[PATCH 4.4 069/104] loop: Get rid of loop_index_mutex

[Greg Kroah-Hartman]

4.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Jan Kara <j...@suse.cz>

commit 0a42e99b58a208839626465af194cfe640ef9493 upstream.

Now that loop_ctl_mutex is global, just get rid of loop_index_mutex as
there is no good reason to keep these two separate and it just
complicates the locking.

Signed-off-by: Jan Kara <j...@suse.cz>
Signed-off-by: Jens Axboe <ax...@kernel.dk>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>

---
 drivers/block/loop.c |   39 ++++++++++++++++++++-------------------
 1 file changed, 20 insertions(+), 19 deletions(-)

--- a/drivers/block/loop.c
+++ b/drivers/block/loop.c
@@ -81,7 +81,6 @@
 #include <asm/uaccess.h>
 
 static DEFINE_IDR(loop_index_idr);
-static DEFINE_MUTEX(loop_index_mutex);
 static DEFINE_MUTEX(loop_ctl_mutex);
 
 static int max_part;
@@ -1571,9 +1570,11 @@ static int lo_compat_ioctl(struct block_
 static int lo_open(struct block_device *bdev, fmode_t mode)
 {
        struct loop_device *lo;
-       int err = 0;
+       int err;
 
-       mutex_lock(&loop_index_mutex);
+       err = mutex_lock_killable(&loop_ctl_mutex);
+       if (err)
+               return err;
        lo = bdev->bd_disk->private_data;
        if (!lo) {
                err = -ENXIO;
@@ -1582,7 +1583,7 @@ static int lo_open(struct block_device *
 
        atomic_inc(&lo->lo_refcnt);
 out:
-       mutex_unlock(&loop_index_mutex);
+       mutex_unlock(&loop_ctl_mutex);
        return err;
 }
 
@@ -1591,12 +1592,11 @@ static void lo_release(struct gendisk *d
        struct loop_device *lo;
        int err;
 
-       mutex_lock(&loop_index_mutex);
+       mutex_lock(&loop_ctl_mutex);
        lo = disk->private_data;
        if (atomic_dec_return(&lo->lo_refcnt))
-               goto unlock_index;
+               goto out_unlock;
 
-       mutex_lock(&loop_ctl_mutex);
        if (lo->lo_flags & LO_FLAGS_AUTOCLEAR) {
                /*
                 * In autoclear mode, stop the loop thread
@@ -1604,7 +1604,7 @@ static void lo_release(struct gendisk *d
                 */
                err = loop_clr_fd(lo);
                if (!err)
-                       goto unlock_index;
+                       return;
        } else {
                /*
                 * Otherwise keep thread (if running) and config,
@@ -1613,9 +1613,8 @@ static void lo_release(struct gendisk *d
                loop_flush(lo);
        }
 
+out_unlock:
        mutex_unlock(&loop_ctl_mutex);
-unlock_index:
-       mutex_unlock(&loop_index_mutex);
 }
 
 static const struct block_device_operations lo_fops = {
@@ -1897,7 +1896,7 @@ static struct kobject *loop_probe(dev_t
        struct kobject *kobj;
        int err;
 
-       mutex_lock(&loop_index_mutex);
+       mutex_lock(&loop_ctl_mutex);
        err = loop_lookup(&lo, MINOR(dev) >> part_shift);
        if (err < 0)
                err = loop_add(&lo, MINOR(dev) >> part_shift);
@@ -1905,7 +1904,7 @@ static struct kobject *loop_probe(dev_t
                kobj = NULL;
        else
                kobj = get_disk(lo->lo_disk);
-       mutex_unlock(&loop_index_mutex);
+       mutex_unlock(&loop_ctl_mutex);
 
        *part = 0;
        return kobj;
@@ -1915,9 +1914,13 @@ static long loop_control_ioctl(struct fi
                               unsigned long parm)
 {
        struct loop_device *lo;
-       int ret = -ENOSYS;
+       int ret;
+
+       ret = mutex_lock_killable(&loop_ctl_mutex);
+       if (ret)
+               return ret;
 
-       mutex_lock(&loop_index_mutex);
+       ret = -ENOSYS;
        switch (cmd) {
        case LOOP_CTL_ADD:
                ret = loop_lookup(&lo, parm);
@@ -1931,7 +1934,6 @@ static long loop_control_ioctl(struct fi
                ret = loop_lookup(&lo, parm);
                if (ret < 0)
                        break;
-               mutex_lock(&loop_ctl_mutex);
                if (lo->lo_state != Lo_unbound) {
                        ret = -EBUSY;
                        mutex_unlock(&loop_ctl_mutex);
@@ -1943,7 +1945,6 @@ static long loop_control_ioctl(struct fi
                        break;
                }
                lo->lo_disk->private_data = NULL;
-               mutex_unlock(&loop_ctl_mutex);
                idr_remove(&loop_index_idr, lo->lo_number);
                loop_remove(lo);
                break;
@@ -1953,7 +1954,7 @@ static long loop_control_ioctl(struct fi
                        break;
                ret = loop_add(&lo, -1);
        }
-       mutex_unlock(&loop_index_mutex);
+       mutex_unlock(&loop_ctl_mutex);
 
        return ret;
 }
@@ -2036,10 +2037,10 @@ static int __init loop_init(void)
                                  THIS_MODULE, loop_probe, NULL, NULL);
 
        /* pre-create number of devices given by config or max_loop */
-       mutex_lock(&loop_index_mutex);
+       mutex_lock(&loop_ctl_mutex);
        for (i = 0; i < nr; i++)
                loop_add(&lo, i);
-       mutex_unlock(&loop_index_mutex);
+       mutex_unlock(&loop_ctl_mutex);
 
        printk(KERN_INFO "loop: module loaded\n");
        return 0;