diff mbox series

[2/7] loop: clarify __module_get()/module_put() usage

Message ID 20220129071500.3566-3-penguin-kernel@I-love.SAKURA.ne.jp (mailing list archive)
State New, archived
Headers show
Series [1/7] loop: revert "make autoclear operation asynchronous" | expand

Commit Message

Tetsuo Handa Jan. 29, 2022, 7:14 a.m. UTC 
These are used in order to block loop_exit() while holding backing files.

Cc: Jan Kara <jack@suse.cz>
Cc: Christoph Hellwig <hch@lst.de>
Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
---
 drivers/block/loop.c | 16 ++++------------
 1 file changed, 4 insertions(+), 12 deletions(-)
diff mbox series

Patch

diff --git a/drivers/block/loop.c b/drivers/block/loop.c
index 150012ffb387..3a87c33df2ec 100644
--- a/drivers/block/loop.c
+++ b/drivers/block/loop.c
@@ -959,9 +959,6 @@  static int loop_configure(struct loop_device *lo, fmode_t mode,
 		return -EBADF;
 	is_loop = is_loop_device(file);
 
-	/* This is safe, since we have a reference from open(). */
-	__module_get(THIS_MODULE);
-
 	/*
 	 * If we don't hold exclusive handle for the device, upgrade to it
 	 * here to avoid changing device under exclusive owner.
@@ -1027,6 +1024,8 @@  static int loop_configure(struct loop_device *lo, fmode_t mode,
 	lo->use_dio = lo->lo_flags & LO_FLAGS_DIRECT_IO;
 	lo->lo_device = bdev;
 	lo->lo_backing_file = file;
+	/* Block loop_exit() while holding backing file. */
+	__module_get(THIS_MODULE);
 	lo->old_gfp_mask = mapping_gfp_mask(mapping);
 	mapping_set_gfp_mask(mapping, lo->old_gfp_mask & ~(__GFP_IO|__GFP_FS));
 
@@ -1077,8 +1076,6 @@  static int loop_configure(struct loop_device *lo, fmode_t mode,
 		bd_abort_claiming(bdev, loop_configure);
 out_putf:
 	fput(file);
-	/* This is safe: open() is still holding a reference. */
-	module_put(THIS_MODULE);
 	return error;
 }
 
@@ -1144,8 +1141,6 @@  static void __loop_clr_fd(struct loop_device *lo, bool release)
 	/* let user-space know about this change */
 	kobject_uevent(&disk_to_dev(lo->lo_disk)->kobj, KOBJ_CHANGE);
 	mapping_set_gfp_mask(filp->f_mapping, gfp);
-	/* This is safe: open() is still holding a reference. */
-	module_put(THIS_MODULE);
 	blk_mq_unfreeze_queue(lo->lo_queue);
 
 	disk_force_media_change(lo->lo_disk, DISK_EVENT_MEDIA_CHANGE);
@@ -1185,12 +1180,9 @@  static void __loop_clr_fd(struct loop_device *lo, bool release)
 	lo->lo_state = Lo_unbound;
 	mutex_unlock(&lo->lo_mutex);
 
-	/*
-	 * Need not hold lo_mutex to fput backing file. Calling fput holding
-	 * lo_mutex triggers a circular lock dependency possibility warning as
-	 * fput can take open_mutex which is usually taken before lo_mutex.
-	 */
+	/* Release backing file and unblock loop_exit(). */
 	fput(filp);
+	module_put(THIS_MODULE);
 }
 
 static int loop_clr_fd(struct loop_device *lo)