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>

1 files changed, 4 insertions, 3 deletions

diff --git a/net/wanrouter/wanproc.c b/net/wanrouter/wanproc.c
index c44d96b3a437..11f25c7a7a05 100644
--- a/net/wanrouter/wanproc.c
+++ b/net/wanrouter/wanproc.c
@@ -27,7 +27,7 @@
 #include <linux/module.h>
 #include <linux/wanrouter.h>    /* WAN router API definitions */
 #include <linux/seq_file.h>
-#include <linux/smp_lock.h>
+#include <linux/mutex.h>
 
 #include <net/net_namespace.h>
 #include <asm/io.h>
@@ -66,6 +66,7 @@
  *      /proc/net/router
  */
 
+static DEFINE_MUTEX(config_mutex);
 static struct proc_dir_entry *proc_router;
 
 /* Strings */
@@ -85,7 +86,7 @@ static void *r_start(struct seq_file *m, loff_t *pos)
         struct wan_device *wandev;
         loff_t l = *pos;
 
-        lock_kernel();
+        mutex_lock(&config_mutex);
         if (!l--)
                 return SEQ_START_TOKEN;
         for (wandev = wanrouter_router_devlist; l-- && wandev;
@@ -104,7 +105,7 @@ static void *r_next(struct seq_file *m, void *v, loff_t *pos)
 static void r_stop(struct seq_file *m, void *v)
         __releases(kernel_lock)
 {
-        unlock_kernel();
+        mutex_unlock(&config_mutex);
 }
 
 static int config_show(struct seq_file *m, void *v)