From: Yu Kuai <yukuai1@huaweicloud.com>
To: mpatocka@redhat.com, heinzm@redhat.com, xni@redhat.com,
agk@redhat.com, snitzer@kernel.org, dm-devel@lists.linux.dev,
song@kernel.org, yukuai3@huawei.com, jbrassow@f14.redhat.com,
neilb@suse.de, shli@fb.com, akpm@osdl.org
Cc: linux-kernel@vger.kernel.org, linux-raid@vger.kernel.org,
yukuai1@huaweicloud.com, yi.zhang@huawei.com,
yangerkun@huawei.com
Subject: [PATCH v3 00/12] dm-raid: fix v6.7 regressions
Date: Sat, 27 Jan 2024 15:47:42 +0800 [thread overview]
Message-ID: <20240127074754.2380890-1-yukuai1@huaweicloud.com> (raw)
From: Yu Kuai <yukuai3@huawei.com>
Changes in v3:
- fix a problem in patch 5;
- add patch 12;
Changes in v2:
- replace revert changes for dm-raid with real fixes;
- fix dm-raid5 deadlock that exist for a long time, this deadlock is
triggered because another problem is fixed in raid5, and instead of
deadlock, user will read wrong data before v6.7, patch 9-11;
First regression related to stop sync thread:
The lifetime of sync_thread is designed as following:
1) Decide want to start sync_thread, set MD_RECOVERY_NEEDED, and wake up
daemon thread;
2) Daemon thread detect that MD_RECOVERY_NEEDED is set, then set
MD_RECOVERY_RUNNING and register sync_thread;
3) Execute md_do_sync() for the actual work, if it's done or
interrupted, it will set MD_RECOVERY_DONE and wake up daemone thread;
4) Daemon thread detect that MD_RECOVERY_DONE is set, then clear
MD_RECOVERY_RUNNING and unregister sync_thread;
In v6.7, we fix md/raid to follow this design by commit f52f5c71f3d4
("md: fix stopping sync thread"), however, dm-raid is not considered at
that time, and following test will hang:
shell/integrity-caching.sh
shell/lvconvert-raid-reshape.sh
This patch set fix the broken test by patch 1-4;
- patch 1 fix that step 4) is broken by suspended array;
- patch 2 fix that step 4) is broken by read-only array;
- patch 3 fix that step 3) is broken that md_do_sync() doesn't set
MD_RECOVERY_DONE; Noted that this patch will introdece new problem that
data will be corrupted, which will be fixed in later patches.
- patch 4 fix that setp 1) is broken that sync_thread is register and
MD_RECOVERY_RUNNING is set directly, md/raid behaviour, not related to
dm-raid;
With patch 1-4, the above test won't hang anymore, however, the test
will still fail and complain that ext4 is corrupted;
Second regression related to frozen sync thread:
Noted that for raid456, if reshape is interrupted, then call
"pers->start_reshape" will corrupt data. And dm-raid rely on md_do_sync()
doesn't set MD_RECOVERY_DONE so that new sync_thread won't be registered,
and patch 3 just break this.
- Patch 5-6 fix this problem by interrupting reshape and frozen
sync_thread in dm_suspend(), then unfrozen and continue reshape in
dm_resume(). It's verified that dm-raid tests won't complain that
ext4 is corrupted anymore.
- Patch 7 fix the problem that raid_message() call
md_reap_sync_thread() directly, without holding 'reconfig_mutex'.
Last regression related to dm-raid456 IO concurrent with reshape:
For raid456, if reshape is still in progress, then IO across reshape
position will wait for reshape to make progress. However, for dm-raid,
in following cases reshape will never make progress hence IO will hang:
1) the array is read-only;
2) MD_RECOVERY_WAIT is set;
3) MD_RECOVERY_FROZEN is set;
After commit c467e97f079f ("md/raid6: use valid sector values to determine
if an I/O should wait on the reshape") fix the problem that IO across
reshape position doesn't wait for reshape, the dm-raid test
shell/lvconvert-raid-reshape.sh start to hang at raid5_make_request().
For md/raid, the problem doesn't exist because:
1) If array is read-only, it can switch to read-write by ioctl/sysfs;
2) md/raid never set MD_RECOVERY_WAIT;
3) If MD_RECOVERY_FROZEN is set, mddev_suspend() doesn't hold
'reconfig_mutex' anymore, it can be cleared and reshape can continue by
sysfs api 'sync_action'.
However, I'm not sure yet how to avoid the problem in dm-raid yet.
- patch 9-11 fix this problem by detecting the above 3 cases in
dm_suspend(), and fail those IO directly.
If user really meet the IO error, then it means they're reading the wrong
data before c467e97f079f. And it's safe to read/write the array after
reshape make progress successfully.
There are also some other minor changes: patch 8 and patch 12;
Yu Kuai (12):
md: don't ignore suspended array in md_check_recovery()
md: don't ignore read-only array in md_check_recovery()
md: make sure md_do_sync() will set MD_RECOVERY_DONE
md: don't register sync_thread for reshape directly
md: export helpers to stop sync_thread
dm-raid: really frozen sync_thread during suspend
md/dm-raid: don't call md_reap_sync_thread() directly
dm-raid: remove mddev_suspend/resume()
dm-raid: add a new helper prepare_suspend() in md_personality
md: export helper md_is_rdwr()
md/raid456: fix a deadlock for dm-raid456 while io concurrent with
reshape
dm-raid: fix lockdep waring in "pers->hot_add_disk"
drivers/md/dm-raid.c | 78 ++++++++++++++++++++++++-----------
drivers/md/md.c | 96 ++++++++++++++++++++++++++++----------------
drivers/md/md.h | 16 ++++++++
drivers/md/raid10.c | 16 +-------
drivers/md/raid5.c | 61 +++++++++++++++-------------
5 files changed, 167 insertions(+), 100 deletions(-)
--
2.39.2
next reply other threads:[~2024-01-27 7:52 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-01-27 7:47 Yu Kuai [this message]
2024-01-27 7:47 ` [PATCH v3 01/12] md: don't ignore suspended array in md_check_recovery() Yu Kuai
2024-01-27 7:47 ` [PATCH v3 02/12] md: don't ignore read-only " Yu Kuai
2024-01-27 7:47 ` [PATCH v3 03/12] md: make sure md_do_sync() will set MD_RECOVERY_DONE Yu Kuai
2024-01-27 7:47 ` [PATCH v3 04/12] md: don't register sync_thread for reshape directly Yu Kuai
2024-01-27 7:47 ` [PATCH v3 05/12] md: export helpers to stop sync_thread Yu Kuai
2024-01-27 7:47 ` [PATCH v3 06/12] dm-raid: really frozen sync_thread during suspend Yu Kuai
2024-01-27 7:47 ` [PATCH v3 07/12] md/dm-raid: don't call md_reap_sync_thread() directly Yu Kuai
2024-01-27 7:47 ` [PATCH v3 08/12] dm-raid: remove mddev_suspend/resume() Yu Kuai
2024-01-27 7:47 ` [PATCH v3 09/12] dm-raid: add a new helper prepare_suspend() in md_personality Yu Kuai
2024-01-27 7:47 ` [PATCH v3 10/12] md: export helper md_is_rdwr() Yu Kuai
2024-01-27 7:47 ` [PATCH v3 11/12] md/raid456: fix a deadlock for dm-raid456 while io concurrent with reshape Yu Kuai
2024-01-27 7:47 ` [PATCH v3 12/12] dm-raid: fix lockdep waring in "pers->hot_add_disk" Yu Kuai
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