* [PATCH v3] loop: fix I/O error on fsync() in detached loop devices
@ 2021-01-07 18:17 Mauricio Faria de Oliveira
2021-01-08 0:23 ` Ming Lei
0 siblings, 1 reply; 2+ messages in thread
From: Mauricio Faria de Oliveira @ 2021-01-07 18:17 UTC (permalink / raw)
To: Jens Axboe
Cc: Ming Lei, linux-block, Gabriel Krisman Bertazi, Eric Desrochers
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);
--
2.27.0
^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: [PATCH v3] loop: fix I/O error on fsync() in detached loop devices
2021-01-07 18:17 [PATCH v3] loop: fix I/O error on fsync() in detached loop devices Mauricio Faria de Oliveira
@ 2021-01-08 0:23 ` Ming Lei
0 siblings, 0 replies; 2+ messages in thread
From: Ming Lei @ 2021-01-08 0:23 UTC (permalink / raw)
To: Mauricio Faria de Oliveira
Cc: Jens Axboe, linux-block, Gabriel Krisman Bertazi, Eric Desrochers
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>
--
Ming
^ permalink raw reply [flat|nested] 2+ messages in thread
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2021-01-07 18:17 [PATCH v3] loop: fix I/O error on fsync() in detached loop devices Mauricio Faria de Oliveira
2021-01-08 0:23 ` Ming Lei
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