[PATCH 5/8] loop: only take lo_mutex for the first reference in lo_open

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



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@xxxxxx>
Tested-by: Darrick J. Wong <djwong@xxxxxxxxxx>
---
 drivers/block/loop.c | 13 ++++++++++---
 1 file changed, 10 insertions(+), 3 deletions(-)

diff --git a/drivers/block/loop.c b/drivers/block/loop.c
index b58dc95f80d96..f349ddfc0e84a 100644
--- a/drivers/block/loop.c
+++ b/drivers/block/loop.c
@@ -1725,13 +1725,20 @@ static int lo_open(struct block_device *bdev, fmode_t mode)
 	struct loop_device *lo = bdev->bd_disk->private_data;
 	int err;
 
+	/*
+	 * Note: this requires disk->open_mutex to protect against races
+	 * with lo_release.
+	 */
+	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




[Index of Archives]     [Linux RAID]     [Linux SCSI]     [Linux ATA RAID]     [IDE]     [Linux Wireless]     [Linux Kernel]     [ATH6KL]     [Linux Bluetooth]     [Linux Netdev]     [Kernel Newbies]     [Security]     [Git]     [Netfilter]     [Bugtraq]     [Yosemite News]     [MIPS Linux]     [ARM Linux]     [Linux Security]     [Device Mapper]

  Powered by Linux