[PATCH v2 2/2] loop: use killable lock in ioctls

[Omar Sandoval]

From: Omar Sandoval <osan...@fb.com>

Even after the previous patch to drop lo_ctl_mutex while calling
vfs_getattr(), there are other cases where we can end up sleeping for a
long time while holding lo_ctl_mutex. Let's avoid the uninterruptible
sleep from the ioctls.

Signed-off-by: Omar Sandoval <osan...@fb.com>
---
 drivers/block/loop.c | 29 +++++++++++++++++++----------
 1 file changed, 19 insertions(+), 10 deletions(-)

diff --git a/drivers/block/loop.c b/drivers/block/loop.c
index 93a60bda7608..264abaaff662 100644
--- a/drivers/block/loop.c
+++ b/drivers/block/loop.c
@@ -1360,7 +1360,10 @@ static int lo_ioctl(struct block_device *bdev, fmode_t 
mode,
        struct loop_device *lo = bdev->bd_disk->private_data;
        int err;
 
-       mutex_lock_nested(&lo->lo_ctl_mutex, 1);
+       err = mutex_lock_killable_nested(&lo->lo_ctl_mutex, 1);
+       if (err)
+               goto out_unlocked;
+
        switch (cmd) {
        case LOOP_SET_FD:
                err = loop_set_fd(lo, mode, bdev, arg);
@@ -1545,16 +1548,20 @@ static int lo_compat_ioctl(struct block_device *bdev, 
fmode_t mode,
 
        switch(cmd) {
        case LOOP_SET_STATUS:
-               mutex_lock(&lo->lo_ctl_mutex);
-               err = loop_set_status_compat(
-                       lo, (const struct compat_loop_info __user *) arg);
-               mutex_unlock(&lo->lo_ctl_mutex);
+               err = mutex_lock_killable(&lo->lo_ctl_mutex);
+               if (!err) {
+                       err = loop_set_status_compat(lo,
+                                                    (const struct 
compat_loop_info __user *)arg);
+                       mutex_unlock(&lo->lo_ctl_mutex);
+               }
                break;
        case LOOP_GET_STATUS:
-               mutex_lock(&lo->lo_ctl_mutex);
-               err = loop_get_status_compat(
-                       lo, (struct compat_loop_info __user *) arg);
-               /* loop_get_status() unlocks lo_ctl_mutex */
+               err = mutex_lock_killable(&lo->lo_ctl_mutex);
+               if (!err) {
+                       err = loop_get_status_compat(lo,
+                                                    (struct compat_loop_info 
__user *)arg);
+                       /* loop_get_status() unlocks lo_ctl_mutex */
+               }
                break;
        case LOOP_SET_CAPACITY:
        case LOOP_CLR_FD:
@@ -1959,7 +1966,9 @@ static long loop_control_ioctl(struct file *file, 
unsigned int cmd,
                ret = loop_lookup(&lo, parm);
                if (ret < 0)
                        break;
-               mutex_lock(&lo->lo_ctl_mutex);
+               ret = mutex_lock_killable(&lo->lo_ctl_mutex);
+               if (ret)
+                       break;
                if (lo->lo_state != Lo_unbound) {
                        ret = -EBUSY;
                        mutex_unlock(&lo->lo_ctl_mutex);
-- 
2.16.2