We will drop loop_ctl_mutex before calling blkdev_reread_part() in
order to fix circular locking dependency between bdev->bd_mutex and
loop_ctl_mutex. To do that we need to make sure that we won't touch
"struct loop_device" after releasing loop_ctl_mutex.
As a preparation step, this patch reorganizes loop_reread_partitions()
callers. According to Ming Lei, calling loop_unprepare_queue() before
loop_reread_partitions() (like we did until 3.19) is fine. Therefore,
this patch will not cause user visible changes.
Signed-off-by: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx>
Cc: Ming Lei <ming.lei@xxxxxxxxxx>
---
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 920cbb1..4b05a27 100644
--- a/drivers/block/loop.c
+++ b/drivers/block/loop.c
@@ -632,6 +632,11 @@ static void loop_reread_partitions(struct loop_device *lo,
struct block_device *bdev)
{
int rc;
+ char filename[LO_NAME_SIZE];
+ const int num = lo->lo_number;
+ const int count = atomic_read(&lo->lo_refcnt);
+
+ memcpy(filename, lo->lo_file_name, sizeof(filename));
/*
* bd_mutex has been held already in release path, so don't
@@ -641,13 +646,13 @@ static void loop_reread_partitions(struct loop_device *lo,
* must be at least one and it can only become zero when the
* current holder is released.
*/
- if (!atomic_read(&lo->lo_refcnt))
+ if (!count)
rc = __blkdev_reread_part(bdev);
else
rc = blkdev_reread_part(bdev);
if (rc)
pr_warn("%s: partition scan of loop%d (%s) failed (rc=%d)\n",
- __func__, lo->lo_number, lo->lo_file_name, rc);
+ __func__, num, filename, rc);
}
static inline int is_loop_device(struct file *file)
@@ -730,9 +735,9 @@ static int loop_change_fd(struct loop_device *lo, struct block_device *bdev,
loop_update_dio(lo);
blk_mq_unfreeze_queue(lo->lo_queue);
- fput(old_file);
if (lo->lo_flags & LO_FLAGS_PARTSCAN)
loop_reread_partitions(lo, bdev);
+ fput(old_file);
return 0;
out_putf:
@@ -971,16 +976,18 @@ static int loop_set_fd(struct loop_device *lo, fmode_t mode,
set_blocksize(bdev, S_ISBLK(inode->i_mode) ?
block_size(inode->i_bdev) : PAGE_SIZE);
+ /*
+ * Grab the block_device to prevent its destruction after we
+ * put /dev/loopXX inode. Later in loop_clr_fd() we bdput(bdev).
+ */
+ bdgrab(bdev);
+
lo->lo_state = Lo_bound;
if (part_shift)
lo->lo_flags |= LO_FLAGS_PARTSCAN;
if (lo->lo_flags & LO_FLAGS_PARTSCAN)
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).
- */
- bdgrab(bdev);
return 0;
out_putf:
@@ -1033,6 +1040,7 @@ 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;
+ bool reread;
if (lo->lo_state != Lo_bound)
return -ENXIO;
@@ -1096,12 +1104,13 @@ static int loop_clr_fd(struct loop_device *lo)
module_put(THIS_MODULE);
blk_mq_unfreeze_queue(lo->lo_queue);
- if (lo->lo_flags & LO_FLAGS_PARTSCAN && bdev)
- loop_reread_partitions(lo, bdev);
+ reread = (lo->lo_flags & LO_FLAGS_PARTSCAN) && bdev;
+ loop_unprepare_queue(lo);
lo->lo_flags = 0;
if (!part_shift)
lo->lo_disk->flags |= GENHD_FL_NO_PART_SCAN;
- loop_unprepare_queue(lo);
+ if (reread)
+ loop_reread_partitions(lo, bdev);
mutex_unlock(&loop_ctl_mutex);
/*
* Need not hold loop_ctl_mutex to fput backing file.
--
1.8.3.1
