Revert "block/loop: Use global lock for ioctl() operation."

Closes: #928125

debian/changelog

+linux (4.9.168-2) UNRELEASED; urgency=medium
+
+  * Revert "block/loop: Use global lock for ioctl() operation."
+    (Closes: #928125)
+
+ -- Salvatore Bonaccorso <carnil@debian.org>  Thu, 02 May 2019 21:27:20 +0200
+
 linux (4.9.168-1) stretch; urgency=medium
   * New upstream stable update:

debian/patches/bugfix/all/Revert-block-loop-Use-global-lock-for-ioctl-operatio.patch

+From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
+Date: Mon, 29 Apr 2019 15:56:26 +0200
+Subject: Revert "block/loop: Use global lock for ioctl() operation."
+Origin: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=2f4ca7ab3b879b8029fc87809bf93c4dc2246817
+Bug-Debian: https://bugs.debian.org/928125
+
+This reverts commit 3ae3d167f5ec2c7bb5fcd12b7772cfadc93b2305 which is
+commit 310ca162d779efee8a2dc3731439680f3e9c1e86 upstream.
+
+Jan Kara has reported seeing problems with this patch applied, as has
+Salvatore Bonaccorso, so let's drop it for now.
+
+Reported-by: Salvatore Bonaccorso <carnil@debian.org>
+Reported-by: Jan Kara <jack@suse.cz>
+Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
+Cc: Jens Axboe <axboe@kernel.dk>
+Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
+---
+ drivers/block/loop.c | 42 +++++++++++++++++++++---------------------
+ drivers/block/loop.h |  1 +
+ 2 files changed, 22 insertions(+), 21 deletions(-)
+
+diff --git a/drivers/block/loop.c b/drivers/block/loop.c
+index 28ce17405aab..9f840d9fdfcb 100644
+--- a/drivers/block/loop.c
++++ b/drivers/block/loop.c
+@@ -82,7 +82,6 @@
+ 
+ static DEFINE_IDR(loop_index_idr);
+ static DEFINE_MUTEX(loop_index_mutex);
+-static DEFINE_MUTEX(loop_ctl_mutex);
+ 
+ static int max_part;
+ static int part_shift;
+@@ -1034,7 +1033,7 @@ static int loop_clr_fd(struct loop_device *lo)
+ 	 */
+ 	if (atomic_read(&lo->lo_refcnt) > 1) {
+ 		lo->lo_flags |= LO_FLAGS_AUTOCLEAR;
+-		mutex_unlock(&loop_ctl_mutex);
++		mutex_unlock(&lo->lo_ctl_mutex);
+ 		return 0;
+ 	}
+ 
+@@ -1083,12 +1082,12 @@ static int loop_clr_fd(struct loop_device *lo)
+ 	if (!part_shift)
+ 		lo->lo_disk->flags |= GENHD_FL_NO_PART_SCAN;
+ 	loop_unprepare_queue(lo);
+-	mutex_unlock(&loop_ctl_mutex);
++	mutex_unlock(&lo->lo_ctl_mutex);
+ 	/*
+-	 * Need not hold loop_ctl_mutex to fput backing file.
+-	 * Calling fput holding loop_ctl_mutex triggers a circular
++	 * Need not hold lo_ctl_mutex to fput backing file.
++	 * Calling fput holding lo_ctl_mutex triggers a circular
+ 	 * lock dependency possibility warning as fput can take
+-	 * bd_mutex which is usually taken before loop_ctl_mutex.
++	 * bd_mutex which is usually taken before lo_ctl_mutex.
+ 	 */
+ 	fput(filp);
+ 	return 0;
+@@ -1351,7 +1350,7 @@ 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(&loop_ctl_mutex, 1);
++	mutex_lock_nested(&lo->lo_ctl_mutex, 1);
+ 	switch (cmd) {
+ 	case LOOP_SET_FD:
+ 		err = loop_set_fd(lo, mode, bdev, arg);
+@@ -1360,7 +1359,7 @@ static int lo_ioctl(struct block_device *bdev, fmode_t mode,
+ 		err = loop_change_fd(lo, bdev, arg);
+ 		break;
+ 	case LOOP_CLR_FD:
+-		/* loop_clr_fd would have unlocked loop_ctl_mutex on success */
++		/* loop_clr_fd would have unlocked lo_ctl_mutex on success */
+ 		err = loop_clr_fd(lo);
+ 		if (!err)
+ 			goto out_unlocked;
+@@ -1396,7 +1395,7 @@ static int lo_ioctl(struct block_device *bdev, fmode_t mode,
+ 	default:
+ 		err = lo->ioctl ? lo->ioctl(lo, cmd, arg) : -EINVAL;
