Revert "loop: Get rid of loop_index_mutex"

This reverts commit 6a8f1d8d701462937ce01a3f2219af5435372af7 which is
commit 0a42e99b58a208839626465af194cfe640ef9493 upstream.

It does not work properly in the 4.9.y tree and causes more problems
than it fixes, so revert it.

Reported-by: Thomas Lindroth <thomas.lindroth@gmail.com>
Reported-by: Jan Kara <jack@suse.cz>
Cc: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/block/loop.c b/drivers/block/loop.c
index 4af7b08..3fa04ce 100644 (file)
--- 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;
@@ -1559,11 +1560,9 @@ static int lo_compat_ioctl(struct block_device *bdev, fmode_t mode,
 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;
@@ -1572,7 +1571,7 @@ static int lo_open(struct block_device *bdev, fmode_t mode)
 
        atomic_inc(&lo->lo_refcnt);
 out:
-       mutex_unlock(&loop_ctl_mutex);
+       mutex_unlock(&loop_index_mutex);
        return err;
 }
 
@@ -1581,11 +1580,12 @@ static void lo_release(struct gendisk *disk, fmode_t mode)
        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
@@ -1593,7 +1593,7 @@ static void lo_release(struct gendisk *disk, fmode_t mode)
                 */
                err = loop_clr_fd(lo);
                if (!err)
-                       return;
+                       goto unlock_index;
        } else {
                /*
                 * Otherwise keep thread (if running) and config,
@@ -1602,8 +1602,9 @@ static void lo_release(struct gendisk *disk, fmode_t mode)
                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 = {
@@ -1889,7 +1890,7 @@ static struct kobject *loop_probe(dev_t dev, int *part, void *data)
        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);
@@ -1897,7 +1898,7 @@ static struct kobject *loop_probe(dev_t dev, int *part, void *data)
                kobj = NULL;
        else
                kobj = get_disk(lo->lo_disk);
-       mutex_unlock(&loop_ctl_mutex);
+       mutex_unlock(&loop_index_mutex);
 
        *part = 0;
        return kobj;
@@ -1907,13 +1908,9 @@ static long loop_control_ioctl(struct file *file, unsigned int cmd,
                               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);
@@ -1927,6 +1924,7 @@ static long loop_control_ioctl(struct file *file, unsigned int cmd,
                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);
@@ -1938,6 +1936,7 @@ static long loop_control_ioctl(struct file *file, unsigned int cmd,
                        break;
                }
                lo->lo_disk->private_data = NULL;
+               mutex_unlock(&loop_ctl_mutex);
                idr_remove(&loop_index_idr, lo->lo_number);
                loop_remove(lo);
                break;
@@ -1947,7 +1946,7 @@ static long loop_control_ioctl(struct file *file, unsigned int cmd,
                        break;
                ret = loop_add(&lo, -1);
        }
-       mutex_unlock(&loop_ctl_mutex);
+       mutex_unlock(&loop_index_mutex);
 
        return ret;
 }
@@ -2030,10 +2029,10 @@ 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;