From 4ceddce55eb35d15b0f87f5dcf6f0058fd15d3a4 Mon Sep 17 00:00:00 2001 From: Mauricio Faria de Oliveira Date: Mon, 22 Feb 2021 12:41:23 -0300 Subject: loop: fix I/O error on fsync() in detached loop devices 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 Signed-off-by: Eric Desrochers Signed-off-by: Mauricio Faria de Oliveira Tested-by: Gabriel Krisman Bertazi Reviewed-by: Ming Lei Signed-off-by: Jens Axboe --- drivers/block/loop.c | 3 +++ 1 file changed, 3 insertions(+) (limited to 'drivers/block') diff --git a/drivers/block/loop.c b/drivers/block/loop.c index 578fc034db3f..81d20ec93375 100644 --- a/drivers/block/loop.c +++ b/drivers/block/loop.c @@ -1212,6 +1212,9 @@ static int __loop_clr_fd(struct loop_device *lo, bool release) 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); -- cgit v1.2.3