+ 	}
+-	mutex_unlock(&loop_ctl_mutex);
++	mutex_unlock(&lo->lo_ctl_mutex);
+ 
+ out_unlocked:
+ 	return err;
+@@ -1529,16 +1528,16 @@ static int lo_compat_ioctl(struct block_device *bdev, fmode_t mode,
+ 
+ 	switch(cmd) {
+ 	case LOOP_SET_STATUS:
+-		mutex_lock(&loop_ctl_mutex);
++		mutex_lock(&lo->lo_ctl_mutex);
+ 		err = loop_set_status_compat(
+ 			lo, (const struct compat_loop_info __user *) arg);
+-		mutex_unlock(&loop_ctl_mutex);
++		mutex_unlock(&lo->lo_ctl_mutex);
+ 		break;
+ 	case LOOP_GET_STATUS:
+-		mutex_lock(&loop_ctl_mutex);
++		mutex_lock(&lo->lo_ctl_mutex);
+ 		err = loop_get_status_compat(
+ 			lo, (struct compat_loop_info __user *) arg);
+-		mutex_unlock(&loop_ctl_mutex);
++		mutex_unlock(&lo->lo_ctl_mutex);
+ 		break;
+ 	case LOOP_SET_CAPACITY:
+ 	case LOOP_CLR_FD:
+@@ -1582,7 +1581,7 @@ static void __lo_release(struct loop_device *lo)
+ 	if (atomic_dec_return(&lo->lo_refcnt))
+ 		return;
+ 
+-	mutex_lock(&loop_ctl_mutex);
++	mutex_lock(&lo->lo_ctl_mutex);
+ 	if (lo->lo_flags & LO_FLAGS_AUTOCLEAR) {
+ 		/*
+ 		 * In autoclear mode, stop the loop thread
+@@ -1599,7 +1598,7 @@ static void __lo_release(struct loop_device *lo)
+ 		loop_flush(lo);
+ 	}
+ 
+-	mutex_unlock(&loop_ctl_mutex);
++	mutex_unlock(&lo->lo_ctl_mutex);
+ }
+ 
+ static void lo_release(struct gendisk *disk, fmode_t mode)
+@@ -1645,10 +1644,10 @@ static int unregister_transfer_cb(int id, void *ptr, void *data)
+ 	struct loop_device *lo = ptr;
+ 	struct loop_func_table *xfer = data;
+ 
+-	mutex_lock(&loop_ctl_mutex);
++	mutex_lock(&lo->lo_ctl_mutex);
+ 	if (lo->lo_encryption == xfer)
+ 		loop_release_xfer(lo);
+-	mutex_unlock(&loop_ctl_mutex);
++	mutex_unlock(&lo->lo_ctl_mutex);
+ 	return 0;
+ }
+ 
+@@ -1814,6 +1813,7 @@ static int loop_add(struct loop_device **l, int i)
+ 	if (!part_shift)
+ 		disk->flags |= GENHD_FL_NO_PART_SCAN;
+ 	disk->flags |= GENHD_FL_EXT_DEVT;
++	mutex_init(&lo->lo_ctl_mutex);
+ 	atomic_set(&lo->lo_refcnt, 0);
+ 	lo->lo_number		= i;
+ 	spin_lock_init(&lo->lo_lock);
+@@ -1926,19 +1926,19 @@ 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);
++		mutex_lock(&lo->lo_ctl_mutex);
+ 		if (lo->lo_state != Lo_unbound) {
+ 			ret = -EBUSY;
+-			mutex_unlock(&loop_ctl_mutex);
++			mutex_unlock(&lo->lo_ctl_mutex);
+ 			break;
+ 		}
+ 		if (atomic_read(&lo->lo_refcnt) > 0) {
+ 			ret = -EBUSY;
+-			mutex_unlock(&loop_ctl_mutex);
++			mutex_unlock(&lo->lo_ctl_mutex);
+ 			break;
+ 		}
+ 		lo->lo_disk->private_data = NULL;
+-		mutex_unlock(&loop_ctl_mutex);
++		mutex_unlock(&lo->lo_ctl_mutex);
+ 		idr_remove(&loop_index_idr, lo->lo_number);
+ 		loop_remove(lo);
+ 		break;
+diff --git a/drivers/block/loop.h b/drivers/block/loop.h
+index a923e74495ce..60f0fd2c0c65 100644
+--- a/drivers/block/loop.h
++++ b/drivers/block/loop.h
+@@ -55,6 +55,7 @@ struct loop_device {
+ 
+ 	spinlock_t		lo_lock;
+ 	int			lo_state;
++	struct mutex		lo_ctl_mutex;
+ 	struct kthread_worker	worker;
+ 	struct task_struct	*worker_task;
+ 	bool			use_dio;
+-- 
+2.11.0
+

debian/patches/series

@@ -104,6 +104,7 @@ bugfix/all/xen-time-do-not-decrease-steal-time-after-live-migra.patch
 bugfix/all/nfsd-increase-DRC-cache-limit.patch
 bugfix/all/netfilter-xt_hashlimit-fix-integer-divide-round-to-z.patch
 bugfix/all/efi-libstub-unify-command-line-param-parsing.patch
+bugfix/all/Revert-block-loop-Use-global-lock-for-ioctl-operatio.patch
 
 # Miscellaneous features
 features/all/netfilter-nft_ct-add-notrack-support.patch