Adding Alexey and Liu from Acronis.
Lesha, Liu, please check questions from Alexander in the comments below.
--
Best regards,
Konstantin Khorenko,
Virtuozzo Linux Kernel Team
On 12.10.2022 21:04, Alexander Atanasov wrote:
Hello,
On 12.10.22 21:08, Konstantin Khorenko wrote:
Sashas, can you please review the patch from Liu?
And i wonder if we need similar patch for dm-qcow driver.
comments bellow.
-------- Forwarded Message --------
Subject: [Devel] [PATCH RH9] dm-ploop: port the standby mode feature.
Date: Mon, 3 Oct 2022 15:42:32 +0800
From: Liu Kui <kui....@acronis.com>
To: de...@acronis.com
==========================
commit f5df00558e645959ab08b198681004679d4a3595
Author: Anton Nefedov <anton.nefe...@virtuozzo.com>
Date: Fri Nov 16 12:46:28 2018 +0300
ploop: move to standby mode after fsync() error too
Extend bdadef81aba5 'ploop: add a standby mode' so it covers fsync().
https://pmc.acronis.com/browse/VSTOR-17613
Signed-off-by: Anton Nefedov <anton.nefe...@virtuozzo.com>
Acked-by: Andrey Zaitsev <azait...@virtuozzo.com>
Acked-by: Sergey Lysanov <slysa...@virtuozzo.com>
===========================
Patchset description:
ploop: more cases for standby mode
standby mode motivation:
commit bdadef81aba572fdcfd59e4c5c7b18736c962ebd
Author: Andrei Vagin <ava...@openvz.org>
Date: Thu Mar 1 11:07:34 2018 +0300
ploop: add a standby mode
This mode shows that a delta lease was stolen and it is
impossible to
handle any requests.
We want to know about this situation from the iscsi target.
When HA
decides that the current target is broken, it can initialize
another
target with the same delta. In this case, the first target has
to complete
all in-porgress commands and set the
ASCQ_04H_ALUA_TG_PT_STANDBY bit in
their status.
In Linux, bio-s are always completed with EIO in error cases,
so we need
another way how to determine this state. This patch addes a new
block
queue flag QUEUE_FLAG_STANDBY.
Anton Nefedov (3):
ploop: move standby mode setting to separate function
ploop: move to standby mode after fsync() error too
ploop: move to standby after -ENOTCONN too
Signed-off-by: Liu Kui <kui....@acronis.com>
---
drivers/md/dm-ploop-map.c | 25 ++++++++++++++++++++++++-
drivers/md/dm-ploop-target.c | 4 ++++
drivers/md/dm-ploop.h | 2 ++
include/linux/blkdev.h | 2 ++
4 files changed, 32 insertions(+), 1 deletion(-)
diff --git a/drivers/md/dm-ploop-map.c b/drivers/md/dm-ploop-map.c
index e8288e522e28..8f1f614b7746 100644
--- a/drivers/md/dm-ploop-map.c
+++ b/drivers/md/dm-ploop-map.c
@@ -1163,6 +1163,23 @@ static void ploop_queue_resubmit(struct pio *pio)
queue_work(ploop->wq, &ploop->worker);
}
+static void check_standby_mode(struct ploop *ploop, long res) {
+ struct request_queue *q = ploop->queue;
+ int prev;
+
+ /* move to standby if delta lease was stolen or mount is gone */
+ if (res != -EBUSY && res != -ENOTCONN && res != -EIO) {
+ return;
+ }
+
+ spin_lock_irq(&q->queue_lock);
+ prev = blk_queue_flag_test_and_set(QUEUE_FLAG_STANDBY, q);
+ spin_unlock_irq(&q->queue_lock);
+
+ if (!prev)
+ pr_info("ploop: switch into standby mode\n");
+}
What guarantees that we got EBUSY, EIO or ENOTCONN for the reasons
listed in the description - "This mode shows that a delta lease was
stolen and it is impossible to handle any requests." - what if we got
such an error for other reason? If the problem comes from nfs why not
suspend device mapper from there ?
Also do this errors actually reach dm-ploop ? From my recent tests i
observed that if you have and EIO the filesystem gets it and remounts RO
- it might not reach ploop code at all. Even if you suspend/resume the
queue it would not help with the RO fs.
