Re: [PATCH 2/3] md: Set MD_BROKEN for RAID1 and RAID10
From: Xiao Ni <hidden>
Date: 2022-01-31 08:29:44
On Thu, Jan 27, 2022 at 11:39 PM Mariusz Tkaczyk [off-list ref] wrote:
quoted hunk ↗ jump to hunk
There is no direct mechanism to determine raid failure outside personality. It is done by checking rdev->flags after executing md_error(). If "faulty" flag is not set then -EBUSY is returned to userspace. -EBUSY means that array will be failed after drive removal. Mdadm has special routine to handle the array failure and it is executed if -EBUSY is returned by md. There are at least two known reasons to not consider this mechanism as correct: 1. drive can be removed even if array will be failed[1]. 2. -EBUSY seems to be wrong status. Array is not busy, but removal process cannot proceed safe. -EBUSY expectation cannot be removed without breaking compatibility with userspace. In this patch first issue is resolved by adding support for MD_BROKEN flag for RAID1 and RAID10. Support for RAID456 is added in next commit. The idea is to set the MD_BROKEN if we are sure that raid is in failed state now. This is done in each error_handler(). In md_error() MD_BROKEN flag is checked. If is set, then -EBUSY is returned to userspace. As in previous commit, it causes that #mdadm --set-faulty is able to fail array. Previously proposed workaround is valid if optional functionality[1] is disabled. [1] commit 9a567843f7ce("md: allow last device to be forcibly removed from RAID1/RAID10.") Signed-off-by: Mariusz Tkaczyk <redacted> --- drivers/md/md.c | 17 ++++++++----- drivers/md/md.h | 62 +++++++++++++++++++++++++-------------------- drivers/md/raid1.c | 41 +++++++++++++++++------------- drivers/md/raid10.c | 33 ++++++++++++++++-------- 4 files changed, 91 insertions(+), 62 deletions(-)diff --git a/drivers/md/md.c b/drivers/md/md.c index f888ef197765..fda8473f96b8 100644 --- a/drivers/md/md.c +++ b/drivers/md/md.c@@ -2983,10 +2983,11 @@ state_store(struct md_rdev *rdev, const char *buf, size_t len) if (cmd_match(buf, "faulty") && rdev->mddev->pers) { md_error(rdev->mddev, rdev); - if (test_bit(Faulty, &rdev->flags)) - err = 0; - else + + if (test_bit(MD_BROKEN, &rdev->mddev->flags)) err = -EBUSY; + else + err = 0; } else if (cmd_match(buf, "remove")) { if (rdev->mddev->pers) { clear_bit(Blocked, &rdev->flags);@@ -7441,7 +7442,7 @@ static int set_disk_faulty(struct mddev *mddev, dev_t dev) err = -ENODEV; else { md_error(mddev, rdev); - if (!test_bit(Faulty, &rdev->flags)) + if (test_bit(MD_BROKEN, &mddev->flags)) err = -EBUSY; } rcu_read_unlock();@@ -7987,12 +7988,14 @@ void md_error(struct mddev *mddev, struct md_rdev *rdev) if (!mddev->pers->sync_request) return; - if (mddev->degraded) + if (mddev->degraded && !test_bit(MD_BROKEN, &mddev->flags)) set_bit(MD_RECOVERY_RECOVER, &mddev->recovery); sysfs_notify_dirent_safe(rdev->sysfs_state); set_bit(MD_RECOVERY_INTR, &mddev->recovery); - set_bit(MD_RECOVERY_NEEDED, &mddev->recovery); - md_wakeup_thread(mddev->thread); + if (!test_bit(MD_BROKEN, &mddev->flags)) { + set_bit(MD_RECOVERY_NEEDED, &mddev->recovery); + md_wakeup_thread(mddev->thread); + } if (mddev->event_work.func) queue_work(md_misc_wq, &mddev->event_work); md_new_event();diff --git a/drivers/md/md.h b/drivers/md/md.h index bc3f2094d0b6..1eb7d0e88cb2 100644 --- a/drivers/md/md.h +++ b/drivers/md/md.h@@ -234,34 +234,42 @@ extern int rdev_clear_badblocks(struct