845,7 @@ static int ppp_unattached_ioctl(struct net *net, struct ppp_file *pf,
 	default:
 		err = -ENOTTY;
 	}
-	unlock_kernel();
+	mutex_unlock(&ppp_mutex);
 	return err;
 }