[PATCH 12/16] loop: Move special partition reread handling in loop_clr_fd()

Jan Kara
2018-11-08T13:01:12Z

The call of __blkdev_reread_part() from loop_reread_partition() happens
only when we need to invalidate partitions from loop_release(). Thus
move a detection for this into loop_clr_fd() and simplify
loop_reread_partition().

This makes loop_reread_partition() safe to use without loop_ctl_mutex
because we use only lo->lo_number and lo->lo_file_name in case of error
for reporting purposes (thus possibly reporting outdate information is
not a big deal) and we are safe from 'lo' going away under us by
elevated lo->lo_refcnt.

Signed-off-by: Jan Kara <jack@suse.cz>
---
drivers/block/loop.c | 33 +++++++++++++++++++--------------
1 file changed, 19 insertions(+), 14 deletions(-)

diff --git a/drivers/block/loop.c b/drivers/block/loop.c
index ea5e313908b1..f1d7a4fe30fc 100644
--- a/drivers/block/loop.c
+++ b/drivers/block/loop.c
@@ -630,18 +630,7 @@ static void loop_reread_partitions(struct loop_device *lo,
{
int rc;

- /*
- * bd_mutex has been held already in release path, so don't
- * acquire it if this function is called in such case.
- *
- * If the reread partition isn't from release path, lo_refcnt
- * must be at least one and it can only become zero when the
- * current holder is released.
- */
- if (!atomic_read(&lo->lo_refcnt))
- rc = __blkdev_reread_part(bdev);
- else
- rc = blkdev_reread_part(bdev);
+ 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);
@@ -1095,8 +1084,24 @@ 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);
+ if (lo->lo_flags & LO_FLAGS_PARTSCAN && bdev) {
+ /*
+ * bd_mutex has been held already in release path, so don't
+ * acquire it if this function is called in such case.
+ *
+ * If the reread partition isn't from release path, lo_refcnt
+ * must be at least one and it can only become zero when the
+ * current holder is released.
+ */
+ if (!atomic_read(&lo->lo_refcnt))
+ err = __blkdev_reread_part(bdev);
+ else
+ err = blkdev_reread_part(bdev);
+ pr_warn("%s: partition scan of loop%d failed (rc=%d)\n",
+ __func__, lo->lo_number, err);
+ /* Device is gone, no point in returning error */
+ err = 0;
+ }
lo->lo_flags = 0;
if (!part_shift)
lo->lo_disk->flags |= GENHD_FL_NO_PART_SCAN;
--
2.16.4