Re: [PATCH] loop: fix I/O error on fsync() in detached loop devices
From: Gabriel Krisman Bertazi <hidden>
Date: 2021-01-02 05:14:59
Mauricio Faria de Oliveira [off-list ref] writes:
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.
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
Signed-off-by: Mauricio Faria de Oliveira <redacted>
Co-developed-by: Eric Desrochers <redacted>
Signed-off-by: Eric Desrochers <redacted>This sign-off chain is not sorted correctly. See Documentation/process/submitting-patches.rst. Other than that, I think the fix makes sense. Tested-by: Gabriel Krisman Bertazi <redacted>
quoted hunk
--- drivers/block/loop.c | 3 +++ 1 file changed, 3 insertions(+)diff --git a/drivers/block/loop.c b/drivers/block/loop.c index e5ff328f0917..49517482e061 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 (!(lo->lo_flags & LO_FLAGS_READ_ONLY) && filp->f_op->fsync) + blk_queue_write_cache(lo->lo_queue, false, false); + /* freeze request queue during the transition */ blk_mq_freeze_queue(lo->lo_queue);
-- Gabriel Krisman Bertazi