+
static void ploop_data_rw_complete(struct pio *pio)
{
bool completed;
@@ -1175,6 +1192,7 @@ static void ploop_data_rw_complete(struct pio *pio)
ploop_queue_resubmit(pio);
return;
}
+ check_standby_mode(pio->ploop, pio->ret);
pio->bi_status = errno_to_blk_status(pio->ret);
}
@@ -1815,8 +1833,10 @@ void do_ploop_fsync_work(struct work_struct *ws)
ret = vfs_fsync(file, 0);
while ((pio = ploop_pio_list_pop(&flush_pios)) != NULL) {
- if (unlikely(ret))
+ if (unlikely(ret)) {
+ check_standby_mode(ploop, ret);
pio->bi_status = errno_to_blk_status(ret);
+ }
ploop_pio_endio(pio);
}
}
@@ -1869,6 +1889,9 @@ int ploop_clone_and_map(struct dm_target *ti,
struct request *rq,
struct ploop_rq *prq;
struct pio *pio;
+ if (blk_queue_standby(ploop->queue))
+ return DM_MAPIO_KILL;
+
if (blk_rq_bytes(rq) && ploop_rq_valid(ploop, rq) < 0)
return DM_MAPIO_KILL;
diff --git a/drivers/md/dm-ploop-target.c b/drivers/md/dm-ploop-target.c
index 4b50487b7fb5..677ecb3432f4 100644
--- a/drivers/md/dm-ploop-target.c
+++ b/drivers/md/dm-ploop-target.c
@@ -20,6 +20,7 @@
#include <linux/uio.h>
#include <linux/error-injection.h>
#include "dm-ploop.h"
+#include "dm-core.h"
#define DM_MSG_PREFIX "ploop"
@@ -363,6 +364,9 @@ static int ploop_ctr(struct dm_target *ti,
unsigned int argc, char **argv)
INIT_WORK(&ploop->event_work, do_ploop_event_work);
init_completion(&ploop->inflight_bios_ref_comp);
+ ploop->queue = ti->table->md->queue;
This looks wrong, ploop struct alread have a ptr to ti.
Tables are reloaded in some cases and it is possible that table/md/queue
change.
+ blk_queue_flag_clear(QUEUE_FLAG_STANDBY, ploop->queue);
+
for (i = 0; i < 2; i++) {
release = i ? ploop_inflight_bios_ref_exit1 :
ploop_inflight_bios_ref_exit0;
diff --git a/drivers/md/dm-ploop.h b/drivers/md/dm-ploop.h
index 5d953278a976..2502718c131f 100644
--- a/drivers/md/dm-ploop.h
+++ b/drivers/md/dm-ploop.h
@@ -229,6 +229,8 @@ struct ploop {
struct timer_list enospc_timer;
bool event_enospc;
+
+ struct request_queue *queue;
};
struct ploop_rq {
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 8fcd753c70b0..c2ebcdae3770 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -434,6 +434,7 @@ struct request_queue {
#define QUEUE_FLAG_RQ_ALLOC_TIME 27 /* record rq->alloc_time_ns */
#define QUEUE_FLAG_HCTX_ACTIVE 28 /* at least one blk-mq hctx is
active */
#define QUEUE_FLAG_NOWAIT 29 /* device supports NOWAIT */
+#define QUEUE_FLAG_STANDBY 30 /* unable to handle read/write
requests */
#define QUEUE_FLAG_MQ_DEFAULT ((1 << QUEUE_FLAG_IO_STAT) | \
(1 << QUEUE_FLAG_SAME_COMP) | \
@@ -480,6 +481,7 @@ bool blk_queue_flag_test_and_set(unsigned int flag,
struct request_queue *q);
#define blk_queue_fua(q) test_bit(QUEUE_FLAG_FUA, &(q)->queue_flags)
#define blk_queue_registered(q) test_bit(QUEUE_FLAG_REGISTERED,
&(q)->queue_flags)
#define blk_queue_nowait(q) test_bit(QUEUE_FLAG_NOWAIT,
&(q)->queue_flags)
+#define blk_queue_standby(q) test_bit(QUEUE_FLAG_STANDBY,
&(q)->queue_flags)
extern void blk_set_pm_only(struct request_queue *q);
extern void blk_clear_pm_only(struct request_queue *q);
Why introduce a new queue flag?
Why can't device mapper suspend be used ?
Why not use the existing ploop code to defer and retry pios?
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