[PATCH 4.4 30/65] Revert "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: Greg Kroah-Hartman <gre...@linuxfoundation.org>

This reverts commit 611f77199cd763e6b7c0462c2f199ddb3a089750 which is
commit 0a42e99b58a208839626465af194cfe640ef9493 upstream.

It is not needed in the 4.4.y tree at this time.

Reported-by: Jan Kara <j...@suse.cz>
Cc: Jens Axboe <ax...@kernel.dk>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>
---
 drivers/block/loop.c |   39 +++++++++++++++++++--------------------
 1 file changed, 19 insertions(+), 20 deletions(-)

--- a/drivers/block/loop.c
+++ b/drivers/block/loop.c
@@ -81,6 +81,7 @@
 #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;
@@ -1570,11 +1571,9 @@ static int lo_compat_ioctl(struct block_
 static int lo_open(struct block_device *bdev, fmode_t mode)
 {
        struct loop_device *lo;
-       int err;
+       int err = 0;
 
-       err = mutex_lock_killable(&loop_ctl_mutex);
-       if (err)
-               return err;
+       mutex_lock(&loop_index_mutex);
        lo = bdev->bd_disk->private_data;
        if (!lo) {
                err = -ENXIO;
@@ -1583,7 +1582,7 @@ static int lo_open(struct block_device *
 
        atomic_inc(&lo->lo_refcnt);
 out:
-       mutex_unlock(&loop_ctl_mutex);
+       mutex_unlock(&loop_index_mutex);
        return err;
 }
 
@@ -1592,11 +1591,12 @@ static void lo_release(struct gendisk *d
        struct loop_device *lo;
        int err;
 
-       mutex_lock(&loop_ctl_mutex);
+       mutex_lock(&loop_index_mutex);
        lo = disk->private_data;
        if (atomic_dec_return(&lo->lo_refcnt))
-               goto out_unlock;
+               goto unlock_index;
 
+       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)
-                       return;
+                       goto unlock_index;
        } else {
                /*
                 * Otherwise keep thread (if running) and config,
@@ -1613,8 +1613,9 @@ 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 = {
@@ -1896,7 +1897,7 @@ static struct kobject *loop_probe(dev_t
        struct kobject *kobj;
        int err;
 
-       mutex_lock(&loop_ctl_mutex);
+       mutex_lock(&loop_index_mutex);
        err = loop_lookup(&lo, MINOR(dev) >> part_shift);
        if (err < 0)
                err = loop_add(&lo, MINOR(dev) >> part_shift);
@@ -1904,7 +1905,7 @@ static struct kobject *loop_probe(dev_t
                kobj = NULL;
        else
                kobj = get_disk(lo->lo_disk);
-       mutex_unlock(&loop_ctl_mutex);
+       mutex_unlock(&loop_index_mutex);
 
        *part = 0;
        return kobj;
@@ -1914,13 +1915,9 @@ static long loop_control_ioctl(struct fi
                               unsigned long parm)
 {
        struct loop_device *lo;
-       int ret;
-
-       ret = mutex_lock_killable(&loop_ctl_mutex);
-       if (ret)
-               return ret;
+       int ret = -ENOSYS;
 
-       ret = -ENOSYS;
+       mutex_lock(&loop_index_mutex);
        switch (cmd) {
        case LOOP_CTL_ADD:
                ret = loop_lookup(&lo, parm);
@@ -1934,6 +1931,7 @@ 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);
@@ -1945,6 +1943,7 @@ 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;
@@ -1954,7 +1953,7 @@ static long loop_control_ioctl(struct fi
                        break;
                ret = loop_add(&lo, -1);
        }
-       mutex_unlock(&loop_ctl_mutex);
+       mutex_unlock(&loop_index_mutex);
 
        return ret;
 }
@@ -2037,10 +2036,10 @@ 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_ctl_mutex);
+       mutex_lock(&loop_index_mutex);
        for (i = 0; i < nr; i++)
                loop_add(&lo, i);
-       mutex_unlock(&loop_ctl_mutex);
+       mutex_unlock(&loop_index_mutex);
 
        printk(KERN_INFO "loop: module loaded\n");
        return 0;