[PATCH 5/8] loop: only take lo_mutex for the first reference in lo_open
From: Christoph Hellwig <hch@lst.de>
Date: 2022-01-26 15:51:01
Subsystem:
block layer, the rest · Maintainers:
Jens Axboe, Linus Torvalds
lo_refcnt is only incremented in lo_open and decremented in lo_release, and thus protected by open_mutex. Only take lo_mutex when lo_open is called the first time, as only for the first open there is any affect on the driver state (incremental opens on partitions don't end up in lo_open at all already). Signed-off-by: Christoph Hellwig <hch@lst.de> --- drivers/block/loop.c | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-)
diff --git a/drivers/block/loop.c b/drivers/block/loop.c
index 43980ec69dfdd..4b0058a67c48e 100644
--- a/drivers/block/loop.c
+++ b/drivers/block/loop.c@@ -1725,13 +1725,16 @@ static int lo_open(struct block_device *bdev, fmode_t mode) struct loop_device *lo = bdev->bd_disk->private_data; int err; + if (atomic_inc_return(&lo->lo_refcnt) > 1) + return 0; + err = mutex_lock_killable(&lo->lo_mutex); if (err) return err; - if (lo->lo_state == Lo_deleting) + if (lo->lo_state == Lo_deleting) { + atomic_dec(&lo->lo_refcnt); err = -ENXIO; - else - atomic_inc(&lo->lo_refcnt); + } mutex_unlock(&lo->lo_mutex); return err; }
--
2.30.2