On 12/4/20 2:22 AM, Sami Tolvanen wrote:
Hi,
On Wed, Dec 2, 2020 at 4:48 PM Hyeongseok Kim <hyeongseok@xxxxxxxxx> wrote:
If emergency system shutdown is called, like by thermal shutdown,
dm device could be alive when the block device couldn't process
I/O requests anymore. In this status, the handling of I/O errors
by new dm I/O requests or by those already in-flight can lead to
a verity corruption state, which is misjudgment.
So, skip verity work for I/O error when system is shutting down.
Thank you for the patch. I agree that attempting to correct I/O errors
when the system is shutting down, and thus generating more I/O that's
likely going to fail, is not a good idea.
Signed-off-by: Hyeongseok Kim <hyeongseok@xxxxxxxxx>
---
drivers/md/dm-verity-target.c | 12 +++++++++++-
1 file changed, 11 insertions(+), 1 deletion(-)
diff --git a/drivers/md/dm-verity-target.c b/drivers/md/dm-verity-target.c
index f74982dcbea0..ba62c537798b 100644
--- a/drivers/md/dm-verity-target.c
+++ b/drivers/md/dm-verity-target.c
@@ -64,6 +64,15 @@ struct buffer_aux {
int hash_verified;
};
+/*
+ * While system shutdown, skip verity work for I/O error.
+ */
+static inline bool verity_is_system_shutting_down(void)
+{
+ return system_state == SYSTEM_HALT || system_state == SYSTEM_POWER_OFF
+ || system_state == SYSTEM_RESTART;
+}
Which of these states does the system get to during an emergency
shutdown? Can we simplify this by changing the test to system_state >
SYSTEM_RUNNING?
I only saw that it was SYSTEM_POWER_OFF or SYSTEM_RESTART, I wonder if
I/O error can occur in SYSTEM_SUSPEND state.
As far as I know, this could be happen in emergency shutdown case,
can you explain if you have a case when I/O error can occur by
SYSTEM_SUSPEND?
+
/*
* Initialize struct buffer_aux for a freshly created buffer.
*/
@@ -564,7 +573,8 @@ static void verity_end_io(struct bio *bio)
{
struct dm_verity_io *io = bio->bi_private;
- if (bio->bi_status && !verity_fec_is_enabled(io->v)) {
+ if (bio->bi_status &&
+ (!verity_fec_is_enabled(io->v) || verity_is_system_shutting_down())) {
verity_finish_io(io, bio->bi_status);
return;
}
Otherwise, this looks good to me. However, I'm now wondering if an I/O
error should ever result in verity_handle_err() being called. Without
FEC, dm-verity won't call verity_handle_err() when I/O fails, but with
FEC enabled, it currently does, assuming error correction fails. Any
thoughts?
Yes, I have thought about this, and to be honest, I think verity or FEC
should not call verity_handle_error() in case of I/O errors.
But, because I couldn't know the ability of FEC, I only focused on not
breaking curent logics other than system shutdown && I/O errors case.
Sami
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