4.20-stable review patch. If anyone has any objections, please let me know.
------------------
From: Jan Kara jack@suse.cz
commit 7ccd0791d98531df7cd59e92d55e4f063d48a070 upstream.
loop_clr_fd() has a weird locking convention that is expects loop_ctl_mutex held, releases it on success and keeps it on failure. Untangle the mess by moving locking of loop_ctl_mutex into loop_clr_fd().
Signed-off-by: Jan Kara jack@suse.cz Signed-off-by: Jens Axboe axboe@kernel.dk Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- drivers/block/loop.c | 49 +++++++++++++++++++++++++++++-------------------- 1 file changed, 29 insertions(+), 20 deletions(-)
--- a/drivers/block/loop.c +++ b/drivers/block/loop.c @@ -1027,15 +1027,22 @@ loop_init_xfer(struct loop_device *lo, s
static int __loop_clr_fd(struct loop_device *lo) { - struct file *filp = lo->lo_backing_file; + struct file *filp = NULL; gfp_t gfp = lo->old_gfp_mask; struct block_device *bdev = lo->lo_device; + int err = 0;
- if (WARN_ON_ONCE(lo->lo_state != Lo_rundown)) - return -ENXIO; + mutex_lock(&loop_ctl_mutex); + if (WARN_ON_ONCE(lo->lo_state != Lo_rundown)) { + err = -ENXIO; + goto out_unlock; + }
- if (filp == NULL) - return -EINVAL; + filp = lo->lo_backing_file; + if (filp == NULL) { + err = -EINVAL; + goto out_unlock; + }
/* freeze request queue during the transition */ blk_mq_freeze_queue(lo->lo_queue); @@ -1082,6 +1089,7 @@ static int __loop_clr_fd(struct loop_dev if (!part_shift) lo->lo_disk->flags |= GENHD_FL_NO_PART_SCAN; loop_unprepare_queue(lo); +out_unlock: mutex_unlock(&loop_ctl_mutex); /* * Need not hold loop_ctl_mutex to fput backing file. @@ -1089,14 +1097,22 @@ static int __loop_clr_fd(struct loop_dev * lock dependency possibility warning as fput can take * bd_mutex which is usually taken before loop_ctl_mutex. */ - fput(filp); - return 0; + if (filp) + fput(filp); + return err; }
static int loop_clr_fd(struct loop_device *lo) { - if (lo->lo_state != Lo_bound) + int err; + + err = mutex_lock_killable_nested(&loop_ctl_mutex, 1); + if (err) + return err; + if (lo->lo_state != Lo_bound) { + mutex_unlock(&loop_ctl_mutex); 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 @@ -1113,6 +1129,7 @@ static int loop_clr_fd(struct loop_devic return 0; } lo->lo_state = Lo_rundown; + mutex_unlock(&loop_ctl_mutex);
return __loop_clr_fd(lo); } @@ -1447,14 +1464,7 @@ static int lo_ioctl(struct block_device mutex_unlock(&loop_ctl_mutex); break; case LOOP_CLR_FD: - err = mutex_lock_killable_nested(&loop_ctl_mutex, 1); - if (err) - return err; - /* loop_clr_fd would have unlocked loop_ctl_mutex on success */ - err = loop_clr_fd(lo); - if (err) - mutex_unlock(&loop_ctl_mutex); - break; + return loop_clr_fd(lo); case LOOP_SET_STATUS: err = -EPERM; if ((mode & FMODE_WRITE) || capable(CAP_SYS_ADMIN)) { @@ -1690,7 +1700,6 @@ out: static void lo_release(struct gendisk *disk, fmode_t mode) { struct loop_device *lo; - int err;
mutex_lock(&loop_ctl_mutex); lo = disk->private_data; @@ -1701,13 +1710,13 @@ static void lo_release(struct gendisk *d if (lo->lo_state != Lo_bound) goto out_unlock; lo->lo_state = Lo_rundown; + mutex_unlock(&loop_ctl_mutex); /* * In autoclear mode, stop the loop thread * and remove configuration after last close. */ - err = __loop_clr_fd(lo); - if (!err) - return; + __loop_clr_fd(lo); + return; } else if (lo->lo_state == Lo_bound) { /* * Otherwise keep thread (if running) and config,