loop: Split setting of lo_state from loop_clr_fd

Move setting of lo_state to Lo_rundown out into the callers. That will
allow us to unlock loop_ctl_mutex while the loop device is protected
from other changes by its special state.

Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/drivers/block/loop.c b/drivers/block/loop.c
index 4c37578989c41ac59ad6d88283ef61963c67e426..eb01a685da4e0737bdbae9a42ee3cf6466bd9fa1 100644 (file)
--- a/drivers/block/loop.c
+++ b/drivers/block/loop.c
@@ -975,7 +975,7 @@ static int loop_set_fd(struct loop_device *lo, fmode_t mode,
                loop_reread_partitions(lo, bdev);
 
        /* Grab the block_device to prevent its destruction after we
-        * put /dev/loopXX inode. Later in loop_clr_fd() we bdput(bdev).
+        * put /dev/loopXX inode. Later in __loop_clr_fd() we bdput(bdev).
         */
        bdgrab(bdev);
        return 0;
@@ -1025,31 +1025,15 @@ loop_init_xfer(struct loop_device *lo, struct loop_func_table *xfer,
        return err;
 }
 
-static int loop_clr_fd(struct loop_device *lo)
+static int __loop_clr_fd(struct loop_device *lo)
 {
        struct file *filp = lo->lo_backing_file;
        gfp_t gfp = lo->old_gfp_mask;
        struct block_device *bdev = lo->lo_device;
 
-       if (lo->lo_state != Lo_bound)
+       if (WARN_ON_ONCE(lo->lo_state != Lo_rundown))
                return -ENXIO;
 
-       /*
-        * If we've explicitly asked to tear down the loop device,
-        * and it has an elevated reference count, set it for auto-teardown when
-        * the last reference goes away. This stops $!~#$@ udev from
-        * preventing teardown because it decided that it needs to run blkid on
-        * the loopback device whenever they appear. xfstests is notorious for
-        * failing tests because blkid via udev races with a losetup
-        * <dev>/do something like mkfs/losetup -d <dev> causing the losetup -d
-        * command to fail with EBUSY.
-        */
-       if (atomic_read(&lo->lo_refcnt) > 1) {
-               lo->lo_flags |= LO_FLAGS_AUTOCLEAR;
-               mutex_unlock(&loop_ctl_mutex);
-               return 0;
-       }
-
        if (filp == NULL)
                return -EINVAL;
 
@@ -1057,7 +1041,6 @@ static int loop_clr_fd(struct loop_device *lo)
        blk_mq_freeze_queue(lo->lo_queue);
 
        spin_lock_irq(&lo->lo_lock);
-       lo->lo_state = Lo_rundown;
        lo->lo_backing_file = NULL;
        spin_unlock_irq(&lo->lo_lock);
 
@@ -1110,6 +1093,30 @@ static int loop_clr_fd(struct loop_device *lo)
        return 0;
 }
 
+static int loop_clr_fd(struct loop_device *lo)
+{
+       if (lo->lo_state != Lo_bound)
+               return -ENXIO;
+       /*
+        * If we've explicitly asked to tear down the loop device,
+        * and it has an elevated reference count, set it for auto-teardown when
+        * the last reference goes away. This stops $!~#$@ udev from
+        * preventing teardown because it decided that it needs to run blkid on
+        * the loopback device whenever they appear. xfstests is notorious for
+        * failing tests because blkid via udev races with a losetup
+        * <dev>/do something like mkfs/losetup -d <dev> causing the losetup -d
+        * command to fail with EBUSY.
+        */
+       if (atomic_read(&lo->lo_refcnt) > 1) {
+               lo->lo_flags |= LO_FLAGS_AUTOCLEAR;
+               mutex_unlock(&loop_ctl_mutex);
+               return 0;
+       }
+       lo->lo_state = Lo_rundown;
+
+       return __loop_clr_fd(lo);
+}
+
 static int
 loop_set_status(struct loop_device *lo, const struct loop_info64 *info)
 {
@@ -1691,11 +1698,14 @@ static void lo_release(struct gendisk *disk, fmode_t mode)
                goto out_unlock;
 
        if (lo->lo_flags & LO_FLAGS_AUTOCLEAR) {
+               if (lo->lo_state != Lo_bound)
+                       goto out_unlock;
+               lo->lo_state = Lo_rundown;
                /*
                 * In autoclear mode, stop the loop thread
                 * and remove configuration after last close.
                 */
-               err = loop_clr_fd(lo);
+               err = __loop_clr_fd(lo);
                if (!err)
                        return;
        } else if (lo->lo_state == Lo_bound) {