md_rdev *rdev, sector_t s, int sectors, int is_new); struct md_cluster_info; -/* change UNSUPPORTED_MDDEV_FLAGS for each array type if new flag is added */ +/** + * enum mddev_flags - md device flags. + * @MD_ARRAY_FIRST_USE: First use of array, needs initialization. + * @MD_CLOSING: If set, we are closing the array, do not open it then. + * @MD_JOURNAL_CLEAN: A raid with journal is already clean. + * @MD_HAS_JOURNAL: The raid array has journal feature set. + * @MD_CLUSTER_RESYNC_LOCKED: cluster raid only, which means node, already took + * resync lock, need to release the lock. + * @MD_FAILFAST_SUPPORTED: Using MD_FAILFAST on metadata writes is supported as + * calls to md_error() will never cause the array to + * become failed. + * @MD_HAS_PPL: The raid array has PPL feature set. + * @MD_HAS_MULTIPLE_PPLS: The raid array has multiple PPLs feature set. + * @MD_ALLOW_SB_UPDATE: md_check_recovery is allowed to update the metadata + * without taking reconfig_mutex. + * @MD_UPDATING_SB: md_check_recovery is updating the metadata without + * explicitly holding reconfig_mutex. + * @MD_NOT_READY: do_md_run() is active, so 'array_state', ust not report that + * array is ready yet. + * @MD_BROKEN: This is used to stop writes and mark array as failed. + * + * change UNSUPPORTED_MDDEV_FLAGS for each array type if new flag is added + */ enum mddev_flags { - MD_ARRAY_FIRST_USE, /* First use of array, needs initialization */ - MD_CLOSING, /* If set, we are closing the array, do not open - * it then */ - MD_JOURNAL_CLEAN, /* A raid with journal is already clean */ - MD_HAS_JOURNAL, /* The raid array has journal feature set */ - MD_CLUSTER_RESYNC_LOCKED, /* cluster raid only, which means node - * already took resync lock, need to - * release the lock */ - MD_FAILFAST_SUPPORTED, /* Using MD_FAILFAST on metadata writes is - * supported as calls to md_error() will - * never cause the array to become failed. - */ - MD_HAS_PPL, /* The raid array has PPL feature set */ - MD_HAS_MULTIPLE_PPLS, /* The raid array has multiple PPLs feature set */ - MD_ALLOW_SB_UPDATE, /* md_check_recovery is allowed to update - * the metadata without taking reconfig_mutex. - */ - MD_UPDATING_SB, /* md_check_recovery is updating the metadata - * without explicitly holding reconfig_mutex. - */ - MD_NOT_READY, /* do_md_run() is active, so 'array_state' - * must not report that array is ready yet - */ - MD_BROKEN, /* This is used in RAID-0/LINEAR only, to stop - * I/O in case an array member is gone/failed. - */ + MD_ARRAY_FIRST_USE, + MD_CLOSING, + MD_JOURNAL_CLEAN, + MD_HAS_JOURNAL, + MD_CLUSTER_RESYNC_LOCKED, + MD_FAILFAST_SUPPORTED, + MD_HAS_PPL, + MD_HAS_MULTIPLE_PPLS, + MD_ALLOW_SB_UPDATE, + MD_UPDATING_SB, + MD_NOT_READY, + MD_BROKEN, }; enum mddev_sb_flags {diff --git a/drivers/md/raid1.c b/drivers/md/raid1.c index 7dc8026cf6ee..b222bafa1196 100644 --- a/drivers/md/raid1.c +++ b/drivers/md/raid1.c@@ -1615,30 +1615,37 @@ static void raid1_status(struct seq_file *seq, struct mddev *mddev) seq_printf(seq, "]"); } +/** + * raid1_error() - RAID1 error handler. + * @mddev: affected md device. + * @rdev: member device to remove. + * + * Error on @rdev is raised and it is needed to be removed from @mddev. + * If there are more than one active member, @rdev is always removed. + * + * If it is the last active member, it depends on &mddev->fail_last_dev: + * - if is on @rdev