From: Mauricio Faria de Oliveira mfo@canonical.com
commit 4ceddce55eb35d15b0f87f5dcf6f0058fd15d3a4 upstream.
There's an I/O error on fsync() in a detached loop device if it has been previously attached.
The issue is write cache is enabled in the attach path in loop_configure() but it isn't disabled in the detach path; thus it remains enabled in the block device regardless of whether it is attached or not.
Now fsync() can get an I/O request that will just be failed later in loop_queue_rq() as device's state is not 'Lo_bound'.
So, disable write cache in the detach path.
Do so based on the queue flag, not the loop device flag for read-only (used to enable) as the queue flag can be changed via sysfs even on read-only loop devices (e.g., losetup -r.)
Test-case:
# DEV=/dev/loop7
# IMG=/tmp/image # truncate --size 1M $IMG
# losetup $DEV $IMG # losetup -d $DEV
Before:
# strace -e fsync parted -s $DEV print 2>&1 | grep fsync fsync(3) = -1 EIO (Input/output error) Warning: Error fsyncing/closing /dev/loop7: Input/output error [ 982.529929] blk_update_request: I/O error, dev loop7, sector 0 op 0x1:(WRITE) flags 0x800 phys_seg 0 prio class 0
After:
# strace -e fsync parted -s $DEV print 2>&1 | grep fsync fsync(3) = 0
Co-developed-by: Eric Desrochers eric.desrochers@canonical.com Signed-off-by: Eric Desrochers eric.desrochers@canonical.com Signed-off-by: Mauricio Faria de Oliveira mfo@canonical.com Tested-by: Gabriel Krisman Bertazi krisman@collabora.com Reviewed-by: Ming Lei ming.lei@redhat.com Signed-off-by: Jens Axboe axboe@kernel.dk Signed-off-by: Hanjun Guo guohanjun@huawei.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/block/loop.c | 3 +++ 1 file changed, 3 insertions(+)
--- a/drivers/block/loop.c +++ b/drivers/block/loop.c @@ -1224,6 +1224,9 @@ static int __loop_clr_fd(struct loop_dev goto out_unlock; }
+ if (test_bit(QUEUE_FLAG_WC, &lo->lo_queue->queue_flags)) + blk_queue_write_cache(lo->lo_queue, false, false); + /* freeze request queue during the transition */ blk_mq_freeze_queue(lo->lo_queue);