From: Mauricio Faria de Oliveira <mfo@xxxxxxxxxxxxx>
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@xxxxxxxxxxxxx>
Signed-off-by: Eric Desrochers <eric.desrochers@xxxxxxxxxxxxx>
Signed-off-by: Mauricio Faria de Oliveira <mfo@xxxxxxxxxxxxx>
Tested-by: Gabriel Krisman Bertazi <krisman@xxxxxxxxxxxxx>
Reviewed-by: Ming Lei <ming.lei@xxxxxxxxxx>
Signed-off-by: Jens Axboe <axboe@xxxxxxxxx>
Signed-off-by: Hanjun Guo <guohanjun@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
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);
