| Message ID | 20210107181734.128296-1-mfo@canonical.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [v3] loop: fix I/O error on fsync() in detached loop devices | expand |
On Thu, Jan 07, 2021 at 03:17:34PM -0300, Mauricio Faria de Oliveira wrote: > 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> > --- > drivers/block/loop.c | 3 +++ > 1 file changed, 3 insertions(+) > > v3: > - Disable write cache based on QUEUE_FLAG_WC, not just > !LO_FLAGS_READ_ONLY, as the former can be enabled in > sysfs even for LO_FLAGS_READ_ONLY, thus not disabled > later. Mention that in commit message. (thanks, Ming) > v2: > - Fix ordering of Co-developed-by:/Signed-off-by: tags. > (thanks, Krisman) > - Add Tested-by: tag. (likewise.) > > diff --git a/drivers/block/loop.c b/drivers/block/loop.c > index e5ff328f0917..e94a11dbb5bd 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); Reviewed-by: Ming Lei <ming.lei@redhat.com>
diff --git a/drivers/block/loop.c b/drivers/block/loop.c index e5ff328f0917..e94a11dbb5bd 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);
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> --- drivers/block/loop.c | 3 +++ 1 file changed, 3 insertions(+) v3: - Disable write cache based on QUEUE_FLAG_WC, not just !LO_FLAGS_READ_ONLY, as the former can be enabled in sysfs even for LO_FLAGS_READ_ONLY, thus not disabled later. Mention that in commit message. (thanks, Ming) v2: - Fix ordering of Co-developed-by:/Signed-off-by: tags. (thanks, Krisman) - Add Tested-by: tag. (likewise.)