is removed. + * - if is off, @rdev is not removed, but recovery from it is disabled (@rdev is + * very likely to fail). + * In both cases, &MD_BROKEN will be set in &mddev->flags. + */ static void raid1_error(struct mddev *mddev, struct md_rdev *rdev) { char b[BDEVNAME_SIZE]; struct r1conf *conf = mddev->private; unsigned long flags; - /* - * If it is not operational, then we have already marked it as dead - * else if it is the last working disks with "fail_last_dev == false", - * ignore the error, let the next level up know. - * else mark the drive as failed - */ spin_lock_irqsave(&conf->device_lock, flags); - if (test_bit(In_sync, &rdev->flags) && !mddev->fail_last_dev - && (conf->raid_disks - mddev->degraded) == 1) { - /* - * Don't fail the drive, act as though we were just a - * normal single drive. - * However don't try a recovery from this drive as - * it is very likely to fail. - */
Hi Mariusz From my view, it's better to keep those comments although you add some comments before the function. These comments are helpful to understand this function.
quoted hunk ↗ jump to hunk
- conf->recovery_disabled = mddev->recovery_disabled; - spin_unlock_irqrestore(&conf->device_lock, flags); - return; + + if (test_bit(In_sync, &rdev->flags) && + (conf->raid_disks - mddev->degraded) == 1) { + set_bit(MD_BROKEN, &mddev->flags); + + if (!mddev->fail_last_dev) { + conf->recovery_disabled = mddev->recovery_disabled; + spin_unlock_irqrestore(&conf->device_lock, flags); + return; + } } set_bit(Blocked, &rdev->flags); if (test_and_clear_bit(In_sync, &rdev->flags))diff --git a/drivers/md/raid10.c b/drivers/md/raid10.c index dde98f65bd04..7471e20d7cd6 100644 --- a/drivers/md/raid10.c +++ b/drivers/md/raid10.c@@ -1945,26 +1945,37 @@ static int enough(struct r10conf *conf, int ignore) _enough(conf, 1, ignore); } +/** + * raid10_error() - RAID10 error handler. + * @mddev: affected md device. + * @rdev: member device to remove. + * + * Error on @rdev is raised and it is needed to be removed from @mddev. + * If there is (excluding @rdev) enough members to operate, @rdev is always
s/is/are/g
+ * removed.
+ *
+ * Otherwise, it depends on &mddev->fail_last_dev:
+ * - if is on @rdev is removed.
+ * - if is off, @rdev is not removed.
+ *
+ * In both cases, &MD_BROKEN will be set in &mddev->flags.
+ */
static void raid10_error(struct mddev *mddev, struct md_rdev *rdev)
{
char b[BDEVNAME_SIZE];
struct r10conf *conf = mddev->private;
unsigned long flags;
- /*
- * If it is not operational, then we have already marked it as dead
- * else if it is the last working disks with "fail_last_dev == false",
- * ignore the error, let the next level up know.
- * else mark the drive as failed
- */
spin_lock_irqsave(&conf->device_lock, flags);
+
if (test_bit(In_sync, &rdev->flags) && !mddev->fail_last_dev
&& !enough(conf, rdev->raid_disk)) {The check of mddev->fail_last_dev should be removed here.
- /* - * Don't fail the drive, just return an IO error. - */
It's the same. These comments can directly give people notes. raid10 will return bio here with an error. Is it better to keep them here? Best Regards Xiao
- spin_unlock_irqrestore(&conf->device_lock, flags);
- return;
+ set_bit(MD_BROKEN, &mddev->flags);
+
+ if (!mddev->fail_last_dev) {
+ spin_unlock_irqrestore(&conf->device_lock, flags);
+ return;
+ }
}
if (test_and_clear_bit(In_sync, &rdev->flags))
mddev->degraded++;
--
2.26.2