NeilBrown <neilb@xxxxxxx> writes:
> It is only safe to choose not to write to a bad block if that bad
> block is safely recorded in metadata - i.e. if it has been
> 'acknowledged'.
>
> If it hasn't we need to wait for the acknowledgement.
>
> We support that using rdev->blocked wait and
> md_wait_for_blocked_rdev by introducing a new device flag
> 'BlockedBadBlock'.
>
> This flag is only advisory.
> It is cleared whenever we acknowledge a bad block, so that a waiter
> can re-check the particular bad blocks that it is interested it.
>
> It should be set by a caller when they find they need to wait.
> This (set after test) is inherently racy, but as
> md_wait_for_blocked_rdev already has a timeout, losing the race will
> have minimal impact.
>
> When we clear "Blocked" was also clear "BlockedBadBlocks" incase it
> was set incorrectly (see above race).
>
> We also modify the way we manage 'Blocked' to fit better with the new
> handling of 'BlockedBadBlocks' and to make it consistent between
> externally managed and internally managed metadata. This requires
> that each raidXd loop checks if the metadata needs to be written and
> triggers a write (md_check_recovery) if needed. Otherwise a queued
> write request might cause raidXd to wait for the metadata to write,
> and only that thread can write it.
>
> Before writing metadata, we set FaultRecorded for all devices that
> are Faulty, then after writing the metadata we clear Blocked for any
> device for which the Fault was certainly Recorded.
>
> The 'faulty' device flag now appears in sysfs if the device is faulty
> *or* it has unacknowledged bad blocks. So user-space which does not
> understand bad blocks can continue to function correctly.
> User space which does, should not assume a device is faulty until it
> sees the 'faulty' flag, and then sees the list of unacknowledged bad
> blocks is empty.
>
> Signed-off-by: NeilBrown <neilb@xxxxxxx>
Probably you also need this patch:
>From 76320c4fdaed91f26a083a9337bb5a5503300e0e Mon Sep 17 00:00:00 2001
From: Namhyung Kim <namhyung@xxxxxxxxx>
Date: Wed, 27 Jul 2011 00:59:26 +0900
Subject: [PATCH] md: update documentation for md/rdev/state sysfs interface
Previous patches in the bad block series extended behavior of
rdev's 'state' interface but lacked documentation update.
Fix it.
Signed-off-by: Namhyung Kim <namhyung@xxxxxxxxx>
---
Documentation/md.txt | 14 +++++++++-----
1 files changed, 9 insertions(+), 5 deletions(-)
diff --git a/Documentation/md.txt b/Documentation/md.txt
index 923a6bddce7c..fc94770f44ab 100644
--- a/Documentation/md.txt
+++ b/Documentation/md.txt
@@ -360,18 +360,20 @@ Each directory contains:
A file recording the current state of the device in the array
which can be a comma separated list of
faulty - device has been kicked from active use due to
- a detected fault
+ a detected fault or it has unacknowledged bad
+ blocks
in_sync - device is a fully in-sync member of the array
writemostly - device will only be subject to read
requests if there are no other options.
This applies only to raid1 arrays.
- blocked - device has failed, metadata is "external",
- and the failure hasn't been acknowledged yet.
+ blocked - device has failed, and the failure hasn't been
+ acknowledged yet by the metadata handler.
Writes that would write to this device if
it were not faulty are blocked.
spare - device is working, but not a full member.
This includes spares that are in the process
of being recovered to
+ write_error - device has ever seen a write error.
This list may grow in future.
This can be written to.
Writing "faulty" simulates a failure on the device.
@@ -379,9 +381,11 @@ Each directory contains:
Writing "writemostly" sets the writemostly flag.
Writing "-writemostly" clears the writemostly flag.
Writing "blocked" sets the "blocked" flag.
- Writing "-blocked" clears the "blocked" flag and allows writes
- to complete.
+ Writing "-blocked" clears the "blocked" flags and allows writes
+ to complete and possibly simulates an error.
Writing "in_sync" sets the in_sync flag.
+ Writing "write_error" sets writeerrorseen flag.
+ Writing "-write_error" clears writeerrorseen flag.
This file responds to select/poll. Any change to 'faulty'
or 'blocked' causes an event.
--
1.7.6
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